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Polymer
Journal Prestige (SJR): 1.097
Citation Impact (citeScore): 4
Number of Followers: 141  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0032-3861
Published by Elsevier Homepage  [3163 journals]
  • Preparation of novel polyimide nanocomposites with high mechanical and
           tribological performance using covalent modified carbon nanotubes via
           Friedel-Crafts reaction
    • Abstract: Publication date: 15 August 2018Source: Polymer, Volume 150Author(s): Chunying Min, Dengdeng Liu, Zengbao He, Songjun Li, Kan Zhang, Yudong Huang Novel polyimide nanocomposites with excellent mechanical and tribological properties were achieved using amine functionalized multi-walled carbon nanotubes (MWCNT-NH2). MWCNT-NH2 was successfully obtained through Friedel-Crafts acylation and nitroreduction. PI nanocomposites with different contents of MWCNT-NH2 were prepared via in-situ polymerization. In contrast with the properties of pure PI or PI/MWCNT blends, the tribological properties, mechanical properties, and thermal performance of PI/MWCNT-NH2 nanocomposites were evidently improved due to the homogeneous dispersion of MWCNT-NH2 in PI matrix as well as the strong interfacial covalent bonds between MWCNT-NH2 and the PI matrix. Notably, it was demonstrated that the PI/MWCNT-NH2 nanocomposite adding with 0.7 wt% MWCNT-NH2 exhibited the best tribological properties in consideration of the friction coefficient (0.310) and wear rate (2.234 × 10−4 mm3/Nm) under dry sliding condition. Furthermore, the resulting PI/MWCNT-NH2 nanocomposites possessed the combined excellent tribological and mechanical properties, evidencing their potential applications in the field of the friction materials and other high-performance areas.Graphical abstractImage 1
       
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    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s):
       
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    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s):
       
  • Calendar
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s):
       
  • Surface functionalization of upconversion nanoparticles using visible
           light-mediated polymerization
    • Abstract: Publication date: Available online 20 July 2018Source: PolymerAuthor(s): Ali Bagheri, Zahra Sadrearhami, Nik Nik M. Adnan, Cyrille Boyer, May Lim Lanthanide-doped upconversion nanoparticles (UCNPs) have unique photoluminescent properties which are useful in many biomedical applications. However, to extend their practical use prior surface modification is essential. Herein, we present a straightforward and generic visible light-mediated method for growing a polymer shell with controlled architecture from the UCNPs surfaces (i.e. “grafting from”) and demonstrate an application in the delivery of nitric oxide (NO). Our approach has the advantage that no external photocatalyst or initiator is required to initiate the polymerization of the polymer chains. A silica layer was initially generated on the surfaces of the UCNPs as a platform for tethering 4-cyano-4-((dodecylsulfanylthiocarbonyl) sulfanyl) pentanoic acid (CDTPA), a chain transfer agent. The polymerization of functional monomers (glycidyl methacrylate (GMA), poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) or hydroxyethyl methacrylate (HEMA) were then initiated using CDTPA as initiator/chain transfer agent under blue (460 nm, 0.7 mW/cm2) or green (530 nm, 0.7 mW/cm2) light. The PGMA layer can be used to chemically attach various functional molecules onto the UCNPs surface without affecting the luminescence properties of the particles. The polymers also improve the colloidal stability of the UCNPs in water and biocompatibility of the UCNPs. These particles were then used to store and release NO by functionalizing their surfaces with N-diazeniumdiolates (NONOate) moieties. Using the NONOate functionalized UCNPs, relatively slow and controlled release of NO over 6 h can achieved.Graphical abstractImage 1
       
  • The photo-optical and electrochemical activity promoted by
           trifluoromethyl-substituted and ortho-catenated triphenylamine core in
           poly(ether-imide)s
    • Abstract: Publication date: Available online 19 July 2018Source: PolymerAuthor(s): Mariana-Dana Damaceanu, Catalin-Paul Constantin, Maria Bruma, Roman S. Begunov A new series of five thermally and dimensionally stable aromatic poly(ether-imide)s consisting of an electron donating ortho-catenated triphenylamine (TPA) derivative bearing two trifluoromethyl groups and various electron-accepting phthalimide moieties were synthesized and thoroughly investigated. These polyimides display excellent organosolubility, unexpectedly even in ethanol, which allows their processing in environmentally friendly conditions. The twisting of the backbone structure induced by the ortho-catenated TPA core significantly affects their electronic properties. It was found that the CF3-substituted TPA moiety may facilitate dual intramolecular charge transfer (ICT) transitions, an aspect not highlighted yet for this class of polymers. In addition, we brought evidence for the occurrence of Förster excitation energy transfer (FRET) between the two ICT excited states that modulates the light emission toward the green-yellow spectral range, another novelty encountered at these polymers. The electron-withdrawing CF3 units directly graphthed on the triphenylamine core induced a fine-tuning of HOMO-LUMO energy levels, leading to low LUMO levels and energy band gaps. The novel characteristics endow the developed polymers with a wide application prospect, especially in the field of biology and opto-electronics.Graphical abstractImage 1
       
  • Cavitation phenomenon and mechanical properties of partially disentangled
           polypropylene
    • Abstract: Publication date: Available online 19 July 2018Source: PolymerAuthor(s): Andrzej Pawlak, Justyna Krajenta, Andrzej Galeski The mechanical properties of polypropylene samples with three different densities of macromolecular entanglements were examined in tensile test. The experiments were performed at temperatures of 20–100 °C. SAXS, WAXS, DSC and SEM techniques were used to study the evolution of polypropylene internal structure with deformation. It was found that properties of polymer at yield were not changed by reduction of entanglements. The strain hardening phase of deformation depended on the density of molecular network formed by entanglements and the increase of stress was faster when polypropylene is more entangled. It was observed enhanced cavitation in partially disentangled polypropylene. The cavitation in disentangled polymer was possible not only at low temperatures, but even when the tensile deformation was performed at temperature of 100 °C.Graphical abstractImage 1
       
  • l-Glutamate&rft.title=Polymer&rft.issn=0032-3861&rft.date=&rft.volume=">Ring-opening cryo-polymerization of N-carboxy-α-amino acid anhydride of
           γ-benzyl l-Glutamate
    • Abstract: Publication date: Available online 19 July 2018Source: PolymerAuthor(s): Xi-Chuan Li, Chuan-Shan Hu, Hui-Juan Li, Peng-Yun Li, Abdul Haleem, Wei-Dong He Ring-opening polymerization (ROP) of N-carboxy-α-amino acid anhydride (NCA) of γ-benzyl l-glutamate (BLG) was investigated under frozen condition for the first time. This cryo-ROP was performed in DMSO or 1,4-dioxane below the freezing point of polymerization mixture. The kinetics was monitored with proton nuclear magnetic resonance spectroscopy and gel permeation chromatography, disclosing the well control over molecular weight, living polymerization features and considerable polymerization rate. Compared with the polymerization proceeded at 30 °C, which showed weak linearity regarding the dynamics of the reaction and relatively broad distribution of molecular weight, the cryo-ROP exhibited excellent first order kinetics as well as narrow molecular distribution.Graphical abstractImage 1
       
  • Novel semi-alicyclic polyimide membranes: Synthesis, characterization, and
           gas separation properties
    • Abstract: Publication date: Available online 18 July 2018Source: PolymerAuthor(s): Chae-Young Park, Eun-Hee Kim, Jong Hak Kim, Young Moo Lee, Jeong-Hoon Kim To develop membrane materials for gas separation, a series of semi-alicyclic polyimides was synthesized using one-step thermal solution imidization from an alicyclic dianhydride with non-planar twisted structure, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and five aromatic diamines. All synthesized polyimides exhibited amorphous structures and superior thermal stability, with high glass transition temperatures (242–288 °C) withstanding high operation temperature and pressure. They also showed excellent solubility in many polar organic solvents commonly used in the fabrication of gas separation membranes. The gas permeation properties of the polyimide membranes were measured for six representative gases (H2, CO2, O2, CO, N2, and CH4). The gas permeabilities and selectivities of polyimide membranes were significantly influenced by the chemical structure of the diamines, which could be explained reasonably by the kinetic diameter of gases, the fractional free volumes and d-spacing values of the polyimides. Two DOCDA-based polyimides also showed very high selectivities for H2/CH4 and CO2/CH4 and slightly low permeabilities for H2 and CO2, which performances were comparable to the commercial polyimide materials, P84® and Matrimid® used in gas separation field.Graphical abstractImage 1
       
  • Self-healing, reprocessing and sealing abilities of polysulfide-based
           polyurethane
    • Abstract: Publication date: Available online 18 July 2018Source: PolymerAuthor(s): Wentong Gao, Mengyao Bie, Yiwu Quan, Jinyan Zhu, Wanqing Zhang Polyurethanes are known for their satisfactory mechanical strength, which is highly desired for various applications. Poly(ethyl formal disulfide)-based materials have excellent self-healing ability because of containing abundant exchangeable disulfide bonds, while their strength is relatively low (< 0.8 MPa). Combining the advantages of the two materials, in this article, we synthesized self-healable polysulfide-based polyurethanes with a tensile strength of 2.62−5.80 MPa. After healing at 75 °C for 24 h or 100 °C for 4 h, the tensile strength of a fully cut optimized sample (PSPU-15) recovered to 90.8 and 93.1% of the original value 2.62 MPa, respectively, with the damaged incision disappearing and the sealing integrity fully recovered. Furthermore, the sample PSPU-15 possessed good reprocessing ability, retaining the tensile strength of 2.66−2.40 MPa after repeated processing. These outcomes indicated that polysulfide-based polyurethane is an attractive paradigm towards sustainable industrial applications.Graphical abstractImage
       
  • Towards the development of electrospun mats from
           poly(ε-caprolactone)/poly(ester amide)s miscible blends
    • Abstract: Publication date: Available online 18 July 2018Source: PolymerAuthor(s): Miguel L. Lamas, Mafalda S. Lima, Ana C. Pinho, David Tugushi, Ramaz Katsarava, Elisabete C. Costa, Ilídio J. Correia, Arménio C. Serra, Jorge F.J. Coelho, Ana C. Fonseca In this work, electrospun mats made from miscible poly(ε-caprolactone) (PCL)/poly(ester amide) (PEA) blends were prepared, for the first time. The well-known immiscibility issues between these two type of polymers were overcome through the synthesis of a novel tailor-made compatibilizer blocky PEA, comprising well defined PCL and PEA8L6 blocks (PCL-PEA8L6). The PCL-PEA8L6 was synthesized for the first time in this work and was characterized in terms of its chemical structure and thermal properties. Regarding the mats, it was found that their properties (morphology, porosity, wettability, thermomechanical) can be easily adjusted by the ratio of the components of the mixture to be electrospun. Increasing amounts of PEA led to more hydrophilic mats, with enhanced in vitro degradability, both hydrolytic and enzymatic. The in vitro cytotoxicity tests carried out with normal human dermal fibroblasts (NHDF) revealed that the samples do not elicit any acute adverse effect on the cells. Moreover, the NHDF were able to grow and proliferate in the surface of the electrospun mats. The data presented in this contribution is a proof-of-concept that can be used to address immiscibility issues between different types of polymers broadly used in biomedical applications.Graphical abstractImage 1
       
  • Examining the nature of the network formation during epoxy polymerization
           initiated using ionic liquids
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Fiona C. Binks, Gabriel Cavalli, Michael Henningsen, Brendan J. Howlin, Ian Hamerton A commercial diglycidyl ether of bisphenol A monomer (BaxxoresTM ER 2200, eew 182 g/mole) is thermally polymerized in the presence of an ionic liquid, 1-ethyl-3-methylimidazolium acetate at a variety of loadings (5-45 wt %). The loss modulus data for cured samples containing 5 wt % initiator display at least two thermal transitions and the highest storage modulus occurs in the sample that has been cured for the shortest time at the lowest temperature. Samples that are exposed to higher temperatures (140, 150 °C) yield more heterogenous networks, whereas following exposure to a much shorter/lower temperature cure schedule (80 °C) exhibits a considerably higher damping ability than the other samples, coupled with a lower glass transition temperature. Differential scanning calorimetry reveals that the latter sample achieves a conversion of 95 %, while crosslink densities for the DGEBA samples containing 5 wt % and 15 wt % are respectively 9.5 x 10-3 mol. dm-3 and 1.2 x 10-3 mol. dm-3 (when cured to 80 °C) and 2.0 x 10-2 mol. dm-3 and 2.4 x 10-3 mol. dm-3 (when cured to 140 °C).Graphical abstractImageDemonstrating the influence of ionic liquid concentration on polyetherification behaviour of DGEBA
       
  • Comparison of the effects of post-spinning drawing and wet stretching on
           regenerated silk fibers produced through straining flow spinning
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Rodrigo Madurga, Alfonso M. Gañán-Calvo, Gustavo R. Plaza, José Miguel Atienza, Gustavo V. Guinea, Manuel Elices, Patricia A. López, Rafael Daza, Daniel González-Nieto, José Pérez-Rigueiro Straining Flow Spinning is a versatile and robust spinning technique for the production of regenerated silkworm silk fibers using mild chemistries. However, reaching high values of tensile strength and strain at breaking requires a step of wet-stretching in water, which limits scalability and the practical usage of the technique. Here, we show that adding a post-spinning drawing step to the procedure improves the performance of the fibers, and allows the development of a scalable process. It is also shown that the properties of the fiber can be tuned by varying the parameters of the post-spinning step. Finally, equivalence is established between the discrete wet-stretching process and the continuous post-spinning drawing step.Graphical abstractImage 1
       
  • Synthesis of diblock copolymer nano-assemblies: Comparison between PISA
           and micellization
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Habib Khan, Mengjiao Cao, Wenfeng Duan, Tengyuan Ying, Wangqing Zhang RAFT dispersion polymerization following the formulation of polymerization induced self-assembly (PISA) and micellization of pre-prepared amphiphilic block copolymers in block-selective solvents are generally used to prepare block copolymer nano-assemblies. Herein, we make a comparison between these two methods by employing two typical block copolymers of poly(acrylic acid)-block-polystyrene (PAA-b-PS) and poly(ethylene glycol)-block-polystyrene (PEG-b-PS). It is found that the block copolymer nano-assemblies prepared by these two methods are similar with each other when the solvophilic block is relatively long and the solvophobic block is relatively short. Otherwise, the block copolymer nano-assemblies by these two methods are different. The possible reasons leading to the difference between PISA and micellization are discussed, and the kinetic factors including temperature, polymer concentration and solvent are ascribed. It is thought that the present study is helpful to clarify how the kinetic factors beyond the block copolymer itself affecting block copolymer morphology.Graphical abstractImage 1
       
  • Synthesis, characterization of chiral poly(ferrocenyl-schiff base)
           iron(II) complexes/RGO composites with enhanced microwave absorption
           properties
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Chongbo Liu, Lin Li, Zhang Xiang, Wei-Ya Chen, Z. John Zhang, Yuancheng Qin, Dezhi Chen Chiral poly(ferrocenyl-Schiff Bases) iron(II) complexes (CPSC)/Reduced graphene oxide (RGO) composites with excellent microwave absorption properties have been successfully prepared. The structures of poly(ferrocenyl-Schiff Bases) and their iron(II) complexes were characterized with IR, MS, HNMR, GPC, elemental analysis, etc. The morphology of CPSC and their composite materials were studied through SEM and TEM analysis. The conductivity, optical activity, electromagnetic parameter and microwave absorption properties of composite materials were also studied in details. The results show that chiral composites own much better microwave absorption properties and wider bandwidth compared to corresponding achiral composites. The maximum RL of chiral CPSC/RGO composite (CM-PL1B) reaches at −52.6 dB at 10.0 GHz with a thickness of 2.5 mm, and the bandwidth of RL less than −10 dB can reach up to 4.6 GHz (from 11.2 to 15.8 GHz), the remarkably enhanced microwave absorption properties are also discussed at length.Graphical abstractCPSC/RGO composites with excellent microwave absorption properties have been successfully prepared, characterized and tested. The results show that chiral composites own much better microwave absorption properties and wider bandwidth compared to corresponding achiral composites.Image 1
       
  • Carboxylated multiwalled carbon nanotubes effect on dynamic mechanical
           behavior of soft films composed of multilayer polymer structure
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Farzad Zahedi, Iraj Amiri Amrae Dynamic mechanical properties due to incorporation of carboxylated multiwalled carbon nanotubes into three-layer polymer structure, with high damping property, via in situ emulsion polymerization and also blending are studied in detail. Using of storage modulus, loss modulus and damping behavior obtained from the DMA was investigated the manner of carboxylated MWCNTs into and onto the three-layer polymer structure. It was observed that different morphology and topology were formed using these two manufacturing methods. Also, it was observed that dynamic mechanical and damping properties are due to complex and multifunctional parameters such as adhesion, constrained chains, molecular optimum mobility between polymer and nanotubes.Graphical abstractGraphical abstract for this article
       
  • Analysis of the effect of block copolymers on interfacial tension in
           immiscible polymer blends
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Ivan Fortelný, Josef Jůza Simple theoretical models show that concentration of a compatibilizing A-B block copolymer at the interface between the phases of A and B homopolymers in immiscible polymer blends increases with increasing chain length of copolymers or homopolymers. Copolymers with block lengths comparable to chain length of the blend components reduce interfacial tension most efficiently. Distribution of the block copolymer between the interface and the bulk phases is studied assuming that it is controlled by the rules of equilibrium thermodynamics. Analysis is based on Leibler's mean field theory and its modification by Noolandi. The analysis shows that the distribution of the copolymer between the interface and the bulk phases changes in a broad range depending on the system parameters. Substantial part of the added copolymer can be localized at the interface in contrast to assumptions used in previous analyses.Graphical abstractImage 1
       
  • Controlling the properties of radiation-synthesized thermoresponsive
           oligoether methacrylate hydrogels by varying the monomer side-chain
           length; self-composite network containing crystalline phase
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Krzysztof Piechocki, Marcin Kozanecki, Slawomir Kadlubowski, Barbara Pacholczyk-Sienicka, Piotr Ulanski, Tadeusz Biela A series of thermo-responsive hydrogels have been synthesized by radiation-induced crosslinking polymerization in bulk based on; oligoether methacrylates (OEGMAs) of side chain lengths of 2–19 EG; monomer units. Side chain lengths have been shown to have a pronounced; effect on synthesis parameters (monomers of longer side chains are more; easily crosslinked, and the inert atmosphere promotes crosslinking more; than air) and hydrogel properties (the thermal stability of obtained; networks and their swelling capacities, as well as the temperature of; Volume Phase Transition (VPT), increase with increasing oligoether side; group length, while the VPT becomes less narrow). Networks based on; oligoether methacrylates of sufficiently long side chains (over 7 monomer; units) are capable of partial crystallization, forming self-composites, and the crystalline phase is chemically linked to a continuous, coherent; polymer network.Graphical abstractImage 1
       
  • Microscopic Theory of Heterogeneous Phase Inversion in Rubber/Plastic
           Blends
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Zhaoyang Wei, Nanying Ning, Ming Tian, Liqun Zhang, Jianguo Mi Despite many investigations, phase inversion in rubber/plastic blends and its origin are far from being understood. Here we focus on the heterogeneous phase inversion in partially miscible blend of polyolefin elastomer (POE) and polypropylene (PP) using the classical density functional approach. We have shown that the blend decomposes into the POE-rich and PP-rich phases on the surfaces of POE or PP domains. For example, the free energy barriers and critical sizes of the POE-rich droplets on the two surfaces obviously decrease compared to the analogous values in the homogeneous nucleation. These values can be further reduced after introduction of nanoparticles, which act as the compatibilizer, improving morphology and final properties of the blend. These results indicate different phase inversion mechanisms in the blend, and can explain why different sizes of nanoparticles can observed in experiments.Graphical abstractFor Table of Contents use onlyImage
       
  • Diphenylsilane-containing linear and rigid whole aromatic
           poly(azomethine)s. Structural and physical characterization
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): A. Tundidor-Camba, C.M. González-Henríquez, M.A. Sarabia-Vallejos, L.H. Tagle, P.A. Sobarzo, A. González, R.A. Hauyón, A.P. Mariman, C.A. Terraza Six new whole aromatic poly(azomethine)s with different rigidity were prepared from three diamines and two dialdehydes, all of them containing a diphenylsilane moiety as a central structural element. Two amines containing biphenyl moieties were obtained for the first time. Thus, the synthesized polymers contain two silicon atoms in the repeat unit, where methyl and/or phenyl groups bonded to them, complete the tetra-valence of the heteroatom. The new materials were structurally characterized by means of FT-IR, solid NMR and elemental analysis. Solubility was tested in several organic solvents at room temperature and 40 °C and the inherent viscosity was determined. GPC analysis showed oligomeric chains of five repetitive units for the tested samples. Additionally, thermal behavior was studied by TGA and DSC analysis, by evidencing materials highly stable and rigid. Band gaps values ranging between 2.71 and 3.14 eV were obtained from UV/Vis and DRS analysis. The spin-coating technique was used to prepare films from soluble samples in NMP and their thicknesses were determined by the ellipsometric method. From these samples, and using AFM and four-point techniques, the effect of the annealing time on the roughness and conductivity of the films was studied. In accordance with the appropriate thermal and conductivity properties of the new silylated materials (which has a whole aromatic structure), could be proposed as an alternative for applications in the optoelectronics field.Graphical abstractImage 1
       
  • Porous carbon prepared from polyacrylonitrile for lithium-sulfur battery
           cathodes using phase inversion technique
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Soumyadip Choudhury, Dieter Fischer, Peter Formanek, Frank Simon, Manfred Stamm, Leonid Ionov In this paper, a time and resource efficient way of preparing porous carbon cathode for lithium-sulfur batteries with superior cycle stability has been demonstrated. In this simple work, we used commercially available polymer as carbon source and non-solvent mixture as porogen or pore former. The cathode has been fabricated by using polyacrylonitrile as base polymer via phase inversion route. By this technique, a highly porous substrate material is generated by dipping a semi-gelled film of polyacrylonitrile in non-solvent mixture. After oxidative crosslinking followed by pyrolysis under inert atmosphere results a highly porous nitrogen doped carbon material, which was further hybridized with sulfur via melt diffusion of elemental sulfur. This cathode material shows although relatively low specific capacity (Cycle 1: ca. 1050 mAh/gsulfur, cycle 500: ca. 400 mAh/gsulfur), but excellent cycle stability over 500 charging-discharging cycles is displayed.Graphical abstractImage
       
  • Designer poly(urea-siloxane) microspheres with controlled modulus and
           size: Synthesis, morphology, and nanoscale stiffness by AFM
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Hubert Gojzewski, Jagoda Obszarska, Agnes Harlay, Mark A. Hempenius, G. Julius Vancso Crosslinked poly(urea-siloxane) (PUS) copolymer microspheres with diameters ranging from 0.8 to 1.8 μm with diameter polydispersity indices between 1.15 and 1.60 were synthesized in one-step precipitation polymerization in water-acetone solvent mixtures at room temperature. The spheres were obtained using aminopropyl-terminated siloxanes, isophorone diisocyanate and a tetrafunctional isocyanate crosslinker, employing a systematically varied molar ratio. The length of the siloxanes was controlled to obtain spheres with pre-determined Young's modulus values. Phase separation between soft disiloxane/poly(dimethylsiloxane) segments and hard isophorone bisurea units was observed with an excellent special resolution of ∼5 nm using atomic force microscopy (AFM). AFM mapping of the Young's modulus was achieved utilizing the PeakForce Quantitative Nanomechanical Mapping (QNM) mode. This AFM method allowed us to also measure the values of elasticity moduli of individual microspheres, ranging from 200 to 900 MPa. The microspheres can be used as filler to fine-tune the properties of composite materials, particularly with regard to elasticity. The hydrophobicity was also varied as indicated by water contact angle values between 122° - 132°. These features open the possibility of preparing designer composites for a range of applications from coatings to the biomedical field.Graphical abstractImage 1
       
  • In dedication to Professor Garth L. Wilkes
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s):
       
  • Study on phase transition behavior and lamellar orientation of uniaxially
           stretched poly(ʟ-lactide) / cellulose nanocrystal-graft-poly(ᴅ-lactide)
           blend
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Selvaraj Nagarajan, Jian Hu, Hao Wu, Yongxin Duan, Jianming Zhang Towards the development of high-performance green composites, the surface functionalized cellulose nanocrystals (CNC) have been widely used as reinforcement along with biopolymer. In our previous work, it has been demonstrated that CNC grafted with PDLA (CNC-g-PDLA) could improve the crystal nucleation density and heat distraction ability of PLLA matrix via the PLLA/PDLA stereocomplex interaction. Herein, to understand the role of CNC-g-PDLA on the deformation behavior of PLLA/CNC-g-PDLA nanocomposites, the melt-quenched PLLA/CNC-g-PDLA nanocomposite was uniaxially stretched at 160 °C with various draw ratios. The stretched PLLA/CNC-g-PDLA composites allow us to discriminate the crystal transformation and crystal orientation of three individual components in the composites, that is, (i) PLLA matrix, (ii) PLLA/PDLA stereocomplex existed as interfacial phase, and (iii) CNC reinforcement. The results indicate that PLLA α′ and PLLA/PDLA stereocomplex crystals (βC) appear at the initial stage of drawing process. The disordered α′ transforms to ordered α and β forms gradually with increasing in draw ratio, whereas βC-crystals keep almost unchanged during the whole drawing process. The calculation on orientation function of various crystals suggests that the lamellaes of α form have the largest orientation degree along the stretching axis. Meanwhile,CNC nanoparticles and the βC crystals form the nano-dimensional shish kebab structure during stretching and present relatively low orientation. This study provides the physical insight to guide the preparation of high performance PLLA nanocomposites with hierarchical crystal and orientation structure.Graphical abstractImage 1
       
  • Fracture mechanism of high impact strength polypropylene containing carbon
           nanotubes
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Po-Hsiang Wang, Sourangsu Sarkar, Prabhakar Gulgunje, Nikhil Verghese, Satish Kumar In our earlier contribution, it was shown that with the addition of 1 wt% functionalized multiwall carbon nanotube (f-MWNT), an unprecedented 152% increase in PP impact strength without a significant loss in stiffness and ductility can be achieved. In context of these observations, this work examined the impact fracture mechanism of such PP/f-MWNT nanocomposite, in which the PP interphase was tailored by the same co-solvent solution process. The nanotube-matrix stress transfer efficacy in PP/f-MWNT as compared to that of PP/pristine MWNT (p-MWNT) was determined by Raman spectroscopy. The calculated interfacial shear strength (τi) is 17.8 MPa in PP/f-MWNT and 2.2 MPa in PP/p-MWNT, suggesting improved matrix-CNT adhesion in the former. This strong interfacial adhesion allows CNTs to bridge the opening crack, absorb fracture energy and promote local plastic deformation of the polymer matrix. Such process was demonstrated using SEM fractography where breakage/pull out of the CNTs, microcracks, and the intensive fibril formation accompanied with the extension of the PP matrix were captured at the impact fracture surface. Both the interfacial shear strength and the SEM fractography supported the hypothesis that better matrix-CNT adhesion can be achieved through interphase engineering.Graphical abstractImage 1
       
  • Excellent Thermal Stability P(BeA-co-MMA) Microcapsules with High Thermal
           Energy Storage Capacity
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Yuchen Mao, Jin Gong, Meifang Zhu, Hiroshi Ito Low thermal stability and the shortage of core leakage strongly limit the application of conventional energy storage microcapsules. This study focuses on a novel strategy to develop a new phase change material with excellent thermal durability without core leakage. The new phase change materials is a P(BeA-co-MMA) copolymer microcapsule with crystalline n-alkane side chains. Under the protection of polymer main chains as the shell or skeleton structure on a nano-scale, the crystalline side chains as the core will no longer suffer loss and will maintain stablity in use. The chemical composition, inner homogeneous structure, thermoregulation properties, crystalline behaviour and thermal stability are discussed. The P(BeA-co-MMA) microcapsules provide energy storage capacity in the temperature range of 48–62 °C with the highest enthalpy of 105.1 J·g–1. The 5% weight loss temperature (T5%) is more than 315 °C, which is high enough to withstand the general polymer processing temperature to open the possibility of developing energy storage modified fibre and polymer materials as functional fillers.Graphical abstractImage Copolymer P(BeA-co-MMA) microcapsules with uniform sphere are successfully synthesized from BeA and MMA through suspension polymerization. The long n-alkane side chain of copolymer derived from BeA form crystal microcells at room temperature and change into random with the temperature increasing, which provides energy storage capacity. This crystal transition is kept in microcells by polymer main chains as skeleton structure on nano-scale. The strong interaction force between shell and core parts overcomes the shortage of core leakage and ensures the excellent thermal durability.
       
  • Salt-inactive hydrophobic association hydrogels with fatigue resistant and
           self-healing properties
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Jiajun Xu, Xiuyan Ren, Guanghui Gao Traditional hydrophobic association (HA) hydrogels can obtain excellent mechanical properties in the presence of anionic surfactants. However, such surfactants are sensitive to salt solutions, resulting in large fluctuation of mechanical properties for hydrogels. Here, a combined surfactant consisting of anionic surfactants (sodium dodecyl sulfate, SDS) and amphoteric surfactants (dodecyl dimethyl betaine, BS-12) was successfully introduced into HA hydrogels as stable physical crosslinking points. The resulting SDS/BS-12-HA hydrogels exhibited high tensile stress up to about 700 kPa. Moreover, the hydrogels demonstrated salt-inactive, self-healing and fatigue resistance properties owing to their unique dynamic and reversible physical crosslinking structure. Therefore, it's envisioned that this work may open a new method to develop a soft salt-inactive material with stable and excellent mechanical properties for extending the application range of hydrogels.Graphical abstractImage 1
       
  • Effect of solvent selectivity on supramolecular assemblies of block
           copolymer by solvent-vapor annealing
    • Abstract: Publication date: Available online 17 July 2018Source: PolymerAuthor(s): Eunhye Kim, Sungmin Park, Young-Soo Han, Tae-Hwan Kim Nanoparticles with well-ordered structures have attracted great attention recently due to its potential application, including data storage media, microelectronics and sensors. Herein, we report a strategy of the periodic arrays of iron oxide nanoparticle with supramolecular thin films. The thin films of PS-b-P2VP/FAA supramolecules were solvent-vapor annealed with mixed solvent-vapor condition of toluene: ethanol: water = 9: 1: 0.06 in volumetric ratio. The supramolecular thin film exhibits the structural change of disorder – vertical cylinder – vertical lamellae – mixture (cylinder and lamellae) - cylindrical morphology triggered by the addition of small amount of water due to the change of the solvent selectivity with major block depending on time, leading to the periodic arrays of iron oxide nanoparticle. We expect that this result can provide key information to fabricate the self-assembled naostructure of block copolymers by using the solvent-vapor processing without complicated procedures.Graphical abstractImage 1
       
  • Rouse dynamics in PEO-PPO-PEO block-copolymers in aqueous solution as
           observed through fast field-cycling NMR relaxometry
    • Abstract: Publication date: Available online 12 July 2018Source: PolymerAuthor(s): Carla C. Fraenza, Carlos Mattea, Germán D. Farrher, Amín Ordikhani-Seyedlar, Siegfried Stapf, Esteban Anoardo We present a proton fast field-cycling (FFC) NMR relaxometry study of the molecular dynamics in three different deuterated water-dispersed triblock copolymers of ethylene oxide (EO) and propylene oxide (PO):EO80PO27EO80(F68), EO141PO44EO141 (F108), and EO101PO56EO101(F127). Independently of the phase and molecular arrangement, bi-exponential decays of the magnetization during the spin-lattice relaxation process could be observed for F127, while mono-exponential decays were measured for F68 and F108. This fact has been attributed to the relative ratio of PEO and PPO protons for each case. In F127, each component of the magnetization decay could be associated with a particular block of the co-polymer. A direct consequence of this fact is the independent characterization of the molecular dynamics of each block. It was found that the dominant relaxation mechanism can be attributed to the Rouse model, and it seems to be independent on whether the molecules are incorporated into a micelle, or as individual unimers in the aqueous solution. The experimental results and the provided explanation are consistent with entanglement-free self-assembled structures, and a fast exchange of unimers between the micellar structure and the solvent. This particular feature was also investigated in F68 and F108, although for these cases a mono-exponential decay of the magnetization was observed. NMR relaxometry results are complemented with other relaxation experiments in the rotating frame, NMR spectroscopy and atomic-force microscopy.Graphical abstractImage 1
       
  • The effects of functional nanofillers on the reaction kinetics,
           microstructure, thermal and mechanical properties of water blown rigid
           polyurethane foams
    • Abstract: Publication date: Available online 12 July 2018Source: PolymerAuthor(s): Mercedes Santiago-Calvo, Josías Tirado-Mediavilla, José Luis Ruiz-Herrero, Miguel Ángel Rodríguez-Pérez, Fernando Villafañe The use of functional nanofillers to improve the properties of rigid polyurethane (PU) foams has caused the need for a better understanding of how these nanofillers modify the reaction kinetic of the PU system. In this study, different nanoclays and nanosilicas are used as functional nanofillers. Analysis of the kinetic data obtained by in-situ FTIR spectroscopy monitoring allows to correlate the isocyanate consumption with the type of nanoparticles. The quantification of urethane and urea, obtained by deconvolution of the carbonyl region absorptions, enables to follow the blowing and gelling reactions during the foaming process. These reactions are correlated to the nature of the chemical groups present on the surface of the nanoparticles added. In addition, the effect of the modification of the reaction kinetics on the density, cellular structure, thermal conductivity and mechanical properties is herein discussed.Graphical abstractImage 1
       
  • Entanglement dynamics in ultra-high molecular weight polyethylene as
           revealed by dielectric spectroscopy
    • Abstract: Publication date: 15 August 2018Source: Polymer, Volume 150Author(s): Stavros X. Drakopoulos, Georgios C. Psarras, Giuseppe Forte, Ignacio Martin-Fabiani, Sara Ronca With the help of Broadband Dielectric Spectroscopy, it has been possible to study the molecular dynamics of disentangled Ultra High Molecular Weight Polyethylene in a wide temperature and frequency range. Catalytic ashes of aluminum oxide act as dielectric probes, allowing the identification of five different processes: an αc-process due to movements in the crystalline phase, two γ-processes attributed to amorphous chain portions close to the crystalline lamellae, and two β-processes that we have attributed to the disentangled and entangled amorphous phases. The entanglement formation has been followed by isothermal runs and a model that predicts the energy spent to form entanglements as a function of time and temperature is thereby proposed. This model allowed us to calculate the associated activation energy of the entanglement process.Our work advances further the understanding of entanglement dynamics of ultra-high molecular weight polymers, and the proposed model could prove useful to describe other similar processes such as cross-linking.Graphical abstractImage 1
       
  • Structure and rheological behavior of polypropylene interphase at high
           carbon nanotube concentration
    • Abstract: Publication date: 15 August 2018Source: Polymer, Volume 150Author(s): Po-Hsiang Wang, Sourangsu Sarkar, Prabhakar Gulgunje, Nikhil Verghese, Satish Kumar The structure of the interphase in polypropylene (PP)/multiwall carbon nanotube (MWNT) nanocomposite was characterized by thermal analysis and wide angle X-ray diffraction. The interphase was composed of non-covalently coated PP on acid functionalized MWNT (f-MWNT), where the volume of interphase increases with increased f-MWNT concentration from 1 wt% to 30 wt%. Larger lamella thickness, crystallinity, and smaller crystal size with respect to the bulk polymer were found at the interphase. Also, the thermal stability of the nanocomposite containing high volume fraction of interphase was demonstrated to be higher than that of the neat PP. Using designed thermal treatment, the interphase was successfully converted into a highly ordered crystalline structure with extended chain conformation. The understanding and control over the interphase formation at nanoscale afforded the observation of an unprecedented macroscopic rheological behavior where the viscosity and elastic modulus increased as temperature increased. A schematic showing polymer-CNT interaction at elevated temperature was proposed and verified. It is concluded that the constrained flow under high temperature originates from extended and immobile polymer chains at the interphase.Graphical abstractImage 1
       
  • Reduced physical aging rates of polylactide in polystyrene/polylactide
           multilayer films from fast scanning calorimetry
    • Abstract: Publication date: 15 August 2018Source: Polymer, Volume 150Author(s): Xavier Monnier, Samira Fernandes Nassar, Sandra Domenek, Alain Guinault, Cyrille Sollogoub, Eric Dargent, Nicolas Delpouve The physical aging behavior of amorphous polylactide constrained against polystyrene in layers of 300 nm, thanks to the layer–multiplying co–extrusion process, was investigated by fast–scanning calorimetry (FSC). By cooling down the sample from the liquid state to the glassy one at very fast scanning rates, it was possible to investigate the structural relaxation of the polymer glass at high temperatures for which the time needed to reach the equilibrium was shortened. Therefore it was possible to perform the study of physical aging in experimental conditions providing an expanded view of the structural relaxation for short aging times. Taking benefit of this property, it was highlighted that the aging kinetics of polylactide occurred significantly slower in the multilayer film, in comparison with a bulk amorphous film. The process of recovery in the multilayer system was found to occur at similar rates, or even slower, than in a three–layer film in which polylactide reached its maximum extent of crystallinity. This was attributed to mobility hindrance that might be inherent to the extrusion conditions or associated with the presence of capped interfaces with polystyrene.Graphical abstractImage 1
       
  • Surface-initiated RAFT polymerization from vapor-based polymer coatings
    • Abstract: Publication date: 15 August 2018Source: Polymer, Volume 150Author(s): Gowthamy Venkidasubramonian, Domenic Kratzer, Vanessa Trouillet, Nicolas Zydziak, Matthias Franzreb, Leonie Barner, Joerg Lahann Surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization was used to synthesize poly(methyl methacrylate) (PMMA) and poly[2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammoniumhydroxide (PMEDSAH) brushes grafted from reactive poly[p-xylylene] surfaces. The synthetic approach involved functionalization of substrates via chemical vapor deposition polymerization of an electron-deficient alkynyl-functionalized [2.2]paracyclophane derivative. An azide-functionalized RAFT agent was anchored to the resulting poly[(p-xylylene-4-methyl propiolate)-co-p-xylylene] films via copper-free click-chemistry. Subsequent SI-RAFT polymerization yielded PMMA and PMEDSAH films with narrow dispersity which was further tuned by varying the concentration of a sacrificial RAFT agent in solution. Polymer dispersity was determined by size exclusion chromatography to be in the range of 1.2–1.4 for both polymers. This work provides a novel surface modification strategy to decorate a wide range of different substrates with polymer brushes, thereby eliminating the need for cumbersome modification protocols, which so far had to be established for each substrate material independently.Graphical abstractImage 1
       
  • l-lactic+acid-co-l-2-hydroxybutanoic+acid)s”+[Polymer+72+(2015)+202–211]&rft.title=Polymer&rft.issn=0032-3861&rft.date=&rft.volume=">Corrigendum to “Cocrystallization of monomer units in lactic acid-based
           biodegradable copolymers, poly(l-lactic acid-co-l-2-hydroxybutanoic
           acid)s” [Polymer 72 (2015) 202–211]
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Hideto Tsuji, Tadashi Sobue
       
  • Superior comprehensive performance of a rigid-rod
           poly(hydroxy-p-phenylenebenzobisoxazole) fiber
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Jianting Zhang, Ningren Jin, Jianrong Gao The novel poly(hydroxy-p-phenylenebenzobisoxazole) (HPBO) was synthesized by different polymerization routes, including hydroxy-orderly distributed polymer (ord-HPBO) and hydroxy-randomly distributed polymer (ran-HPBO). Surface elemental composition, thermal stability, intrinsic viscosity, UV resistance, surface morphology, mechanical and interfacial properties of HPBO fiber were investigated. ATR-FTIR and EDS spectrums identify the formation of mono-hydroxyl modified polymer. Excellent thermal stability (up to 600 °C), mechanical properties (tensile strength of 4.32 GPa, modulus of 169.7 GPa) and rheological spinnability of ran-HPBO-AS via HD self-polymerization route were obtained. Meanwhile, the SEM after UV irradiation indicated that the photostability of HPBO is better than PBO. The interfacial shear strength (IFSS) between HPBO-AS fiber and epoxy resin is 21.7 MPa, 87.1% higher than that of PBO-AS fiber. Comparing different HPBO synthesis routes, the self-polymerization of HD salt route is believed to be a feasible route for industrial production and the ran-HPBO is expected to become a new generation of high-performance fiber.Graphical abstractImage 1
       
  • Shell of amphiphilic molecular bottlebrush matters as unimolecular micelle
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Yi Chen, Houbo Zhou, Ziyang Sun, Huaan Li, Huahua Huang, Lixin Liu, Yongming Chen Molecular bottlebrushes (MBBs) with a hydrophobic core and a hydrophilic shell may exist as well-defined unimolecular nanoparticles in water. However, they may also aggregate to form large particles if the structure of the hydrophilic and hydrophobic segments fail to be rationally controlled. Herein, a series of core-shell amphiphilic MBBs with a poly (ε-caprolactone) (PCL) backbone bearing two block copolymer side chains, poly (butyl acrylate)-b-poly ((oligo (ethylene glycol) acrylate) (PBA-b-POEGA) and poly (butyl acrylate)-b-poly (ethylene glycol) (PBA-b-PEG), were synthesized through grafting-from and grafting-onto strategies. Their hydrophilic shells are different in topology: POEGA is comblike whereas PEG is linear. The stability of the two kinds of MBB with the similar composition as unimolecular nanoparticles in water and their encapsulation capacity for guest-molecule were evaluated. Compared to the MBB with a linear PEG shell, those with comblike POEGA side chains remained stable against aggregation as demonstrated by atomic force microscopy and dynamic light scattering measurement. The MBB with a POEGA shell also displayed a much higher encapsulating capacity to a model guest molecule, pyrene, by hydrophobic interaction. This study provides guidance to the rational preparation of MBBs for applications as molecular vehicles.Graphical abstractImage 1
       
  • Novel composite proton exchange membrane with long-range proton transfer
           channels constructed by synergistic effect between acid and base
           functionalized graphene oxide
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Yumin Huang, Tao Cheng, Xuechun Zhang, Wenluan Zhang, Xiaobo Liu In this work, two different functionalized graphene oxide (GO), sulfonic acid functionalized GO (SGO) and amino functionalized GO (NGO), were synthesized and incorporated into the sulfonated poly(arylene ether nitrile) (SPEN) by single doping and codoping. It was found that the codoping of SGO and NGO contributed to the enhancement of proton exchange membrane performance. These two functionalized GO as fillers were uniformly dispersed in SPEN matrix and their synergistic effect created the long-range proton transfer channels along fillers/SPEN matrix interfaces. Meanwhile, acid-base pairs which was induced by strong interfacial interactions between fillers and SPEN matrix provided new and low-energy-barrier pathways for proton hopping, facilitating the proton conduction via Grotthuss mechanism. Among all the membranes, the codoped S/N-3 composite membrane exhibited the highest proton conductivity (0.064 S·cm−1 at 20 °C and 0.21 S·cm−1 at 80 °C). Besides, it was endowed with unprecedented dimensional stability, especially in high temperature (just 12.75% at 80 °C). Also, low methanol permeability was conferred owing to methanol trapping effect of two functionalized GO. Furthermore, S/N-3 composite membrane showed a superior selectivity of 4.48 × 105S⋅cm−3⋅s, which was nearly 10 times of that of commercialized Nafion 117. Our investigation provides a new strategy on the design of high performance composite membranes for applications of PEMs and other related fields.Graphical abstractImage 1
       
  • Wet spun polyacrylontrile-based hollow fibers by blending with alkali
           lignin
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Bing Zhang, Chunxiang Lu, Yaodong Liu, Pucha Zhou Alkali lignin, a by-product of commercialized paper making process, is an abundant and environmental-friendly material. In this paper, polyacrylontrile (PAN) -based hollow fiber was fabricated by one-step wet-spinning technique through blending with alkali lignin at different ratios. The phase diagram of the blends was determined by titration method. When alkali lignin is added into the PAN solution, the clouding points move away from polymer-DMSO axis, and miscibility gap increases. The phase separation of PAN was slowed down by mixing with alkali lignin which resulted in the formation of hollow structure and promoted the pore formation in the wall. This work clearly explains the roles that alkali lignin plays in the system consisting of polymer, solvent and nonsolvent, and provides a feasible method to produce PAN-based hollow fibers.Graphical abstractImage 1
       
  • Thermosets derived from diallyl-containing main-chain type benzoxazine
           polymers
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Chien Han Chen, Ching Hsuan Lin, Tung I. Wong, Meng Wei Wang, Tzong Yuan Juang To achieve high-performance thermosets, three diallyl-containing main-chain type benzoxazine polymers, (MCBP) were prepared from Mannich condensation of 2,2′-diallyl bisphenol A, paraformaldehyde, and three diamines: 4,4′-diaminodiphenylmethane (DDM), 4,4′-oxydianiline (ODA), and 2,2′-bis(4-(4-aminophenoxy)phenyl)propane (BAPP), respectively. These MCBPs can be cured and general a phenolic hydroxyl type benzoxazine thermosets even though no free ortho and free para positions to the oxygen of oxazine in their structures. After thermally curing, the resulting thermosets display much higher Tg than the thermosets of 2,2′-diallyl bisphenol A/aniline-based, 2-allyl phenol/DDM-based, and 2-allylphenol/ODA-based benzoxazine, demonstrating the advantage of MCBP on thermal properties over monomer type benzoxazines. The refractive index of the thermosets is higher than 1.689 at 589 nm, which is relatively high compared with other polymers. These results demonstrate the advantage of diallyl-containing MCBPs on thermal properties and refractive index over allyl-containing monomer type benzoxazines.Graphical abstractImage 1
       
  • Effect of the incorporation of an Ag nanoparticle interlayer on the
           photovoltaic performance of green bulk heterojunction water-soluble
           polythiophene solar cells
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Massimiliano Lanzi, Elisabetta Salatelli, Loris Giorgini, Martina Marinelli, Filippo Pierini Two water-soluble regioregular poly(3-alkylthiophene)s, incorporating aminic groups at the end of the side chains, have been synthesized using a post-polymerization functionalization procedure on a ω-bromine substituted polyalkylthiophene. The high solubility of the obtained polymers in water allowed for the preparation of “green” bulk heterojunction solar cells which reached a power conversion efficiency of 4.85% when PC61BM was used as electron-acceptor material. Improved optical absorption and photocurrent have been obtained by interposing a layer of Ag nanoparticles between the buffer and the photoactive layer, leading to a final power conversion efficiency of 5.51%.Graphical abstract3D Optimization of PT6NEt (top) and PT6Pir (bottom) repeating units.Image 1
       
  • 1,4-Diketo-pyrrolo[3,4-c]pyrroles (DPPs) based insoluble polymer films
           with lactam hydrogens as renewable fluoride anion chemosensor
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Haichang Zhang, Kun Yang, Chao Chen, Yanhui Wang, Zhenzhen Zhang, Liangliang Tang, Qikun Sun, Shanfeng Xue, Wenjun Yang Manipulating the sub-units of conjugated co-polymers was a convenient and promising strategy for developing novel functional materials. Here a soluble alternating copolymer (P-Boc) consisted of 9,9-dialkylfluorene and 1,4-diketo-2,5-di(t-butoxycarbonyl)-3,6-diphenyl-pyrrolo[3,4-c]-pyrrole was designed and synthesized. Heating the spin-coated P-Boc film could afford an insoluble polymer film (P-2H) with multiple lactam hydrogen units by the removal of the t-butoxycarbonyl groups. Unlike the small molecules with lactam hydrogen, the P-2H film was insoluble and exhibited the remarkable naked-eye visible color change and a new long-wavelength absorption band in the fluoride anion-containing organic solution. The naked-eye visible and spectroscopic detection limits for fluoride anion were ∼10−6 and ∼10−8 M, respectively. Moreover, the fluoride anions bonded with P-2H film could be easily removed by immersing in acidic solutions, and the resulting P-2H film could again probe fluoride anion. Energy dispersive X-ray spectroscopy analysis indicated that most lactam units in P-2H film could bond fluoride anions and the bonded fluoride anions could be removed quantitatively. These results demonstrated that P-2H was not only an efficient and renewable fluoride anion chemosensor but also might become a promising fluoride anion extractor.Graphical abstractPreparation, characterization, and application of DPP-based insoluble polymer film with lactam hydrogens through thermal annealing its solution-processed precursor polymer film for fluoride anion sensors; the fluoride anion detection limitation as low as 10−8 M.Image 1
       
  • Development of new nonlinear optical polymers based on epoxy- amine
           oligomers with Bi-chromophore fragments in the side chain
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Gulshat N. Nazmieva, Tatiana А. Vakhonina, Nataliya V. Ivanova, Anastasiya V. Sharipova, Olga D. Fominykh, Maxim A. Smirnov, Marina Yu Balakina, Oleg G. Sinyashin For the first time bichromophore nonlinear optically active compounds, 3,5-bis [2- (N-ethyl-4- (4′-nitrophenylazo) anilino) ethoxy] benzyl alcohol, DF1, and 3,5-bis [6- (N-methyl-4- (4′-nitrophenylazo) anilino) hexaoxy] benzyl alcohol, DF2, have been synthesized. The synthesis of the epoxy-amine oligomers containing DF1 and DF2 dendritic fragments in the side chain was preceded by molecular design which demonstrated that the hexyl groups, binding the chromophores to the branching center in DF2, are able to provide greater mobility of the chromophores compared to the ethyl groups in DF1, thus determining the preference of the former from the viewpoint of NLO activity.Bi-chromophore compounds were introduced into the side chain of epoxy amine oligomers using the esterification reaction under mild conditions by the Steglich method. As a result, oligomers OAB-DF1 (Tg = 122 °C) and OAB-DF2 (Tg = 107 °C) were obtained with good yields, the degree of functionalization was 60 mol% and 45 mol%, respectively. The values of the NLO coefficients, d33, were measured by second harmonic generation technique; they are equal to 29 pm/V for OAB-DF1 and 40 pm/V for OAB-DF2.Graphical abstractImage 1
       
  • Chemistry, polymer dynamics and mechanical properties of a two-part
           polyurethane elastomer during and after crosslinking. Part II: moist
           conditions
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Bettina Zimmer, Christophe Nies, Christian Schmitt, Cristo Paulo, Wulff Possart This work addresses the impact of fabrication conditions (curing procedure, moisture) on the properties of a two-part polyurethane system. While Part I treats the chemical, dielectric and mechanical properties during cure and storage in dry conditions, this second part focuses on these properties, along with the caloric glass transition, in moist conditions, with moisture being introduced at different times during and right after cure. It is shown that the presence of water during fabrication severely affects final properties (increased polymer mobility, reduced mechanical stiffness) by reacting with isocyanate (forming primary amines and urea) and thereby lowering crosslink density, even for seemingly uncritical humidity conditions. Other chemical side reactions involving moisture are also identified. Water furthermore accelerates polymer dynamics substantially. Overall, moisture during cure and storage is clearly identified as a cause for property variations of PU.Graphical abstractImage 1
       
  • First electrospun immobilized molybdenum complex on bio iron oxide
           nanofiber for green oxidation of alcohols
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Sedighe Abbaspour Noghi, Atena Naeimi, Hooshang Hamidian Bio iron oxide was synthesized from natural Sesbania sesban plant and modified by a molybdenum complex (Fe2O3/MoSB). Fe2O3/MoSB was deposited on polyvinyl alcohol (PVA) using a conventional single nozzle electrospinning technique (PVA/Fe2O3/MoSB). TEM, SEM, AFM, FT-IR, TGA, EDAX, and elemental analysis were used to determine fiber compositional information. The catalytic efficiency of electrospun PVA/Fe2O3/MoSB nanofiber in the oxidation of alcohols was exploited. The green reactions were conducted at solvent free conditions as a green media in the presence of H2O2 to have the desired aldehydes and tert-butyl hydrogen peroxide to obtain acid products in high yields and excellent selectivity. The survival of this nanocomposite was investigated and it could be reused and recycled in consecutive runs.Graphical abstractImage 1
       
  • Development of hybrid magnetorheological elastomers by 3D printing
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): A.K. Bastola, M. Paudel, L. Li Intelligent or smart materials have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as temperature, pH, electric or magnetic fields, etc. Magnetorheological (MR) materials are a class of smart materials whose properties can be varied by applying an external magnetic field. In this work, the possibility of employing a suitable 3D printing technology for the development of one of the smart MR materials, the magnetorheological elastomer (MRE) has been explored. In order to achieve such 3D printing, a multi-material printing is implemented, where a controlled volume of MR fluid is encapsulated within an elastomer matrix in the layer-by-layer fashion. The choice of printing materials determines the final structure of the 3D printed hybrid MR elastomer. Printing with a vulcanizing MR suspension produces the solid MR structure inside the elastomer matrix while printing with a non-vulcanizing MR suspension (MR fluid) results in the structures that the MR fluid is encapsulated inside the elastomer matrix. The 3D printability of different materials has been studied by measuring their rheological properties and we found that the highly shear thinning and thixotropic properties are important for 3D printability. The quality of the printed filaments strongly depends on the key printing parameters such as extrusion pressure, initial height and feed rate. The experimental results from the forced vibration testing show that the 3D printed MR elastomers could change their elastic and damping properties when exposed to the external magnetic field. Furthermore, the 3D printed MR elastomer also exhibits the anisotropic behavior when the direction of the magnetic field is changed with respect to the orientation of the printed filaments. This study has demonstrated that the 3D printing is viable for fabrication of hybrid MR elastomers with controlled structures of magnetic particles or MR fluids.Graphical abstractImage 1
       
  • UV-mediated synthesis of pNIPAM-crosslinked double-network alginate
           hydrogels: Enhanced mechanical and shape-memory properties by metal ions
           and temperature
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Eun Jung Choi, Seonggyun Ha, Jookyeong Lee, Thathan Premkumar, Changsik Song Allyl-substituted alginate (Alg) underwent gelation with N-isopropylacrylamide (NIPAM) monomers via UV-mediated radical reactions, resulting in a multi-responsive double-network hydrogel. The amount of NIPAM available for crosslinking affected several properties of the resulting Alg-NIPAM hydrogels. As more NIPAM was incorporated, the volume phase transition temperature (VPTT) and swelling properties of the Alg-NIPAM hydrogels decreased. Metal-ion addition caused increased crosslinking of the Alg-NIPAM hydrogels, allowing shape-memory of the materials due to their dual responsiveness to temperature and metal ions. Additional crosslinking caused the hydrogels to become stiffer, showing the ability to regulate the mechanical properties of the hydrogels. As a proof-of-concept, reversible shape changes under temperature and ionic cycling were demonstrated.Graphical abstractImage 1
       
  • An improved visco-hyperelastic model charactering the electromechanical
           behaviour of dielectric polymers
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Mengzhou Chang, Zhenqing Wang, Wenyan Liang Dielectric polymers can achieve large, reliable deformation in response to an external electric field and have attracted significant interest as actuators and transducers. The electromechanical performance depends on the interaction between the visco-hyperelastic behaviour of materials and the Maxwell stress caused by the electric field. However, the mechanisms of complex structures, such as a surface-treated and filler-reinforced space system, are still not completely understood. A mechanical model for evaluating the surface effect and electromechanical performance is first proposed on the basis of visco-hyperelastic theory and statistical mechanics. Then, several factors affecting the geometry and material properties of complex structures are quantitatively investigated. The model will contribute to the development of dielectric polymers because its theoretical predictions are in agreement with existing experimental data.Graphical abstractA model evaluating the electromechanical behaviour of polymer is proposed on the basis of visco-hyperelastic theory and statistical mechanics method.Image 1
       
  • Photo-curable acrylate polyurethane as efficient composite membrane for
           CO2 separation
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Hossein Molavi, Akbar Shojaei, Seyyed Abbas Mousavi The current investigation was to present composite membranes with strong interfacial adhesion between top polymeric selective layer and the bottom micro-porous support layer with appropriate gas permeation behavior and practically suitable processing characteristics. To this end, a series of acrylate-terminated polyurethanes (APUs) based on poly (ethylene glycol) (PEG) with different molecular weights (Mn) of 600, 1000, 1500, 2000 and 4000 g/mol, toluene diisocyanate (TDI), and 2-hydroxyethyl methacrylate (HEMA) were synthesized. Composite membranes were prepared with UV-curable acrylate-terminated polyurethane/acrylate diluent (APUAs) as selective layer and polyester/polysulfone (PS/PSF) as support layer. FTIR-ATR and DSC analyses indicated that the micro-phase separation of soft and hard segments increased by increasing the molecular weight of PEG. The experimental results revealed that the gas permeation behavior of APUA was mostly similar with rubbery materials; however, its morphological characteristics such as degree of micro-phase separation and crosslinking density are influential for the overall gas permeation behavior. It was revealed that the adhesion of APUA membranes to support layer was found to be strong and did not deteriorate after swelling in water. APUA composite membranes also exhibited very good long term gas permeation stability due to its stable structure originated from the cross-linked network.Graphical abstractImage 1
       
  • Cationic scavenging by polyaniline: Boon or bane from synthesis point of
           view of its nanocomposites
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Vipin Kumar, Siwat Manomaisantiphap, Kouhei Takahashi, Teruya Goto, Natsuki Tsushima, Tatsuhiro Takahashi, Tomohiro Yokozeki This work establishes the fact that Polyaniline (PANI) contributes to cationic scavenging on the polymerization of a cross linking polymer, i.e. Divinylbenzene (DVB), resulting in a significant change in the properties of the PANI-based DVB resin system. Furthermore, it is also shown that the cationic scavenging is directly related to the degree of doping of PANI and its dispersion state. Various intermediate doped PANI was added with a fixed amount of DVB to prepare thermosetting matrices. The degree of doping of PANI was assessed with the DSC, FT-IR, and UV-VIS-NIR analyses before mixing with DVB matrix. It has been shown that the Polyaniline (PANI) agglomerates broke and a uniform dispersion was obtained with an increased degree of doping, which led to more exposed amines groups of PANI. These groups acted as scavengers to the cationic polymerization of the DVB monomer. DSC and viscosity measurement of the uncured PANI-DBSA/DVB resin system confirmed the scavenging effect of PANI on the curing profile and subsequently to the electrical and mechanical properties of the cured composites. This paper presents a detailed analysis of the advantages and disadvantages of the scavenging behavior of PANI in the context of preparing PANI-based polymer composites.Graphical abstractImage 1
       
  • A new recyclable crosslinked polymer combined polyurethane and epoxy resin
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Yong-Jin Peng, Xin He, Qiang Wu, Ping-Chuan Sun, Chang-Jun Wang, Xue-Zheng Liu Inspired by the nature material, a crosslinked network structure of polyurethane/epoxy resin composite material was built through Diels-Alder (DA) reversible covalent bond reaction between the dienes and dienophile group on the side chain of epoxy resin and polyurethane respectively. The synthesized composite material combined the advantages of polyurethane and epoxy resin. The hard segments of polyurethane and epoxy resin were closely combined through the DA reaction and high density hydrogen bonding. The strength, hardness and toughness of the composite material were greatly enhanced. DA covalent bonds can be reversible with varying the temperature, which led to the heat reprocessing ability of the synthesized composite material. The well-established structure-property relationship shown in this paper could further provide guidance for fabrication of high performance recyclable material with precisely controllable microstructures and behaviors.Graphical abstractImage 1
       
  • Form II to I transformation of polybutene-1 and copolymer of butene-1 and
           ethylene: A role of amorphous phase
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Chang Liu, Zhijie Zhang, Shaoyong Huang, Quan Chen Polymorphic transformation from the form II to form I crystal was investigated for isotactic polybutene-1 (PB) and butene-1/ethylene copolymers (PBE) with differential scanning calorimetry (DSC) and dielectric response spectroscopy (DRS). DRS detected the so-called α relaxation of segments within the amorphous phase, and DSC traced a degree of form II to I transformation with time. It turned out that incorporation of the ethylene comonomers in PBE suppressed the crystallization and plasticized the amorphous phase, and the II to I transformation was greatly accelerated in particular at low T close to Tg. To normalize Tg enabled normalization of the α relaxation frequency (detected in DRS), but not the II to I transformation rate (detected in DSC): extra acceleration was noted for samples with a number fraction of ethylene monomers of 4.3% or higher. The extra acceleration is attributed to (1) heterogeneity of segmental mobility that facilitates the crystal growth and (2) crystal defects accumulating at the fold surface that cause internal stress to accelerate the nucleation.Graphical abstractImage 1
       
  • Synthesis and characterization of sustainable polyurethane foams based on
           polyhydroxyls with different terminal groups
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): M. Stanzione, V. Russo, M. Oliviero, L. Verdolotti, A. Sorrentino, M. Di Serio, R. Tesser, S. Iannace, M. Lavorgna Several bio-based polyhydroxyls are successfully synthesized by using succinic acid, obtained via Arundo donax fermentation and characterized by 1H NMR, GPC, and FT-IR analyses. Furthermore, the bio-based polyhydroxyls, consisting of a wide spectrum of compounds in terms of chemical structure and molecular weight, are used as substitute of conventional polyol in the formulations of Polyurethane and random Urethane-Amide Copolymer bio-based foams. The influence of both amount and typology of bio-based polyhydroxyls on bio-based foam properties is investigated through kinetic analysis, thermo-mechanical characterization, and morphological analysis. The results highlight that the replacement of conventional polyol with the bio-based polyester polyhydroxyls affects the foaming process and consequently the final properties of the free-foamed materials. In particular, the compressive modulus increases by about 140% for a bio-based polyhydroxyl content of 50 wt% together with an increase in foam density. A further increase of these adducts results in a decrease of the glass transition temperature and the mechanical performances. However, the experimental results demonstrate the potentiality of these bio-based foams as commodity in several applications.Graphical abstractImage 1
       
  • Nanostructuration effect on the mechanical properties of PMMA toughened by
           a triblock acrylate copolymer using multilayer coextrusion
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Juan-Sebastián Montana, Sébastien Roland, Emmanuel Richaud, Guillaume Miquelard-Garnier Multilayer coextrusion was used to obtain nanolayered films of self-assembled commercial triblock copolymer poly(methyl methacrylate-b-butyl acrylate-b-methyl methacrylate) (MAM) confined by poly (methyl methacrylate) (PMMA). A double level of organization is achieved: the obtained films are made of thousands of alternating continuous nanolayers of each component, while within the nanolayers, MAM is self-assembled with a cylindrical morphology. The mechanical properties of the resulting films were compared to those of virgin PMMA and to classically extruded PMMA/MAM blends with the same compositions where no control of the nanostructure can be achieved. It is shown that significant reinforcement can be obtained with the multilayer films compared to virgin PMMA (on the order of 20 times in terms of fracture toughness) but also compared to classical blends, by a factor from 2 to 4. Reinforcing glassy thermoplastics has been a major industrial challenge due to their usually brittle behavior in the temperature range they are used. This industrially scalable one-step process shows promises for the design of nano-laminated organic glasses with high impact resistance.Graphical abstractImage 1
       
  • High temperature thermochromic polydiacetylene supported on
           polyacrylonitrile nanofibers
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Odwa Mapazi, Kgabo P. Matabola, Richard M. Moutloali, Catherine J. Ngila Polydiacetylene (PDA) are polymers known to switch from blue to red when exposed to environmental stimuli. This paper reports on electrospun composite nanofibers of polyacrylonitrile (PAN) and a high temperature PDA. The effect of PAN on the thermal and thermochromic properties of the PDA was studied. PDA to PAN mass ratio in the composites was varied and an unusually high loading of 30 wt% PDA was achieved. Scanning and transmission electron microscopies (SEM, TEM) revealed a randomly-packed morphology of nanofibers with well dispersed PDA particles inside. Through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), the heat resistant PAN nanofibers were found to increase the reversible temperature range of the embedded PDA while also improving its thermal stability. Naked eye observations suggested that the composite thermochromic sensor can be reversed from temperatures around 200 °C - a big improvement from just 156 °C - while ultraviolet–visible spectroscopy (UV–vis) studies showed that there was a progressive deterioration of the conjugated PDA backbone which ultimately resulted in complete loss of reversibility and colorimetric character at 230 °C.Graphical abstractImage 1
       
  • Multilevel structure analysis of polyimide fibers with different chemical
           constitutions
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Huanyu Lei, Mengying Zhang, Hongqing Niu, Shengli Qi, Guofeng Tian, Dezhen Wu It is stressed that the structure plays a decisive role on the property of materials. Materials generally with rigid molecular chains possess outstanding mechanical performances. However, this structure-property relationship is ambiguous in some polyimide (PI) materials. In this study, three typical homo-PI fibers, derived from pyromellitic dianhydride(PMDA)/p-phenylene diamine(PDA), PMDA/4,4′-oxidianiline (ODA) and 3,3′,4,4′-biphenyldianhydride (BPDA)/PDA respectively, were prepared by a two-step wet-spinning method. The tensile strength and modulus of the BPDA/PDA PI fiber were higher than that of the PMDA/ODA PI fiber, while the PMDA/PDA PI fiber was too brittle to take the tensile test. Nevertheless, the rheology and dynamic thermomechanical analysis(DMA) results indicated that the rigidity order of polymer chain was PMDA/PDA > PMDA/ODA > BPDA/PDA. Accordingly, the chain conformations of different PI fibers were described by molecular simulation, and a molecular packing model was proposed to explain this structure-property contradiction.Graphical abstractImage 1
       
  • Design and synthesis of 2D A1-π-A2 copolymers impact on fullerene network
           for efficient polymer solar cells
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Sung Jae Jeon, Tae Ho Lee, Yong Woon Han, Doo Kyung Moon A new building block of two-dimensional (2D) A1-π-A2 copolymers for P(dDTPz-ID) and P(dDTPz-DTBT) was designed and synthesized. Their structures have two strong acceptor units (isoindigo and benzothiadiazole derivatives) in the backbone, respectively. It displayed a benefit of A1-A2 building blocks, which is complementary and broad light absorption from 300 to 750 nm due to acceptors with different withdrawing strengths. Also, the introduction of dangling-thiophene, π unit allowed the formation of 2D-strcuture, which and led to effective and inter-chain packing of PC71BM for both copolymers. Two copolymers exhibited enhanced π-π stacking properties and had predominant face-on structure, which was confirmed by XRD. We also reviewed the optical, electrochemical, morphological, charge transport properties and performance compared with A1-A2 copolymers for P(DTPz-ID) and P(DTPz-DTBT), respectively. The inverted device fabricated with optimized condition for P(dDTPz-DTBT) showed efficient charge transport from enhanced energy alignment, high Voc and dipole moment and fine morphology, and thus obtained 5.0% of best power conversion efficiency (PCE).Graphical abstractImage 1
       
  • Molecular dynamics of polysiloxane polar-nonpolar co-networks and blends
           studied by dielectric relaxation spectroscopy
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Mihai Asandulesa, Valentina Elena Musteata, Adrian Bele, Mihaela Dascalu, Sergei Bronnikov, Carmen Racles Polar-nonpolar silicone materials of different morphology and composition were investigated by means of broadband dielectric relaxation spectroscopy in order to elucidate the effect of polar content and nature of the interface on the segmental mobility of polydimethylsiloxane (PDMS) chains. The variation of dielectric parameters with temperature revealed two distinct α-relaxations corresponding to dynamic glass transitions of the components, while another polarization phenomenon was evidenced due to accumulations of charges at the interphases between the two polymers with different electrical properties. It was found that the secondary β-relaxation was favored by the increased content of polar groups, while this parameter had the reverse influence on both αPDMS and αP62, restricting the PDMS chain segment mobility. The activation energy of the interfacial polarization decreased with the polarity, showing increased mobility of charge carriers and less restriction to the interfacial polarization.Graphical abstractImage 1
       
  • Enhancing the ferroelectric performance of P(VDF-co-TrFE) through
           modulation of crystallinity and polymorphism
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Nicoletta Spampinato, Jon Maiz, Giuseppe Portale, Mario Maglione, Georges Hadziioannou, Eleni Pavlopoulou The functional properties of P(VDF-co-TrFE) are strongly dependent on its structure, which, in turn, depends on processing conditions applied. In this work we investigate the P(VDF-co-TrFE) processing-structure-function relationships, in order to find the thermal conditions that result in optimum ferroelectric performance in thin film configuration. Our results show that annealing temperature affects mostly the remnant polarization value, Pr, while annealing time has a severe effect on the coercive field, Ec. An optimized ferroelectric functionality, in terms of high Pr of about 90 mC/m2 and low Ec of 50 MV/m, is achieved and rationalized through structural analysis by means of GIWAXS. The best performing structure exhibits a high degree of crystallinity, a preferential orientation of the crystallites with the polymer chains parallel to the substrate and the occurrence of three ferroelectric phases. A deconvolution study demonstrates the presence of a moderately unstable ferroelectric phase that is designated to facilitate ferroelectric switching. Our findings show that a single step of 15 min annealing at 135 °C leads to high performance P(VDF-co-TrFE) structure, proving that the 2 h-long annealing step that is traditionally applied is not necessary.Graphical abstractImage 1
       
  • The effect of structure evolution upon heat treatment on the
           beta-nucleating ability of calcium pimelate in isotactic polypropylene
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Yang Yue, Dingding Hu, Qinglong Zhang, Jinyou Lin, Jiachun Feng Calcium pimelate (CaPim) is known as one of the most stable and effective β-nucleating agents for isotactic polypropylene (iPP). To establish the structure-properties relationships of CaPim, the structure and corresponding β-nucleating ability of as-synthesized CaPim and CaPim annealed at temperature (Ta) varying from 130 to 330 °C were investigated. Our results revealed that as-synthesized CaPim and CaPim annealed at a relatively lower Ta were crystalline hydrates. However, the highly ordered crystalline structure would irreversibly destroyed and transformed to a weakly ordered form when treated at about 180 °C, accompanied by the complete deprivation of crystal water. The weakly ordered CaPim still maintained relatively high ordered degree at Ta range of 180–290 °C, but a further increase of Ta leads to the conversion of CaPim to disordered amorphous form. The measurements of relative β-form content (kβ) of iPP samples containing 0.05 wt% of various annealed CaPim suggested that the β-nucleating selectivity was closely correlated to the ordered degree of CaPim. As expected, the crystalline CaPim could induce high kβ values of 0.82–0.91. Interestingly, the weakly ordered CaPim with residual ordered structure still showed a rather high β-selectivity with kβ values of 0.53–0.68, while the amorphous CaPim almost lost its β-nucleating ability. Combined with the epitaxial crystallization theory, a probable mechanism on the correlation between structure and β-nucleating selectivity of CaPim was proposed.Graphical abstractImage 1
       
  • Strictly linear polyethylene using Co-catalysts chelated by fused
           bis(arylimino)pyridines: Probing ortho-cycloalkyl ring-size effects on
           molecular weight
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Hongyi Suo, Ivan I. Oleynik, Chantsalnyam Bariashir, Irina V. Oleynik, Zheng Wang, Gregory A. Solan, Yanping Ma, Tongling Liang, Wen-Hua Sun Six examples of α,α′-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridine-cobalt(II) chlorides, [2,3:5,6-{C4H8C(NAr)}2C5HN]CoCl2 (Ar = 2-(C5H9)-6-MeC6H3Co1, 2-(C6H11)-6-MeC6H3Co2, 2-(C8H15)-6-MeC6H3Co3, 2-(C5H9)-4,6-Me2C6H2Co4, 2-(C6H11)-4,6-Me2C6H2Co5, 2-(C8H15)-4,6-Me2C6H2Co6), containing N-aryl groups that differ in either the ring size of the ortho-cycloalkyl substituents or the para-R group (R = H, Me), have been synthesized using a one-pot template approach. The molecular structure of Co1 highlights the ring puckering of both the ortho-cyclopentyl substituents and the two pyridine-fused seven-membered rings; a square-based pyramidal geometry is conferred about the metal center. On activation with either methylaluminoxane (MAO) or modified MAO (MMAO), all six complexes afforded strictly linear polyethylene (all Tm's > 130 °C) with high molecular weight (Mw up to 64.3 kg mol−1). Furthermore, all precatalysts displayed high activities (up to 2 × 106 g PE mol-1 (Co) h−1) at temperatures between 20 and 60 °C with the catalytic activities correlating with the type of ortho-cycloalkyl substituent: cyclohexyl (Co2, Co5) > cyclopentyl (Co1, Co4) > cyclooctyl (Co6, Co3) for either R = H or Me. The narrow unimodal distributions of the resulting polymers are consistent with single-site active species for the catalysts.Graphical abstractThe α,α′-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridine-cobalt(II) chlorides, activated with MAO or MMAO, afforded strictly linear polyethylene with high molecular weight.Image 1
       
  • Constructing advanced dielectric elastomer based on copolymer of acrylate
           and polyurethane with large actuation strain at low electric field
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Yu Zhao, Jun-Wei Zha, Li-Juan Yin, Sheng-Tao Li, Yong-Qiang Wen, Zhi-Min Dang Dielectric elastomers (DEs) are kinds of advanced functional materials, attracting more attention due to that they can used to fabricate ingenious devices. In this work, a series of advanced DEs based on the copolymer of polyurethane (PU) and acrylate, were chemically prepared through the condensation polymerization between p (BA-HEA), the n-butyl acrylate (BA) and hydroxyethyl acrylate (HEA) copolymer and diphenyl methane diisocyanate (MDI), named as p (BA-HEA)@MDI. The absence of urethane group was confirmed by infrared spectroscopy measurements. And the DEs show a decreased elastic modulus and an improved elongation at break with the decreasing content of MDI. For the absence of strong polar urethane group, the dielectric permittivity of new DEs still keeps at a relatively high value. And the p (BA-HEA)@MDI-3 shows the highest electromechanical sensitivity and the foreseeable highest actuation strain (14.4%) at a relatively low electric field (15.2 kV/mm) without any pre-strains, which is almost 2 times of that of VHB 4910 (acrylic adhesive tape, 3 M Corporation). The present work provides a new strategy to design high performance dielectric elastomers.Graphical abstractImage 1
       
  • Coarse-grained molecular dynamics modeling of reaction-induced phase
           separation
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Chunyu Li, Alejandro Strachan We develop a model to describe reaction-induced phase separation in thermoplastic-toughened thermoset polymers at molecular scales. To achieve the temporal and spatial scales required for phase separation we use coarse-grained molecular dynamics where beads represent bi-functional epoxy, a di-amine crosslinker and monomers in the thermoplastic. The model describes the curing of the thermoset using a distance criterion to identify chemical reactions on the fly during a molecular dynamics simulation. We characterize how composition, curing temperature and conversion degree affect the onset of phase separation and domain growth. The onset of phase separation in terms of degree of cure depends on cure temperature and the subsequent growth of domain size during cure can be described with two power laws. Interestingly, the domain size vs. time following quenching after cure also follows power-law behavior but with exponent of approximately ¼, lower than those observed in simple binary mixtures and linear chain polymers.Graphical abstractImage 1
       
  • Nanowires of conjugated polymer prepared by tuning the interaction between
           the solvent and polymer
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Liang Chen, Kefeng Zhao, Xinxiu Cao, Jiangang Liu, Xinhong Yu, Yanchun Han The nanowire of conjugated polymer with higher density is desirable for its improved charge transport. However, at a higher solution concentration, the conjugated polymer chain entanglement is severe and not beneficial for the nucleation to grow nanowires. In this paper, we control the equilibrium of entanglement ↔ disentanglement ↔ nucleation and growth by tuning the radius of interaction (Ra) between the solvent and conjugated polymer. At the critical Ra, the disentangled polymer chain could nucleate to form nanowires because its content is moderately supersaturated. Thus, the equilibrium of entanglement ↔ disentanglement is broken and the entangled polymer chain is further continuously disentangled to provide easier diffusivity of chains for nanowire formation. Accordingly, the dense nanowires of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno-[3,2-b]thiophene] (PBTTT-C14) were formed in the mixed solvent carbon disulfide (CS2): cyclohexylbenzene (ChB) = 3:7 (Ra = 2.56) at a higher concentration of 1 mg/ml by aging. The density of the nanowire increased with increasing concentration and aging time. The nanowires were more than 10 μm in length and about 20 nm in width. The contrast was obvious in transmission electron microscopy which indicated the high electronic density and the high crystallinity of the nanowires.Graphical abstractImage 1
       
  • 3-D magnetic graphene oxide-magnetite poly(vinyl alcohol) nanocomposite
           substrates for immobilizing enzyme
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Yanyun Li, Tao Jing, Gaofeng Xu, Jingzhi Tian, Mengyao Dong, Qian Shao, Bin Wang, Zhikang Wang, Yongjie Zheng, Changlong Yang, Zhanhu Guo Three-dimensional magnetic graphene oxide-magnetite polyvinyl alcohol (3D-GO/PVA/Fe3O4) nanocomposites were successfully prepared. The morphology was characterized and analyzed through scanning electron microscope (SEM) and transmission electron microscope (TEM). The chemical structure and the crystal structure were explored by X-ray powder diffraction (XPS), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction spectra (XRD). The magnetic property was obtained by vibrating sample magnetometer (VSM). The specific surface area and the average pore size were determined by Brunauer-Emmett-Teller (BET) and Barrett–Joyner–Halenda (BJH). The specific surface and the average pore size of 3D-GO/PVA/Fe3O4 nanocomposites were 388.87 m2g-1 and 9.6 nm, and the higher specific surface indicated that the three-dimensional structure avoided the aggregation for GO sheets. The large saturation magnetization (Ms) of the nanocomposites of 30.5 emu/g enabled the easy cycling of the nanocomposites. The 3D-GO/PVA/Fe3O4 nanocomposites exhibited better performance for porcine pancreatic lipase (PPL) enzyme immobilization. The maximum immobilization efficiency was 91%, and the enzyme immobilized 3D-GO/PVA/Fe3O4 nanocomposites reached up to 90% of their activities. After 10 cycles of reuse, the activity of immobilized enzyme remained about 70.8% of the initial activity. The stability test revealed that the activity of immobilized enzyme remained up to 71.1% at 4 °C for 56 days.Graphical abstractImage 1
       
  • l-dopa+to+thermally+resistive carbonaceous+nanocomposite+of+a+new+catechol-grafted+poly(amide-imide)&rft.title=Polymer&rft.issn=0032-3861&rft.date=&rft.volume=">From Parkinson's chemotropic agent l-dopa to thermally
           resistive carbonaceous nanocomposite of a new catechol-grafted
           poly(amide-imide)
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Mehdi Ahmadi, Kurosh Rad-Moghadam, Mehdi Hatami N,N′-Pyromellitoyl-bis-L-(3,4-dihydroxyphenyl)alanine was synthesized, as a new diacid monomer, from condensation reaction of l-dopa and pyromellitic anhydride. Polycondensation of this chiral monomer with the commercially available 4,4′-diaminodiphenylsulfone was achieved by using triphenylphosphite, as coupling agent, and calcium chloride, as dehydrating agent, in a mixture of N-methyl-2-pyrolidone and pyridine, giving a fairly high yield of a novel optically active poly(amide-imide) (PAI). This catechol containing PAI shows excellent adhesion to carboxylated carbon nanotubes, as forcing it to adopt a semi-crystalline structure in the interface with the nanotubes and thereby results in formation of a thermally stable and nearly homogeneous nanocomposite. FT-IR study revealed that much of this adhesion arises from H-bonding of the carboxylated nanotubes with the carbonyl groups of the PAI. The uniform distribution of the nanotubes in the PAI matrix was confirmed by FE-SEM and TEM micrographs of their nanocomposite. Thermogravimetric analysis of the PAI and its nanocomposites with 5, 10, and 15 wt% of carboxylated carbon nanotubes indicates that their decomposition occur in the temperature range of 347–365 °C. The limiting oxygen indices for the PAI and its nanocomposites were found to be in the range of 37.9–43.1. The polymer and its nanocomposites were characterized by additional techniques.Graphical abstractA novel thermally stable catechol grafted poly(amide-imide) was synthesized by starting from l-dopa. The chiral polymer has shown great affinity for adsorption onto carboxylated carbon nanotubes to form homogeneous composites with enhanced thermal stability.Image 1
       
  • Programmable electro-optical performances in a dual-frequency liquid
           crystals / polymer composite system
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Xiao Liang, Mei Chen, Shumeng Guo, Xiao Wang, Shuaifeng Zhang, Lanying Zhang, Huai Yang Liquid crystals (LCs)/polymer composites are promising candidates for the next-generation of large-area processible and flexible electro-optical (E-O) materials due to their combination of the fast-responsive characteristics of LCs and the excellent physical properties of polymer. However, the current LCs/polymer system, represented by the polymer dispersed liquid crystals (PDLC), are suffering from limitations of their normally opaque optical states, because the porous polymer matrix in PDLCs are lack of orientation control over LCs. Herein we promote a new category of LCs/polymer composite film from a polymeric system containing dual-frequency liquid crystals, liquid-crystalline polymerizable monomers and isotropic polymerizable monomers. By creating a polymer-stabilized-liquid-crystal like polymer microstructure within a PDLC like porous matrix, the promoted composite film features programmable electro-optical performances, excellent flexibility and enhanced robustness. Most importantly, the normal optical states can be regulated from opaque to transparent through microstructure control, showing great potential E-O applications in practical uses.Graphical abstractImage 1
       
  • Ultrahigh oxygen permeability of chemically-modified membranes of novel
           (co)polyacetylenes having a photodegradative backbone and crosslinkable
           side chains
    • Abstract: Publication date: 1 August 2018Source: Polymer, Volume 149Author(s): Mingyu Zhang, Toshiki Aoki, Lijia Liu, Jianjun Wang, Masahiro Teraguchi, Takashi Kaneko Four new partly modified membranes of novel (co)polyacetylenes having a photodegradative backbone and crosslinkable side chains showed excellent performances as oxygen permselective membranes, that is, ultrahigh oxygen permeability (PO2) with relatively high oxygen permselectivity (α = PO2/PN2). In α vs. PO2 plots, two of them showed a performance close to Robeson's upper bound 2008 and the other two exceeded Robeson's upper bound 1991. The combination of the rigid main chain of the (co)polymers, the regular structure of the supramolecular polymer, and the flexible crosslinking structure may have produced these excellent performances.Graphical abstractImage 1
       
  • Low-temperature sintering of stereocomplex-type polylactide nascent
           powder: The role of optical purity in directing the chain interdiffusion
           and cocrystallization across the particle interfaces
    • Abstract: Publication date: Available online 11 July 2018Source: PolymerAuthor(s): Dongyu Bai, Xingyuan Diao, Yilong Ju, Huili Liu, Hongwei Bai, Qin Zhang, Qiang Fu Recently, we proposed a novel strategy for fabricating high-performance stereocomplex-type polylactide (SC-PLA) products through low-temperature (180–210 °C, lower than the melting temperature of SC crystallites) sintering from its nascent powder, without serious thermal degradation involved in the conventional melt processing at higher temperatures. During the sintering, some poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) chains from adjacent powdery particles can interdiffuse across the interfaces and subsequently co-crystallize into new SC crystallites capable of welding the interfaces. The interfacial strength is dominated by the content of the newly-formed SC crystallites, however, the fast cocrystallization of PLLA/PDLA chains could hinder their sufficient interdiffusion at the interfaces and thus only limited interface-localized SC crystallites could be formed. In this work, we attempt to substantially promote the chain interdiffusion via depressing the cocrystallization rate. To do this, SC-PLA nascent powders with different optical purities of the lactate units were prepared, and the role of optical purity in directing the chain interdiffusion and cocrystallization has been investigated. Very interestingly, we demonstrate that decreasing optical purity (from 99.5 to 96%) is favorable for the formation of numerous SC crystallites at the interfaces because the lowering of cocrystallization rate enables more PLLA/PDLA chains to interdiffuse sufficiently before their cocrystallization. As a result, SC-PLA products with superior heat resistance have been fabricated by the sintering of low-optical-purity SC-PLA powder. These fascinating findings could not only provide new understanding on the low-temperature sintering mechanism of SC-PLA powders but also greatly expand the possibilities for the fabrication of SC-PLA products with superb properties.Graphical abstractImage 1
       
  • Acceleration of crystal transformation from crystal form II to form I in
           Polybutene-1 induced by nanoparticles
    • Abstract: Publication date: Available online 11 July 2018Source: PolymerAuthor(s): Xing-Xing Zhang, Yan-Kai Li, Zhao-Yan Sun The influence of nanofillers on the crystal transformation from crystal form II to form I of isotactic polybutene-1(PB-1) was investigated by differential scanning calorimetry (DSC), in situ wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. Two types of silicate clay both having one-dimensional structure, halloysite nanotube (HNT) and palygorskite (PGS), were used as nanofillers of PB-1. PGS accelerates the transformation from crystal form II to I for PB-1 more efficiently than HNT, which is attributed to the lattice match of crystal structure between PGS and form I as confirmed by the WAXD and SAXS tests. Moreover, hydrophobically modified clays MPGS and MHNT were used to improve the miscibility between nanoparticle and PB-1. However, transformation kinetics study indicates that the acceleration effect of MPGS is greatly decreased due to the shield of lattice match although the miscibility of the composites is improved, while that of MHNT is increased due to the improvement of miscibility. These results provide direct evidence that the existence of crystallographic relationships is another important factor to accelerate the crystal transformation from form II to I in PB-1.Graphical abstractImage 1
       
  • Competition and miscibility of isodimorphism and their effects on band
           spherulites and mechanical properties of poly(butylene
           succinate-co-cis-butene succinate) unsaturated aliphatic copolyesters
    • Abstract: Publication date: Available online 11 July 2018Source: PolymerAuthor(s): Yang Yu, Zhiyong Wei, Liuchun Zheng, Chenhao Jin, Xuefei Leng, Yang Li Unsaturated copolyesters poly(butylene succinate-co-cis-butene succinate) (P(BS-co-cBS)) were the first time prepared by polycondensation in combination with stannous octoate as catalyst and 4-methoxyphenol as radical inhibitor, achieving linear random copolyesters with a number-average molecular weight up to 38.2 kg/mol. The cis-2-butene-1, 4-diol used in this work showed a peculiarity of no isomerization or cross-linking side reaction even at high reaction temperatures, due to the high chemical stability of the unconjugated cis-double bond. Isodimorphic behavior between butylene succinate (BS) and cis-butane succinate (cBS) in P(BS-co-cBS) was evidenced by DSC and WAXD analyses. Then, the competition and miscibility of isodimorphism between BS and cBS units were further investigated by thermodynamic analyses. The significant discrepancy in competition and miscibility between BS and cBS units from conformational geometry demonstrated unique physicochemical properties and structure-properties relationships in such system of unsaturated copolyesters. A great impact of competition and miscibility on band spherulites and mechanical properties of the copolyesters was observed and discussed. In conclusion, our work here not only clarifies the effect of cis-double bond on isodimorphism in the unsaturated copolyesters, but also gives an insight into the mechanism of how the competition and miscibility regulates their physical properties.Graphical abstractImage 1
       
  • In situ generation of a self-dispersed β-nucleating agent with increased
           nucleation efficiency in isotactic polypropylene
    • Abstract: Publication date: Available online 11 July 2018Source: PolymerAuthor(s): Shicheng Zhao, Wei Qin, Zhong Xin, Shuai Zhou, Hanzhang Gong, Yeming Ni, Ke Zhang Addition of a β-nucleating agent (β-NA) is the most effective method of preparing β-nucleated isotactic polypropylene (β-iPP); however, the poor dispersion and agglomeration of β-NAs limit nucleation efficiency. To solve this problem, a self-dispersing β-NA strategy was developed based on in situ preparation of β-NA (instead of pre-addition) during the processing of iPP. Zinc adipate (ZnAA), a typical β-NA, was chosen; self-dispersed ZnAA (ZnAA(IS)) was prepared in situ from its reaction precursors adipic acid (AA) and zinc oxide (ZnO) during extrusion of iPP. In situ preparation of ZnAA(IS) led to a significantly higher nucleation efficiency than pre-addition of ZnAA. The β-crystal content (kβ value) of nucleated iPP prepared with ZnAA(IS) reached 0.99, significantly higher than iPP prepared with ZnAA. Moreover, the impact strength of 0.1 wt % ZnAA(IS)/iPP composites was nearly 5.3-fold higher than neat iPP with a net gain in reinforcement (157%) compared to pre-addition of ZnAA. To explain these phenomena, we proposed mechanism for the self-dispersion of β-NA in the context of in situ generation of β-NA during iPP processing; the mechanism was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Polarized Optical Microscopy (POM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) data. Therefore, this strategy and method of preparing β-NA in situ offers unique advantages that will advance the production and application of β-iPP. Furthermore, this strategy could potentially be extended to solve issues of poor dispersion and agglomeration for other additives.Graphical abstractImage 1
       
  • Thin film mechanical characterization of UV-curing acrylate systems
    • Abstract: Publication date: Available online 6 July 2018Source: PolymerAuthor(s): R. Anastasio, E.E.L. Maassen, R. Cardinaels, G.W.M. Peters, L.C.A. van Breemen This study presents the mechanical characterization of UV-curing acrylate systems. UV-curable polymers are commonly used in the stereolithography (SLA) technique to build multi-layered objects. Typically, the mechanical properties of the 3D-printed product are affected by the intrinsic material heterogeneity along the sample thickness. To understand what determines this heterogeneity, single layers of UV-curable polymer are characterized and the effect of process conditions on the mechanical properties is studied. Micro-compression experiments are carried out to determine the intrinsic mechanical properties which are representative of one single UV-cured layer. To determine the right conditions to generate maximally-cured micropillars, the evolution with irradiation time of monomer conversion, glass-transition temperature and yield stress has first been studied. Thereto, micrometer-sized pillars and dog-bone shaped samples have been prepared via UV-curing. Micro-compression measurements on maximally-cured micropillars are performed to study possible size effects. The results reveal that with decreasing pillar size, the yield stress decreases. Tensile measurements are performed on dog-bone shaped samples which have been processed in the same way as compared to the compression samples. These tensile tests show higher yield stress values when compared with compression tests. This size effect can be attributed to the rinsing with acetone during the sample preparation that leads to a removal of monomer from the crosslinked network. As a consequence, in the real 3D-printing process, the mechanical properties will depend on the feature size. In conclusion, a method is presented to determine the mechanical properties of one single layer of material used in the rapid-prototyping SLA process. The experimental procedure we adopted requires only a few millilitres of material and, therefore, is well suited for screening materials under real SLA process conditions.Graphical abstractImage 1
       
  • Mechanical response of double-network gels with dynamic bonds under
           multi-cycle deformation
    • Abstract: Publication date: Available online 6 July 2018Source: PolymerAuthor(s): A.D. Drozdov, J. deClaville Christiansen Mechanical behavior of double-network (DN) gels with covalent and non-covalent bonds under multi-cycle loading depends strongly on time, strain rate and deformation program. A model is developed for the viscoelastic and viscoplastic responses of a polymer network with permanent and temporary junctions. Viscoelasticity is modeled as breakage and reformation of temporary bonds driven by thermal fluctuations. Viscoplasticity is treated as sliding of permanent junctions with respect to their initial positions in the network. Slippage occurs when a junction becomes unbalanced due to transition of a chain linked by this junction from its active state into the dangling state. Analysis of observations in tensile tests with various strain rates, relaxation tests, loading-unloading tests, and multi-cycle tests with various deformation programs on a series of DN gels shows that the experimental stress–strain diagrams are described correctly by the governing equations, material parameters evolve consistently with experimental conditions, and predictions of the model are in quantitative (where sufficient data are provided) and qualitative agreement with experimental data. In particular, numerical simulation demonstrates the ability of the model to describe the Mullins effect in DN gels.Graphical abstractImage 1
       
  • Zirconium-chitosan hydrogel beads for removal of boron from aqueous
           solutions
    • Abstract: Publication date: Available online 6 July 2018Source: PolymerAuthor(s): Joanna Kluczka, Małgorzata Gnus, Alicja Kazek-Kęsik, Gabriela Dudek In this study, zirconium(IV)-chitosan (Zr-CTS) hydrogel beads were synthesized for boron(III) removal. Zr-CTS was characterized by a series of experimental techniques, including SEM, XRD and FTIR. Kinetic, isotherm, and thermodynamic investigations were employed to understand the adsorption behavior. It was found that boron removal is a pH-dependent process, having the highest performance at pH 6–7. It was also shown that the process of boron adsorption follows the pseudo-second-order kinetic model and is dependent on Zr(IV) content in hydrogel beads, achieving the maximum adsorption capacity of 24.5 mg/g. Thermodynamic constants demonstrated a feasible, spontaneous, and endothermic adsorption. Boron removal by Zr-CTS was found to occur through the adsorption of boron species on the surface of amorphous zirconium hydroxide via complexation mechanism. The results indicated that due to its efficiency in removing boron, good regeneration capacity and convenient form, Zr-CTS might be considered as a promising adsorbent for water purification.Graphical abstractImage 1
       
  • Wet stable and mechanically robust cellulose nanofibrils (CNF) based
           hydrogel
    • Abstract: Publication date: Available online 5 July 2018Source: PolymerAuthor(s): Muhammad R. Hossen, Nayereh Dadoo, David G. Holomakoff, Aimee Co, William M. Gramlich, Michael D. Mason Freeze dried, highly porous materials made from cellulose nanofibrils (CNF) hydrogels are capable of absorbing and storing a significant quantity of liquid inside their 3D structure, with total absorption capacity increasing linearly with porosity. One of the challenges of freeze dried high porosity CNF gels is their propensity to break down rapidly in aqueous environments. Here we explore a method to overcome this deficiency by incorporating methacrylate functionalized carboxymethyl cellulose (MetCMC) into the CNF system followed by UV irradiation leading to crosslinking of the methacrylate groups of MetCMC. The resultant polymer composite matrix successfully maintains a robust 3D structure, without collapsing, even when rewetted and stored in water. When freeze dried, the CNF-MetCMC composite maintains its size and shape whereas air drying induces significant shrinkage. In contrast, air dried CNF-MetCMC hydrogels swell when rewetted. Swelling and shrinkage of CNF-MetCMC hydrogels were tuned by controlling the ratio between CNF and MetCMC in the composite. The crosslinking between the methacrylate groups of MetCMC also enhances the dry and wet modulus of CNF-MetCMC gels significantly. We invoke a simple model involving a balance between hydrogen bonding and crosslinking to explain these data.Graphical abstractImage 1
       
  • Oxygen diffusivity and permeation through polymers at elevated temperature
    • Abstract: Publication date: Available online 5 July 2018Source: PolymerAuthor(s): Mathew C. Celina, Adam Quintana Oxygen permeability (P), diffusivity (D) and solubility (S) properties are representative of gaseous diffusion in polymers and required for the understanding of polymer physics driven phenomena as well as the quantification of mass transport or polymer degradation processes when diffusion limited oxidation effects result in spatially dependent oxidation behavior. Precise P, D, S characterization data for O2 in polymeric materials at elevated temperatures have not been reported due to instrumental challenges and competitive reactively driven oxygen loss (oxidation reactions), although estimations have been accomplished from indirect measurements of oxidation depths when analyzed with theoretical degradation models. This study offers an overview on experimental approaches which have been applied to the characterization of a range of thin polymer films. As an overview, the O2 permeation features of three epoxy thermo-set materials, polyimides (Kapton and bismaleimides), and polypropylene for 25–140 °C were investigated with time-dependent flux measurements and yield permeation data which so far have not been available in the literature. Arrhenius plots of P for two epoxies (828/D230 and 828/D400) show the influence of the glass transition temperature, and intriguingly a transition originates mostly through noticeable changes in S but not D. Multiple material behaviors demonstrating the influence of reactive oxygen loss are discussed. Polymer oxidation chemistry will often interfere with physical permeation measurements at elevated temperatures, in conflict with perhaps the expectation for simple non-reactive O2 transport. Misleading data may result unless the underlying reactive oxidative loss is considered and compensated for, or permeation data are compared at multiple O2 partial pressures to validate non-reactive experimental conditions.Graphical abstractImage 1
       
  • Microphase structure of polyurethane-polyurea copolymers as revealed by
           solid-state NMR: Effect of molecular architecture
    • Abstract: Publication date: Available online 5 July 2018Source: PolymerAuthor(s): Maxim V. Mokeev, Stepan A. Ostanin, Natalia N. Saprykina, Vjacheslav V. Zuev 1H spin-diffusion solid-state NMR, in combination with other techniques, was utilized to investigate the effect of molecular architecture, solubility parameter of hard and soft segments, and their length on the domain size, interphase thickness and degree of phase separation in polyurethane-ureas based on oligomeric 4,4′-diisicyanate diphenylmethane, methylene-bis-(2-chloroaniline) and polyols based on polyethylene oxide, polypropylene oxide and polybutadiene with different length. Polyurethane-ureas based on polyethylene oxide soft blocks did not form rigid domains as a result of absence of microphase separation. The domain sizes of the hard segments in polyurethane-ureas under study practically did not show any dependence on their composition, but interphase thicknesses are higher for systems based on polybutadiene soft blocks. This indicates that the degree of phase separation depends strongly not only on the binary thermodynamic interaction between hard and soft segments in polyurethane-ureas, but is also influenced by their molecular architectures in the experimental temperature range.Graphical abstractImage 1
       
  • Synthesis of polyaniline/graphene/MoS2 nanocomposite for high performance
           supercapacitor electrode
    • Abstract: Publication date: Available online 4 July 2018Source: PolymerAuthor(s): Shatrudhan Palsaniya, Harshal B. Nemade, Ashok Kumar Dasmahapatra Conducting polymers are usually good candidates for electrode materials of supercapacitors in spite of their lower cyclic stability, which can further be improved by combining with suitable nanofillers. In this work, we report the synthesis of nanocomposites of polyaniline (PANI), with equal weight% of graphene (G) and MoS2, prepared via in-situ oxidative polymerization of PANI, along with PANI-G binary nanocomposites. The morphological analysis confirms the formation of well-dispersed composite materials, and the ternary composite appears to be an interlayered structure of graphene and MoS2, encapsulating the PANI nanorods. As a result, the ternary composite exhibits an excellent supercapacitance behavior, suitable for energy storage applications as revealed by an enhanced cyclic stability. The ternary composite PANI-G-MoS2 symmetric electrode measurement exhibits a remarkably high specific capacitance (Cs, 142.30 F g−1) over binary composites under galvanostatic charge-discharge (GCD) cycles. The improved cyclic stability has contributed significantly in recovering the capacitance retention as high as 98.11% in comparison with pure PANI (∼40%) and binary composites (∼60–96%). Further, PANI-G-MoS2 symmetric electrode (viz., based on two electrode measurement) exhibits a high energy density (2.65 Wh kg−1) at a power density of 119.21 W kg−1, which is attributed to the high charge transport phenomenon occurs at the interfacial region between electrodes and electrolyte.Graphical abstractImage 1
       
  • Determination of phase specific localization of carbon black in ternary
           rubber blends: a macroscopic approach by Fourier transform infrared
           spectroscopy (FTIR)
    • Abstract: Publication date: Available online 4 July 2018Source: PolymerAuthor(s): A.D. Sarma, H.H. Le, A. Das, S. Wießner, K.W. Stöckelhuber, A.K. Bhowmick, G. Heinrich The phase specific localization of the reinforcing fillers like carbon black (CB), which has been known to influence the physical and mechanical performance of the rubber blends, can be determined by different characterization techniques, however, only for binary rubber blends. They have been failed so far when applied for more complicated systems like filled ternary rubber blends. In the present work we introduced a new technique using the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) with germanium crystal for characterization of the specific localization of CB in a ternary blend of solution styrene butadiene rubber (SBR), butadiene rubber (BR) and natural rubber (NR). It is the first time we could follow the change of the amount of CB localized in each phase of this blend along the mixing time. CB firstly is incorporated into the NR phase and then it obviously migrates from the NR phase to the SBR phase as a function of mixing time that corresponds very well with the theoretical prediction based on the Z-model using the surface tension values of the filler and rubber blend components. The interaction between CB rubber components can be qualitatively proved by the shift of the FTIR peak. Thermogravimetric analysis (TGA) was used to support the results obtained by the FTIR method. The study was further extended to follow the CB distribution in multi-step mixing.Graphical abstractImage
       
  • Synergistic conductivity increase in polypyrrole/molybdenum disulfide
           composite
    • Abstract: Publication date: Available online 3 July 2018Source: PolymerAuthor(s): Udit Acharya, Patrycja Bober, Miroslava Trchová, Alexander Zhigunov, Jaroslav Stejskal, Jiří Pfleger Polypyrrole/molybdenum disulfide (PPy/MoS2) composites were synthesized by in-situ chemical polymerization of pyrrole in the presence of MoS2 flakes. The conductivity of the composite with a moderate content of PPy (15–30 wt%) reached 13 S cm−1, which is markedly higher than the conductivity of both the pristine PPy and MoS2, 1 and 10−6 S cm−1, respectively. The improved conductivity was explained by a formation of ordered thin PPy films with high conductivity at the MoS2 surface. At higher pyrrole content, globular PPy was formed in the bulk of the composite resulting in an increase of a disordered polymer fraction, and the conductivity decreased. The composite conductivity is thus controlled not only by content of PPy but also by the proportions between ordered and disordered PPy phases. The structural and morphological characterization of composite materials is based on Fourier-transform infrared and Raman spectroscopies, wide-angle X-ray diffraction, and scanning and transmission electron microscopies. The charge-carrier transport in the composites fits the Mott variable-range hopping mechanism.Graphical abstractImage 1
       
  • High-performance polyimide copolymer fibers derived from
           5-anino-2-(2-hydroxy-4-aminobenzene)-benzoxazole: Preparation, structure
           and properties
    • Abstract: Publication date: Available online 29 June 2018Source: PolymerAuthor(s): Xuemin Dai, Feng Bao, Long Jiao, Haibo Yao, Xiangling Ji, Xuepeng Qiu, Yongfeng Men A series of high-performance polyimide copolymer (co-PI) fibers containing phenylenebenzoxazole moiety with one hydroxyl group are synthesized based on the copolymerization of 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) with two diamine monomers, namely, p-phenylenediamine (p-PDA) and 5-anino-2-(2-hydroxy-4-aminobenzene)-benzoxazole (p-mHBOA), through a two-step method. The molar ratio of p-PDA/p-mHBOA varies from 10/0 to 0/10. Influences of the p-mHBOA moieties on the thermal stability, crystal structure, crystal orientation, microvoid morphology, and mechanical properties are systemically investigated. Fourier transform infrared results confirm that intra/inter molecular hydrogen bonds come from the OH group and nitrogen atom of the benzoxazole group and/or OH group and the oxygen atom of the carbonyl group of cyclic imide. The glass transition temperatures (Tgs) of co-PI fibers are in the range of 290 °C–318 °C. The prepared fibers show excellent thermal stabilities, and their T5% is within 528 °C–542 °C in air. Two-dimensional wide-angle X-ray diffraction spectra indicate that homo-PI and co-PI fibers present a regularly arranged polymer chains along the fiber axial direction. Moreover, the ordered molecular packing along the transversal direction of fibers is destroyed by the copolymerization. Small-angle X-ray scattering results show that co-PI fibers with optimal mechanical properties exhibit the shortest average length (L) and the smallest radius (R¯) of microvoids. When the p-mHBOA/p-PDA molar ratio is 5/5, the fracture strength and initial modulus can reach approximately 30.31 cN/dtex (4.40 GPa) and 894.88 cN/dtex (129.8 GPa), respectively. The relationship between structure and mechanical properties is also discussed.Graphical abstractImage 1
       
  • Mechanical and thermal behavior dependence on graphite and oxidized
           graphite content in polyester composites
    • Abstract: Publication date: Available online 26 June 2018Source: PolymerAuthor(s): P. González García, R. Ramírez-Aguilar, M. Torres, Edgar A. Franco-Urquiza, J. May-Crespo The influence of 0.1, 0.25, and 0.5 wt% of graphite and graphite oxide on the thermal and mechanical behavior of a PP-70 polyester resin was analyzed. According to the infrared spectra, the addition of graphite particles reduce the intensity of the ester groups reflecting a physical interaction between the filler and the polymer. The thermogravimetric analysis revealed a slightly increase in the decomposition temperature from 400 to 415 °C when 0.25 wt% of graphite oxide particles were incorporated. Dynamic-mechanical analysis behavior of polymer composites showed low interaction of graphite particles with polyester matrix, which changed the thermo-mechanical stability of composites. The flexural behavior for the two composites, obtained from stress-strain curves, showed that incorporation of 0.5 wt% of graphite and graphite oxide reduces the stiffness from 2700 to 2100 and 2250 MPa; in addition, the strength was also decreased from 98.1 to 68.2 and 63.5 MPa; respectively.Graphical abstractIt is possible to observe a maximum peak at 97 °C and a second peak around 145 °C for the polyester resin. However the presence of graphite fillers seems to inhibit the formation of the second peak. When the fillers are introduced into the thermoset polymer, the glass transition temperature curve changes its shape and it is considerably shifted. However, graphite oxide tends to agglomerate, which causes a reduction in the molecular movement of the polyester chains.Image 1
       
  • Resin filling into nano-sized pore on metal surface analyzed by all-atom
           molecular dynamics simulation over a variety of resin and pore sizes
    • Abstract: Publication date: Available online 19 June 2018Source: PolymerAuthor(s): Hodaka Mori, Nobuyuki Matubayasi Nano-scale roughening of a metal surface emerges as an efficient scheme for better adhesion of the metal and resin. In the present work, we address the filling of a mixture of polyphenol and polyglycidylether of o-cresol formaldehyde novolac and a set of their oligomers into nano-sized pores on aluminum surface by conducting all-atom molecular dynamics simulation. A variety of resin and pore sizes were examined, and it was found that the pore is filled to several tens of % at practically employed pressure when the radius of gyration of resin is smaller than ∼ 1/10 of the pore radius. An impractically high pressure is required for larger resins, on the other hand, and an efficient filling can be achieved only with a resin that is smaller in size than the pore by an order of magnitude. The stress map was also analyzed in and around the pore, and it was observed that the local stress is not distributed uniformly unless the resin is small. This indicates that a common rate of pushing does not lead to the relaxation of the resin structure, suggesting in turn that a more effective filling may be possible with reduced rate of pushing.Graphical abstractImage 1
       
  • A hydrophilic coumarin-based polyester for ambient-temperature
           initiator-free 3D printing: Chemistry, rheology and interface formation
    • Abstract: Publication date: Available online 6 June 2018Source: PolymerAuthor(s): Sudhanva R. Govindarajan, Tanmay Jain, Jae-Won Choi, Abraham Joy, Irada Isayeva, Katherine Vorvolakos Initiator-free, photocurable, low-toxicity, viscoelastic polymer inks are attractive materials for creating low-modulus 3D-printed elastomeric biomedical constructs. In this work, we describe the synthesis, characterization, and 3D printing/crosslinking of a hydrophilic coumarin-PEG polyester (CPP). The viscoelastic CPP melt can be extruded at room temperature and deposited into layer-by-layer patterns. Upon UV irradiation, the coumarin pendant groups undergo [2 + 2] photocyclization, creating a thermoset network without the use of monomers, photoinitiators or propagating radicals. Voxel-voxel adhesion experiments between crosslinked and uncrosslinked material were performed to examine interfacial dynamics in a native, unperturbed state, and various attempts at 3D printing were made to assess the impact of printing conditions on the ultimate printed structure. Rheological analysis indicates a transition point where elastic behavior overtakes viscous behavior at increasing shear rate. It is hypothesized that this transition point corresponds with changes in interface formation from “sticky” to “bouncy” behavior in voxel-voxel adhesion and 3D printing processes. Tensile-mode dynamic mechanical analysis (DMA) and X-Ray microtomography (microCT) experiments reveal interfacial defect accumulation that results in deterioration of macroscopic structural and mechanical properties.Graphical abstractImage 1
       
  • Rational design of epoxy/ ZIF-8 nanocomposites for enhanced suppression of
           copper ion migration
    • Abstract: Publication date: Available online 26 May 2018Source: PolymerAuthor(s): Seok Hwan Lee, Hean Young Seo, Yong Sik Yeom, Jong Eun Kim, Heseong An, Jong-Suk Lee, Hae-Kown Jeong, Kyung-Youl Baek, Kie Yong Cho, Ho Gyu Yoon Various failure modes derived from the electrochemical migration (ECM) through the dielectric polymer layers have been considered as critical issues in the electronic devices. Herein, we for the first time suggested the rationally designed epoxy/zeolitic imidazolate framework-8 (ZIF-8) nanocomposite materials for efficient suppression of copper ion migration based on the plausible reaction mechanisms of metal metathesis addressed by sequential cleaving and ligating between metal ions (Zn2+ and Cu2+) and 2-methylimidazole (2-mim) ligands. The fabrication process for epoxy/ZIF-8 (EZ) nanocomposites was first examined to optimize the crosslinking system. The capability of the metal ion capture in the epoxy/ZIF-8 (EZ) nanocomposites was examined using the aqueous solution containing Cu2+ ions. In addition, the ECM suppression properties were evaluated using the thermal humidity bias (THB) model testing. The representative model investigations with the EZ nanocomposites exhibited substantially enhanced copper ion adsorption and suppression of copper migration in comparison to those of epoxy. Hence, the EZ nanocomposites can be one promising material to alleviate the undesired ECM behavior in electronic device applications.Graphical abstractImage 1
       
  • Solvent-cast 3D printing of polysulfone and polyaniline composites
    • Abstract: Publication date: Available online 19 May 2018Source: PolymerAuthor(s): Ziyi Miao, Jiho Seo, Michael A. Hickner Polysulfone (PSU) and polysulfone/polyaniline (PANI) composites were 3D printed by solvent-cast direct write deposition. Traditional material extrusion techniques require the application of heat to melt the polymer during extrusion and printing. This type of thermal processing poses potential limitations for printing polymers that have high processing temperatures or thermally degrade. PSU is a thermally stable polymer, but has an elevated glass transition temperature of 185–190 °C and is highly viscous in the melt. On the other hand, polyaniline is a semiconducting polymer that thermally degrades before melting By using solvent-based inks, PSU and PSU/PANI composites were 3D printed at room temperature using direct write deposition. PSU inks consisted of PSU dissolved in a mixture of dichloromethane (DCM) and dimethylformamide (DMF). The DCM evaporated quickly to harden the extruded filament, while the DMF evaporated slowly to allow for a smoother extruded filament and more consistent extrusion with well-bonded layers. Best results were obtained with PSU concentrations at 35–40 wt% with a DCM:DMF volume ratio of 5:1. The optimized PSU/PANI inks consisted of 30 wt% undoped PANI, and 35 wt% doped PANI, with 20 wt% PSU solution in dichloroethane (DCE) used as a binder. Using capillary viscometry it was confirmed that the inks exhibited pseudoplastic behavior, which is expected for polymer solutions and melts. It was shown that objects printed using the PSU/PANI ink are not conductive when undoped PANI was used, but became conductive when the PANI powder was first doped in 1 M H2SO4 before printing. A resistivity of 4.83 Ω-m was achieved with an ink containing 35 wt% doped PANI and 13 wt% PSU.Graphical abstractImage 1
       
  • Additive manufacturing with a flex activated mechanophore for
           nondestructive assessment of mechanochemical reactivity in complex object
           geometries
    • Abstract: Publication date: Available online 11 May 2018Source: PolymerAuthor(s): Bo Cao, Nicholas Boechler, Andrew J. Boydston We used digital light processing additive manufacturing (DLP-AM) to produce mechanochemically responsive test specimens from custom photoresin formulations, wherein designer, flex activated mechanophores enable quantitative assessment of the total mechanophore activation in the specimen. The manufactured object geometries included an octet truss unit cell, a gyroid lattice, and an “8D cubic lattice”. The mechanophore activation in each test specimen was measured as a function of uniaxial compressive strain applied to the structure. Full shape recovery after compression was exhibited in all cases. These proof-of-concept results signify the potential to use flex activated mechanophore for nondestructive, quantitative volumetric assessment of mechanochemistry in test specimens with complex geometries. Additionally, the integration of DLP-AM with flex activated mechanophore build materials enabled the creation of customizable, three-dimensional mechanochemically responsive parts that exhibit small molecule release without undergoing irreversible deformation or fracture.Graphical abstractImage 1
       
  • Exploring side-chain length effect on β-phase of polyfluorene derivatives
           in electrospinning and their optical behavior
    • Abstract: Publication date: Available online 9 May 2018Source: PolymerAuthor(s): Wei Xue, Jin-Yi Lin, Bin Liu, Nai-En Shi, Meng-Na Yu, Wan-Dan Wu, Wen-Sai Zhu, Ling-Hai Xie, Lian-Hui Wang, Wei Huang Unique coplanar β-conformation of polyfluorene, endowed with long effective conjugated length, is promising to form ordered and oriented structures that can result in improved carrier mobility, polarization emission and excellent spectral stability. Herein, a series of polydiarylfluorenes of different side-chains (PHDPF, PODPF or PNDPF) and poly (9-vinylcarbazole) composite nanofibers were prepared via electrospinning approach. It is observed that β-phase can be obtained in PODPF electrospun nanofibers whereas absent in those of PHDPF and PNDPF systems. It can be demonstrated that the optimal chain length for polydiarylfluorenes to β-conformation is an octyl side chain in electrospinning. In contrast with the electrospun nanofibers, there was no β-phase in the corresponding spin-coated film. For the β-phase electrospun nanofibers, the fluorescence quenching sensitivity on 2, 4-dinitrotoluene (DNT) vapor was obviously higher than that of amorphous electrospun nanofibers and spin-coated film, respectively. Synergistic molecular design and electrospun processing may offer a fascinating strategy for the control of polymer conformation to the adjustment of nano and micro optical devices such as organic fluorescence sensors, lasers and light-emitting diodes.Graphical abstractImage 1
       
  • High performance liquid crystalline physical gels prepared by side chain
           liquid crystalline polymers
    • Abstract: Publication date: Available online 9 April 2018Source: PolymerAuthor(s): Jianhang Zhao, Yongjie Yuan, Lei Chen, Ye Li, Hailiang Zhang Liquid crystalline physical gels (LCPGs) with stable mechanical properties and fast electro-optical response properties were prepared through the self-assembly of side chain liquid crystalline polymers (SCLCPs) with different spacer length poly [ω-4′-cyano-(1, 1′-biphenyl)] acrylate (PmACB, m is the spacer length of SCLCP, m = 0, 2, 4) as gelators in a nematic liquid crystal, 4-pentyl-4′-cyanobiphenyl (5CB). The gel-sol phase transition temperature (TGS), micro morphology, mechanical properties and electro-optical properties of LCPGs (SCLCPs/5CB) were systematically studied. The results show that only P0ACB can form stable liquid crystalline physical gels in 5CB and show excellent thermal stability, good self-supporting ability and fast electro-optical response properties. The TGS of 6 wt% P0ACB/5CB gel is 192 °C, and it also showed stable mechanical properties, its storage modulus is about 1.0 × 104 Pa. The threshold voltage (Vth) and saturation voltage (Vsat) of P0ACB/5CB gel with 3 wt% concentration are 0.29 V μm−1and 3.906 V μm−1 respectively, and the off state response time is only 6.748 ms. Moreover, the addition of the polymer does not affect the electro-optical response of the LCPGs.Graphical abstractImage 1
       
  • Structure characterization of UV-curing PEG-b-PPG-b-PEG dimethacrylate
           cross-linked network
    • Abstract: Publication date: Available online 6 April 2018Source: PolymerAuthor(s): Enmin Wang, Abed Hasheminasab, Yuanhao Guo, Mark D. Soucek, Miko Cakmak The molecular structure of a series of newly developed ultraviolet (UV) curable electrical contact stabilization materials, which contain polyethylene glycol (PEG)-block-polypropylene glycol (PPG)-block-polyethylene glycol (PEG) capped with methacrylate functional groups on both ends as the reactive oligomers and a methacrylated PEG as the reactive diluent was studied in detail. The effects of reactive diluents, including functionalities and compositions were investigated via a combination of dynamic mechanical analysis, differential scanning calorimetry, FT-IR spectroscopy and wide angle X-ray diffraction. All the films exhibit completely amorphous state at room temperature regardless of the composition or thermal history. However, a small amount of PPPDI molecular chains undergo crystallization upon slow cooling. This crystallization is completely inhibited when mixed with di-functional reactive diluents, owing to the high cross-link density. The introduction of mono-functional reactive diluents restricts but not completely prevents the crystallization process, which causes the resulting films to be difficult to crystallize to lower crystallinity levels. On the other hand, adding non-reactive diluents transforms the resulting films to become a fast-crystallizing material, as a result of the low cross-link density and a large portion of unreacted oligomers along with the unreactive component. Additionally, the degree of heterogeneity for the cross-linked networks is generally increased by the addition of reactive diluents. The molecular structures of PEG-b-PPG-b-PEG dimethacrylate cross-linked networks as well as mixed with different types of reactive diluents at both room temperature and crystallizing temperature were proposed.Graphical abstractImage 1
       
  • Photo-polymerization induced viscoelastic phase separation of
           trimethylolpropane triacrylate/poly (styrene-co-methyl methacrylate)
           blends
    • Abstract: Publication date: Available online 19 March 2018Source: PolymerAuthor(s): Nazanin Naderi, Saeed Rastegar, Mohsen Mohseni, Manoochehr Khorasani Phase separation of trimethylolpropanetriacrylate/poly(styrene-co-methylmethacrylate) induced by UV-irradiation (photo-PIPS) has been studied. Three poly(St-co-MMA) with St:MMA monomer ratio of 25:75, 50:50 and 75:25 were synthesized with average molecular weight of Mw ≈ 5 × 104 and average Tg being ≈345 K, due to stereoirregularity in their structure. Difference in TMPTA/poly(St-co-MMA) blends compatibility caused different extents of photo-PIPS and final conversion status depended on the copolymer type and amount. Optical microscopy used to study time-evolution of photo-PIPS. SEM observation showed that, within studied range of copolymer content, droplet domains of copolymer-rich phase appeared in TMPTA-rich matrix through viscoelastic photo-PIPS and in copolymer-rich domains network-like structures of TMPTA were formed. Also some columns were created due to copolymer extrusion to the surface of the sample. Size of the copolymer-rich domains, their formation procedure and size of the columns depended on the copolymer type and amount. SEM Carbon-mapping confirmed copolymer extrusion to the surface. Based on AFM phase-mode images medium-, low- and high-modulus regions were detected and assigned to the TMPTA-rich matrix phase, copolymer-rich phase and TMPTA-rich phase of copolymer-rich domains, respectively. These corresponds to peaks of tan δ curves used to determine mentioned phases composition.Graphical abstractImage 1
       
  • Functional siloxanes with photo-activated, simultaneous chain extension
           and crosslinking for lithography-based 3D printing
    • Abstract: Publication date: Available online 24 February 2018Source: PolymerAuthor(s): Justin M. Sirrine, Viswanath Meenakshisundaram, Nicholas G. Moon, Philip J. Scott, Ryan J. Mondschein, Tobin F. Weiseman, Christopher B. Williams, Timothy E. Long A novel, poly(dimethyl siloxane)-based photopolymer that exhibits simultaneous linear chain extension and crosslinking was suitable for vat photopolymerization additive manufacturing. Photopolymer compositions consisted of dithiol and diacrylate functional poly(dimethyl siloxane) oligomers, where simultaneous thiol-ene coupling and free radical polymerization provided for linear chain extension and crosslinking, respectively. Compositions possessed low viscosity before printing and the modulus and tensile strain at break of a photocured, higher molecular weight precursor after printing. Photorheology and soxhlet extraction demonstrated highly efficient photocuring, revealing a calculated molecular weight between crosslinks of 12,600 g/mol and gel fractions in excess of 90% while employing significantly lower molecular weight precursors (i.e. 
       
  • H-bonding tuned phase transitions of a strong microphase-separated
           polydimethylsiloxane-b-poly(2-vinylpyridine) block copolymer
    • Abstract: Publication date: Available online 5 February 2018Source: PolymerAuthor(s): Ling-Ying Shi, Wei-Wei Lei, Fen Liao, Jing Chen, Meng Wu, Yi-Yi Zhang, Chen-Xin Hu, Lu Xing, Yu-Lin Zhang, Rong Ran The phase behaviors of a polydimethylsiloxane-b-poly(2-vinylpyridine) block copolymer (PDMS-b-P2VP, DV) tuned by the supramolecular self-assembly approach with the 1-pyrenebutyric acid (PBA) as additive were investigated. The PDMS-b-P2VP block copolymer (D10kV12.5k, the molecular weight of the PDMS and P2VP were 10000 and 12500 g mol−1, respectively) with volume fraction of P2VP (fP2VP) of 52% exhibited hexagonally perforated layer (HPL) morphology after dried from the solution, and the nanostructure transformed to gyroid structure after thermal annealing above 140 oC, which were indicated by the small-angle X-ray diffraction (SAXS) and transmission electron microscopy (TEM) results. Through solution blending method, a series of H-bonding supramolecular complexes of PDMS-b-P2VP with PBA were fabricated. The Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) experiments demonstrated that the PBA molecules uniformly interacted with P2VP through H-bonding and the glass transition temperature of P2VP(PBA)x decreased with the increase of the mole ratio (x) of PBA/2VP. Due to the increase of the volume fraction of P2VP(PBA)x and that of the stretching extent of the P2VP backbone as the x value increased in the supramolecular complexes, the microphase-separated nanostructures transformed from HPL to hexagonally packed cylinder (HEX), then to body centered cubic (BCC) structure and then to disordered spheres morphologies. When the PDMS-b-P2VP(PBA)x complexes were heated above 120 oC, the H-bonding between the P2VP and PBA was broken and the PBA became compatible within both PDMS and P2VP domains and thus the nanostructure of the PDMS-b-P2VP(PBA)x complexes transformed accordingly. Therefore, a variety of the nanostructures and structural transformations were induced by the H-bonding formation and disassociation based on one block copolymer.Graphical abstractVarieties of nanostructures and structure transitions were obtained based on a strong microphase-separated block copolymer tuned by H-bonding formation and dissociation.Image 1
       
  • Drawing behavior and mechanical properties of ultra-high molecular weight
           polyethylene blends with a linear polyethylene wax
    • Abstract: Publication date: Available online 3 February 2018Source: PolymerAuthor(s): Lihua Shen, John Severn, Cees W.M. Bastiaansen Ultra-high molecular weight polyethylene (UHMWPE; Mw = 103 kg/mol) is blended with a low molecular weight, linear polyethylene (PEwax; Mw = 1 kg/mol) and the solid state drawing behavior and mechanical properties are explored. The results indicate that the low molecular weight polyethylene wax acts as a solvent for the UHMWPE which leads to an improvement in rheological properties and the maximum attainable draw ratio of the blends. The maximum attainable Young's modulus of the drawn films increases with more than a factor 2 without removal of the solvent. Moreover, it is found that the maximum attainable tensile strength of the drawn blends also increases significantly from ∼1 GPa to ∼1.5 GPa upon addition of 60 wt% of the PEwax. Based on these results, a new route is proposed for the processing of highly oriented polyethylene, which has certain characteristics in common with both melt spinning and solution spinning but, in fact, is neither of the two.Graphical abstractImage 1
       
  • Chemical modification and printability of shear-thinning hydrogel inks for
           direct-write 3D printing
    • Abstract: Publication date: Available online 1 February 2018Source: PolymerAuthor(s): Patrick T. Smith, Amrita Basu, Abhijit Saha, Alshakim Nelson Shear-thinning hydrogels are often employed in direct-write 3D printing, however, the viscoelastic behaviors that define a printable hydrogel have not been fully established. Herein, we demonstrate a library of hydrogel inks based on the incorporation of water-soluble reactive meth(acrylate) monomers into F127-dimethacrylate hydrogels. This strategy afforded printed hydrogels with a broad range of chemical functionalities and mechanical properties. A systematic investigation was also performed to correlate the printability and mechanical properties to the viscoelastic properties of the hydrogel ink formulations. The materials with a high dynamic yield stress afforded extruded filaments that correlated well with the inner diameter of the printing nozzle. The static yield stress of the material was correlated to the extrusion pressure and print speed required for optimal printing. Thus, this study provides a guide for the future development of hydrogel inks for direct-write 3D printing along with a new set of functional hydrogel inks.Graphical abstractImage 1
       
  • Interlayer diffusion of surface segregating additives to improve the
           isotropy of fused deposition modeling products
    • Abstract: Publication date: Available online 12 January 2018Source: PolymerAuthor(s): Neiko P. Levenhagen, Mark D. Dadmun It is well known that 3D printed parts prepared by fused deposition modeling (FDM) exhibit large anisotropy of mechanical properties. For instance, the mechanical properties observed of samples printed orthogonal to the print bed (transverse) are significantly weaker than those printed parallel to the bed (longitudinal). This behavior is a result of poor interlayer adhesion from limited diffusion and entanglement of chains across the interlayer interface. To improve the diffusion and entanglement of adjacent layers, our group has implemented a process in which bimodal blends comprised of a parent, high molecular weight polymer blended with an identical but low molecular weight (LMW) polymer is utilized. These bimodal blends lead to significant enhancements in the mechanical properties of samples printed in the transverse orientation. Additionally, the moduli, regardless of print orientation, become nearly identical, indicating a more isotropic part. To more fully understand this behavior, we report the impact of LMW architectures on the improvement of structural properties of 3D printed parts. The decrease in anisotropy of mechanical properties of PLA bimodal blends containing 2-arm (linear), 3-arm and 4-arm PLA stars (Mw of arm- ∼11 k) at loadings of 3, 10, and 15 mol% are tested under the same protocol as previous linear specimens. With the addition of just 3 mol% of each LMW additive, increases in the maximum stress from 15% to 100% are observed for samples printed in the transverse orientation. A significant improvement in layer adhesion and a significantly more isotropic part is thus realized, where the 3-arm star exhibits optimal performance. Interpretation of the data presented leads to the conclusion that this is true because the 3-arm star most efficiently diffuses to the inter-filament interface and entangles with the linear polymer.Graphical abstractImage 1
       
 
 
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