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Journal Prestige (SJR): 1.097
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ISSN (Print) 0032-3861
Published by Elsevier Homepage  [3184 journals]
  • Glass fiber reinforced PLA composite with enhanced mechanical properties,
           thermal behavior, and foaming ability
    • Abstract: Publication date: Available online 13 September 2019Source: PolymerAuthor(s): Guilong Wang, Dongmei Zhang, Gengping Wan, Bo Li, Guoqun ZhaoPolylatic acid (PLA) and PLA foams show a promising prospect for replacing the traditional petroleum-based polymers and foams. However, PLA shows poor ductility, thermal stability and foaming ability, and its application is significantly limited. Herein, silane-modified glass fibers (m-GF) were adopted to improve the mechanical properties, thermal stability, and foaming ability of PLA. PLA/m-GF composites with different GF contents were firstly prepared by twin-screw compounding. Microscopic morphology analysis showed that silane-modified GF has a good bonding with PLA matrix, and increasing GF content led to slight decreased of GF length. Mechanical testing showed that GF led to simultaneously enhanced strength, rigidness, and toughness. The higher the GF content is, the more obvious the reinforcement effect is. With 20 wt% GF, the PLA/m-GF composite shows almost 2-fold enhanced strength and rigidness, and more than 3-fold enhanced impact toughness than the pure PLA. The outstanding mechanical properties arises from the strengthening effect of the GF network skeleton that shows good bonding with PLA matrix. Thermal analysis showed that GF led to increased heat deflection temperature but reduced melt flow index of PLA. Foaming experiments showed that GF can dramatically improve the foaming ability by increasing expansion ratio and refining cellular morphology. Microcellular PLA/m-GF foam with an expansion ratio of up to 20-fold and cell sizes less than 10 μm was achieved. Thus, the strong PLA/m-GF composites and their foams show a promising future in preparing lightweight structural components used in many applications such as automotive and aircraft industries.Graphical abstractImage 1
  • Chain-walking polymerization of 3-heptene with phenyl substituted
           α-diimine nickel catalysts
    • Abstract: Publication date: Available online 13 September 2019Source: PolymerAuthor(s): Fuzhou Wang, Guoyong Xu, Qingshan Li, Ryo Tanaka, Yuushou Nakayama, Takeshi ShionoThe first example of a 3-alkene polymerization has been successfully achieved with 3-heptene in the presence of phenyl-substituted α-diimine nickel precatalysts activated by dMMAO, and compared with the corresponding linear alkenes, i.e., 1-pentene, 2-hexene and 4-octene polymerizations. The microstructures of the produced poly(3-heptene), which consists of ethyl, propyl and butyl branches indicated the 3,4- and 4,3-insertion, followed by chain-walking, with incorporation of a small fraction of long methylene sequences of 1,7-enchainment via monomer-isomerization.Late-transition metal catalyzed polymerization reactions of internal alkenes to synthesize novel polyolefin materials are highly important and also highly challenging. Upon activation with dried modified methylaluminoxane (dMMAO), the first example of a 3-alkene polymerization has been successfully achieved for 3-heptene catalyzed by phenyl-substituted α-diimine nickel complexes in comparison, and compared with the polymerizations of the corresponding linear alkenes, i.e., 1-pentene, 2-hexene and 4-octene. The results indicate that the polymerization of 3-heptene was achieved via chain-walking to generate branched amorphous polymers with glass transition temperature of ca. −68 °C. The microstructures of the produced poly(3-heptene) indicated the 3,4- and 4,3-insertion followed by chain-walking, the latter being predominant. The NMR analyses of the polymers showed that the obtained poly(3-heptene) possessed ethyl, propyl and butyl branches and a small amount of the long methylene sequence of 1,7-enchainment via monomer-isomerization. The branches structures were significantly dependent on the polymerization temperature, and the content of propyl branches derived from 3,4-insertion decreased with an increase in the polymerization temperature.Graphical abstractImage 1
  • Laser-triggered shape memory based on thermoplastic and thermoset matrices
           with silver nanoparticles
    • Abstract: Publication date: Available online 13 September 2019Source: PolymerAuthor(s): Nattawat Yenpech, Varol Intasanta, Suwabun ChirachanchaiStimuli responsive shape memory polymers (SMPs) are challenging theme as the materials not only shows the shape changing under the traditional thermal treatment but also under other external stimuli. The present work proposes an in-situ ring opening polymerization (ROP) to combine the thermoset hard segment, i.e. polybenzoxazine, and thermoplastic soft segment, i.e. polycaprolactone and silver nanoparticles (AgNPs) as the laser-trigger. The melamine-based benzoxazine (mBz) plays its important role in allowing the ROP to create the thermoset polybenzoxazine network (PmBz) as well as providing many hydroxyl groups to further conjugation with thermoplastic polycaprolactone matrices (PCL). The AgNPs are the good alternative to select based on their function to be expressed by the very low energy (violet laser at 408 nm, 780 mW) and the surface modifiable with disulfide polycaprolactone (SS-PCL) hybridization for the highly miscible and readily dispersible in PCL matrices. The present work, for the first time, proposes light-triggered SMPs via simple molecular design and synthesis based on an in-situ ROP to combine PmBz thermoset networks and PCL thermoplastic matrices with the AgNPs-PCL to provide the light-thermal responsive function.Graphical abstractImage 1
  • Design and fabrication of a low-cost pilot-scale melt-processing system
    • Abstract: Publication date: Available online 12 September 2019Source: PolymerAuthor(s): David M. Wirth, Jonathan K. PokorskiMelt processing of polymeric materials is a ubiquitous technique for forming, shaping, refining and homogenizing polymers and polymer composites. Melt-processing techniques are the primary manufacturing method of consumer and industrial thermoplastic parts, especially when using commodity polymers with high-throughput production. Melt-processing, however, is underutilized in academic laboratories when developing high value-added materials due to the capital expense of the equipment and relatively large-scale required to carry out such processing. These concerns make pilot-scale melt-processing challenging, particularly for new polymers or polymer composites where materials can only be generated in small-scale at reasonable costs. The current study designs and evaluates a bench-top, sub-milliliter volume extrusion and injection-molding device, which sources parts from current 3D print technology at minimal expense. The plans presented will open this convenient technique to academic research laboratories interested in pilot-scale experiments. A systematic approach to melt processing of PLA, PLGA, and PCL polymer composites is demonstrated. Characterization of the dispersion of pharmaceuticals, small molecules and nanoparticles in melt processed polymers is presented as a demonstration of potential utility.Graphical abstractImage 1
  • Aging of natural rubber studied via fourier-transform rheology and double
           quantum NMR to correlate local chain dynamics with macroscopic mechanical
    • Abstract: Publication date: Available online 12 September 2019Source: PolymerAuthor(s): Shouliang Nie, Jorge Lacayo-Pineda, Norbert Willenbacher, Manfred WilhelmNowadays mainly the linear rheological properties of natural rubber (NR) vulcanizate during aging are studied, even though NR is rheologically nonlinear under most application conditions. Here, the nonlinearity was quantified via Fourier transform rheology (FT-Rheology) using I3/1, the relative intensity of the 3rd harmonic. The crosslink density and the content of defects were investigated by the 1H double quantum nuclear magnetic resonance (DQ-NMR). For aerobic aging at 120 °C, the crosslink density increases, but later turns into a broader mesh size distribution with more defects. Accordingly, the rheological nonlinearity of the material increases in the earlier stage and then decreases. For mechanical aging, the nonlinearity continuously decreases as a function of the fatigue cycle numbers, whereas the local crosslink density of the polymer network remains constant. This behavior can be assigned to the micro-cracks generated along adjacent network defects, which are larger than the detection scale of DQ-NMR. Compared to the linear rheological parameters, storage modulus G′ and loss factor tanδ, I3/1 exhibits higher sensitivity to the aging of crosslinked NR under both high temperature aerobic and mechanical fatigue conditions.Graphical abstractImage 1
  • Crystallization and crystalline dynamics of poly(3-hydroxybutyrate) /
           poly(4-vinylphenol) polymer blends studied by low-frequency vibrational
    • Abstract: Publication date: Available online 11 September 2019Source: PolymerAuthor(s): Dian Marlina, Hiromichi Hoshina, Yukihiro Ozaki, Harumi SatoComposition- and temperature-dependent far-infrared (FIR), terahertz (THz), and low-frequency Raman spectra of poly(3-hydroxybutyrate) (PHB)/Poly(4-vinylphenol) (PVPh) polymer blends were measured to investigate the effects of PVPh in PHB crystallization. FIR, low-frequency Raman, and wide angle X-ray diffraction (WAXD) studies revealed that PVPh reduces the crystallinity of PHB in blends without a significant change in the crystal structure. The FIR and low-frequency Raman spectra divided the blends into three categories: high-ordered crystalline, less-ordered crystalline, and amorphous. A new peak was observed at 135 cm−1 in the FIR spectra of the PHB/PVPh blends, which may be assigned to the less-ordered crystalline phase of PHB, predicting the inter-molecular hydrogen-bond interactions of PHB/PVPh. The intensity ratio of the peaks at 97 and 82 cm−1 changed with the blending ratio variations owing to the crystalline dynamics of PHB. Deformation of the PHB helical structure occurred first, followed by weakening of the intra-molecular hydrogen-bond within PHB. Shifts of several peaks were observed in the FIR and low-frequency Raman spectra, suggesting that the intra-molecular hydrogen-bond (-C-H…O=C) within PHB weakened with temperature. The novelty of the present study is to demonstrate that low-frequency vibrational spectroscopy is very sensitive to monitor changes from the intra-molecular hydrogen bonding to inter-molecular hydrogen bonding between PHB and PVPh.Graphical abstractImage 1
  • Nonlinear and linear viscoelastic behaviors of thermoplastic vulcanizates
           containing rubber nanoparticle agglomerates
    • Abstract: Publication date: Available online 10 September 2019Source: PolymerAuthor(s): Shangqing Li, Hongchi Tian, Baoqing Zhang, Guo-Hua Hu, Chen-Yang Liu, Liqun Zhang, Ming TianDependence of the nonlinear and linear viscoelastic behaviors of thermoplastic vulcanizates (TPV) on the content (ϕ) of rubber nanoparticle agglomerates (NPAs) was explored by dynamic oscillation shear tests. Under a large strain, TPV exhibit a ϕ-dependent yield stress (σy) as σy∝ϕ1.53±0.87. As ϕ increases, the rubber NPAs network becomes stronger, and the elastic modulus and viscosity of TPV increase. ϕ-dependent modulus (G0') of TPV is G0'∝ϕ3.18±0.24 in the low-ω region. Rubber NPs agglomerate to form a network more easily than rigid particles. The fractal dimension df (=1.65 ± 0.09) of the rubber NPAs in TPV is lower than the universal df (∼1.8) of rigid particles aggregates. The ϕ-dependent modulus G0' of TPV in the linear viscoelastic region shows G0'∼{(ϕc−ϕ)1,forisolatedrubberNPAs,ϕ≤ϕc(ϕ−ϕc)2.15±0.12,forrubberNPAsnetwork,ϕ≥ϕc, where ϕc is the percolation threshold of ϕ. This study provides an understanding of the viscoelasticity of TPV containing rubber NPAs and their network structure.Graphical abstractImage 1
  • Interaction of photothermal graphene networks with polymer chains and
           laser-driven photo-actuation behavior of shape memory
           polyurethane/epoxy/epoxy-functionalized graphene oxide nanocomposites
    • Abstract: Publication date: Available online 9 September 2019Source: PolymerAuthor(s): Vinay Deep Punetha, Yu-Mi Ha, Young-O. Kim, Yong Chae Jung, Jae Whan ChoThis work demonstrates the fabrication and near infra-red laser-driven shape recovery actuation behavior of bisphenol A diglycidyl ether-functionalized graphene oxide (DGEBA-f-GO)-based polyurethane (PU)/epoxy nanocomposites. DGEBA-f-GO was synthesized as a photothermal filler by treating DGEBA with carboxylated GO in a two-step process. Homogeneously dispersed networks of the photothermal filler were engineered via covalent crosslinking between DGEBA and DGEBA-f-GO in the PU matrix. The crosslinked DGEBA-f-GO net-works act as a near-infrared laser-harvesting framework for the efficient transfer of heat and trigger for shape recovery upon remote actuation. Interaction between the photo-thermal networks of DGEBA-f-GO with polymer chains was analyzed structurally, revealing that the DGEBA-f-GO networks in the nanocomposites stimulate the formation of an integrated netpoint framework in the matrix by interacting with the PU hard segment via hydrogen bonding. Consequently, the shape memory composites reinforced with GO networks showed enhanced laser-driven photo-actuation stress, as well as thermal stability, photothermal behavior, and mechanical properties.Graphical abstractImage 1
  • Glass transition and molecular dynamics in PHPMA-b-POEGMA block
    • Abstract: Publication date: Available online 9 September 2019Source: PolymerAuthor(s): Anna Karatza, Panagiotis Klonos, Stergios Pispas, Apostolos KyritsisIn the present work we study the glass transition and molecular dynamics in new amphiphilic block copolymers based on hydrophilic poly(oligo ethylene glycol methacrylate) (POEGMA) and water-insoluble poly(hydroxyl propyl methacrylate) (PHPMA) prepared by RAFT polymerization. To that aim, we employ here differential scanning calorimetry (DSC) and dielectric spectroscopy (BDS). At dry conditions and up to ∼50 wt% PHPMA, the POEGMA phase dominates on the glass transition (Tg ∼ −60 °C) and on local dynamics of the copolymers, while for larger PHPMA contents (80 wt%) the behaviour is that of the strongly plasticized PHPMA phase (neat PHPMA exhibits remarkably high calorimetric glass transition temperature, Tg ∼80 °C). Interestingly, a single glass transition step was observed for all compositions. For the copolymer rich in PHPMA (80 wt% PHPMA) the endothermic calorimetric step related to glass transition is much broader than in other copolymers, indicating higher spatial heterogeneity in the copolymer. Molecular dynamics by BDS, namely the secondary-local γ and β relaxations and segmental α relaxations (related with the glass transition) were mapped, especially for neat PHPMA for the first time. The presence of polar hydroxyl group in the side group of PHPMA made possible the dielectric study of the molecular mobility within the nano-domains formed by the side chains, like in n-alkyl methacrylates with long alkyl side chains (PE-like mobility). On the other hand, the dynamics in the brush-like structuring POEGMA is recorded quite similar to that in linear poly(ethylene glycol) chains. In the copolymers our results reveal strong intermolecular interactions at the atomic level among the side chains/groups of the two components and a pronounced nano-structured morphology.Graphical abstractImage 1
  • Control of crystal orientation of spatially confined PCL homopolymers by
           cleaving chain-ends of PCL blocks tethered to nanolamella interfaces
    • Abstract: Publication date: Available online 9 September 2019Source: PolymerAuthor(s): Hiroaki Kikuchi, Tomonari Watanabe, Hironori Marubayashi, Takashi Ishizone, Shuichi Nojima, Kazuo YamaguchiWe have examined the crystalline nanomorphology (i.e., crystallinity, melting temperature (reflecting crystal thickness), and crystal orientation) of poly(ε-caprolactone) (PCL) blocks and PCL homopolymers spatially confined in lamellar microdomain structures (nanolamellae) using two polystyrene (PS)-b-PCL diblock copolymers (with either PCL chain-end anchored to nanolamella interfaces) and one PS-b-PCL-b-PS triblock copolymer (with both chain-ends anchored). These copolymers had photocleavable o-nitrobenzyl groups at all the block junctions, so the PCL blocks could be converted into PCL homopolymers by UV irradiation with keeping the nanolamellar geometry. The crystallization of photocleaved PCL homopolymers was achieved by two procedures; (1) the amorphous PCL blocks were first converted into PCL homopolymers and they were crystallized at room temperature (RT) (one-step crystallization) or (2) the PCL blocks were first crystallized at selected temperatures to form some crystalline nanomorphology and then converted into PCL homopolymers to further crystallize and/or anneal at RT (two-step crystallization). The crystallinity and melting temperature of PCL homopolymers were similar for both procedures, suggesting that a certain amount of PCL homopolymers formed lamellar crystals with a comparable thickness. However, the lamellar crystals showed significantly different orientations between two procedures, because some crystal orientation was made by the advance crystallization of PCL blocks and remained unchanged after UV irradiation/subsequent crystallization in two-step crystallization, yielding a substantial difference in the crystal orientation of PCL homopolymers in nanolamellae.Graphical abstractImage 1
  • Solvent-free thermo-reversible and self-healable crosslinked polyurethane
           with dynamic covalent networks based on phenol-carbamate bonds
    • Abstract: Publication date: Available online 9 September 2019Source: PolymerAuthor(s): Jiaxin Shi, Tianze Zheng, Baohua Guo, Jun XuPolyurethanes with dynamic covalent networks have the potential of self-healing, reprocessing and recycling, however, how to improve the efficiency of self-healing and reprocessing, and reduce the use of solvent and costs, are still problems to solve. In this work, we synthesized a cross-linked polyurethane containing dynamic phenol-carbamate bonds from low-cost raw materials without use of solvent. The dynamic polyurethane possesses excellent self-healing and reprocessing properties, which exhibits low relaxation activation energy (92.7 kJ/mol) and can be almost completely healed at 80 °C for 2 h. After remolded for 4 times, the material shows almost little change in mechanical properties. Further studies on the phenol-carbamate bonds give the quantitative reaction equilibrium constants, thermodynamic parameters and dissociation activation energy. In viewpoint of the dynamic properties and easy synthesis of phenol-carbamates, various types of cross-linked polymers containing such dynamic bonds can be further tailor designed.Graphical abstractImage 1
  • Charge-neutral and self-doped cyclopentadithiophene-based conjugated
           polymers: Influence of side chain on optical, electrical, and
           thermoelectric properties
    • Abstract: Publication date: Available online 7 September 2019Source: PolymerAuthor(s): Koji Takagi, Hiroki Yano, Hiroki Ito, Naoki KishiWater-soluble cyclopentadithiophene-based conjugated polymers (CP1–Na, CP2–Na, and CP3–Na) having the sodium propanesulfonate side group and with different comonomer units were synthesized by Suzuki-Miyaura polymerization under the microwave heating at 90 °C for 8 h. Number-averaged molecular weights determined by GPC analyses after exchanging the counter cation ranged from 6200 to 10400. TGA measurements revealed that the degradation temperatures at 10% weight loss of polymers exceed 250 °C. UV–vis–NIR spectra exhibited broad absorptions at 950–1000 nm originated from the polaronic band, in which the intensity of this band was largest for CP3–Na with the bis(methylsulfanyl)methylene unit. The spin density calculated from EPR spectra was largest for CP2–Na with triethylene glycol chains (6.4 × 1016 for 1 mg). The electrical conductivity, Seebeck coefficient, and power factor of CP3–Na were estimated as 9.1 × 10−3 S cm−1, 34 μV K−1, and 1.1 × 10−3 μW m−1 K−2, respectively.Graphical abstractCharge-neutral and self-doped conjugated polymers with the cyclopentadithiophene (CPDT) unit having sodium propanesulfonate were synthesized, where the structure of comonomer was investigated to get information about optical, electrical, and thermoelectric properties of polymers.Image 1
  • A coupling model for cooperative dynamics in shape memory polymer
           undergoing multiple glass transitions and complex stress relaxations
    • Abstract: Publication date: Available online 7 September 2019Source: PolymerAuthor(s): Xiaodong Wang, Yuheng Liu, Haibao Lu, Nan Wu, David Hui, Yong-Qing FuModelling multi-shape memory effect (multi-SME) of shape memory polymers (SMPs) is a critical challenge for fields of mathematics/statistics and condensed-matter physics. These SMPs have a huge number of segments and their thermomechanical behaviors are determined by heating history and cooperative relaxations (e.g., relaxation of all segments occurs simultaneously). In this study, a one-dimensional coupling model was proposed to investigate the cooperative dynamics of multiple glass transitions and thermomechanical behaviors of the SMPs. The overall relaxation behaviors of different tangled segments in the SMPs were formulated based on the Boltzmann’s superposition principle by coupling the highest transition temperature (Tmax) and initial transition temperature (Tmin) of all segments. Dependences of thermomechanical properties and relaxation strains upon the parameters of Tmax, Tmin, relaxation time and heating rate were theoretically investigated. Multiple glass transitions, thermomechanical and shape memory behaviors of the SMPs have been well described using this newly proposed coupling model. Finally, the simulation results were compared with the experimental data, and good agreements between them were obtained.Graphical abstractA new coupling model was proposed to explore the working mechanism of multiple glass transitions and structural relaxations in the SMPs with multi-SMEImage 1020
  • Development of Poly (vinylidene fluoride) and Polyaniline blend with high
           dielectric permittivity, excellent electromagnetic shielding effectiveness
           and Ultra low optical energy band gap: Effect of ionic liquid and
    • Abstract: Publication date: 24 October 2019Source: Polymer, Volume 181Author(s): D. Meher, Suman, N. Karna, B.P. SahooElectrically conductive polymer blends have attracted profound attention as dielectric materials. However, achieving isotropic behavior, electrical stability and low current leakage is still challenging. Here we have synthesized a conductive polymer blend of Polyaniline (PANI) and Poly (vinylidene fluoride) (PVDF) exhibiting relatively high dielectric permittivity (εʹ) together with low band gap. Ionic liquid (IL) has been incorporated and the effect of IL in the dielectric properties are explored. The interfacial adhesion, morphology and the dielectric polarization of the blends are investigated. The electromagnetic shielding effectiveness (EMISE) of the conductive blends is studied in X-band frequency range. The electrical stability and decrease in current loss of the blends has been analyzed through I–V characteristics. The findings reveal that with increase in PANI loading in the temperature range of 25–100 °C and IL incorporation results in excellent dielectric properties for charge storage applications. The high efficiency of absorption and low transmission of electromagnetic radiation by the conductive blends is the main reason for excellent EMISE possessed by the systems which can be used for shielding applications in electronics. The increase in electrical stability and decrease in current leakage ability appear in the form of narrow band gap.Graphical abstractImage 10361
  • Crystal morphology and corresponding physical properties of nascent
           ultra-high molecular weight polyethylene powder with short-branched chains
    • Abstract: Publication date: 24 October 2019Source: Polymer, Volume 181Author(s): Zhi Li, Chunlin Ye, Lingying Feng, Jincheng Xia, Letian Zhang, Wenjing Zhao, Yilun HuDue to the linear and ultra-long molecular chains, ultra-high molecular weight polyethylene (UHMWPE) has been playing a vital role in many fields. Based on more and more demands for special UHMWPE resins, the relationship between microstructure of nascent powder and its corresponding physical properties was investigated in this work, and one special powder with high degree of short-chain branch was fully contrasted with one general-purpose UHMWPE resin. Based on series characterization results, it revealed that short-branched chains led to a decrease on the entanglement density and brought a significant increase in the processing performance and mechanical properties. In addition, the short-branched chains also made a huge difference on crystal morphology of nascent UHMWPE powders. By correlating high-resolution scanning electron microscopy, DSC curves and Raman spectroscopy characteristics, the slurry polymerization mechanism of UHMWPE was deduced, and the corresponding performance of nascent UHMWPE powders was fully explained.Graphical abstractImage 10674
  • Does the nature of chemically grafted polymer onto PVDF decide the extent
           of electroactive β-polymorph'
    • Abstract: Publication date: 24 October 2019Source: Polymer, Volume 181Author(s): Amanuel Gebrekrstos, Goutam Prasanna Kar, Giridhar Madras, Ashok Misra, Suryasarathi BosePVDF, one of the most versatile fluoropolymers, is inert and is difficult to functionalize using conventional approaches. Herein, we attempted a facile and one-pot modification of PVDF via ozonization process. The ozone treated PVDF facilitates in harnessing suitable functional moieties. Using this strategy, two copolymers were designed to achieve crystalline-amorphous and crystalline-crystalline grafts. Their effects on phase transformation, dielectric and piezoelectric behaviors of PVDF were systematically investigated. The microstructure and phase transformation of this modified PVDF copolymer was characterized by XPS, XRD, FTIR, SAXS, and DSC. FTIR results revealed that the extent of polar β phase increased from 38% in untreated PVDF to 84% after ozonization. Interestingly, the enhancement is more pronounced after grafting. For instance, after grafting a crystalline polymer, poly (butylene succinate-co-adipate) (PBSA) onto PVDF near-complete transformation from α to β phase (96%) was observed. This was attributed to the specific covalent interaction between the –OH group in PVDF-OH and –COOH groups of PBSA. This strong covalent interaction helps to align the PVDF chains in trans conformation and as a result more β phase crystals are formed. The long period (Lw) calculated from SAXS for an amorphous graft as in PVDF-g-poly(methyl methacrylate-co-acrylic acid) (PMM-co-AA) and PVDF-g-PBSA decreased significantly as compared to neat PVDF. The remarkably enhanced β phase in the grafted polymers reflected in higher dielectric constant and piezoelectric coefficient (d33) as compared to untreated PVDF. For instance, the PVDF-g-PBSA copolymer showed higher piezoelectric and dielectric constant with low dielectric loss as compared to untreated PVDF. This study attempts to address whether the nature of graft (crystalline vs amorphous) decides the extent of β-PVDF and piezoelectric properties in PVDF copolymers.Graphical abstractImage 1069
  • Immobilized ionic liquid induced electroactive β-phase in
           poly(vinylidene fluoride) thin films
    • Abstract: Publication date: Available online 6 September 2019Source: PolymerAuthor(s): Shumin Yang, Fang Wang, Xiaohui Li, Yangjiang Wu, Tongxin Chang, Zhijun Hu, Gangli AnFerroelectric poly(vinylidene fluoride) (PVDF) has been proposed in the past decades as an electroactive material for various applications in microelectronic devices due to its ferro/piezo/pyroelectric properties. However, fabrication of smooth PVDF thin films with a high content of β-phase and controlled chain orientation is a long-standing problem. Here we report on the control over polymorphs of PVDF thin films by exploring the interfacial ion-dipolar interactions. The ion-dipolar interactions are provided by CF2 bonds of PVDF and imidazolium type ionic liquid immobilized onto substrates via biomimetic catecholic attachment chemistry. By simply melt crystallization of spin-coated PVDF thin films at elevated temperatures, the ferroelectric polar β-phase with a lying-down chain orientation is formed. The thin films exhibit excellent ferro/piezoelectric properties when applying electric field due to the immobilization of ionic liquids. The results may boost the applications of PVDF in microelectronic devices.Graphical abstractImage 1
  • Radiation induced modified CMC-based hydrogel with enhanced reusability
           for heavy metal ions adsorption
    • Abstract: Publication date: Available online 6 September 2019Source: PolymerAuthor(s): Tran Thu Hong, Hirotaka Okabe, Yoshiki Hidaka, Brian A. Omoldi, Kazuhiro HaraThe study attempted solving hazardous heavy-metal problems by creating a new eco-friendly functional hydrogel adsorbent (CSB-hydrogel). By utilizing γ-irradiation induced grafting and co-polymerization, the CSB-hydrogels were synthesized from a main bio-polymer {Sodium Carboxymethyl Cellulose (CMC)} and two active vinyl monomers {Sodium Styrene Sulfonate (SSS) and Bis[2-(Methacryloyloxy)Ethyl] Phosphate (BMEP)}. As well as the compression moduli, the CSB-hydrogels showed significant difference in the swelling capacities with the variety of BMEP-amounts.The author then examined the CSB-hydrogels’ multi-metal-ion adsorption capacities by performing the ion-capturing experiments with a varying species mixture solution and by utilizing ICP-MS analysis technique. The CSB-hydrogels demonstrated their highly-efficient recovery functionalities for most of the metal ions in the solution; especially, higher than 70% for nickel. Moreover, the CSB-hydrogels showed sufficient performance after 4-time repetitive adsorption-desorption treatments. With the high heavy-metal capturing-efficiency and the re-usability, the CSB-hydrogels were revealed to have a high potential as a new eco-friendly environment-purifying material.Graphical abstractImage 1
  • Facile fabrication, mechanical property and flame retardancy of aerogel
           composites based on alginate and melamine-formaldehyde
    • Abstract: Publication date: Available online 6 September 2019Source: PolymerAuthor(s): Xin-Lei Li, Yan-Rong He, Zi-Ming Qin, Ming-Jun Chen, Hong-Bing ChenAerogel composites based on melamine-formaldehyde (MF) and alginate (A) was fabricated with ice-templated method. The preparation process involves two cross-linking processes, in aerogel precursor at room temperature and in dried aerogel at 80 °C (100% humidity), respectively. Cross-linking was demonstrated to be very efficient for improving the mechanical property and water resistance of MF-A aerogels. The obtained aerogels have compressive moduli ranging from 1.2 MPa to 24.1 MPa. All the cross-linked aerogels display good dimensional stability when soaked in water. The morphological study of MF-A aerogels show a layered or network microstructure, with a homogeneous distribution of MF spheres. Due to low density and porous structure, MF-A aerogels have low thermal conductivity from 0.035 to 0.047 W/m K. MF-A aerogels have good thermal stability and extremely low flammability, with LOI value up to 41%. This novel aerogel from partially bio-based raw material would have promising application prospects.Graphical abstractImage 10735
  • Crack Propagation Resistance of Slide-Ring Gels
    • Abstract: Publication date: Available online 6 September 2019Source: PolymerAuthor(s): Chang Liu, Hirokazu Kadono, Koichi Mayumi, Hideaki Yokoyama, Kohzo ItoThe crack propagation behavior of pre-cut slide-ring (SR) gels with movable cross-links is investigated and compared to that of fixed cross-link (FC) gels under uniaxial stretching at a constant speed. Two fracture stages with 20-fold difference in crack velocity are observed for both SR and FC gels. At the beginning, the crack propagates slowly, and the crack propagation resistance is in good accordance with the evaluation based on tearing modulus Tr, the initial slope of J-integral – crack tip opening displacement (CTOD) curve. Higher Tr and slower crack velocity are observed in SR gels compared to FC gels with similar modulus. Moreover, Tr decreases and crack velocity increases with increasing modulus (cross-linking density) for FC gels, whilst both parameters are modulus-independent for SR gels. This means that the slow mode crack propagation resistance of SR gels is dominated by the sliding movement of cross-links instead of cross-linking density. However, as the strain energy input exceeds a critical value, crack accelerates abruptly and overtakes the sliding dynamics of the cross-links, thus the fracture behavior of SR gels resembles that of FC gels. Our results have revealed the strong correlation between the cross-links mobility and crack propagation resistance of SR gels.Graphical abstractImage 10330
  • Direct visualization of the molecular orientation and microstructure of
           glassy transparent polymers after the scratch test based on optical
           microscopy and X-ray scattering
    • Abstract: Publication date: Available online 6 September 2019Source: PolymerAuthor(s): Ken Kojio, Tomoko Kajiwara, Saburo Yamamoto, Aya Fujimoto, Kento Fukada, Chigusa Nagano, Shiori Masuda, Chao-Hung Cheng, Shuhei Nozaki, Kazutaka Kamitani, Atsushi TakaharaThe scratch test was conducted for polycarbonate (PC) and poly(methyl methacrylate) (PMMA) with a load-progressive mode. Changes in the molecular aggregation structure of PC and PMMA induced by the scratch test were investigated based on polarized optical microscopic observation and small-angle X-ray scattering (SAXS) measurement. The scratching coefficient of friction (SCOF), the ratio of tangential load to normal load, of PC was much larger than that of PMMA. The width and depth of the damage on the scratch path was increased monotonically with the increase in the normal load. Hardness obtained by nanoindentation and microindentation tests were similar to those with SCOF, indicating that compression resistance mainly governs the scratch properties. The polarized optical microscopic images revealed that molecules were oriented from the edge to the center of the scratch path at a certain acute angle for both PC and PMMA. SAXS measurement revealed that microfibrils were formed along the direction of stress for PC.Graphical abstractImage 1
  • Simple Model to Predict the Effect of Take-up Pressure on Fibre Diameter
           of PET Melt Spinning
    • Abstract: Publication date: Available online 5 September 2019Source: PolymerAuthor(s): Yijing Qin, Dirk W. SchubertA simplified mathematical model was given based on the actual experimental data from a laboratory-scale poly (ethylene terephthalate) (PET) melt spinning. PET fibres were produced using three virgin and two recycled PET materials at two different processing temperatures of 270 °C and 280 °C. Filament emerging from a spinneret was drawn by high-velocity air moving through an aspirator, where six take-up pressures were used. It was proved that the model with only two adjustable parameters could effectively predict the variation of PET fibre diameter as a function of take-up pressure, and one of the parameters could be estimated using the zero shear viscosity of materials.Graphical abstractImage 105
  • Fine tuning of polymer content for enhanced structure and luminescent
           properties of Eu3+:siloxane–poly(methyl methacrylate) hybrids to be
           applied in photonics
    • Abstract: Publication date: Available online 5 September 2019Source: PolymerAuthor(s): Filipe Augusto de Jesus, Barbara Vasconcelos Santana, Giordano Frederico Cunha Bispo, Cícero Inácio da Silva Filho, Severino Alves Júnior, Mário Ernesto Giroldo Valerio, José Maurício Almeida Caiut, Victor Hugo Vitorino SarmentoThe increasing demand for multifunctional materials for use in several application fields has been encouraging research into luminescent hybrid materials. These have the advantage of combining features of both organic and inorganic matter, which can be tailored to enhance emission conditions. This work aims to elucidate structural/luminescence relations of Eu3+:siloxane–poly(methyl methacrylate) hybrid materials. Polymer content was evaluated through characterization of samples with increasing polymer/Si molar ratios. Results showed that the sample with the highest amount of polymer in its composition, PMMA8, had optimized emission features on account of the larger number of carbonyl groups available for Eu3+ coordination. This enhancement is evidenced by the quantum efficiency (q) and lifetime (τexp) values, which were considerably higher (q  = 24.7% and τexp  = 0.62 ms) for PMMA8 hybrid than for the other samples. Thus, the hydrophobic polymer reduced the interaction of dopant ions to hydroxyl quenching groups and led to better dispersion, minimizing ion–ion energy transfer.Graphical abstractImage 1
  • Fully bio-based polymer blend of polyamide 11 and Poly(vinylcatechol)
           showing thermodynamic miscibility and excellent engineering properties
    • Abstract: Publication date: Available online 5 September 2019Source: PolymerAuthor(s): Takayuki Hirai, Jumpei Kawada, Mamiko Narita, Taiji Ikawa, Hisaaki Takeshima, Kotaro Satoh, Masami KamigaitoFully bio-based polyamide 11 (PA11) and poly(vinylcatechol) (PVCa) blends prepared by melt mixing demonstrate thermodynamic miscibility and excellent engineering properties. The glass transition temperature (Tg) of PA11 increases upon blending with PVCa; an 85/15 wt% PA11/PVCa blend exhibits a Tg 23–26 °C higher than that of PA11 devoid of additives. Morphological observations revealed that the PA11/PVCa blends do not phase-separate, confirming the homogeneity of PA11 and PVCa. Good chemical resistance of the PA11/PVCa blends was confirmed, with the blends resisting morphological changes even after immersion in methanol, which is a good solvent for PVCa. Tensile testing revealed that the PA11/PVCa blends have higher moduli and strengths than PA11. A PA11/nonpolar polystyrene blend was also examined by the same experimental procedure, which revealed that strong hydrogen bonding between PA11 and PVCa is the primary reason for the miscibility and excellent performance of PA11/PVCa blends.Graphical abstractImage 1
  • Parylene based thin-film microfluidic lens array fabricated by iCVD
           nano-adhesive bonding
    • Abstract: Publication date: 24 October 2019Source: Polymer, Volume 181Author(s): Sumin Seo, Jihye Kim, Yo-han Choi, Jae Bem You, Sung Gap Im, Wonhee LeeMicrofluidic lenses that have been fabricated using PDMS have serious limitations due to the high gas permeability of the material, which leads to evaporation of the filling liquid and air bubble formation. We report a fast and reliable method of fabricating flexible, thin-film parylene microfluidic devices, and their application in tunable microfluidic lens arrays. A parylene microfluidic lens was built by molding and bonding 1.4-μm-thick parylene layers using nano-adhesivelayers deposited by initiated chemical vapor deposition (iCVD). The focal length of the lens could be tuned by changing the radius of curvature of the lens and/or changing the refractive indices of the filling liquids. The parylene microfluidic lens showed a large range of focal length tuning, and high reproducibility over hundreds of cycles.Graphical abstractImage 1
  • Highly bluish-white light emissive and redox active conjugated
    • Abstract: Publication date: 24 October 2019Source: Polymer, Volume 181Author(s): K. Rohini Das, M. Jinish Antony, Shinto VargheseAn efficient fluorescent and redox type conjugated poly-N-phenyl anthranilic acid (PNPA) was synthesised via chemical oxidative polymerisation of N-phenyl anthranilic acid (NPA) using FeCl3 as oxidising agent in ethanol medium. The polymer in sulphuric acid solution denoted as PNPA-H have highly intense bluish-white fluorescence. The intense bluish-white light emission of polymer was quenched upon the addition of oxidising analytes like Ce4+, MnO4− and Cr2O72- ions. The fluorescence quenching concentration at which the above three analytes oxidises the polymer were determined from three independent methods like naked eye fluorescence detection, UV–visible spectroscopy and spectrofluorometry. The mechanism of fluorescence quenching has been explained on the basis of the oxidation of diphenyl benzidine dicarboxylic acid repeating units of PNPA-H (in reduced form) into non-fluorescent diphenyl diquinoid dicarboxylic acid units (in oxidised form) by the oxidising analytes. The mole ratio plot of [analyte]/[polymer] against fluorescence intensity have revealed different stoichiometry for a particular analyte leading to quenching of fluorescence of polymer, which have striking influence on the redox potential of the analytes. The limit of detection (LOD) for naked eye fluorescence quenching was found to be 0.5 μM, 0.75 μM, and 25 μM for Ce4+, MnO4− and Cr2O72- respectively and sensitivity of quenching action was obtained highest for MnO4− ions and least for Cr2O72- ions from stern-volmer plots. The oxidised and non-fluorescent diphenyl diquinoid dicarboxylic acid units of PNPA-H have been reduced back to fluorescent diphenyl benzidine dicarboxylic units with reducing biomolecules like ascorbic acid, which indicate the redox reversibility of the system.Graphical abstractImage 1
  • Polyurea-acrylic hybrid emulsions: Characterization and film properties
    • Abstract: Publication date: 24 October 2019Source: Polymer, Volume 181Author(s): Ian Drake, Gregoire Cardoen, Andrew Hughes, Alan I. Nakatani, Brian Landes, John Reffner, Ralph EvenA polyurea macromer (PUM) nanodispersion acted as a reservoir of stabilizing agent for a thermally initiated acrylic emulsion polymerization process to form binders characterized by a highly phase separated core-shell morphology. The synthesized binders (referred to as PUM-Binders) exhibited distinct dried film mechanical properties that were tied to both the state of hydration and morphology. Films from PUM-Binders exhibited higher König hardness and storage modulus when compared to films from blends of traditional acrylic latex with PUM nanodispersion at the same PUM level. König hardness and modulus increased with increasing levels of PUM for both approaches, however the closed cell foam morphology of the PUM-binder films exhibited optimal hardness and modulus retention. A separate set of PUM-Binders was prepared with varying levels of butyl acrylate (BA) and methyl methacrylate (MMA). Mechanical properties of the resulting transparent films were evaluated by dynamic mechanical analysis (DMA) and by tensile strength measurements. It was found that both tensile strength and elongation decreased with increasing BA. Increasing levels of BA were hypothesized to lead to higher degrees of phase separation between PUM and acrylic. Finally, a specific PUM/acrylic blend zone in the shell is assigned and attributed to the property differences observed.Graphical abstractImage 1
  • Achieving high thermal conductivity and mechanical reinforcement in
           ultrahigh molecular weight polyethylene bulk material
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Yan-Fei Huang, Zhi-Guo Wang, Wan-Cheng Yu, Yue Ren, Jun Lei, Jia-Zhuang Xu, Zhong-Ming LiExploring pure polymers with high thermal conductivity (TC) is promising to overcome the side effect of conventional thermally conductive polymer-based composites. However, the geometrical shape of high TC polymers was limited to the fibers and/or thin films. Here, we employed a home-made solid-state extrusion (SPE) apparatus to prepare a bulk material of ultrahigh molecular weight polyethylene (UHMWPE) with high TC. The in-plane TC reached 3.30 W/mK, which was 588% higher than that of the high-pressure (HP) molded counterpart (0.48 W/mK). Moreover, the TC of SPE UHMWPE showed an anisotropic ratio as high as 750%, which favored the heat dissipation along the in-plane direction as revealed by infrared thermal imaging. The increased and highly anisotropic TC was attributed to the formation of cylindrical crystals, highly oriented lamellae, as well as the monoclinic form of UHMWPE generated during SPE processing. Benefiting from this unique architecture, the mechanical performance was also greatly intensified, where the ultimate tensile strength increased from 41.6 MPa for HP UHMWPE to 107.7 MPa for SPE UHMWPE. The current study opens up a new pathway to fabricate bulk polymers with simultaneous enhancement of thermal conductivity and mechanical performance, which has great potential for the applications in thermal management fields.Graphical abstractA highly thermal conductive and anisotropic UHMWPE bulk material was prepared by solid phase extrusion.Image 1
  • Further investigation of the relationship between polymer structure and
           HDPE post yield properties
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Jeff S. Fodor, Paul J. DesLauriers, Mark J. Lamborn, Salah U. HamimUsing typical characterization methods (hyphenated chromatography and calorimetry), the effects of molecular weight and short chain branching (SCB) on relative rates of crystallization and the resulting effects on the post yield tensile properties were quantified for a robust set of high-density polyethylene samples. A semi-empirical chain folding equation coupled with the new structure parameters PSP4 (tie molecule content) and the average number of lamella segments per chain (ALSC) were proposed. These parameters are based on a random polymer walk, including passes through the crystalline lamella, the number of times a chain folds in each lamella and the subsequent effects on the end to end distance of the polymer chain, . Intuitively, the current approach is expected to yield enhanced correlations to mechanical performance since, in addition to maintaining the improvements in lamella size calculation, persistence length dependence on SCB content, and multi-ties per chain, it also accounts for polymer chain folding and lamella orientation. Results showed that homopolymers had a significantly higher level of chain folding compared to copolymers. Moreover, as the length of the SCB increased from ethyl to butyl, less folding was predicted thereby leaving more of the polymer chain to form tie molecules. The quantity PSP43/ALSC, exhibited a linear relationship with strain hardening modulus (SHM) with excellent correlation for a diverse set of unimodal and bimodal resins made using different catalyst systems, which included homopolymers, copolymers, and blends of different catalyst type and modality. Given the simplicity of calculation, use of actual polymer data, and the good predictability offered for SHM for a diverse set of resins, these primary structure parameters (PSP4 and ALSC) have high potential to contribute to the in-depth understanding of polymer structure-property relationships.Graphical abstractLeft side: New property structure parameter developed to include effect of chain folding. Chains modeled as a two step random walk. Right side: Correlation of the new parameters to strain hardening modulus for a diverse set of resins.Image 1075
  • A simple and convenient route to synthesize novel hyperbranched Poly(amine
           ester) with multicolored fluorescence
    • Abstract: Publication date: Available online 4 September 2019Source: PolymerAuthor(s): Yuqun Du, Tian Bai, Hongxia Yan, Yan Zhao, Weixu Feng, Wanqing LiMulticolored fluorescence stemed from the nonconventional luminescent polymers without aromatic units is an interesting and meaningful property. So far, a few such polymers bearing multicolored fluorescence are reported; its species, however, are relatively little. Herein, we synthesized a kind of novel water-soluble hyperbranched poly(amine ester) (HPAE) via a straightforward transesterification polycondensation reaction using inexpensive and easily available chemicals. Intriguingly, the pure HPAE could emit blue, green and red luminescence when irradiated by different excitation wavelengths. The TEM result shows that the synergy effect of intra-/intermolecular hydrogen bonds and hydrophobic effect could induce the HPAE to self-assemble and form supramolecular HPAE in water. Such supramolecular HPAE further promote to form stronger through-space conjugation, thus which is favourable for the emission. In addition, the significant solvent and pH dependence profiles of luminescence intensity are also observed. In particular, the HPAE can be used to detect metal ions, and there is strong selective quenching in respect of Fe3+. Therefore, the HPAE show a potential probe for Fe3+.Graphical abstractImage 1
  • Elevation of the flow temperature of gels formed by nano fibers of
           Poly(L-lactic acid) by surface crystallization induced by block copolymers
    • Abstract: Publication date: Available online 3 September 2019Source: PolymerAuthor(s): Yasuhiro Matsuda, Takahiro Fukui, Shun-ich Ishima, Atsushi Takahara, Shigeru TasakaBlock copolymers of poly(l-lactic acid) (PLLA) and polystyrene with different lengths of PLLA blocks entered into the network structures of PLLA gels formed with complex crystals with solvent molecules. The induced changes of the structure and the flow temperature of the gels were investigated to elucidate the mechanism of the block copolymers to elevate the flow temperature. The block copolymer with shorter PLLA blocks elevated the flow temperature of the PLLA gels from 40 °C to 70 °C by immersing in the block copolymer solution with a lower concentration (0.5 wt%). For the block copolymers with longer PLLA blocks, higher concentrations (2.0 wt%) were necessary to elevate the flow temperature to 70 °C, and the flow temperature was elevated to 80 °C by immersing more concentrated solutions (3.0 wt%). This behavior can be explained by assuming that the surface crystallization of PLLA fibers induced by the block copolymers elevated the flow temperature to 70 °C, and the reinforcement of the fibers by spherical structure of the block copolymers elevated the flow temperature to 80 °C, was proposed based on the experimental results.Graphical abstractImage 1
  • Carbazolevinylene and phenylenevinylene polymers by ring-opening
           metathesis polymerization and their characterization, nanoaggregates and
           optical and electrochemical properties
    • Abstract: Publication date: Available online 3 September 2019Source: PolymerAuthor(s): Ching-Ju Liu, Chao-Chi Wang, Dong-Lin Kuo, Chin-Yang YuHomopolymers and random and block copolymers containing carbazolevinylenes and phenylenevinylenes were synthesized by ring-opening metathesis polymerization of the ring-strained monomers such as carbazolephanedienes and cyclophanedienes in the presence of the third generation Grubbs’ initiator. The different molar ratios of the individual blocks were prepared by simply altering the monomer to initiator ratio. The polydispersity index of the block copolymers was relatively low and was in a range of 1.25–1.35. The absorption band of the copolymers with three different ratios of the individual block mainly exhibited a combination of the absorption band of the two individual homopolymers. The energy transfer of the block polymers from carbazolevinylenes to phenylenevinylenes is more effective in solid state than in solution. The emission color of the block copolymer solution can be changed from blue to yellow depending on the volume ratio of the mixture of THF and methanol. The carbazolevinylene and phenylenevinylene block polymers with a molar ratio of 40:51 exhibited unique network-like aggregates containing several spherical nanoparticles with the average diameter of 38 nm.Graphical abstractHomopolymers and random and block copolymers containing carbazolevinylenes and phenylenevinylenes were synthesized by ring-opening metathesis polymerization. The absorption band of the copolymers with three different ratios of the individual block mainly exhibited a combination of the absorption band of the two individual homopolymers. The emission color of the block copolymer solution changed from blue to yellow depending on the volume ratio of the mixture of THF and methanol. The carbazolevinylene and phenylenevinylene block polymers in a molar ratio of 40:51 exhibited unique network-like aggregates containing several spherical nanoparticles with the average diameter of 38 nm.Image 1
  • Corrigendum to “Anti-colon cancer effect of matrix protein gene therapy
           with nanoparticles” [Polymer 170 (2019) 148–156]
    • Abstract: Publication date: Available online 30 August 2019Source: PolymerAuthor(s): Bilan Wang, Daoke Yang, Yangmei Shen
  • The effects of staged mixing on the dispersion of reinforcing fillers in
           elastomer compounds
    • Abstract: Publication date: Available online 30 August 2019Source: PolymerAuthor(s): Alex McGlasson, Kabir Rishi, Gregory Beaucage, Vishak Narayanan, Michael Chauby, Andrew Mulderig, Vikram Kuppa, Jan Ilavsky, Mindaugas RackaitisKinetically mixed reinforcing fillers are dispersed by accumulated strain. Processing conditions such as mixing geometry, intensity and the duration of mixing are key elements on controlling accumulated strain. A simple method to modify mechanical mixing is the mixing schedule which involves the timing of filler additions to a compound. For example, it is known that simultaneous addition of oil with filler is disadvantageous to dispersion, while the incorporation of oil after filler addition enhances dispersion. The simplest case of mixing schedule involves timed filler additions into an elastomer, for instance in a single stage or in two-stages. This study explores the effects of staged mixing on nanoscale dispersion based on a colloidal model. Dispersion is quantified using a pseudo-thermodynamic approach coupled with ultra-small angle x-ray scattering. It was found that single stage mixing yields optimal nano-dispersion for carbon-coated silica and carbon black in polybutadiene using an internal mixer.Graphical abstractImage 1
  • Large-scale molecular dynamics simulation of perfluorosulfonic acid
           membranes: Remapping coarse-grained to all-atomistic simulations
    • Abstract: Publication date: Available online 30 August 2019Source: PolymerAuthor(s): An-Tsung Kuo, Yusuke Miyazaki, Changwoon Jang, Tatsuya Miyajima, Shingo Urata, Steven O. Nielsen, Susumu Okazaki, Wataru ShinodaWe combined two reverse mapping methods, a predetermined fragment database and fragment rotation, to generate atomistic configurations from coarse-grained structures. The combined method together with molecular dynamics simulations was applied to simulate perfluorosulfonic acid (PFSA) membranes with large length scales and to explore the origin of fracture under a uniaxial tensile loading. Through the analysis of voids in the deformed membrane, we found that void growth with tensile loading takes place at the boundary of the hydrophobic and hydrophilic regions, which may be the origin of the fracture in the PFSA membrane. This study demonstrates an efficient reverse mapping method, which is useful for simulating proton exchange membranes with realistic chain lengths.Graphical abstractImage 1
  • Stable-jet length controlling electrospun fiber radius: Model and
    • Abstract: Publication date: Available online 29 August 2019Source: PolymerAuthor(s): Sailing Lei, Zhenzhen Quan, Hongnan Zhang, Xiaohong Qin, Rongwu Wang, Jianyong YuGenerally, the precise prediction and control on the radius of electrospun polymer fibers is critical for their applications but still remains challenging. In the current work, a model has been established to predict the radius. It is shown that the correlation between the stable-jet length and the terminal fiber radius satisfies a scaling law with a power exponent −2/3 for fully charged fibers, while the exponent becomes smaller for the case in which the fibers are partly charged on surface during electrospinning. And a good agreement between the experimental and theoretical values for electrospinning poly(methyl methacrylate) (PMMA) fibers is obtained, thus further verifying the correctness of derived model between the stable-jet length and the terminal fiber radius.Graphical abstractImage 1
  • Effect of thermo-oxidation on loss of plasticizers, on crystalline
           features and on properties in a metallocene isotactic polypropylene
    • Abstract: Publication date: Available online 27 August 2019Source: PolymerAuthor(s): Enrique Blázquez-Blázquez, Rosa Barranco-García, María L. Cerrada, Ernesto PérezIncorporation of a low content of several plasticizers into a metallocene isotactic polypropylene (iPP) has been performed in order to learn about their stability and performance by the action of a thermo-oxidative degradation treatment at 95 °C for different times. Comparison with the behavior exhibited by the material with di(2-ethylhexyl) phthalate (DEHP) is established for a feasible replacement of its use for contributing to environmental and human health preservation. Dependence of these aggressive degrading conditions on plasticizer loss is analyzed as well as elucidation of degradation influence on the iPP crystalline characteristics. The results show that chemical changes associated with this degradation process hinder formation of the orthorhombic γ crystalline lattice and postpone the overall crystallization capability. Accordingly, the final features in the film surface and the mechanical response are significantly affected by degradation time. The TOTM plasticizer can be considered an excellent candidate for DEHP substitution.Graphical abstractImage 1
  • Synergistic and antagonistic effect of chain lengths below and above
           critical value on polyelectrolyte complex
    • Abstract: Publication date: Available online 27 August 2019Source: PolymerAuthor(s): Dongxiao Yin, Wei Pan, Dehai LiangThe effects of chain length and polydispersity on polyelectrolyte complexes (PEC) have not been fully clarified. In this work, we chose oligonucleotide and oligolysine, both of which have uniform length, and studied the chain length effect on their complex by time-resolved laser light scattering and atomic force microscopy. Results show that the chain length of oligolysine has to reach a critical value for the occurrence of complexation with 21 bp oligonucleotides, suggesting that PEC is an all-or-non process. However, the oligolysine with the chain length below critical value still plays a role if it is mixed with other oligolysine whose chain length is above the critical value. If oligonucleotide is in excess, the combination of oligolysines with chain lengths below and above critical value exhibits synergistic effect to enhance the PEC formation, while they exhibit antagonistic effect to deteriorate the PEC formation if oligolysine is in excess. Our study not only gains insight in the mechanism of PEC by polydispersed samples, but also helps to design and fabricate complexes with desirable structure and kinetics by combining polyelectrolytes with different chain lengths.Graphical abstractImage 1
  • Hydroentangled polymer nonwovens: Prediction of jet streaks and surface
    • Abstract: Publication date: Available online 23 August 2019Source: PolymerAuthor(s): Gen Li, Abhilash Sankaran, Alexander L. Yarin, Behnam PourdeyhimiHere, the dynamic model of polymer fibers in hydroentanglement is used to predict the appearance of the so-called jet streaks and surface roughness. The mechanism of formation of jet streaks is explained. It is shown that the staggered two-row water jets which are widely used in industry help to optimize surface roughness and reduce the jet streaks. It is also shown that the jet width ratio plays an important role in minimizing the surface roughness at different jet pressures. Furthermore, a novel numerical method of re-construction of the 3-D surface topography from discrete data is developed to visualize the jet streaks. Also, in the experiments of this work, the optical images of jet streaks on hydroentangled polymer nonwovens are analyzed. The streaks period is measured by using the Fast Fourier Transform (FFT) and the surface topography is visualized by using optical profilometer. The predicted optimal jet width ratio is compared to the experimental results and a good agreement is found.Graphical abstractImage 1
  • Non-linear viscoelasticity of epoxy resins: Molecular simulation-based
           prediction and experimental validation
    • Abstract: Publication date: Available online 22 August 2019Source: PolymerAuthor(s): Robin Unger, Wibke Exner, Behrouz Arash, Raimund RolfesThe precise knowledge of the temperature-dependent non-linear viscoelastic material behaviour of polymers is of great importance for engineering applications. The present work is a contribution to meet the challenge of bridging the inherently different time scales of molecular dynamics (MD) and experiments by providing a consistent comparison and assessment of viscoelastic theories. For this reason, the physically motivated theories for viscoelasticity of Eyring and Argon as well as the Cooperative model are evaluated with regard to their predictive capability for the characterisation of the viscous behaviour over a broad range of temperatures and strain rates. MD simulations of tensile tests are performed and the effect of strain rate and temperature on the yield stress is examined. The distinctive feature of this study is to demonstrate that viscoelastic theories can be successfully calibrated using only MD results. For a comparison to experimental data, we conduct tensile tests at three different strain rates and at three temperatures in the glassy regime. Experimental validation confirms the predictive capability of the Argon model, which can provide an accurate formulation of epoxy viscoelasticity for physically motivated constitutive models. The present study not only underlines the ability of MD simulations for identifying and characterising physical phenomena on the molecular level, but also shows that molecular simulations can substitute experimental tests for the characterisation of the viscoelastic material behaviour of polymers.Graphical abstractImage 1
  • Correlation between enthalpy relaxation and mechanical response on
           physical aging of polycarbonate in relation to the effect of molecular
           weight on ductile-brittle transition
    • Abstract: Publication date: Available online 19 August 2019Source: PolymerAuthor(s): Akihiro Ohara, Hiroya KodamaA series of physical aging experiments at different annealing temperature and times was conducted on three kinds of polycarbonates (PCs) with different molecular weight using a differential scanning calorimetry and a tensile test. The enthalpy relaxation kinetics was well modeled by existing empirical equation using Kohlausch-Williams-Watts (KWW) function and effects of annealing temperature and times for the model parameters were clarified. A good correlation between the kinetics of enthalpy relaxation and that of yield stress was found. A dependence of the molecular weight on the physical aging kinetics could be attributed to its effect on the glass transition temperature.Graphical abstractImage 1
  • Construction of polydisperse polymer model and investigation of heat
           conduction: A molecular dynamics study of linear and branched
    • Abstract: Publication date: Available online 18 August 2019Source: PolymerAuthor(s): Yoshiaki Kawagoe, Donatas Surblys, Hiroki Matsubara, Gota Kikugawa, Taku OharaMolecular dynamics (MD) simulation is a powerful tool for investigating the molecular mechanism of heat conduction in polymers. However, existing MD studies are mostly on monodisperse polymers and the effect of polydispersity, which typically occurs in commercial polymers, remains to be clarified. In this work, various types of polydisperse polyethylenimine (PEI) composed of molecules having different molecular weights and branching structures were constructed by in silico step-growth polymerization. The effect of the polydispersity and molecular structure on heat conduction in PEI was investigated using all-atom MD simulations. The number and weight fraction distributions of the polydisperse pure-linear PEI agreed well with the Flory-Schulz distributions, and therefore it can be concluded that the in silico polymerization used in this work reasonably mimics the step-growth-like polymerization observed in the actual synthesis of PEI. Thermal conductivity increased with increase in the radius of gyration dependent on the degree of branching of the molecules. In addition, thermal conductivity of a polydisperse PEI exhibited a similar value to that of a monodisperse PEI of a representative polymer chain in the polydisperse system. By analyzing in detail the thermal energy transfer among and inside molecules, their microscopic mechanisms could be understood and it was discovered that the average molecular weight is a critical factor in determining heat conduction.Graphical abstractImage 1
  • Waterborne pH responsive hydrogels: Synthesis, characterization and
           selective pH responsive behavior around physiological pH
    • Abstract: Publication date: Available online 14 August 2019Source: PolymerAuthor(s): Mohd Avais, Subrata Chattopadhyay– pH responsive hydrogels, which selectively show highest swelling capacity around physiological pH (∼7.4) compared to both acidic and basic pH, are not known. In the current work, such hydrogels are prepared using one pot synthetic approach by reacting branched PEI with an azetidinium based crosslinker in water. Swelling capacity of the hydrogels are studied to understand the influence of crosslinking density and pH. The swelling capacity (SC) of the hydrogels increase with increasing crosslinking density as expected. Further swelling capacity shows an excellent pH responsive behavior which is selectively higher around physiological pH (∼7.4), when compared to pH 4, 7, 9.2 and 12. Selective swelling behavior around physiological pH also expected to influence the pH responsive drug release kinetics. To study that, drug encapsulated hydrogels are prepared and their release kinetics is studied as a function of pH. Both swelling capacity and drug release have shown very similar pH responsive trend and selectively higher drug release was observed around pH 7.4.Graphical abstractImage 1
  • Crack propagation under static and dynamic boundary conditions
    • Abstract: Publication date: Available online 14 July 2019Source: PolymerAuthor(s): Yuko Aoyanagi, Ko OkumuraVelocity jumps observed for crack propagation under a static boundary condition have been used as a controlling factor in developing tough rubbers. However, the static test requires many samples to detect the velocity jump. On the contrary, crack propagation performed under a dynamic boundary condition is timesaving and cost-effective in that it requires only a single sample to monitor the jump. In addition, recent experiments show that velocity jump occurs only in the dynamic test for certain materials, for which the velocity jump is hidden in the static test because of the effect of stress relaxation. Although the dynamic test is promising because of these advantages, the interrelation between the dynamic test and the more established static test has not been explored in the literature. Here, by using two simulation models, we elucidate this interrelation and clarify a universal condition for obtaining the same results from the two tests, which will be useful for designing the dynamic test.Graphical abstractImage 1
  • Mass spectrometry of polyurethanes
    • Abstract: Publication date: Available online 2 July 2019Source: PolymerAuthor(s): Tiffany M. Crescentini, Jody C. May, John A. McLean, David M. HerculesThis review covers the applications of mass spectrometry (MS) and its hyphenated techniques to characterize polyurethane (PU) synthetic polymers and their respective hard and soft segments. PUs are commonly composed of hard segments including methylene bisphenyl diisocyanate (MDI) and toluene diisocyanate (TDI), and soft segments including polyester and polyether polyols. This literature review highlights MS techniques such as electrospray ionization (ESI), matrix assisted laser/desorption ionization (MALDI), ion mobility-mass spectrometry (IM-MS), and computational methods that have been used for the characterization of this polymer system. Here we review specific case studies where MS techniques have elucidated unique features pertaining to the makeup and structural integrity of complex PU materials and PU precursors.Graphical abstractImage 1081
  • High refractive index polythiourethane networks with high mechanical
           property via thiol-isocyanate click reaction
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Yaya Jia, Bingjie Shi, Junsu Jin, Jichao LiHigh refractive index polymers (HRIPs), especially sulfur-containing HRIPs, play an important role in optical materials; particularly the thermosetting sulfur-containing polyurethane is widely used in optical lenses. To understand the effect of thiol and isocyanate structures on thermosetting polythiourethane properties, a comprehensive study of the basic thermal, optical and mechanical properties of the obtained polythiourethane network structure was conducted, which results indicated that in addition to functionality and the presence of rigid groups affect the glass transition temperature, the conjugation effect and steric hindrance effect in the structure can also cause more changes in the glass transition temperature. All polythiourethane materials formed uniform and densely crosslinked network structures. Due to the introduction of highly polarizable sulfur atoms in 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol (GST) and benzene rings in bis(isocyanatomethyl)benzene (XDI), the resulting polythiourethanes exhibited a high refractive index of 1.6559 (589 nm) and a tensile strength of 95.64 MPa while the Abbe's number was 33.24, fully meeting the lens requirements. The important structure-property relationships of polythiourethane will be helpful for the rational design of HRIPs.Graphical abstractImage 1
  • Fabrication of a new PVDF/SbSI nanowire composite for smart wearable
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Marcin Jesionek, Bartłomiej Toroń, Piotr Szperlich, Włodzimierz Biniaś, Dorota Biniaś, Stanisław Rabiej, Anna Starczewska, Marian Nowak, Mirosława Kępińska, Jan DecIn this paper, a new fabrication method for Polyvinylidene fluoride/SbSI nanowire composite is presented. Polyvinylidene fluoride (PVDF) is a specialist thermoplastic fluoropolymer with very good mechanical, chemical and thermal properties. Additionally, PVDF shows piezoelectric, pyroelectric, and ferroelectric properties. Antimony sulfoiodide (SbSI) nanowires (lateral dimensions of 10 nm–100 nm and lengths up to a few micrometres) are also piezoelectric compound with one of the best electromechanical and piezoelectric coefficient (k33 = 0.9 and dV = 0.9 × 10−9 C/N). SbSI nanowires have been added to improve piezoelectric properties of PVDF. The prepared SbSI nanowires were bound with PVDF in a mass ratio of 15:85, which was the fibre formation input with the addition of SbSI nanowires at different take-up velocities. An active layer of nanogenerator was prepared from the fabricated PVDF/SbSI nanowire composite. The preliminary investigations of compression and vibrations, allowed for the determination of the composites open circuit voltage 1.2 Vp-p and 2.5 Vp-p, respectively. Generated powers under impact have reached values PS = 408.8(52) μW/cm2 and PV = 3.464(53) mW/cm3, respectively.Graphical abstractImage 1086258
  • Graphene and carbon nanotube reinforced epoxy nanocomposites: A review
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Navjot Pal Singh, V.K. Gupta, Amrinder Pal SinghThe continuous demand for low weight, economical and high strength materials have been the driving force for the search of new materials. The discovery of carbon nanofillers, viz. graphene (Ga) and carbon nanotubes (CNTs), has brought tremendous revolution in the field of epoxy-based nanocomposites. The extraordinary thermo-mechanical, electrical and flame-retardant properties offered by Ga and CNTs have led to the development of Ga/CNT-epoxy nanocomposites. The paper reviews the research conducted in the last ten years pertaining to the fabrication, characterization and applications of Ga/CNTs-epoxy composites. The major challenges faced by the researchers in developing epoxy nanocomposites for high performance applications are also highlighted. It is revealed by simultaneously reinforcing Ga and CNTs in epoxy, one could resolve major issues like poor dispersion and agglomeration of nanofillers in epoxy, which can help in developing ultra-high-performance nanocomposites. But further research is needed to explore the full potential of Ga/CNTs/epoxy hybrid nanocomposites.Graphical abstractImage 103
  • Intrinsic ambipolar transport for the traditional conducting or hole
           transport ionic blend polymer PEDOT:PSS
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Hai-Tong Cai, Hui Xu, Chao Tang, Jie Li, Zhi-Yao Yang, Shang-Hui Ye, Wei HuangIn traditional viewpoint, poly-3,4-ethylenedioxythiophene: polystyrenesulfonate (PEDOT:PSS) in solid state photoelectronic device is considered to be conducting or hole transporting polymer. So at the beginning, this work researched the conducting mechanism of PEDOT:PSS, which leads to that the PEDOT:PSS should not be good conductor. Then one simple model is used to theoretically analyse the carrier dynamics, and its results show that PEDOT:PSS should be ambipolar polymer in theory. Based on the theory, the hole- and electron-only diodes fabricated by PEDOT:PSS are investigated through the impedance spectroscopy method, and such experimental data fully proved the theoretical results. Besides the ambipolar characteristic, mobility verse E1/2 curves show the abnormal negative slopes, that hole and electron mobilities decrease with the increment of biased electric field, which is not in accordance with the common standpoint that the charge carrier should be accelerated by electric field. Thus such experimental data in further propel us to propose the concepts of HOMO trap and LUMO trap, which exists in the energy space of frontier orbital and decelerates the movement of charge carrier.Graphical abstractImage 1
  • l -lactide&rft.title=Polymer&rft.issn=0032-3861&">Benzannulated N-heterocyclic plumbylene: An efficient catalyst in ring
           opening polymerization of l -lactide
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Tzung-Han Lin, Gene-Hsiang Lee, Shie-Ming Peng, Ching-Wen Chiu, Hsuan-Ying ChenMain-group metal-based catalysts have attracted considerable attentions due to their complementary reactivities to transition metals. In searching for the catalytic application of heavy divalent Group 14 derivatives, we came to discover that the benzannulated N-heterocyclic plumbylene (1) could serve as an effective catalyst for ring-opening polymerization of l-lactide (L-LA) at room temperature. In the presence of benzyl alcohol (BnOH), 97% conversion of L-LA was accomplished in 10 min under a catalyst loading of merely 0.3 mol% ([LA]:[1]:[BnOH] = 400:1.2:1.2, [1] = 1.2 mM). Compared to the polymeric plumbylene ([Pb(μ-OiPr)2]∞), the excellent catalytic activity of 1 at ambient temperature may be ascribed to the steric and electronic stabilizations of the Pb2+ center by the organic backbone. Thus, thermal activation is no longer required to expose the Lewis acidic metal center for polymerization.Graphical abstractImage 1
  • Transform poly (lactic acid) packaging film from brittleness to toughness
           using traditional industrial equipments
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Cao Zengwen, Hongwei Pan, Yunjing chen, Junjia Bian, Lijing Han, Huiliang Zhang, Lisong Dong, Yuming YangIn order to produce the poly lactide (PLA) packaging film with excellent toughness, we adopted a new technological process: isothermal crystallization and then blowing film at the temperature lower than that completely melting of PLA crystals. The elongation at break of PLA film increased to around 67.50% and 104.83% in the transverse direction (TD) and machine direction (MD), respectively. Besides, the tensile strength increased to about 45.4 MPa and 78.0 MPa in TD and MD, respectively. The desirable balance between tension ductility and strength of film attributed to the introduced crystal-cross linked network. During blow molding, the crystallization fields and surrounding linked non-crystalline regions oriented and formed a network under the effect of inflating and pulling forces. The crystal network, bearing the external forces, induced the amorphous regions plastic deformation during stretching, and so improved the tension toughness and strength of PLA film.Graphical abstractImage 1
  • Highly interconnected macroporous structures made from starch
           nanoparticle-stabilized medium internal phase emulsion polymerization for
           use in cell culture
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Fatemeh Kavousi, Nasser NikfarjamA highly interconnected uniform pore structure was prepared through polymerization of medium internal phase Pickering emulsion, called polyMIPPE, are reported. Citric acid crosslinked starch nanoparticle (CSTN) with particle size of 50 nm, as an amphiphilic pH-sensitive particulate stabilizer, was used to prepare stable sunflower oil-in-water emulsions. The polyMIPPEs were obtained through the copolymerization of acrylamide (AM) with N,N′-methylenebisacrylamide (MBAA) in the continuous phase followed by extraction of internal phase. The effect of main parameters such as pH, CSTN and AM content on the size and size distribution of the emulsion droplets as well as the pore size and interconnectivity of the related polyMIPPEs were investigated. Results showed that the best interconnected pore structure (with a pore size of 6.2 μm, pore throat size of 2.0 μm, pore volume of 61% and porosity of 80%) was obtained for the sample included 0.7 wt% of CSTN, 3.75 M of AM, AM/MBAA molar ratio of 9.14 and oil volume fraction of 62.5%. It was concluded that the employed force caused by volume contraction during the polymerization is high enough to tear films between the pores to create large pore throats, namely higher interconnectivity. Preliminary cell culture and biocompatibility assessments with human neuroblastoma cells indicated that the prepared porous materials have no significant detrimental effect on cell adhesion. It is believed that these materials could be presented as a promising culture substrates for various biomedical applications.Graphical abstractImage 1
  • Microphase separation of poly(propylene monothiocarbonate)-b-poly(ethylene
           oxide) block copolymers induced by differential interactions with salt
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Xiao-Han Cao, Jia-Liang Yang, Rui-Yang Wang, Xing-Hong Zhang, Jun-Ting XuThis work describes the microphase separation behavior of poly(propylene monothiocarbonate)-b-poly(ethylene oxide) (PPMTC-b-PEO) block copolymers (BCPs), a type of new sulfur-containing block copolymer, induced by lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI). PPMTC-b-PEO BCPs with a fixed PEO block length but different PPMTC block lengths were synthesized and doped by LiTFSI. Temperature-variable small-angle X-ray scattering result indicates that microphase separation of the PPMTC-b-PEO BCPs can be induced by differential interactions with LiTFSI. However, the ability of LiTFSI to induce microphase separation in PPMTC-b-PEO BCPs does not monotonically increase with the doping ratio (r = [Li+]/([EO] + [PMTC])). It is observed that stronger microphase separation usually occurs at r = 1/12 and 1/6, but microphase separation is weaker at r = 1/24 and 1/3. In most cases, microphase-separated but disordered structures are obtained. Particularly, ordered lamellar structure is formed at suitable doping ratio and block composition. FTIR result confirms the differential complexation of LiTFSI with PEO and PPMTC. LiTFSI preferentially interacts with PEO at low rs, but also strongly interacts with PPMTC at high rs. This work provides a new method to prepare solid polymer electrolytes with double conductive nano-phases, which may be beneficial to both conducting and mechanical properties.Graphical abstractImage 1
  • l -malic+acid)&rft.title=Polymer&rft.issn=0032-3861&">Green and biomass-derived materials with controllable shape memory
           transition temperatures based on cross-linked Poly( l -malic acid)
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Yaxin Qiu, Qianru Wanyan, Wenyuan Xie, Zhifeng Wang, Ming Chen, Defeng WuAn interesting biomass-derived shape memory polymer (SMP) based on cross-linked poly(l-malic acid) (PMA), with reconfigurable permanent shape and tunable shape memory transition temperature (Ttrans), was developed in this work. The amorphous cross-linked network was constructed in PMA using eco-friendly 1,8-octanediol as the cross-linker through a catalyst-free two-step way. The relations between crosslinking density (d) and glass transition temperature (Tg), as well as the mechanical strengths of as-obtained cross-linked PMA (CPMA) were then evaluated. Both the strengths and the Ttrans are easily tunable by controlling curing times. Moreover, the permanent shape of CPMA is reconfigurable due to additional crosslinking in the heat treatment process. It also shows good diversity of processing approaches. This work is the first report to achieve good strengths on the biodegradable PMA and to activate its shape memory effect, opening up a window of application of PMA as the smart material or even as the common plastics.Graphical abstractImage 1
  • Influence of hydroxyl-terminated polybutadiene liquid on rheology of fumed
           silica filled cis-polybutadiene rubber
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Qingxu Zhang, Huilong Xu, Yihu Song, Qiang ZhengHydroxyl-terminated polybutadiene (HTPB) liquid is used to mediate the dispersity of fumed silica in cis-polybutadiene rubber (BR) to prepare nanocomposites. The introduction of HTPB promotes the dispersion of both hydrophilic and hydrophobic silicas (A200 and R974), which improves the reinforcement efficiency, delays the onset strain amplitude of nonlinear softening and enlarges the high-order harmonics in the nonlinearity region. Influence of HTPB on the linear and nonlinear rheological responses are well accounted for by data superposition on the basis of the rheological responses of the matrix. It is evidenced for the first time that the rheological nonlinearity may be enhanced in the case of improved filler dispersity. This is understandable taking the intrinsic nonlinearity of the matrix and the strain amplification effect induced by filler into consideration.Graphical abstractImage 10533
  • Bromine-functionalized poly(carbonate-co-lactide)s: Synthesis,
           characterization and post-polymerization functionalization
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Longfei Li, Hong Zhai, Tao Wang, Xibo Qiu, Na Qiang, Peng Dong, Ying Bai, Ai-Yun Peng, Daping QuanThe ring-opening copolymerization of lactide with carbonate is an available strategy to incorporate reactive groups to the pendent sites of copolymer for further functional modification. A series of random and block copolymers were synthesized from l-lactide (L-LA) and 2-bromomethyl-2-methyltrimethylene carbonate (BMTC) using dodecanol as initiator and stannous octoate as catalyst. The structures of the copolymers were characterized by nuclear magnetic resonance (1H NMR, 13C NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The composition of the copolymers can be controlled through changing the feed ratios of nBMTC/nL-LA. It was found the random P(BMTC-co-LLA) copolymers had the semicrystalline characteristic due to the relative long block-like segments of PLLA (LL, PLLA = 5.3–7.3) and the polar interactions from bromo groups, but their crystallinity (Xc, PLLA) and melting temperature (Tm, PLLA) decreased when the BMTC content increased. The Xc, PLLA and Tm, PLLA of P(BMTC-b-PLLA) block copolymers were relatively higher than the corresponding random copolymers, and approached gradually to the pure PLLA with the increase of the molecular weight of PLLA block. Finally, the pendent bromo groups of P(BMTC-co-LLA) were easily transformed into azides, which could proceed the azide-alkyne click reaction smoothly and quantitatively at room temperature.Graphical abstractImage 1
  • Hybrid and hollow Poly(N,N-dimethylaminoethyl methacrylate) nanogels as
           stimuli-responsive carriers for controlled release of doxorubicin
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Sakineh Hajebi, Amin Abdollahi, Hossein Roghani-Mamaqani, Mehdi Salami-KalajahiSmart drug-delivery systems based on stimuli-responsive polymers are extensively studied because of their advantages in controlled release of anti-cancer drugs in response to induced stimuli. To develop a smart drug-delivery system, silica nanoparticles modified with 3-(trimethoxysilyl) propyl methacrylate (MPS) were used in inverse emulsion polymerization of N,N-dimethylaminoethyl methacrylate with N,N-methylene bisacrylamide in different amounts (MBA: 2, 4, and 8 mol%). The temperature- and pH-responsive hybrid core-shell nanoparticles were used for preparation of hollow poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) nanogels by hydrolysis of the silica cores. Fourier-transform infrared spectroscopy was used to confirm the surface modification of silica nanoparticles with MPS. Successful synthesis of the hybrid and hollow nanogels was investigated by thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. In addition, temperature-responsivity and phase separation behavior of the hybrid and hollow nanogels were studied by UV/Vis spectroscopy. The UV/Vis spectra showed that the absorption intensity was increased with increasing MPS and MBA contents in basic conditions. The hollow nanogels showed higher swelling/deswelling ratio compared to the hybrid nanogels in acidic media (pH 3.5) and at temperatures above the volume phase transition temperature (70 °C). Some of the hybrid and hollow nanogels with different crosslinking densities were used as smart drug carriers for doxorubicin (DOX), and their release behavior were investigated at different pH (3.5 and 7.5) by UV/Vis spectroscopy. The release profiles display that release of DOX has increased in pH of 3.5, and the hollow nanogels showed lower release contents than the hybrid nanogels because of diffusion and encapsulation of DOX molecules in the hollow space. The experimental release profiles confirmed that DOX release percentage in the hybrid nanogels was more than the hollow ones, while loading capacity of the hollow nanogels was higher. The Korsmeyer-Peppas model showed the best fitting with the experimental results of DOX release from PDMAEMA carriers.Graphical abstractImage 1
  • Anisotropic photoconductivity of aromatic and semi-aliphatic polyimide
           films: Effects of charge transfer, molecular orientation, and polymer
           chain packing
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Chiaki Takemasa, Teppei Chino, Ryohei Ishige, Shinji AndoThe anisotropic photoconductive properties of polyimide (PI) films prepared using seven types of dianhydrides and a diamine containing a diphenyl-benzidine structure featuring rigid linear structure and strong electron-donating ability were analyzed. Photoirradiation wavelength dependences of the in-plane and out-of-plane photocurrents, which are known as anisotropic photocurrent spectra, were investigated in comparison with optical absorption spectra, the degrees of molecular aggregation, in-plane/out-of-plane orientation of PI chains, and ordered structures formed in film state. We have previously reported that intermolecular charge transfer (CT) interaction is a key factor for increasing the out-of-plane photoconductivity of PI films because they determine the efficiency of charge separation. However, when sufficient charge carriers are generated in thin PI films via photo irradiation, in which penetration depth of irradiated light is sufficiently larger than the film thickness, suppression of charge recombination by reducing molecular chain packing is rather effective at enhancing both the in-plane and out-of-plane photoconductivity. This is because the mobility of carriers is significantly increased in the dense aggregation structures, and thus collisions between carriers becomes more frequent, which led to higher recombination efficiency. Furthermore, the photocurrent anisotropy was increased as the degree of in-plane orientation of the main PI chains increased, which agrees with the fact that charged carriers are preferentially transported between PI chains. Accordingly, promoting charge transport efficiency by reducing PI chain packing and increasing the out-of-plane orientation of PI chains are essential to increase the in-plane photoconductivity of PI films.Graphical abstractImage 1
  • Composition-dependent multicomponent diffusivity of 2,5-lutidine with
           acetonitrile in polyurethane
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Mark J. Varady, Devon A. Boyne, Thomas P. Pearl, Robert H. Lambeth, Brent A. MantoothEvaluation and prediction of multicomponent diffusion in polymers is an important area of research since it occurs in several fields associated with mass transport including membrane separations, preparation of polymer films, and material decontamination. The functional dependence of the diffusivity on the composition in a multicomponent system is critical for accurately predicting transport in these processes. Here, the composition dependent diffusivity of 2,5-lutidine in polyurethane with acetonitrile as a co-penetrant was experimentally determined using Fourier transform infrared spectroscopy (FTIR) to acquire differential sorption curves for lutidine across the composition space and fitting a multicomponent diffusion model to the data. The free volume theory of diffusion was used to develop a mathematical expression for the composition-dependent diffusivity, and shows good agreement with the experimental data for both single and multicomponent cases. The lutidine diffusivity was found to vary up to two orders of magnitude with ACN concentration, and the importance of capturing this dependence quantitatively is highlighted by applying the multicomponent diffusion model with the best-fit values to predict previously published data for lutidine desorption from polyurethane.Graphical abstractImage 1
  • New zwitterionic polyurethanes containing pendant carboxyl-pyridinium with
           shape memory, shape reconfiguration, and self-healing properties
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Xuan Xiao, Heng Chen, Shaojun ChenIn this paper, novel zwitterionic polyurethane containing pendant carboxyl-pyridinium were successfully prepared with N,N-bis(2-hydroxyethyl) isonicotinamide (BINA) and hexamethylene diisocyanate (HDI), followed by zwitterionization with 4-bromobutyric acid. The structure, morphology and properties, including shape memory, shape reconfiguration and self-healing properties, were carefully investigated. The obtained results showed that introduction of zwitterionic units reduced glass transition temperature. The shape recovery increased with increasing carboxyl zwitterion content. Finally, good shape memory properties with 99% shape memory and 99% shape recovery was achieved. Additionally, the carboxyl-pyridinium zwitterionic polyurethane had good shape reconfiguration properties, and new permanent shapes could be reconfigured easily upon heating. Moreover, the carboxyl-pyridinium zwitterionic polyurethanes possessed moisture-induced self-healing properties, where its complex structure was self-repaired in a humidity-rich environment after inevitable damage. This study opens a new door to intelligent zwitterionic polymers, which is highly significance in the field of smart biomedical.Graphical abstractThis paper reports a novel zwitterionic polyurethane containing pendant carboxyl-pyridinium (CZPs). The shape recovery increased with increasing carboxyl zwitterion content. CZPs were reconfiguration at high temperatures, and new permanent shapes could be reconfigured easily upon heating. Moreover, CZPs possessed moisture-sensitive self-healing properties.Image 1
  • Wettability of graphene by molten polymers
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Maria Giovanna Pastore Carbone, Daniele Tammaro, Anastasios C. Manikas, George Paterakis, Ernesto Di Maio, Costas GaliotisGraphene wetting by polymers is a critical issue to both the success of polymer-aided transfer of large size sheets onto specific substrates and to the development of well performing nanocomposites. Here we show for the first time that high temperature contact angle measurements can be performed to investigate the wettability of CVD graphene by molten polymers. In particular, poly(methyl methacrylate), a widely used polymer support for CVD graphene transfer, has been adopted herein for this proof-of-concept study and the values of contact angle and work of adhesion have been provided in the temperature range 170–200 °C.Graphical abstractImage 1
  • Ultra-fast bull's eye-like self-healing using CNT heater
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Heejin Kim, Alexander L. Yarin, Min Wook LeeIn the present work, carbon nanotubes (CNTs) are dispersed in the polydimethylsiloxane (PDMS) matrix and used as an embedded heating source. The electrically conductive CNT layer provides the Joule heating of the released healing materials into cracks. This accelerates the release and polymerization (self-healing) rates. It is demonstrated that with this modification the healing process, which originally required at least 24 h, is shortened to only 10 min. In addition, it is proved that this approach works very well even in the low-temperature environment, where otherwise, the healing efficiency is low because of the high viscosity of the healing agents and reduced rate of the polymerization reaction. The bull's eye-like geometry proposed in this work can be replicated to protect large areas.Graphical abstractImage 10268
  • Friction properties of polyacrylamide hydrogel particle/HDPE composite
           under water lubrication
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Chaobao Wang, Xiuqin Bai, Conglin Dong, Zhiwei Guo, Chengqing YuanIn order to apply the hydration lubrication of soft material in heavy load engineering fields, a series of polyacrylamide (PAAm) hydrogel particle/high-density polyethylene (HDPE) composites were prepared. Their mechanical property, soaking surface morphology, wettability, friction property and lubrication mechanism were experimentally obtained and analyzed. The results show that PAAm hydrogel particles played an important role in the lubrication and antifriction of composites, and the friction properties of 1 wt% PAAm hydrogel particle composite were superior to others of different concentrations. The present study suggests that the composite possesses both the high mechanical properties of HDPE and the excellent hydration lubrication of PAAm hydrogel particles. This finding will provide a novel approach for improving friction properties of water-lubricated materials and are conducive to practical application in engineering fields.Graphical abstractImage 1
  • Synthesis, structure and gas separation properties of ethanol-soluble,
           amphiphilic POM-PBHP comb copolymers
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Kihoon Kim, Dong A. Kang, Jung Tae Park, Ki Chul Kim, Jong Hak KimWe report the synthesis of a series of alcohol-soluble comb copolymers, specifically poly(oxyethylene methacrylate)-co-poly(2-(4-benzoyl-3-hydroxy phenoxy) ethyl acrylate) (POM-PBHP), with various compositions, as well as their use in CO2 capture membranes. The POM-PBHP comb copolymers were synthesized through a low-cost free-radical polymerization method and analyzed based on Fourier transform infrared spectroscopy and nuclear magnetic resonance. The interactions and structures of the comb copolymers were characterized via X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The comb copolymers showed good solubility in volatile nontoxic ethanol, allowing them to be coated onto microporous polymer supports to form thin-film composite membranes. While both neat POM and PBHP membranes showed very poor separation properties, the POM-PBHP comb copolymers were effective at separating CO2 from N2. This is because the POM chains with ether oxygen groups have a strong affinity for CO2, leading to high CO2 permeance, whereas the rigid PBHP chains with aromatic rings hinder N2 permeance based on reduced chain mobility. All the full-atomistic molecular dynamics simulations based on density functional theory were also used to characterize the molecular structure and binding energy for CO2, which is consistent with the experimental results. The performance of the membranes was greatest when the content of PBHP in the copolymer was 15 wt%. The CO2/N2 selectivity and CO2 permeability reached 46.6 and 111 Barrer, respectively, which represents one of the highest values for alcohol-soluble, additive-free polymeric membranes and is similar to that of commercial PEBAX membrane.Graphical abstractImage 103663
  • Manipulating the sequences of block copolymer patterns on corrugated
    • Abstract: Publication date: Available online 20 August 2019Source: PolymerAuthor(s): Sungjune ParkThis paper describes manipulating the sequences of cylinder-forming block copolymer patterns on corrugated substrates. Upon thermal annealing, the topographic corrugation of the substrate generates a spontaneous flow-field of the block copolymer and induces thickness-dependent microdomains. The corrugation gradient has some range of surface roughness characterized by its topographic parameters. When the substrate topography matches the dimensions of the intrinsic surface relief structures of the block copolymer, the surface roughening is suppressed by inverted terrace formation, and sequenced patterns of in-plane cylinders and nonbulk lamella phases are generated. As soon as the surface roughening forms on the corrugated substrate with a roughness parameter lower than that of the surface relief structures, the reverse sequences of the alternative microphase separated structures are developed. However, enhanced mobility of the block copolymer induced by solvent annealing suppresses the pattern sequencing and the in-plane cylinders with a relatively high degree of ordering generated over the entire surface of the corrugated substrate. This observation may further enable new approaches for manipulating the sequences of spatially registered hierarchical surface patterns of block copolymers.Graphical abstractImage 1
  • Pyrrole Oxidative Polymerization By Manganese Oxide (Iv) On Silica Gel
    • Abstract: Publication date: Available online 16 August 2019Source: PolymerAuthor(s): Yu.V. Korshak, M.V. Motyakin, I.V. Plyushchii, A.L. Kovarskii, Ye.N. Degtyarev, A.G. Petrushevska, R.A. Alekperov, V.A. Dyatlov, A.M. Tsatsakis, A.L. Luss, Y.O. MezhuevThe study of pyrrole oxidative polymerization in toluene on the surface of silica gel modified with manganese oxide (IV) was carried out. The kinetics of pyrrole oxidative polymerization on the surface was established, a kinetic model was proposed, and its parameters were calculated. It was shown that the activation energy is close to free energy of the viscous toluene flow that indicates diffusion control of the process. The changes of the specific surface area of silica gel and the pore volume distribution along the radii during the modification with manganese dioxide and the subsequent polymerization of pyrrole were determined.Graphical abstractImage 10629937
  • Improvement in mechanical and thermal properties of polypropylene
           nanocomposites using an extremely small amount of alkyl chain-grafted
           hexagonal boron nitride nanosheets
    • Abstract: Publication date: Available online 15 August 2019Source: PolymerAuthor(s): Saerom Kong, Huiran Seo, Huiseob Shin, Ji-Hoon Baik, Jinwoo Oh, Young-O. Kim, Jong-Chan LeeIn this study, hexagonal boron nitride nanosheets grafted with aliphatic groups (Alkyl-BN) were synthesized by a sonication-assisted alcoholysis reaction using hexagonal boron nitride (hBN) with 1-dodecanol, and a series of polypropylene (PP) nanocomposites were prepared by mixing PP with different amount of Alkyl-BN. The PP/Alkyl-BN nanocomposite containing a very small amount of Alkyl-BN showed much improved mechanical properties than those of neat PP and PP/hBN nanocomposites. For instance, Young's modulus value of PP/Alkyl-BN nanocomposite containing 0.5 wt% of Alkyl-BN is larger than that of neat PP by 17.5% while that of PP/hBN nanocomposite containing 0.5 wt% of hBN is larger by only 1.2%. The tensile strength value of PP/Alkyl-BN was found to be larger than that of the neat PP by 7.4% due to the enhanced interfacial interaction between Alkyl-BN and PP chains. Furthermore, the PP/Alkyl-BN nanocomposites exhibited enhanced thermal conductivity and stability than the neat PP and PP/hBN nanocomposite. This research clearly shows that the improved thermal and mechanical properties of polymer nanocomposites can be achieved with a very low filler content by the enhancement of the interfacial interaction between the filler materials and the polymer matrix.Graphical abstractImage 1
  • Direct introduction of elemental sulfur into polystyrene: A new method of
           preparing polymeric materials with both high refractive index and Abbe
    • Abstract: Publication date: Available online 15 August 2019Source: PolymerAuthor(s): Liping Jiang, Ruixia Kong, Yuliang Yi, Siqi Yang, Yu Mei, Xiaofei Feng, Zhanhai Yao, Jianfu ZhangThe present work proposes a facile but effective method for the design and synthesis of optical polymers with both high refractive index (RI) and Abbe number (AN) by the direct introduction and dispersal of elemental sulfur in polystyrene (PS). The excellent dispersal of the reaction products of elemental sulfur with styrene (St-S) in the PS result in the highest RI of 1.6220 and AN of 27.3. The acceptable uniform dispersal of elemental sulfur in the PS is verified by photographic analysis, optical transmission spectra, scanning electron microscopy, and energy dispersive spectroscopy analyses. The thermal properties of polymeric materials were investigated using thermogravimetric analysis and differential scanning calorimeter. The proposed strategy not only provides a new high RI material for optical applications, but also offers new opportunities for the dispersal of substances into polymeric materials.Graphical abstractImage 1
  • Morphological changes of hydrophobic matrix and hydrophilic ionomers in
           water-swollen perfluorinated sulfonic acid membranes detected using
           small-angle X-ray scattering
    • Abstract: Publication date: Available online 14 August 2019Source: PolymerAuthor(s): So Fujinami, Taiki Hoshino, Tomotaka Nakatani, Tatsuya Miyajima, Takaaki Hikima, Masaki TakataTime-resolved small-angle X-ray scattering (SAXS) was employed to examine the hydration dynamics of perfluorinated sulfonic acid membranes in contact with liquid water. Following thermal pretreatment of the membranes, a peak corresponding to the fluorocarbon polymer backbones was clearly observed in the SAXS profiles, in addition to a peak corresponding to the ionomer clusters consisting of hydrophilic side chains and water molecules. The variation of these two peaks was monitored with a frame time as low as 21 ms, which permitted the successful capture of the subsecond dynamics of water uptake by 25 and 50 μm thick membranes. The dynamics of the initial rapid water uptake were well reproduced using Fick's equation, although the thinner sample exhibited a smaller diffusion coefficient. This result suggests that the surface resistance influences the diffusion of water into the membrane. The initial rapid water absorption was followed by the slow and continuous reconstruction of the polymer structure. The measured dynamics of the two peaks indicated that, during this long-term reconstruction, the increase in the ionomer volume became slower and the fusion of clusters was the dominant factor responsible for increasing the ionomer spacing.Graphical abstractImage 1
  • An A−D−Aʹ−Dʹ strategy enables perylenediimide-based polymer dyes
           exhibiting enhanced electron transport characteristics
    • Abstract: Publication date: Available online 14 August 2019Source: PolymerAuthor(s): Zhonghai Tang, Xuyang Wei, Weifeng Zhang, Yankai Zhou, Congyuan Wei, Jianyao Huang, Zhihui Chen, Liping Wang, Gui YuIn this work, we develop two new A−D−Aʹ−Dʹ type polymer dyes, namely PPDIDTBT and PPDIDTBT-2F, containing perylenediimide (PDI), thiophene, and benzothiadiazole units. Both polymer dyes have high thermal stability and broad absorption throughout the UV–vis region. More importantly, the introduction of the second electron-withdrawing units, benzothiadiazoles, endows both polymer dyes with low-lying LUMO energy levels of −3.85 eV for PPDIDTBT and −3.88 eV for PPDIDTBT-2F. The charge transport properties of the two polymer dyes were examined by fabricating organic field-effect transistors (OFETs) with top-gate/bottom-contact configuration. Both polymer dyes exhibit enhanced electron transport characteristics with the highest electron mobility of 0.070 cm2 V−1 s−1, which is among the highest values for PDI-based polymer semiconductors reported to date. Our results highlight that the A−D−Aʹ−Dʹ strategy is a useful approach in tuning orbital energetic and charge transport properties of polymer dyes for developing high-performance OFETs.Graphical abstractImage 1
  • Realizing mechanically reinforced all-polyethylene materials by dispersing
           UHMWPE via high-speed shear extrusion
    • Abstract: Publication date: Available online 13 August 2019Source: PolymerAuthor(s): Li Zhang, Chen Lu, Peng Dong, Ke Wang, Qin ZhangDue to its extraordinary molecular weight feature (Mw > 106 g/mol), ultra high molecular weight polyethylene (UHMWPE) plays as an appropriate reinforcement for polyethylene. However, ultrahigh molecular weight also causes remarkably high melt viscosity, which hinders the solvent-free processing of UHMWPE. Here, we report a self-reinforcement all-polyethylene material, high density polyethylene (HDPE)/UHMWPE via a melt processing of high-speed shear extrusion. A critical reinforced content of UHMWPE, 0.1 wt%, has been discovered. After reaching such content, the tensile strength and Young's modulus of HDPE can be reinforced remarkably at 500 rpm. Thanks to the high shear, UHMWPE is uniformly dispersed and to form reinforcement network in the HDPE matrix. Interestingly, UHMWPE long chains enable the appearance of lamellae orientation and shish-kebab crystalline morphology in the injection molded parts, which are responsible for the mechanical reinforcement behavior observed. Our current work offers a convenient, solvent-free processing strategy to manufacture super polyolefin blends containing UHMWPE.Graphical abstractImage 1
  • High-performance porous PLLA-based scaffolds for bone tissue engineering:
           Preparation, characterization, and in vitro and in vivo evaluation
    • Abstract: Publication date: Available online 13 August 2019Source: PolymerAuthor(s): Jiajun Ju, Xiangfang Peng, Keqing Huang, Lengwan Li, Xianhu Liu, Chandani Chitrakar, Lingqian Chang, Zhipeng Gu, Tairong KuangPorous poly (l-lactic acid) (PLLA)-based tissue engineering scaffolds have gained growing interests due to their unique structures and properties. However, the simple and green fabrication of PLLA-based scaffolds with uniform and interconnected pore structure, good degradability and hydrophobicity, and excellent biocompatibility remain a major challenge. Herein, we developed a facile, cost-effective and eco-friendly structural manipulation processing with supercritical carbon dioxide (Sc-CO2) foaming technique to prepare porous PLLA/poly (ethylene glycol) (PEG) (95/5 wt%) scaffolds. First, structural manipulation processing was used to manipulate the formation of oriented crystal structure in a PLLA matrix, which could slow down the gas escaping during the Sc-CO2 foaming process. Subsequently, the Sc-CO2 foaming process was utilized to form 3D porous scaffolds, which are suitable for the cell growth, migration and proliferation. The fabricated porous biodegradable scaffold exhibited high porosity (90.3%), uniform and interconnected open-pores, good strengths (11.9 MPa/(g·cm3)), degradabilities and hydrophilicities (75.7 ± 2.1°), as well as excellent in vitro biocompatibilities. For in vivo application, a rabbit model with bone defects was utilized, and both the histological analysis and immunohistochemical analysis results revealed that the obtained porous PLLA/PEG scaffolds support bone tissue engineering.Graphical abstractImage 1
  • Nanoporous poly(ether sulfone) from polylactide-b-poly(ether
           sulfone)-b-polylactide precursor
    • Abstract: Publication date: Available online 12 August 2019Source: PolymerAuthor(s): Jinhee Lee, Jongmin Park, Jaehoon Oh, Sanghwa Lee, Sang Youl Kim, Myungeun SeoWe report a route to synthesize polylactide-b-poly(ether sulfone)-b-polylactide (PLA-b-PES-b-PLA) containing PES and PLA, which provide a mechanically robust framework and a sacrificial template for pore formation, respectively. High-molar mass PES terminated with fluorine groups was synthesized by the step-growth nucleophilic aromatic substitution (SNAr) reaction, and the chain ends were transformed into benzylic hydroxyl groups by chain end modification. Growth of the PLA using the hydroxyl groups as initiating sites via chain-growth ring opening transesterification polymerization (ROTEP) produced the target triblock copolymer. Although the step-growth polymerization produced a PES middle block with high dispersity, small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) analyses indicated the formation of an ordered lamellar morphology. We further demonstrated that a nanoporous PES with slit-like pores could be obtained by selective removal of the PLA.Graphical abstractImage 1
  • A Molecular Dynamics Study of Decomposition of Covalent Adaptable Networks
           in Organic Solvent
    • Abstract: Publication date: Available online 12 August 2019Source: PolymerAuthor(s): Yaguang Sun, Hua Yang, Kai Yu, Yafang Guo, Jianmin QuIt has been recently reported that covalent adaptable networks can be decomposed in organic solvents. This prominent feature provides exciting opportunities to recycle thermosets and their composites. In this paper, a molecular dynamics computational framework is established to investigate the decomposition of an epoxy covalent adaptable network in ethylene glycol solvent via transesterification-type bond exchange reactions. The simulations describe the interdiffusion between polymer and solvent. Additionally, the degradation of polymer network is investigated by calculating the monomer number of each polymer chain and analyzing the evolution of ester conversion. Finally, the covalent adaptable network decomposition in octamethylene glycol is simulated to study the influence of solvent molecule size. This work is the first one to use the molecular dynamics to study the decomposition of covalent adaptable network. The simulation results advance the understandings of the decomposition kinetics and provide a guideline for the selection of suitable solvents.Graphical abstractImage 10659
  • Structural evolution of flow-oriented high density polyethylene upon
           heating: In situ SAXS and WAXD studies
    • Abstract: Publication date: Available online 9 August 2019Source: PolymerAuthor(s): Tao Liao, Xintong Zhao, Xiao Yang, Phil Coates, Ben Whiteside, Zhiyong Jiang, Yongfeng MenThe structural evolution of micro-injection molded high density polyethylene (HDPE) at the molecular and lamellar levels was investigated as a function of temperature during heating process using wide angle ;X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) techniques. The molded sample exhibits a peculiar multilayer structure of skin and shear layers, and is marked by the existence of shish-kebab-like structure with two populations of lamellar stacks. The variations of the long period as well as the average thicknesses of lamellar and amorphous regions with temperature were determined from one-dimensional correlation functions for the respective lamellar stacks. The average length and the misorientation of shish-like formation were calculated using Ruland equation, and the results indicate that the shish-like structure grows in the longitudinal direction with increasing temperature via incorporation of several partially relaxed chains as a result of autocatalytic process. In addition, the degree of orientation of the chains in the crystalline phase was found to increase slightly with increasing temperature below 100 °C, which could be traced back to the formation of additional crystallites with a low degree of orientation after injection molding. These crystalline lamellae built up during the secondary crystallization are less thermally stable than the primary ones, and therefore are melted selectively upon annealing at relatively lower temperatures yielding an overall increase in the molecular orientation.Graphical abstractImage 1
  • Enhanced ferroelectric properties of P(VDF-TrFE) thin films from Nb
           nanopin electrodes
    • Abstract: Publication date: Available online 8 August 2019Source: PolymerAuthor(s): Yoonho Ahn, Jong Yeog SonWe demonstrate the influence of Nb nanopin electrodes on ferroelectric properties of poly(vinylidene fluoride-ran-trifluoroethylene) (P(VDF-TrFE)) thin films deposited using a spin-coating technique. The Nb nanopin electrodes consisting of an array of regular hexagon nanopins were formed by virtue of a multiple anodizing process and an etching process of an Al/Nb/SiO2/Si multilayer structure. An electric field enhancement of the Nb nanopin electrodes contributed to the improved ferroelectric polarizations, low coercive electric fields, and fast switching characteristics of the P(VDF-TrFE) thin-film capacitors. Futhermore, the Nb nanopin electrodes made a significant contribution to low activation energy of domain wall motion. In particular, the study of domain wall motion by piezoresponse force microscopy support that the fast switching properties of the P(VDF-TrFE) capacitors is attributed to the low activation energy for the domain wall motion. This work provides a solution to solve the problem of the high coercive and switching electric fields that have been considered a stumbling block in electronic devices and applications of the P(VDF-TrFE) thin films.Graphical abstractImage 1003158
  • Gas permeation and selectivity characteristics of PSf based nanocomposite
    • Abstract: Publication date: Available online 2 August 2019Source: PolymerAuthor(s): Suchhanda S. Swain, Lakshmi Unnikrishnan SmitaMohanty, Sanjay K. NayakThis study highlights successful development and evaluates the characteristics of graphene-derived nanohybrids (SGO and RSGO) incorporated MMM systems. Pristine GO and modified SiO2 (mSiO2) based membranes have also been prepared to assay the established synergistic effect on the performance. FTIR and WCA studies were carried out to endorse the insertion of different nanofillers into the virgin PSf matrix. SEM with EDS and AFM were accomplished to substantiate the distribution and dispersion pattern of the fillers within the base matrix. From the mechanical analysis, 46% improved tensile strength was perceived for the hybrid MMM system containing SGO. Finally, the dexterity was documented by analyzing the permeation behavior of the prepared membranes towards the selected O2/N2 gas pair. The hybrid PSf/SGO system displayed 605% and 801% higher permeabilities for O2 as compared to the parent counterparts: (PSf/mSiO2, PSf/GO), respectively. Meanwhile, PSf/RSGO membrane exhibited a slightly reduced performance than the former hybrid system.Graphical abstractImage 1
  • Preparation and properties of waterborne polyurethane with star-shaped
           hyperbranched structure
    • Abstract: Publication date: Available online 30 July 2019Source: PolymerAuthor(s): Jie Zhang, Haojun Ren, Pingping Chen, Zhiping Zhang, Chunpu HuThe second-generation hydroxyl-terminated hyperbranched polyester (HB-20) was used as the core, and perfluorooctylethanol (PFOE), monohydroxypolyoxyethylene ether (MPEG) and n-octadecyl alcohol (C18) were grafted to the periphery of HB-20, coupled by isophorone diisocyanate (IPDI) to synthesize four star hyperbranched polymers (SHPs). The structures of the four synthesized typical SHPs were characterized by FT-IR, 1H NMR and 19F NMR. The SHPs obtained were introduced into anionic waterborne polyurethane (WPU) and waterborne polyurethanes (FWPUs) with good storage stability modified by SHPs were prepared. The particle size and morphology of FWPUs were characterized by dynamic laser light scattering and TEM. The surface chemical composition and surface hydrophilic and hydrophobic regions of FWPU film were characterized by XPS and AFM. The surface energy, mechanical properties and thermal properties of FWPU film were determined. The water absorption and moisture permeability of FWPU film were also discussed.Graphical abstractImage 1
  • Self-enhancement in aramid fiber by filling free hydrogen bonding
           interaction sites in macromolecular chains with its oligomer
    • Abstract: Publication date: Available online 28 July 2019Source: PolymerAuthor(s): Cheng Yang, Hang Wu, Yu Dai, Siyi Tang, Longbo Luo, Xiangyang LiuRigid macromolecular chains possess weak mobility and have difficulty with conformational adjustment, resulting in some “free intermolecular interaction sites” of hydrogen bonds. Herein, aramid oligomers (OPBIA) with different average polymerization degree (DP) were synthesized and added in aramid fiber (PBIA) to fill these free interaction sites, aiming to form stronger interchain hydrogen bonding interactions and achieve self-enhancement in mechanical properties of aramid fiber. Variable-temperature Fourier transform infrared spectrometer was employed to in situ monitor the evolution of hydrogen bonds in aramid from 30 °C to 360 °C. The results show that the value of hydrogen bonding enthalpy change is −19.37 kJ mol−1 after adding OPBIA5 (DP = 5) in PBIA, whose absolute value is obviously larger than that of PBIA (−13.14 kJ mol−1). This demonstrates that the oligomer improves intermolecular hydrogen bonding interactions effectively. Correspondingly, the tensile strength and compressive strength of PBIA/OPBIA5 fiber increases by 23.1% and 29.4%, respectively, compared to those of PBIA fiber. Besides, the enhancement of properties is related to the DP of oligomers, OPBIA with low DP has stronger effect on intermolecular hydrogen bonds than OPBIA with high DP. Nevertheless, the oligomer tends to self-aggregate when its DP is too low. In addition, the oligomers can plasticize the macromolecules at high temperatures, which is advantageous for further increasing the orientation and tensile strength of aramid fibers.Graphical abstractImage 1
  • Modeling of the polymerization and crystallization kinetic coupling of
           polyamide 6 synthesized from ε-caprolactam
    • Abstract: Publication date: Available online 28 July 2019Source: PolymerAuthor(s): Céline Vicard, Olivier De Almeida, Arthur Cantarel, Gérard BernhartOptimization of polyamide 6 (PA6) composite manufacturing by liquid processes requires a better prediction of kinetics during synthesis. This study proposes a new modeling approach that considers the interaction between PA6 polymerization and crystallization over a wide temperature range (403–473 K). Different polymerization and crystallization models taken from literature were used in this study. Few attempts to describe the coupling between phenomena have been reported, and all have raised physical limitations. A new coupling equation was adapted from Hillier coupling, first introduced to model secondary crystallization of semi-crystalline thermoplastics. This equation properly predicted kinetics at high temperature when the coupling is limited. However, it failed in predicting the particular crystallization kinetics in the early stages of polymerization at low temperature, as crystallization may require that polymerized chains reach a certain length or concentration in the reactive mixture. A factor was successfully introduced in order to correct the crystallization behavior. From this new model, a wide isothermal Time-Temperature-Transformation (TTT) diagram was produced, which assists in cure path design for composite manufacturing.Graphical abstractImage 1
  • Electrically induced soft actuators based on thermoplastic polyurethane
           and their actuation performances including tiny force measurement
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Chongchao Li, Hong Xia, Juming Yao, Qing-Qing NiMany gel-like soft composites were obtained by using thermoplastic polyurethane (TPU) as the matrix in this work. Different contents of plasticizer dibutyl adipate (DBA) was added to TPU to swell its molecular chains and allowed them to pass through each other easily. These samples were then sandwiched between two electrodes as actuators and their actuation abilities were investigated. The results showed that the largest deflection among those samples was up to 12.11 mm, which corresponds to 48.44% of the length of samples (at 2.86 V μm−1). The deflection increased with increasing of the electric field intensity. Besides, the actuator was able to promptly respond to the change of voltage within 0.12 s. A wide response ability in the frequency region from 0.5 Hz to 10 Hz was confirmed, and the largest amplitude over 22 mm of the actuator was observed at 5 Hz. Furthermore, a new method was proposed in this paper to estimate the tiny force generated by the actuator. The small variation (less than 3%) of the measured results indicated that the proposed method is reliable even at a small bending angle. It is believed that the rapid bending capability and large deformation of the developed actuator at low intensity of electric field will make its considerable contributions to the field of soft robotics or biomaterials.Graphical abstractImage 1
  • Phase behaviour of poly(2, 6-diphenyl-p-phenylene oxide) (PPPO) in mixed
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Róisín A. O'Connell, Alexandra E. Porter, Julia S. Higgins, João T. CabralAbstractThe solution phase behaviour of poly(2, 6-diphenyl-p-phenylene oxide) (PPPO) is investigated by a combination of turbidimetry, infrared spectroscopy, dynamic light scattering and densitometry, combined with calorimetry and X-ray scattering. We select dichloromethane (DCM) and heptane as, respectively, representative good and poor solvents for the polymer. This ternary system results in a miscibility gap which can be utilised for the design and fabrication of PPPO porous materials, membranes and scaffolds via phase inversion. We establish the phase diagram and resolve the kinetic solidification condition arising from the intersection between the coexistence and glass transition curves. PPPO exhibits a high Tg≈ 230 ∘C and is found to crystallise at Tc≈ 336 ∘C, and melt at Tm≈ 423, 445 ∘C with a double endotherm. The kinetics of demixing and (buoyancy-driven) stratification are quantified by optical imaging and the PPPO-rich phase analysed by SAXS/WAXS to resolve both amorphous and crystalline phases. Equipped with this knowledge, we demonstrate the controlled formation of nodular, bicontinuous and cellular morphologies by non-solvent induced demixing.
  • Homogeneous phase crosslinked
           poly(acrylonitrile-co-2-acrylamido-2-methyl-1-propanesulfonic acid)
           conetwork cation exchange membranes showing high electrochemical
           properties and electrodialysis performance
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Sandip Pal, Rakhi Mondal, Suparna Guha, Uma Chatterjee, Suresh K. JewrajkaHerein, we report a simple process for the preparation of homogeneous crosslinked conetwork cation exchange membranes (CEMs). The synthesis strategy is based on sequential reaction of hydrazine hydrate and nitrile moieties of random copolymers of poly(acrylonitrile) and poly (2-acrylamido-2-methyl-1-propanesulfonic acid) (PAN-co-PAMPS). Copolymerization of the two monomers enhances miscibility between relatively hydrophobic PAN and hydrophilic ionic PAMPS domains which prevents microphase separation in the membrane matrices. The homogeneous phase co-continuous morphology with no microphase separation in the membrane matrices was confirmed by the homogeneous distribution of color solutes in the membrane matrices as well as by DSC, DMA, TEM, and AFM analyses. Both crosslinked (conetwork) and uncrosslinked copolymers (different composition) acted as CEMs. The CEMs were employed for desalination via electrodialysis. A representative crosslinked CEM (PAN-PAMPS-1) containing 15 mol% PAMPS exhibited the best desalination performance. Crosslinking of the copolymers improves the transport number, desalination performance, and lowers the power consumption of the membranes. This work thus highlights the benefit of crosslinking of ionic random amphiphilic copolymers to obtain CEMs with improved performance during desalination via electrodialysis.Graphical abstractImage 1
  • Adsorption of polymer chains on heterogeneous surfaces with random
           adsorption sites
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Qing-Hui Yang, Xiao Yang, Meng-Bo LuoThe adsorption time τads of a linear polymer chain onto a heterogeneous surface with randomly distributed adsorption sites decreases with increasing the fraction of adsorption sites ρ but increases with increasing the intra-polymer attraction strength EPP. The scaling behavior of τads with the polymer length N, τads ~ Nα, is independent of ρ but is dependent on EPP. We find α = 1.6 for polymer in random coil state at small EPP and α = 2.0 for polymer in compacted globule state at large EPP. An interesting finding is that τads increases with EPS at small ρ but decreases with EPS at large ρ, indicating that the adsorption mechanism is dependent on the surface property. The adsorption of polymer is accompanied by the extension of polymer conformation as the equilibrium apparent size eq is increased after adsorption. However, at moderate ρ and large EPS, we find eq decreases with increasing ρ, in agreement with experimental observation for DNA adsorption.Graphical abstractImage 109631
  • Structure and properties of Polylactide/Poly(butylene
           succinate)/Organically Modified Montmorillonite nanocomposites with
           high-efficiency intercalation and exfoliation effect manufactured via
           volume pulsating elongation flow
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Ling-cao Tan, Yue He, Jin-ping QuThe Polylactide (PLA)/Poly(butylene succinate)(PBS)/Organically Modified Montmorillonite (OMMT) nanocomposites with different ratio were manufactured via intense volume pulsating elongation flow. The nanostructure, microscopic morphology, crystallization property, thermostability, mechanical properties were well investigated. The processing mechanism was well discussed. The OMMT (C30B) was well dispersed, intercalated, and exfoliated in all the nanocomposites. The interlayer spacing doubled in all the nanocomposites. The clay mainly dispersed in PBS and located at the interface of PLA/PBS in all samples, which could be predicted by the interfacial tension, enthalpic interaction, and wettability parameter. Diameter of the in situ formed PBS fiber decreased as the C30B content increased. Nanocomposites with PBS content range from 30% to 70% displayed the co-continuous structure. The Young's modulus and elongation at break of the blend increased significantly by adding the clay.Graphical abstractImage 10719
  • Novel optimised highly aligned electrospun PEI-PAN nanofibre mats with
           excellent wettability
    • Abstract: Publication date: 10 October 2019Source: Polymer, Volume 180Author(s): Muhammad Omer Aijaz, Mohammad Rezaul Karim, Hamad F. Alharbi, Nabeel H. AlharthiThis study comprehensively optimised the parameters for electrospinning a polyetherimide (PEI) and polyacrylonitrile (PAN) blend to obtain highly aligned (~93%) nanofibres (NFs) mats with an average diameter of ~150 nm. The formation of smooth, constant, and bead-free NFs was observed as the concentration of the PAN solution hosted in the PEI solution increased beyond 50%. To reduce the NFs diameters, the following optimised parameters were used: 20% humidity (ranges from 20% to 60%), 19 kV applied voltage (ranges from 13 to 24 kV), 0.6 mL/h flow rate (ranges from 0.3 to 1.5 mL/h), 150 mm of needle-tip-to-collector distance (ranges from 100 to 300 mm), 2500 rpm of collector speed (ranges from 0 to 2500 rpm), and the other parameters were maintained constant. The fabricated PEI-PAN NFs were characterized by field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and contact angle (CA) measurement to analyse the morphology of the fibres, study their thermal properties, and to confirm the PEI-PAN blending and wettability, respectively. The detailed morphological studies from the FE-SEM images showed the influence of the parameters on the fibres diameter and alignment. The TGA and FTIR results showed an enhancement in the thermal properties of samples S2 (e.g. 75% PEI-25% PAN), S3 (e.g. 50% PEI-50% PAN), and S4 (e.g. 25% PEI-75% PAN) as compared to S5 (e.g. 0% PEI-100% PAN) and good blending between PEI and PAN. The wettability study confirmed the hydrophilic nature of the PEI-PAN blend while considering the orientation of the NFs as the key factor that determines the fusing of the water drops on the NFs mats. The results showed that the water drops on the aligned oriented NFs mats did not fuse even after 60 s and remained at a contact angle of 28.6°. The high alignment and small diameters of the PEI-PAN NFs with good wettability could have potential applications in fields including as biomedical, and environmental as well as in separation processes.Graphical abstractNarrower Diameter and Highly Aligned PEI-PAN Nanofibers from Optimised Electrospinning Conditions to Study Wettability of Electrospun Mats.Image 10235
  • Modelling the distribution of BaTiO3 nanoparticles in a P(VDF70-TrFE30)
           polymer matrix for permittivity calculation
    • Abstract: Publication date: Available online 23 July 2019Source: PolymerAuthor(s): Jonas Hafner, Jürgen Schrattenholzer, Marco Teuschel, Michael Schneider, Daniel Platz, Ulrich SchmidNanocomposites are an exciting field for both research and application related activities as they promise to push the existing limits of many standard materials. For instance, the admixture of inorganic nanoparticles into polymers may lead to materials with novel dielectric properties. However, nanocomposites are highly complex material systems, making the prediction of basic material parameters, such as the permittivity, challenging. In this study, we present a novel method that considers explicitly the statistical distribution of the nanoparticles in the organic matrix, which allows to calculate the permittivity as a function of the nanoparticle volume fraction. We apply this method for the study of spherical barium titanate particles in a poly(vinylidene fluoride70-trifluoethyline30) polymer matrix and show that a transition from randomly distributed nanocomposites to colloidal crystals occurs, which has a tremendous impact on the permittivity of the composite.Graphical abstractImage 1
  • Compositional and structural design of thermoplastic polyurethane/carbon
           based single and multi-layer composite sheets for high-performance X-band
           microwave absorbing applications
    • Abstract: Publication date: Available online 22 July 2019Source: PolymerAuthor(s): Alper Kasgoz, Mehmet Korkmaz, Ali DurmusIn this study, morphological features, dielectric properties, and microwave absorbing performances of thermoplastic polyurethane composite sheets prepared with solution mixing method by using different amounts and types of carbon fillers, carbon black (CB), graphite (G), carbon nanofiber (CNF), and multiwalled carbon nanotube (MWCNT) were investigated, in detail. Microstructural properties and microwave absorbing characteristics of composites were analyzed with scanning electron microscope and vector network analyzer by transmission line method, respectively. Reflection loss (RL) analyses of composites showed that CNF and CNT were more efficient than CB and G for improving the electromagnetic wave absorbing performances of sheets at low filler contents. It was found that the broadest effective absorption area (EAA) (10.03-12.96 GHz) was obtained with the sample having 3 phr of CNF. However, single layer TPU/carbon composite sheets were not effective “RADAR stealth” materials because their RL values were higher than -10 dB at X-band. Thus, multilayer (two, three, and four-layer) composite structures were designed to obtain higher microwave absorption performance within this frequency range via genetic algorithm approach. Multilayer design and modeling works showed that a four-layer composite with a total thickness of 4.8 mm yielded excellent microwave absorbing performance and broad EAA, 6.98-13.415 GHz, at X-band.Graphical abstractImage 10060
  • Precursor assisted crystallization in cross-linked isotactic polypropylene
    • Abstract: Publication date: Available online 22 July 2019Source: PolymerAuthor(s): Jianzhu Ju, Nan Tian, Zhen Wang, Fengmei Su, Haoran Yang, Jiarui Chang, Xueyu Li, Sarmad Ali, Yuanfei Lin, Liangbin LiCombining the extension rheometry and simultaneous in-situ synchrotron radiation small/wide angle X-ray scattering (SAXS/WAXS) measurement, extension induced crystallization of cross-linked isotactic polypropylene (CL-iPP) is studied at different temperature from 130 to 160 °C. After extension at strain of 1.5, precursor is generated before crystallization and the relative stability increases with temperature. Precursor growth is confined due to limited chain diffusion, resulting in a periodic two-dimensional distribution. Crystallization takes place later with the existence of precursor, accompanied with the slowdown of precursor dynamics. Based on the results, a model of precursor assisted crystallization is proposed to illustrate this unique phase behavior.Graphical abstractImage 1
  • Polyamide 6 (PA6) /polyethylene terephthalate (PET) blends with gradient
           and encapsulation structure developed by injection molding
    • Abstract: Publication date: Available online 22 July 2019Source: PolymerAuthor(s): Yan Yan, Yan-Hao Huang, Yue Wang, Zhi-Chao Xiao, Ming-Bo YangIn this work, injection molded Polyamide 6 (PA6)/Polyethylene terephthalate (PET) blends with gradient and overall encapsulation structure were prepared, to which the migration and aggregation process of PET phase should be given credit. The main factors influencing the final morphology, including the viscosity ratio between the blending components and the injection velocity during injection molding, were discussed. It has been found that the final structure is greatly affected by the rheological properties of the blending components. In conclusion, under the fixed blending composition, the optimal gradient and encapsulation structure can be achieved in injection molded PA6/PET blends of D8501-20. Compared to pure PA6 injection sample and the other groups of injection samples, the chemical resistance of D8501-20 is remarkably improved. At the meantime, the mechanical properties of D8501-20 maintain a high value, which allows the PA6/PET injection product with this unique structure to have a considerable potential in industrial manufacturing.Graphical abstractImage 1
  • Effects and limits of highly efficient nucleating agents in thermoplastic
    • Abstract: Publication date: Available online 22 July 2019Source: PolymerAuthor(s): Jon Maiz, Borja Fernández-d´Arlas, Xinye Li, Jens Balko, Elmar Pöselt, Raphaël Dabbous, Thomas Thurn-Albrecht, Alejandro J. MüllerIn this work, we have investigated the effects of several nucleating agents on crystallization kinetics and morphology in a thermoplastic polyurethane (TPU). For one specific nucleating agent (denoted NAII), the nucleation efficiency was almost 100%; this means that this nucleating agent is as efficient as TPU´s self-nuclei. Adding NAII largely increases the crystallization temperature (around 60 °C), the melting temperature, the overall crystallization kinetics, the lamellar thickness, and the crystallinity of TPU. All these remarkable changes (which could improve the mechanical properties) only occur if the material is cooled from the melt below a critical cooling rate. When the cooling rate is higher than this critical value (approximately 200 °C/min), the nucleating action of the nucleating agents (or even of the TPU self-nuclei) is effectively lost, and the crystallization occurs as in neat TPU, but with an important reduction in crystallinity. The practical consequence is that if the TPU employed here is used in injection molding, the nucleating agents of this study can only be effective if they are cooled down at rates below the critical value, i.e., in practice only for samples that have a sufficiently large thickness.Graphical abstractImage 10
  • Understanding the influence of carbon nanotubes on the flow behavior of
           liquid crystalline hydroxypropylcellulose: A Rheo-NMR study
    • Abstract: Publication date: Available online 22 July 2019Source: PolymerAuthor(s): Coro Echeverria, Pedro L. Almeida, João L. Figueirinhas, Maria H. GodinhoHydroxypropylcellulose (HPC) is an important cellulose derivative that has been widely studied due to its water-solubility, biocompatibility and biodegradability, but even more significant due to its ability to form liquid crystalline phases. HPC is able to form, under certain conditions, chiral nematic (cholesteric) structures in water solutions. Previous work confirmed that films prepared from liquid crystalline HPC/water solutions (LC-HPC) gave rise to anisotropic networks, with similar mechanical and optical characteristics of Liquid Crystalline Elastomers (LCE), capable to respond to humidity. It was also demonstrated that the incorporation of carbon nanotubes (CNTs) significantly improved the actuator responsiveness. In the work presented herein, we investigate how the incorporation of carbon nanotubes affects the flow behavior of LC-HPC solutions, and thus the structure-properties relationship, through a detailed Rheo-NMR study. As observed from the results, when shearing the samples, the degree of order reached (maximum quadrupolar peak splitting) by LC-HPC solutions increases with CNT content. Regarding the subsequent relaxation process, only the incorporation of 0.01 wt% of CNTs (lowest content) contributes to a faster recovery of cholesteric structure.Graphical abstractImage 1
  • The effect of Poly(Ethylene oxide) cross-linking structure on the
           mechanical properties and CO2 separation performance of an ion gel
    • Abstract: Publication date: Available online 21 July 2019Source: PolymerAuthor(s): Victor A. Kusuma, Christina Chen, James S. Baker, Megan K. Macala, David HopkinsonIonic liquid gels of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide plasticizing a cross-linked poly(ethylene oxide) are high performance CO2 separation membranes. Here, the effect of polymer cross-link density on the ionic liquid stability, on the mechanical properties of the resulting films, and on the gas separation properties were studied. Cross-link density was modified by changing the chain length of ethoxylated diacrylate and triacrylate monomers, and by incorporating small amounts of short, multifunctional acrylate monomers. Without the ionic liquid acting as permanent plasticizer, higher cross-link density is associated with higher yield strength but lower strain at break, as expected. In a plasticized network, however, the loss in flexibility is not accompanied by higher yield strength, leaving ion gels made from highly cross-linked network more fragile than those having longer, more flexible chains. Lowering cross-link density also allowed more ionic liquids to be incorporated as a phase stable gel and led to better CO2 separation performance.Graphical abstractImage 1
  • Tensile study of melt-spun poly(3-hydroxybutyrate) P3HB fibers: Reversible
           transformation of a highly oriented phase
    • Abstract: Publication date: Available online 19 July 2019Source: PolymerAuthor(s): Edith Perret, Felix A. Reifler, Ali Gooneie, Rudolf HufenusPoly-3-hydroxybutyrate (P3HB) typically crystallizes into the orthorhombic α-form. The additional intense and rather broad equatorial reflection in wide-angle X-ray diffraction (WAXD) patterns seen in our melt-spun P3HB fibers cannot be attributed to the α-form crystals. We propose that a non-crystalline mesophase, which consists of disordered but highly oriented and stretched molecules located between α-crystals, leads to the observed broad equatorial reflection. We show that the transformation of this mesophase from and into the α-form phase is partially reversible under cyclic tensile loading. Structure factor calculations, which are based on atomic positions from molecular dynamics simulations of a set of stretched P3HB molecules, support this model. The WAXD patterns were analyzed with azimuthal, radial, equatorial and meridional scans and the changes in the crystal orientation, changes in the percentages of individual phases and changes in the α-crystal lattice spacings were analyzed as a function of the applied tension. Changes in long spacings, crystal sizes and coherence lengths under cyclic loading were determined with small-angle X-ray scattering (SAXS) measurements. The long spacing between α-crystals increases when tensile stress is applied and it snaps back to the original spacing when the tensile stress is released.Graphical abstractImage 1
  • Studies on the use of filter-based IR detector for short-chain branching
           characterization of polyolefin copolymers with high temperature size
           exclusion chromatography
    • Abstract: Publication date: Available online 21 June 2019Source: PolymerAuthor(s): Tiny Frijns-Bruls, Alberto Ortin, Jos Weusten, Erik GeladéEven though polyolefins are simple polymers from chemical structure point of view, their full characterization in practice is still an intriguing task. Basic macromolecular characteristics of polyethylene or polypropylene like molar mass moments and their distributions (MMD) but also chain conformation and thus information on long-chain branching, can be addressed with high-temperature size-exclusion chromatography (HT-SEC). Hyphenation of infrared detection to size-exclusion chromatography expands possibilities of SEC even more and allows to reveal comonomer incorporation across molecular weight and thus help in the study of catalytic systems used in polyolefin synthesis.Multiband filter-based infrared detector gives an easy and fast access to so-called short chain branching distribution (SCB) vs MMD by coupling to HT-SEC. In our previous work [31], we summarize recent findings on application of a filter-based detector towards characterization of polyolefins synthesized with different catalytic systems and varying comonomer types. In this work, an influence of the comonomer type on the detector calibration line is elaborated. Statistical evaluation of different calibration lines is discussed in detail. Based on this evaluation practical aspects of filter-based IR detectors calibration are mentioned. Finally, numerical computer simulations can predict how much calibration lines deviate from linearity based on the spectra of the polymer and on the bandwidth of the detector filters.Graphical abstractImage 1
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