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Polymer
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0032-3861
Published by Elsevier Homepage  [3185 journals]
  • Understanding the effect of chain entanglement state on melt
           crystallization of the polymer freeze-extracted from solution: The role of
           critical overlap concentration
    • Abstract: Publication date: Available online 18 June 2019Source: PolymerAuthor(s): Yingxiong Wang, Jiaxin Fu, Mingjin Liu, Qiang Fu, Jie Zhang Freeze-drying of dilute polymer solution is a widely accepted method to yield disentangled polymer. By this method, it has been pointed out that samples recovered from dilute solution possess a better crystallization ability than the bulk polymer. Here, the important role of the critical overlap concentration c* in polymer solution is firstly stressed to give a more quantitative understanding in the relation between entanglement state and melt crystallization behavior. Crystallization kinetics of poly (lactic acid) freeze-extracted from dichloromethane solution with various concentration below and above c*, as well as the crystalline structure after isothermal crystallization at 110 °C, were investigated by means of differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). Results indicated that crystallization kinetics and lamellar thickness (Lc) show a strong dependence on precursor solution concentration only when the concentration is lower than the critical value (c*), while above c* the crystallization behavior changes a little. Besides, a more rational method to characterize the chain entanglement state in polymer solution and to select concentrations accordingly was suggested, that is, using a dimensionless variable [η]c which is the product of intrinsic viscosity [η] and solution concentration c.Graphical abstractImage 1
       
  • Deformation mechanism of hard elastic polyethylene film during uniaxial
           stretching: Effect of stretching speed
    • Abstract: Publication date: Available online 18 June 2019Source: PolymerAuthor(s): Yuanfei Lin, Xueyu Li, Xiaowei Chen, Minfang An, Qianlei Zhang, Daoliang Wang, Wei Chen, Panchao Yin, Lingpu Meng, Liangbin Li The effects of stretching speed on the structural evolutions and mechanical behaviors of hard-elastic polyethylene films are studied with in-situ and ex-situ small-angle X-ray scattering (SAXS), scanning electronic microscope (SEM) and tensile tests in a wide stretching speed range (0.04–4 mm/s). Based on the evolutions of structural parameters extracted from SAXS results and the surface morphologies from SEM experiments, the stretching speed space can be divided into two regions with the boundary of 0.8 mm/s. Stress induced microphase separation of amorphous phase triggers the yielding behavior, which distributes more homogeneously with the increase of stretching speed. In region I, microphase separation tends to develop into cavities at smaller strain due to the thorough relaxation process of molecular chains in amorphous phases, which results in the inhomogeneous deformation during further stretching. In region II, the relaxation of molecular chains is not enough to response to the variation of external tensile field, thus inducing the uniform distribution of the occurrence of microphase separation.Graphical abstractImage 1
       
  • Curing behavior and microstructure of epoxy-POSS modified novolac phenolic
           resin with different substitution degree
    • Abstract: Publication date: Available online 18 June 2019Source: PolymerAuthor(s): Zixuan Lei, Jingru Ji, Qianqiu Wu, Junjie Zhang, Yixun Wang, Xinli Jing, Yuhong Liu Easily oxidized group and rigid structure of phenolic resin (PR) network can result in brittleness and low char yield at high temperatures, which limits the widespread applications of PR in harsh environment. Whilst organic-inorganic hybrid material, such as POSS-containing material was introduced to enhance PR, the microstructure and the thermo-mechanical properties of the hybrid material modified PR are not well understood. Therefore, in the work, a novel organic-inorganic hybrid networks (ENH) were prepared with epoxy-polyhedral oligomeric silsesquioxane (EPOSS) modified novolac phenolic resin (EN) and hexamethylenetetramine (HMTA) to further clarify the curing behavior and its relation to microstructure and the resulting thermal-mechanical properties. Here, the curing characteristics of ENH were discussed by usinag advanced isoconversional method and Fourier transform infrared spectroscopy (FTIR). It was revealed that a diversity of crosslinking networks was exhibited after curing ENH, including EPOSS-NR crosslinked, tethered structure, and self-polymerized structure of EPOSS as well as NH networks. When the substitution degree of EPOSS is relatively low, EPOSS serves as a junction point to further improve the crosslinking density of ENH networks, leading to better thermo-mechanical properties, thermal stability and tensile property as well as lower dielectric properties. However, as the self-polymerization of EPOSS increased, the NH network was dramatically disrupted and the thermo-mechanical properties, thermal stability and tensile property of ENH were deteriorated.Graphical abstractImage 1
       
  • A green cascade polymerization method for the facile synthesis of
           sustainable poly(butylene-co-decylene terephthalate) copolymers
    • Abstract: Publication date: Available online 17 June 2019Source: PolymerAuthor(s): Siyuan Xu, Feng Wu, Zhikai Li, Xiang Zhu, Xiaohong Li, Lian Wang, Yongjin Li, Yingfeng Tu Typical semicrystalline aromatic polyesters are synthesized via the condensation polymerization of aromatic diacids with excess diols in vacuum. We demonstrate here a green cascade polycondensation-coupling ring-opening polymerization (PROP) method for the facile incorporation of diols into polyesters in N2, utilizing cyclic oligo(butylene terephthlate)s as monomer and bio-based 1,10-decanediol as initiator. Poly(butylene-co-decylene terephthalate) (PBDT) copolyesters are synthesized with high atom economy (87–99%), and their structures are characterized and confirmed by the 1H quantitative NMR, two dimensional 1H–1H gCOSY and DOSY NMR spectra. Property investigations reveal that with the increment of decanediol content, the glass transition temperature, melting temperature, storage modulus and Young's modulus for PBDT copolyesters decrease, while the toughness increases, respectively. Our results provide a high atom economy PROP method for the synthesis of sustainable PBDT copolyesters, which have lower processing temperatures and improved ductility than poly(butylene terephthalate) (PBT) homopolymers, and could draw attentions for further investigations on the green synthesis of other copolyesters.Graphical abstractImage 1
       
  • Synthesis and self-assembly of Poly(N-octyl
           benzamide)-μ-poly(ε-caprolactone) miktoarm star copolymers displaying
           uniform nanofibril morphology
    • Abstract: Publication date: Available online 15 June 2019Source: PolymerAuthor(s): Chih-Feng Huang, Yi-Shen Huang, Kuan-Yu Lai In this study, we employed an efficient strategy by the combinations of chain-growth condensation polymerization (CGCP), styrenics-assisted atom transfer radical coupling (SA ATRC), and ring-opening polymerization (ROP) to synthesize novel miktoarm (μ) star copolymers. Accordingly, poly(N-octyl benzamide) (PBA) and poly(ε-caprolactone) (PCL) arms were conjugated to form μ-(PBA)2(PCL)m star (m = ca. 4; Mn = ca. 13400; Đ = 1.17; abbr.: μ-(PBA)(PCL)). Thermal properties of homopolymers and μ-(PBA)(PCL) were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). In μ-(PBA)(PCL) star copolymer, notably, an increased Tg of PBA chain (26.3 °C) was detected as well as the melting behavior in Tm (44.8 °C) and the peak profile were significantly changed. It might be due to topological influence on the restriction of both chain mobility and crystallinity. The behaviors of slow crystallization and low crystallinity of μ-(PBA)(PCL) star can be revealed by polarized optical microscopy (POM) and Fourier-transform infrared spectroscopy (FT-IR). We then analyzed morphology of drop-casting thin films of PCL, PBA, and μ-(PBA)(PCL) (co)polymers on Si wafer by atomic force microscopy (AFM). Casting by 1 wt% μ-star solution, we obtained uniform and clear nanofibers with an average diameter of ca. 20 nm. Using grazing-incidence X-ray diffractometer (GI XRD), orthorhombic (110) and (200) diffraction peaks were clear observed. In addition, grazing-incidence small-to-wide angle X-ray diffractometer (GI SWAXS) of μ-(PBA)(PCL) thin film displayed diffraction peaks composed of q/q* peaks of 1:√3 with a periodic size of approximately 16.1 nm that revealed the diameter of the nanofibril morphology.Graphical abstractImage 1
       
  • Fuel cell electrolyte membranes based on copolymers of protic ionic liquid
           [HSO3-BVIm][TfO] with MMA and hPFSVE
    • Abstract: Publication date: Available online 15 June 2019Source: PolymerAuthor(s): V.M. Ortiz-Martínez, Alfredo Ortiz, Verónica Fernández-Stefanuto, Emilia Tojo, Maxime Colpaert, Bruno Améduri, Inmaculada Ortiz Polymeric ionic liquids (PILs) have recently been attracting great attention as new types of electrolytes for polymer exchange membrane fuel cells (PEMFCs), clean energy devices, due to their outstanding properties. In this work, the copolymerization of the ionic liquid (IL) 1-(4-sulphobutyl)-3-vinylimidazolium trifluoromethanesulphonate, [HSO3-BVIm][TfO], with methyl methacrylate (MMA) and perfluoro-3,6-dioxa-4-methyl-7-octene sulfonyl fluoride in its hydrolyzed form (hPFSVE), respectively, was performed for the preparation of structurally new IL copolymer membranes with enhanced conductive properties in comparison with the pristine PIL form. Membranes were synthesized through a facile photopolymerization method under UV radiation. The effect of temperature under wet and dry conditions on the ionic conductivities of the resulting membranes was analyzed. The performances of the new membranes were also assessed in a proton exchange fuel cell for power generation. Both poly ([HSO3-BVIm][TfO]-co-MMA) and poly ([HSO3-BVIm][TfO]-co-hPFSVE) electrolyte membranes offered high conductivity even in dry conditions (in the order 10−3 - 10−2 S cm−1). At low MMA and hPFSVE amounts (10 mol%), the ionic conductivity and power performances of the resulting membranes were enhanced in comparison with the membrane only constituted of the polymerizable IL showing the promising prospects of these ionic liquid-based copolymers as proton exchange membranes, with power outputs up to 45 mW cm−2.Graphical abstractImage 1
       
  • Effects of electron donating and accepting moieties on electrical memory
           behaviors of polymers
    • Abstract: Publication date: Available online 15 June 2019Source: PolymerAuthor(s): Yongjin Kim, Jinseok Lee, Wonsang Kwon, Junman Choi, Jonghyun Kim, Jehan Kim, Moonhor Ree In this study, three different series of vinyl copolymers bearing electron donating and accepting moieties in various compositions and their homopolymers were synthesized by reversible addition-fragmentation chain transfer polymerizations. They all were soluble in conventional organic solvents and gave good quality nanoscale films via conventional coating and drying processes. They were thermally stable up to 242 °C or higher temperatures. Their optical and electrochemical properties as well as electron densities and mass densities were measured. The nanoscale film morphologies were further examined by synchrotron grazing incidence X-ray scattering analysis; they were confirmed as amorphous or structurally-featureless films. All polymers exhibited various electrical properties depending on the polymers and film thicknesses. In particular, only p-type digital memory characteristics were observed within certain film thickness windows, regardless of electron donating polymers, electron accepting polymers, and their copolymers. Moreover, all polymers revealed high memory performances with low switching-ON voltages, high ON/OFF current ratios and high reliabilities even in air ambient conditions. The memory behaviors followed Ohmic conduction and trap-limited space charge limited conduction in the OFF-state and Ohmic conduction in the ON-state. However, the film thickness window showing digital memory characteristics was significantly dependent upon the compositions of electron donating and accepting moieties. Higher fraction of electron donating moieties provided wider film thickness window for digital memory. For this aspect, the electron accepting polymers could gain great benefits, whereas the electron donating polymers could attain only negative impacts. Overall, all polymers of this study are suitable for the low-cost mass production of high-performance programmable memory devices.Graphical abstractImage 1
       
  • Thermal insulation Behavior of Functionally Graded Aerogel: The Role of
           Novolac Molecular-Weight
    • Abstract: Publication date: Available online 15 June 2019Source: PolymerAuthor(s): Mina Noroozi, Mahyar Panahi-Sarmad, Ahmad Reza Bahramian In this research, a novel aerogel with a functionally-graded (FG) structure as a thermal insulator has been fabricated without interfaces through sol-gel polymerization. The effects of molecular-weight (Mw) and initial-solvent concentration as decisive parameters in the microstructure of phenol-formaldehyde aerogels are systematically studied. The results show that a broad spectrum of Mw created via the precise control of the cross-linking (CL) process of the resin. Moreover, the sol-size have been remarkably augmented when increasing the Mw. The porousness structure assessment illustrated that the porosity decreases with enhancing the amount of solvent, but increasing Mw has no significant effect on the porosity of specimens. In FG-aerogel microstructure, more homogeneous distribution in the sol-size and significant decrement in pore size is observed while the Mw and solution concentration are simultaneously increased throughout the structure. Therefore, FG-aerogel structure contains a wide range of porosity, thermal conductivity (0.029 - 0.422 (W⁄(m.K))) and pore size (200-2000 nm) that leads to unique structural features of aerogels.Graphical abstractImage 10
       
  • A novel liquid imidazole-copper (II) complex as a thermal latent curing
           agent for epoxy resins
    • Abstract: Publication date: Available online 15 June 2019Source: PolymerAuthor(s): Bo Yang, Yanyun Mao, Yihui Zhang, Bian Guofeng, Liying Zhang, Yi Wei, Qiuran Jiang, Yiping Qiu, Wanshuang Liu In this study, 1-cyanoethyl-2-ethyl-4-methylimidazole (1C2E4MI) was modified by copper chloride to improve its thermal latency towards epoxy resins. Unexpected complexation between 1C2E4MI and copper chloride was discovered, and two complexes which included a liquid and a solid were generated. The microanalytical results show that the ligand-metal ratios of these two complexes are 7:1 (liquid) and 1:1 (solid), rather than the theoretical 4:1 ratio. The liquid 1C2E4MI-copper (II) complex (Complex-L) exhibits superior miscibility with epoxy resins, and the resulting epoxy systems show distinctly prolonged pot life at 25 and 60 °C. Curing kinetic study indicates the epoxy system containing Complex-L can be cured using a similar manner like that containing 1C2E4MI. Moreover, the epoxy resin cured with Complex-L has glass transition temperature and tensile properties comparable to that cured with 1C2E4MI.Graphical abstractImage 105971
       
  • All-atom molecular dynamics study of impact fracture of glassy polymers.
           I: Molecular mechanism of brittleness of PMMA and ductility of PC
    • Abstract: Publication date: Available online 14 June 2019Source: PolymerAuthor(s): Kazushi Fujimoto, Zhiye Tang, Wataru Shinoda, Susumu Okazaki Molecular mechanism of brittle and ductile impact fractures of glassy polymers has been investigated. We performed atomistic molecular dynamics (MD) calculations for two glassy polymers, brittle poly(methyl methacrylate) (PMMA) and ductile polycarbonate (PC) using the dissociative force fields. The systems were prepared as realistic as possible such that they reproduced the experimental molecular weight distribution, tacticity, radius of gyration, and entanglement density. The calculated system simulated a small portion of the macroscopic specimen near the notch. The simulations adopted a uniaxial extension condition with the lateral pressure maintained as 1 atm. Under this condition, our atomistic models reproduced the brittle fracture of PMMA via cavitation and ductile fracture of PC via shear yielding and strain hardening. The fracture pathways were determined only by the differences in the material. A conceptual bridge between microscopic simulations and macroscopic experimental observations was provided. The brittle fracture of PMMA is found to be caused by the less flexible backbones with fewer entanglements as well as the inhomogeneity of the material. This contrasts with the finding that more flexible backbones with denser entanglement network result in ductility for PC.Graphical abstractImage 1
       
  • Synthesis of medium bandgap copolymers based on benzotriazole for
           non-fullerene organic solar cells
    • Abstract: Publication date: Available online 14 June 2019Source: PolymerAuthor(s): Shanshan Ma, Yu Song, Zhenfeng Wang, Baitian He, Xiye Yang, Li Li, Baomin Xu, Jie Zhang, Fei Huang, Yong Cao Three new copolymer donors based on DCN-alt FTAZ PT-68, PT-810-H, and PT-810-L were synthesized by adjusting the alkyl chains and molecular weight. The copolymers showed deep highest occupied molecular orbital (HOMO) levels of about −5.50 eV due to introducing fluorine atoms and cyano electron-withdrawing groups. Therefore, devices based on the copolymers as donors and ITIC as acceptors had high open-circuit voltages (VOC) exceeding 1.00 V. Due to a dicyanodistyrylbenzene (DCN) unit providing rigid and extended conjugation and reducing the backbone torsion, the blended films had high hole mobility values of about 2.50 × 10−3 cm2 V−1 s−1. Devices with the PT-810: ITIC blended film had the highest power conversion efficiency (PCE) of 7.03%, with an open-circuit voltage of 1.04 V, a short-circuit current density of 12.25 mA/cm2, and a fill factor of 55%. These results provide guidance for the design of high-efficiency photovoltaic materials.Graphical abstractBenzotriazole-based medium bandgap copolymer donors were synthesis, which show deep HOMO levels of about −5.50 eV. A PCE of 7.03% was obtain with the device based on PT-810-H: ITIC, with a high open-circuit voltage (VOC) exceed 1.00 V and high hole mobility value about 2.50 × 10−3 cm2 V−1 s−1.Image 1
       
  • Enhanced thermal stability and mechanical property of EVA nanocomposites
           upon addition of organo-intercalated LDH nanoparticles
    • Abstract: Publication date: Available online 14 June 2019Source: PolymerAuthor(s): Ji-Hee Lee, Wei Zhang, Hyeon-Ju Ryu, Goeun Choi, J. Yoon Choi, Jin-Ho Choy Organo-intercalated layered double hydroxides (LDHs)/ethylene vinyl acetate (EVA) nanocomposites were synthesized using the solution blending method. Pristine layered double hydroxides are not compatible with hydrophobic polymer matrix due to their hydrophilic property. As an attempt to improve the compatibility of LDHs with hydrophobic EVA, positively charged LDH surface was modified by incorporating various anionic surfactants. Surfactants were selected by considering the length of aliphatic chains conjugated with and without an aromatic ring such as sodium dodecyl sulfate (DS), sodium dodecylbenzene sulfonate (DBS), and stearate (SA). The organo-intercalated LDHs into EVA resulted in enhanced thermal stability (ΔT0.5 = 7–19 °C, T0.5: temperature at 50 wt% weight loss) and mechanical strength of the EVA nanocomposites depending on the type and the loading concentration of organo-intercalated LDHs compared to these of intact EVA. Especially, SA-LDH had higher enhancement efficiency in elongation at break than DS-LDH and DBS-LDH. It is, therefore, concluded that organo-intercalated LDHs using suitable anionic surfactants are potential inorganic materials that can be considered as a nanofiller with high thermal stability and mechanical property.Graphical abstractImage 1
       
  • Preparation and characterization of boronic acid- functionalized
           halloysite Nanotube/Poly(vinyl alcohol) nanocomposites
    • Abstract: Publication date: Available online 14 June 2019Source: PolymerAuthor(s): Masaru Mukai, Wei Ma, Keiko Ideta, Atsushi Takahara Organic-inorganic nanocomposite films consisting of surface functionalized halloysite nanotube (HNT) and poly (vinyl alcohol) (PVA) with improved mechanical and thermal properties were prepared. The surface of HNT was modified with boronic acid by two different methods. In the first method, a boronic acid group bearing a triethoxysilane was synthesized and used to modify HNT directly. In the second method, HNT was modified by 3-aminopropyltriethoxysilane (APTES) and 4-formylphenylboronic acid sequentially. The surface-modified HNT was characterized by ζ-potential, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The nanocomposite films were prepared by solvent casting, followed by compression molding. The molecular aggregation structure and physicochemical properties were investigated by UV–Vis spectrophotometry, differential scanning calorimetry, wide-angle X-ray diffraction, tensile test, and dynamic mechanical analysis.Graphical abstractImage 1
       
  • Mixed-matrix membranes based on 6FDA-ODA polyimide and Silicalite-1 with
           homogeneous spatial distribution of particles
    • Abstract: Publication date: Available online 14 June 2019Source: PolymerAuthor(s): Petra Diblíková, Petr Sysel, Pavel Čapek We report an experimental procedure leading to defect-free mixed-matrix membranes with a homogeneous spatial distribution of filler particles, volume fractions of which are within the interval [0.10, 0.35]. A polyimide matrix was synthetized from 4,4´-(hexafluoroisopropylidene) diphtalic anhydride and 4,4′-oxydianiline in the solution with N,N-dimethylformamide. (3-aminopropyl) triethoxysilane was used as a linker to improve the phase contact between silicalite-1 particles and the polyimide matrix. We found that a homogeneous spatial distribution of particles in the resulting membrane was achieved if kinematic viscosity of a polyimide precursor solution was greater than 9.5 cm2 s−1. To do so, an initial mass fraction of the solids in the solution, a reaction temperature and a concentration of water in the solvent had to carefully be selected and controlled. Besides these conditions, we fine-tuned the process of imidization, particularly the rate of evaporation of N,N-dimethylformamide. We arrived at the conclusion that its effect on reproducibility of the entire process was minor rather than major. In addition, we characterised microstructures of the resulting membranes by imaging in a scanning electron microscope. In this context we examined two ways of preparation of membrane specimens and showed that back-scattered electron imaging of polished sections obtained using a metallographic technique clearly outperformed the often-used imaging of fractured surfaces. Finally, we evaluated the homogeneity of spatial distributions of particles by means of morphological descriptors, namely a position-dependent volume fraction of the silicalite-1 phase.
       
  • Chain expansion process from knotted globule
    • Abstract: Publication date: Available online 13 June 2019Source: PolymerAuthor(s): Mitsuo Nakata, Yoshiki Nakamura, Yasuyuki Maki, Toshiaki Dobashi Knotting in a polymer chain was investigated by observing the chain expansion process from a collapsed chain for the solution of poly(methyl methacrylate)(PMMA) with Mw = 1.22 × 107 in the mixed solvent tert-butyl alcohol + water(2.5 vol%). Because of very slow phase separation in the solution the chain collapse after a temperature drop and chain expansion after a jump were determined by static light scattering. PMMA chain was shown to collapse rapidly to an unknotted globule, which subsequently contracted slowly to a knotted globule. The chain expansion process from the knotted globule was dominated by the chain compactness and the degree of knotting of the initial globule. A complete chain expansion from a heavily knotted globule often required a very long time indicating an existence of long-lived knots. The chain expansion from the unknotted globule occurred too fast to be followed by scattering experiment.Graphical abstractImage 1
       
  • Application of mean-field theory to the spin casting of polystyrene and
           poly(methyl methacrylate) blend films from toluene
    • Abstract: Publication date: Available online 13 June 2019Source: PolymerAuthor(s): Youmna Mouhamad, Parvaneh Mokarian-Tabari, Richard.A.L. Jones, Mark Geoghegan The Flory-Huggins free energy of mixing is shown to be appropriate for the analysis of the temporal evolution of a ternary blend of polystyrene and poly(methyl methacrylate) during spin-coating from toluene using an in-situ light scattering technique. For the range of concentrations studied, both the onset of film instability and the observation of a scattering ring occur at the same toluene volume fraction. The success of Flory-Huggins theory indicates that polymer chains retain random walk characteristics during spin-coating. It is also concluded that the thermodynamics of phase separation during film formation is independent of the initial solvent concentration.Graphical abstractImage 104864
       
  • Glass transition of a polystyrene surface as detected via two-dimensional
           diffusion of Au atoms during physical vapor deposition
    • Abstract: Publication date: Available online 13 June 2019Source: PolymerAuthor(s): Takashi Sasaki, Yuta Ito, Taichiro Sasai, Satoshi Irie We investigated two-dimensional diffusion of Au atoms across the surface of a polystyrene (PS) film during physical vapor deposition to determine the surface glass transition temperature (Tg). Deposited Au atoms underwent two-dimensional diffusion on the PS surface until they coalesce with other atoms or aggregated particles. The diffusivity of Au on the PS surface was evaluated from the size and the number density of yielded Au nanoparticles. The diffusion coefficient D of Au was found to exhibit a drastic change near 356 K, which was assigned to the surface Tg of the PS substrate. A stronger temperature dependence of D observed near Tg suggests that Au diffusion is coupled with the segmental dynamics of PS. The change in the diffusion coefficient suggests an essential difference in the diffusion mechanism below and above the Tg of the PS surface. We assume that diffusion on a glassy PS surface reflects a more heterogeneous feature of the PS surface than that above Tg. This was qualitatively supported by the results from Monte Carlo simulations with varying activation energy distributions.Graphical abstractImage 1
       
  • High solid content production of environmentally benign ultra-thin
           lignin-based polyurethane films: Plasticization and degradation
    • Abstract: Publication date: Available online 12 June 2019Source: PolymerAuthor(s): Yan Zhang, Jingya Wang, Xiangchen Fang, Jianjun Liao, Xin Zhou, Shumin Zhou, Fudong Bai, Shaozhong Peng Here, an environmentally benign method of minimizing waste creation and production time was proposed to fabricate the ultra-thin polyurethane films (LPUfs). The lignin was used as hard segments and poly(ε-caprolactone) glycol (PCL) served as soft segments through the coupling of hexamethylene diisocyanate (HDI). The modified fabrication method could economize the usage of solvent more than six-fold and reduce the production time within 6 h. Several types of additives such as epoxidized soybean oil (ESO), dioctyl sebacate (DOS), acetyl tributyl citrate (ATBC), cardanol and antisticking agent were incorporated to improve the performance of the films and the ATBC has advantages as plasticizer for the LPUf. The biofilm was flexible and foldable without breaking at the thickness of 20 μm, the optimized elongation at break and tensile strength could reach 246.36% and 16.68 MPa, respectively. Moreover, the bio-polyurethane revealed outstanding UV-shielding capacity and excellent biodegradability in the soil due to the green lignin and PCL. Thus this strategy enabled the high efficient production of sustainable polyurethane from renewable and nontoxic lignin using less organic solvents.Graphical abstractThe flexible and foldable ultra-thin polyurethane film was fabricated by a high solid content method with reducing the usage of solvent more than six-fold and production time within 6 h. This strategy enabled the high efficient production of biodegradable and sustainable polyurethane films from renewable and nontoxic lignin.Image 1
       
  • Influence of water content on alkali metal chloride transport in
           cross-linked Poly(ethylene glycol) Diacrylate.1. Ion sorption
    • Abstract: Publication date: Available online 12 June 2019Source: PolymerAuthor(s): Eui-Soung Jang, Jovan Kamcev, Kentaro Kobayashi, Ni Yan, Rahul Sujanani, Theodore J. Dilenschneider, Ho Bum Park, Donald R. Paul, Benny D. Freeman The relationship between ion size and sorption properties in water swollen uncharged polymers was investigated as a model system for understanding ion sorption and transport in more complex systems (i.e., charged polymer networks). Alkali metal chloride (e.g., LiCl, NaCl, and KCl) sorption coefficients in a series of cross-linked poly(ethylene glycol) diacrylate (XLPEGDA) polymer membranes were measured as a function of external salt concentrations ranging from 0.01 to 1.0 M. The relative order of salt sorption coefficients was: KCl > LiCl > NaCl. This order does not correspond to the order of ion hydration size (i.e., Li+ > Na+ > K+). The alkali metal chloride sorption behavior in XLPEGDA polymers is influenced by both ion hydration and polymer-ion specific interactions. XLPEGDA polymers having three different equilibrium water uptake values were prepared to investigate the effect of water content on salt sorption in these polymers. Generally, ion sorption coefficients increase as polymer water content increases. Salt activity coefficients in the polymers were quantified to better understand the thermodynamic non-ideality of ions in polymer networks. Flory-Rehner theory was used to predict water volume fraction in the polymers equilibrated with salt solution based on salt sorption measurements.Graphical abstractImage 1
       
  • Effect of organic anion with multiple hydrophobic sites on gelation and
           phase separation in aqueous methylcellulose solution: Beyond simple
           salting-in effect
    • Abstract: Publication date: Available online 12 June 2019Source: PolymerAuthor(s): Motoki Shibata, Tsuyoshi Koga, Koji Nishida We studied addition effect of sodium tetraphenylborate (NaBPh4), an organic salt with multiple hydrophobic sites, on thermoresponsive behavior of aqueous methylcellulose (MC) solution. By means of simultaneous measurements of viscosity and light transmittance during heating, it was clarified that the concentration of added NaBPh4 determines which of gelation and phase separation occurs first. Aqueous MC solution without NaBPh4 formed gels below the phase separation temperature, and therefore the phase separation remained incomplete. With increasing the concentration of added NaBPh4, the gelation temperature monotonously increased, whereas the phase separation exhibited complicated behavior. The phase separation temperature in gel phase drastically increased by addition of small amount of NaBPh4 in similar fashion to the gelation temperature, although the phase separation in gel phase faded away when the concentration of NaBPh4 exceeded ca. 0.05 M. Alternatively, liquid-liquid phase separation appeared. In contrast to the phase separation in gel phase, the liquid-liquid phase separation occurred essentially below the gelation temperature and proceeded completely to form macroscopic binary domains. Temperature of the liquid-liquid phase separation decreased initially, but it turned upward when the concentration of added NaBPh4 exceeded ca. 0.15 M and increased drastically with the further addition. In other words, the addition effect of NaBPh4 to the liquid-liquid phase separation switched from salting-out to salting-in. The liquid-liquid phase separation in progress was immobilized by application of additional heating above the gelation temperature. These various structure developments depending on the concentration of added NaBPh4 were observed by optical microscopy (OM) and small-angle light scattering (SALS). On the basis of the experimental results, we proposed a mechanism of the addition effects of organic anion with multiple hydrophobic sites on the gelation and the phase separation of aqueous MC.Graphical abstractImage 1
       
  • Structure and Self-reinforcing Mechanism of Biaxially Oriented
           Polyethylene Pipes Produced by Solid Phase Die Drawing
    • Abstract: Publication date: Available online 12 June 2019Source: PolymerAuthor(s): Chen Kong, Yujie Wang, Lin Ye, Xiaowen Zhao Biaxially oriented polyethylene (PE) pipes were prepared through solid phase die drawing technology. Drawing speed presented a prominent effect on the hoop draw ratio (DRhoop) and axial draw ratio (DRaxial) of the pipes. For pipe with DRhoop/DRaxial of 2.465/1.182, the tensile strength was improved significantly along hoop direction as well as axial direction, reaching respectively 1.75 and 1.3 times of the isotropic sample. Through die drawing, more uniform and dense oriented lamellar structure formed, resulting in the decrease of long period (Lac) and lateral size of the lamellae (Llateral). With increasing DRaxial, in hoop-radial plane, the orientation degree increased first and then decreased, and lamellar twisting became more and more prominent. At low DRaxial, lamellae were arranged mainly perpendicular to hoop direction. However, at high DRaxial, the normal of lamellae deviated from hoop direction to axis, and biaxial orientation structure formed, resulting in biaxial self-reinforcement for PE pipes.Graphical abstractImage 1062
       
  • The molecular weight dependence on physical aging of Polycarbonate
    • Abstract: Publication date: Available online 12 June 2019Source: PolymerAuthor(s): Shotaro Nishitsuji, Yuki Watanabe, Hiroshi Ito, Masaru Ishikawa, Takashi Inoue, Mikihito Takenaka In our previous paper, we reported that the impact value of polycarbonate (PC) increases with increasing molecular weight and decreases upon annealing [Polymer 2012, 53, 895–896]. To clarify these phenomena, the effects of molecular weight and heat treatment on the fracture of PC are investigated in this study. The results show that the stress for craze nucleation increased as the molecular weight increased but was not affected by annealing. The shear modulus and bulk modulus do not exhibit molecular weight dependence, but annealing resulted in a slightly increased shear modulus and a decreased bulk modulus. Furthermore, the amplitude and correlation length of density fluctuations of the Debye–Buche mode in small-angle X-ray scattering profiles were shown to increase upon annealing. On the basis of these results, it is suggested that, as the molecular weight increases, the toughness of PC is enhanced because the increase in molecular weight increases the stress of slippage for entangled molecular chains. In addition, it is proposed that the change in the fraction of fine voids resulting from density fluctuations may affect the toughness, resulting in the reduced toughness observed for annealed PC.Graphical abstractImage 1006
       
  • Publishers Note
    • Abstract: Publication date: Available online 12 June 2019Source: PolymerAuthor(s):
       
  • Regioregularity controlled phase behavior for Poly(3-hexylthiophene): A
           combined study of simple coarse-grained simulation and experiment
    • Abstract: Publication date: Available online 11 June 2019Source: PolymerAuthor(s): Hyeong Jun Kim, Jin-Seong Kim, Youngkwon Kim, Yeon Sik Jung, Bumjoon J. Kim, YongJoo Kim In this study, we developed a simple coarse-grained simulation model framework to investigate the effect of regioregularity (RR) on the crystallization behavior of poly(3-hexylthiophene) (P3HT). To describe the regio-chemistry of P3HT, two different coarse-grained beads were designed to contain either regio-regularly substituted head-to-tail (HT) orientations or regio-irregularly substituted non-HT orientations, and two beads were randomly incorporated in a single polymer where the total RR was tuned from regio-random (RR = 50%) to regio-regular (RR = 100%). Based on our modeling, the crystallization behaviors in both bulk and solution states were investigated. As the number of irregularly substituted non-HT orientations increased, crystallization temperature in the bulk shifted to lower temperature. When the RR of P3HT was lower than a critical RR value, which was 72.2% in our study, the crystallization of the P3HT chains was eventually suppressed. In the solution state, most of high RR P3HT chains stacked in parallel to produce nanowire (NW) structure to maximize the number of π-stackings in the system, whereas the P3HTs formed a globule structure when the RR value decreased below critical RR. To experimentally validate our simulation results, we synthesized a series of P3HTs having precisely controlled RRs from 66% to 95% with comparable molecular weights to the simulation. Well-matched experimental results suggested that our simplified model provides efficient computational guidance to describe the RR effect on crystalline feature of P3HTs for the various possible applications in organic optoelectronics.Graphical abstractImage 1
       
  • Functionalized carbon nanotubes modulate the phase transition behavior of
           thermoresponsive polymer via hydrophilic-hydrophobic balance
    • Abstract: Publication date: Available online 11 June 2019Source: PolymerAuthor(s): Ritu Yadav, Pannuru Venkatesu The world of nano-science is getting popularity due to their vast applications in the field of material science, biotechnology and biomedical research. In this context, carbon-nanotubes (CNTs) have provided new horizons because of their use as molecular transporters. Nonetheless, the low solubility in molecular solvents and cytotoxity of CNTs prevent their utility in biological process. Here, we established increasing solubility and dispersion of CNTs by functionalization with –COOH group that overcome these fundamental limitations. In spite of a broad range of applications of CNTs, it is highly desirable to examine the effect of functionalized CNTs (fCNTs) on the thermoresponsive polymers. In this respect, we have examined the effect of fCNTs on the thermoresponsive behavior of aqueous poly(N-isopropylacrylamide) (PNIPAM) solution by using several techniques such as dynamic light scattering (DLS), differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy and Field emission scanning electron microscope (FESEM). The present results indicate that the presence of fCNTs causes a small increase in the lower critical solution temperature (LCST) of PNIPAM which becomes more pronounced at lower concentration of fCNTs. It reveals that fCNTs indirectly favors the hydrophilic interactions of surrounded water molecules with PNIPAM that eventually stabilizes the coil state of PNIPAM.Graphical abstractImage 1
       
  • Synthesis of soluble, air-stable fully conjugated ladder polymers
    • Abstract: Publication date: Available online 10 June 2019Source: PolymerAuthor(s): Takaaki Hirano, Hitoshi Hanamura, Munenori Inoue, Saori Ueda, Makoto Watanabe, Masao Tanabiki, Koichiro Mikami Herein, we report the synthesis of soluble, air-stable fully conjugated ladder polymers incorporating a BTBT structure as a repeating unit. The ladder polymers were synthesized through a simple process: A Migita-Kosugi-Stille polycondensation, followed by an intramolecular oxidative C–H annulation (Scholl reaction). Absorption and fluorescence spectrometric analyses, as well as theoretical analysis and model reaction revealed that the intramolecular Scholl reaction proceeded efficiently. Electrochemical studies combined with theoretical molecular orbital analysis indicated that the resultant ladder polymers are stable under ambient conditions, because the drastic ascension of the highest-occupied molecular orbital (HOMO) level was suppressed even after ladderization by the Scholl reaction. Furthermore, the bottom-gate, top-contact organic thin-film devices that were fabricated from these ladder polymers operated as solution-processable p-type transistors.Graphical abstractImage 1
       
  • Deformation induced void formation and growth in β nucleated
           isotactic polypropylene
    • Abstract: Publication date: Available online 10 June 2019Source: PolymerAuthor(s): Takahiko Kawai, Syota Soeno, Shin-ichi Kuroda, Shunsuke Koido, Tomoyuki Nemoto, Motonori Tamada In-situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) were carried out to investigate the deformation and the void formation behavior of β nucleated isotactic polypropylene during uniaxial stretching at 100 °C. WAXD results indicated that β crystal started to deform after yielding, followed by recrystallization to α-phase. A quasi-quantitative SAXS analysis was attempted to evaluate the length, width, and relative number of ellipsoidal nano-voids. The length of initial nano-void corresponded well to that of amorphous thickness of iPP. It strongly suggests that the nano-void was generated by the fragmentation of β lamellae. The nano-void length kept increasing exponentially up to the strain of 3, while the number of nano-voids decreased exponentially with the same rate constant as that of the length. In this strain region, the width kept constant. Above results clearly demonstrated that the nano-void grows only by one-dimensional coalescence along PP chain direction. The excellent ductility, i.e. the toughness, of β-PP was attributed to the plasticizing effect of nano-voids, which inhibits the stress concentration at the edge of the void.Graphical abstractImage 1
       
  • Lamellar structures in blends of amorphous–block–main-chain liquid
           crystal–block–amorphous copolymers and amorphous homopolymers: Effects
           of the amorphous homopolymer molecular weight
    • Abstract: Publication date: Available online 10 June 2019Source: PolymerAuthor(s): Mikihiro Hayashi, Junpei Kuribayashi, Masatoshi Tokita T (x-y-x) block copolymers comprising of a main-chain liquid crystal (LC) BB-5 (3-Me) polyester with a number-average molecular weight (Mn) of y kDa connected to poly (ethyl methacrylate) (PEMA) with a Mn of x kDa at both ends form long-range lamellar microdomains with the blocks segregated from one another over a wide-range of compositions. In this study, the lamellar forming T (5.5-39-5.5) and T (11-39-11) copolymers were blended with homoPEMA (Hz) with Mn of z kDa at a concentration of 20 wt% to give the two series of blends T (5.5-39-5.5)/Hz and T (11-39-11)/Hz. These blends were examined for microdomain morphology as a function of the molecular weight ratio of z/x. T (5.5-39-5.5)/Hz formed lamellar microdomains over the investigated z/x range of 0.6–3.8, whereas T (11-39-11)/Hz formed lamellae over a narrower range of 1.2–2.6. The lamellar spacing and the PEMA and LC lamellar thicknesses (dam and dLC) were constant over z/x and dam was greater than dam of the neat copolymer. However, the values of dLC for these two blends were different; T (5.5-39-5.5)/Hz had the same dLC as T (5.5-39-5.5), whereas T (11-39-11)/Hz had a smaller dLC than T (11-39-11). These lamellar thicknesses variations in the blends are discussed based on the conformations of the copolymer blocks and the accommodation fashion of the Hz additives.Graphical abstractImage 1
       
  • A reactive hydrophobically modified ethoxylated urethane (HEUR)
           associative polymer bearing benzophenone terminal groups: Synthesis,
           thickening and photo-initiating reactivity
    • Abstract: Publication date: Available online 10 June 2019Source: PolymerAuthor(s): Tao Guan, Zhukang Du, Xueyi Chang, Dongli Zhao, Shurui Yang, Ning Sun, Biye Ren Hydrophobically modified ethoxylated urethanes (HEURs), as a representative class of associative polymers, are widely used as rheology modifiers in waterborne systems such as coatings, emulsions, inks etc. due to their unique associative network structure and finite relaxation behavior in solution. However, conventional HEURs are non-reactive and generally stay free in final cured films, which may induce some damages to the performance of the coatings. To solve the problem, a new concept of reactive HEUR has been proposed. That is, a reactive HEUR should bear reactive hydrophobic end-groups which can chemically crosslink with matrix resins during the curing process of waterborne coatings. In this work, with the help of the hydrogen abstraction photo-initiating reactivity of benzophenone (BP) group, a reactive HEUR (BPC11HEUR) end-functionalized by a photo-initiator BP moiety has been prepared. In aqueous solution, as demonstrated by steady shear measurement, an exponential increment of solution viscosity along with the increasing of polymer concentration (C) was found when C surpassed its critical percolation concentration (Cp ≈ 23.6 g/L). Besides, ultraviolet (UV) light induced photolysis in aqueous solution manifested a typical photochemical reaction behavior of BPC11HEUR polymer with a final photolysis degree (D) of approximate 78% after 300 s of irradiation. In situ 1H NMR and rheological measurements collectively revealed the efficient photo-initiating reactivity of BPC11HEUR for waterborne UV monomers or resins. Further, rheological measurements demonstrated that the emulsion zero/low shear viscosity can be greatly enhanced by ca. 50 folds for a commercially available waterborne UV polyurethane acrylate emulsion when the addition amount of BPC11HEUR varied from 0 to 1.0 wt%. These results shown that the reactive BPC11HEUR polymer can not only be used to efficiently modify the rheological properties of solutions or emulsions but also can chemically crosslink with waterborne UV acrylic monomers or resins by light irradiation. The work may be of interest for development of reactive HEURs used in waterborne UV coatings, inks, and adhesives, etc.Graphical abstractImage 1
       
  • Graphene oxide grafted with polyoxazoline as thermoresponsive support for
           facile catalyst recycling by reversible thermal switching between
           dispersion and sedimentation
    • Abstract: Publication date: Available online 9 June 2019Source: PolymerAuthor(s): Alexander Kozur, Laura Burk, Ralf Thomann, Pierre J. Lutz, Rolf Mülhaupt Grafting polyoxazolines exhibiting a cloud point temperature (TCP) in the reaction medium onto graphene oxide (TRGO) prepared by thermal reduction of graphite oxide affords thermoresponsive catalyst supports and enables catalyst recycling by thermal switching between dispersion and sedimentation. In a facile grafting-to process the functional groups of the TRGO react with the cationic oxazolinium end groups, obtained by living cationic ring-opening polymerization of 2-ethyl-2-oxazoline, and covalently attach PEtOx having an average molar mass>10 000 g∙mol−1 and a TCP of 65 °C in polar solvents like water. Below the TCP at 25–30 °C stable dispersions of palladium supported on TRGO-g-PEtOx (Pd@TRGO-g-PEtOx) are obtained. As compared to the Pd@TRGO benchmark in the absence of PEtOx, Pd@TRGO-g-PEtOx exhibits higher catalyst activity in Suzuki-Miyaura-coupling reactions. Opposite to Pd@TRGO, Pd@TRGO-g-PEtOx readily agglomerates above TCP at 65 °C and enables easy and complete recovery of the catalyst by filtration and repeated catalyst reuse without encountering neither filtration problems nor drastic losses of catalyst activity.Graphical abstractGrafting of thermoresponsive poly(2-ethyl-2-oxazoline) (PEtOx) onto graphene oxide (TRGO) pepared by thermal reduction of graphite oxide enables switching between TRGO dispersion and sedimentation behavior as a function of temperature. Palladium catalysts supported on TRGO-g-PEtOx (Pd@TRGO-g-PEtOx) are highly active in Suzuki-Miyaura-coupling reactions below its TCP and are recycled by thermal switching from dispersion to sedimentation above its TCP.Image 1
       
  • Synthesis of ultrahigh molecular weight bottlebrush block copolymers of
           ω-end-norbornyl polystyrene and polymethacrylate macromonomers
    • Abstract: Publication date: Available online 7 June 2019Source: PolymerAuthor(s): Ho-Bin Seo, Yong-Guen Yu, Chang-Geun Chae, Myung-Jin Kim, Jae-Suk Lee Well-controlled polystyrene-polymethacrylate bottlebrush block copolymers (BBCPs) of ultrahigh molecular weight using ω-end-norbornyl polystyrene as the macromonomer for the first block were synthesized by combining living anionic polymerization (LAP) and ring-opening metathesis polymerization (ROMP). The ω-end-norbornyl polystyrene (NB-PSt), poly(tert-butyl methacrylate) (NB-PtBMA), poly(methyl methacrylate) (NB-PMMA), and poly(benzyl methacrylate) (NB-PBzMA) macromonomers (MMs) were synthesized by the LAP. The ROMP of the MMs led to poly(NB-g-St) (molecular weight, Mn = 1515 kDa, and dispersity, Ð = 1.12), poly(NB-g-tBMA) (Mn = 1470 kDa, Ð = 1.49), poly(NB-g-MMA) (Mn = 1128 kDa, Ð = 1.42), and poly(NB-g-BzMA) (Mn = 941 kDa, Ð = 1.16) bottlebrush homopolymers at degree of polymerization (DP) of 500. Synthesis of the BBCP, P(NB-g-St)-b-P(NB-g-tBMA) was well-controlled with high molecular weight and a low dispersity (Mn = 3002 kDa, Ð = 1.17) with a total DP of 1000. The self-assembly of the resulting BBCP films revealed periodic lamellar morphologies with characteristic photonic crystal properties.Graphical abstractImage 1
       
  • Non-Enthalpic Enhancement of Spatial Distribution and Orientation of CNTs
           and GNRs in Polymer Nanofibers
    • Abstract: Publication date: Available online 7 June 2019Source: PolymerAuthor(s): Yevgen Zhmayev, George L. Shebert, Shubham Pinge, Prabhleen Kaur, Hongshen Liu, Yong Lak Joo :Multi-wall carbon nanotubes (CNTs) and their unzipped counterparts graphene nanoribbons (GNRs) are promising materials for energy storage applications, due to their unique architecture and properties. However, spatial distribution and orientation in polymer matrices plays a crucial role in determining the charge and mass transfer effectiveness of the nanocomposite. Here, we report a controlled enhancement of dispersion and spatial alignment of CNTs and GNRs via gas-assisted electrospinning (GAES). This methodology obviates the use of surface modifications to ensure effective enthalpic interactions between a substrate and filler, and offers a “single-step” procedure for electrode fabrication. We conducted a rigorous TEM image analysis of as-spun PVA nanofibers and observed an average of 60 and 90 percent improvement in dispersion area due to the application of high but controlled air flow for CNTs and GNRs respectively. Alignment results demonstrate that stiff CNTs respond uniformly to the external deformation applied by GAES, while more the flexible GNRs have an inhomogeneous response.Graphical abstractGraphical abstract for this article
       
  • Tailoring the Thermal Conductivity of Poly(dimethylsiloxane)/Hexagonal
           Boron Nitride Composite
    • Abstract: Publication date: Available online 7 June 2019Source: PolymerAuthor(s): Ziwei Li, Ke Li, Jun Liu, Shui Hu, Shipeng Wen, Li Liu, Liqun Zhang Molecular dynamics (MD) simulation was employed to predict the thermal conductivity of poly(dimethylsiloxane) (PDMS)/hexagonal boron (h-BN) composite. Two MD simulation models were constructed. Model one is h-BN monolayer being adsorbed by PDMS chains, which is designed to examine the influence mechanism of polymer molecules on the heat conduction of h-BN. The polymer molecules were divided into several layers along the normal direction of the h-BN, which had different impacts on the thermal conductivity of h-BN. Model two is PDMS composites with different volume fractions of h-BN monolayer, which is used to investigate the influence of h-BN on thermal conductivity of the composites. Meanwhile, the orientation of the h-BN under the oscillatory shear was also considered. It presents three regimes on the thermal conductivity increased with the packing fraction after shearing. In general, this work opens some insightful avenues for manipulating the thermal conductivity of PDMS/h-BN composite.Graphical abstractImage 1001023
       
  • Rigid nanoparticles promote the softening of rubber phase in filled
           vulcanizates
    • Abstract: Publication date: 26 August 2019Source: Polymer, Volume 177Author(s): Yihu Song, Ruiquan Yang, Miao Du, Xinyan Shi, Qiang Zheng Enhanced mechanical softening accompanying nanoparticles reinforcement of rubber is an important source of energy dissipation and heat buildup of industrially engineered elastomers. Its mechanism previously assigned to damages in the filler network, rubber-filler interface and rubber phase remains controversial in more than 70 years. Through investigating the typical Payne effect of styrene-butadiene rubber gum and its vulcanizates as well as silica filled compounds and vulcanizates and the Mullins effect of unfilled and filled vulcanizates, we herein evidence that the filler-promoted softening of the rubber phase softens the filled elastomer nanocomposites. Especially we show that the Mullins effect is relevantly involved in the disentanglement/re-entanglement of dangling chains superposed on the entropically elastic network of the rubber phase. This paper clarifies that the mechanism of nonlinear mechanical softening for filled rubber compounds and vulcanizates should be rooted in macromolecular chains in the entanglement network (gum and filled compounds) or long dangling chain in non-ideally crosslinked network (vulcanized gum and filled vulcanizates), rather than damages involved in the “filler network” or filler-rubber interface. This suggests that adjusting the nonideally crosslinked network structure of viscoelastic rubber matrix should be able to optimize the use performance of the rubber nanocomposite products.Graphical abstractImage 1
       
  • Application of iterative reconstruction algorithms to mitigate
           CT-artefacts when measuring fiber reinforced polymer materials
    • Abstract: Publication date: 26 August 2019Source: Polymer, Volume 177Author(s): Arnold Wilbers, Ander Biguri, Jennifer Schillings, Joachim Loos In general, fiber reinforced polymer materials are being used in case of challenging mechanical requirements. Important parameters determining performance of such polymer composites are properties of the components as well as the quality of the fiber-polymer interface. For example, porosity or voids particularly at the interface will influence the overall performance of the composite negatively. Therefore, it is of importance to know the actual porosity value to e.g. calculate and predict the mechanical properties. In principle, a CT scan can provide the means to determine the amount, size, and shape of the voids in an X-ray transparent material. The difficulty, which arises in fully organic based i.e. carbon fiber reinforced polymer composites, is the small difference between absorption of X-rays in the carbon fibers versus the surrounding polymer matrix. At certain conditions, when single fibers need to be resolved and voids surrounding the fibers may exist, CT reconstruction artefacts introduced by standard algorithms are visible as “virtual” voids in large quantities severely limiting the correct determination of the actual porosity. On the other hand, in glass fiber reinforced polymer materials, the large density difference between fibers and matrix causes artefacts to appear, too. Specific experimental settings necessary to deal with the high absorption of the glass fibers (beam hardening enforces the use of X-ray filters) cause very low absorption differences between air and the polymer matrix and thus hardly provide information on the existence of voids. Iterative reconstruction techniques, however, are more robust against the encountered CT-reconstruction artifacts and may enable accurate determination of important sample features in polymer composite materials, and especially allow for accurate determination of voids or porosity. This work explores the use of two iterative versus standard reconstruction algorithms (CGLS and SIRT versus FDK) and validates the results with cross-sectional Optical Microscopy. The paper shows that iterative reconstruction algorithms outperform the standard reconstruction algorithm with respect to mitigating the influence of the CT reconstruction artefacts.Graphical abstractImage 1
       
  • Preparation of cyclodextrin-based porous polymeric membrane by bulk
           polymerization of ethyl acrylate in the presence of cyclodextrin
    • Abstract: Publication date: Available online 6 June 2019Source: PolymerAuthor(s): Yuichiro Kobayashi, Yukie Nakamitsu, Yongtai Zheng, Yoshinori Takashima, Hiroyasu Yamaguchi, Akira Harada We disclose an efficient synthesis to prepare polymeric membranes containing cyclodextrins (CDs). Bulk polymerization of ethyl acrylate containing peracetylated γ-CD (PAcγCD) yields a porous polymeric membrane containing CDs [CD membrane (BP)]. Krypton adsorption measurements reveal that the CD membrane (BP) has a porous structure. The specific surface area of the CD membrane (BP) is 10 times higher than that of a CD-based polymeric membrane prepared via solution casting using a solution containing poly(ethyl acrylate) and PAcγCD. Due to the large specific surface area of the CD membrane (BP) and the molecular recognition of CD, the capabilities and selectivity of CD membrane (BP) to separate bisphenol A as an environmental pollutant from water are demonstrated.Graphical abstractImage 1
       
  • The role of pH, ionic strength and monomer concentration on the
           terpolymerization of 2-acrylamido-2-methylpropane sulfonic acid,
           acrylamide and acrylic acid
    • Abstract: Publication date: Available online 5 June 2019Source: PolymerAuthor(s): Alison J. Scott, Thomas A. Duever, Alexander Penlidis The current study examines the effects of important factors (namely, pH, ionic strength and monomer concentration) on the terpolymerization of 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamide (AAm) and acrylic acid (AAc). A good understanding of how these factor levels affect terpolymerization reactivity ratios, and terpolymer composition, microstructure and molecular weight paves the way for the synthesis of custom-made polymers for specific applications. For the range of conditions studied, ionic strength has the greatest influence on reactivity ratios; results indicate that cross-over behavior exists for AMPS-based reactivity ratios. No clear correlation is observed between pH and reactivity ratio estimates (for 5 ≤ pH ≤ 9), but parameter estimation results suggest that the incorporation of acidic comonomers (AMPS and AAc) is affected by pH within this range. Finally, monomer concentration has a dominant impact on molecular weight averages, even when other factors are varied.Graphical abstractImage 1
       
  • Single-ion conducting polymer electrolytes with alternating ionic
           mesogen-like moieties interconnected by poly(ethylene oxide) segments
    • Abstract: Publication date: Available online 5 June 2019Source: PolymerAuthor(s): Hannes Nederstedt, Patric Jannasch Solid single-Li+-ion conducting polymer electrolytes are currently explored for safe high-temperature lithium batteries. In the present work we have prepared and studied materials based on alternating mesogen-like naphthalene sulfonate units interconnected by flexible poly(ethylene oxide) (PEO) segments in order to induce microphase separation and physical crosslinking. These segmented polymers were readily prepared in polycondensations of a naphthalene diol sulfonate and chain-end chlorinated PEO. The ionic content of the final materials was conveniently controlled by using PEOs of different molecular weights. Analysis by X-ray scattering showed a morphology with nanoscopic domains of naphthalene sulfonate units dispersed in a matrix of amorphous PEO segments. The aggregation of the naphthalene sulfonate units increased with temperature up to at least 100 °C, while the crystallization of the PEO segments in some materials reversibly dissolved the naphthalene sulfonate domains upon cooling. The crystallinity decreased and the glass transition temperature increased with decreasing PEO segment length, i.e., increasing in ionic content, because of increasing ionic coordination and a decreasing PEO segment length in-between the naphthalene sulfonate domains. At 80 and 120 °C, the present single-Li+-ion conductors reached conductivities up to 1.4·10−6 and 5.5·10−6 S cm−1, respectively, which after addition of 29 wt % triglyme increased to 2.9·10−6 and 8.2·10−6 S cm−1, respectively. The combined results showed that the macromolecular design with ionic mesogen-like units that form stable physically cross-linked morphologies by interconnecting flexible polyether segments is advantageous for polymer electrolytes for safe high-temperature operation.Graphical abstractImage 1
       
  • Rheological and Mechanical Properties of a Novel Polyamide 6 Synthesized
           by Anionic Polymerization of ε-caprolactam in a Twin-Screw Extruder
    • Abstract: Publication date: Available online 4 June 2019Source: PolymerAuthor(s): Hoyeon Kim, Kyunghwan Oh, Yongsok Seo In this study, we successfully synthesized a novel polyamide 6 (PA6, nylon 6) with a linking agent (a diepoxide) by in-situ reactive extrusion. In order to vary the physical properties of the polymer, a unique strategy was introduced. The linking agent reacted with growing PA6 chains during the anionic polymerization in the extruder. The extrudates appear to have a different structure (chain branching) without forming a network structure, causing a remarkable enhancement in the rheological properties as well as the mechanical properties of the nylon 6 produced. The molar ratio of linking agent to initiator was optimal at 0.1 and the produced polymers exhibit remarkably enhanced physical properties, though their molar masses was not appreciably varied. The melt viscosity of the produced PA6 including the optimum linking agent increased by almost 200 times that of the neat PA6 melt at low shear rate. The dynamic moduli also increased by more than 100 times that of the neat nylon 6. In addition, the mechanical properties were significantly improved with the addition of the linking agent. The elongation at break was almost doubled compared to neat PA6. The optimum compound showed a high toughness behavior.Graphical abstractImage 1062
       
  • Tuning the material properties of a water-soluble ionic polymer using
           different counterions for material extrusion additive manufacturing
    • Abstract: Publication date: Available online 3 June 2019Source: PolymerAuthor(s): Callie E. Zawaski, Emily M. Wilts, Camden A. Chatham, Andre T. Stevenson, Allison M. Pekkanen, Chen Li, Zhiting Tian, Abby R. Whittington, Timothy E. Long, Christopher B. Williams Additive manufacturing (AM) affords the opportunity to print tailored pharmaceuticals to customize the quantity of medicine, number of medicines, and time and rate of release to be adapted for an individual's needs. A series of sulfonated poly(ethylene glycol) (SPEG) polymers for fused filament fabrication (FFF) that (i) dissolves quickly (
       
  • Peroxide-initiated Chemical Modification of Polyolefins: In search of a
           Latent Antioxidant
    • Abstract: Publication date: Available online 3 June 2019Source: PolymerAuthor(s): Christopher Twigg, Kyle Ford, J. Scott Parent The ability of piperidine-based compounds to confer oxidative stability to polyolefin thermosets without compromising the yields of peroxide-initiated crosslinking and monomer grafting is demonstrated. Unlike phenolic, nitroxyl and phosphite antioxidants that lower the concentration of macroradical intermediates that support polyolefin modifications, additives based upon 2,2,6,6-tetramethylpiperidine (TEMPH) are shown to have little to no effect on the extent of LLDPE crosslinking or the conversion of vinyltriethoxysilane (VTEOS) to grafted hydrocarbon adducts. Notwithstanding this lack of interference in radical-mediated polymer modification, this class of hindered light stabilizer (HAS) compounds are shown to limit the extent of radical oxidation of linear low-density polyethylene (LLDPE) in an accelerated aging test. The origins of this paradox are discussed in terms of the current state of knowledge regarding HAS activation. The latent antioxidant concept is extended to an alternate approach, wherein 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl (AOTEMPO) is used as an alkyl radical scavenger bearing an oligomerizable functional group. When added at a fraction of the peroxide loading used to produce an LLDPE thermoset, ATEMPO is shown to provide a predictable induction delay without impacting ultimate crosslink density, and produces polymer-bound alkoxyamine functionality that stabilizes the product against oxidation.Graphical abstractImage 10333879
       
  • Copolymer-enabled stretchable conductive polymer fibers
    • Abstract: Publication date: Available online 3 June 2019Source: PolymerAuthor(s): Guoqiang Tian, Jian Zhou, Yangyang Xin, Ran Tao, Gang Jin, Gilles Lubineau Next-generation stretchable electronics, such as wearable electronics and implantable sensors, require stretchable conductive fibers. Despite their great popularity for wearable electronics, conducting polymers do not sustain deformation very well because of their rigid conjugated backbone. Here, we report the production of stretchable conductive poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT/PSS)- conjugated polymer fibers, using optimal wet-spinning, followed by hot drawing. We engineer the fibers by introducing a copolymer, polyethylene-block-poly (ethylene glycol) (PBP), that modifies both the electrical and mechanical properties of the raw PEDOT/PSS. We then systematically investigate the effects of the PBP fraction (fs) on the properties of the PEDOT/PSS by analyzing the changes in the conductivity, morphology, stretchability, and conformation of the PEDOT chains. We find that the conductivity of PEDOT/PSS increases from 311 ± 8 S/cm to 415 ± 12 S/cm (133% increase), when fs = 0.4, and that the strain of the fibers, at failure, is as high as (ε = 36%) for fs = 0.7, eq. 3x the value of as-spun PEDOT/PSS fibers. Raman and XRD analyses show that the conformational changes from benzoid to quinoid structures, in the PEDOT chains, significantly enhance the conductivity of the fibers. This conformational change facilitate the switch from a coil structure of PEDOT/PSS into a linear or an extended-coil conformation that increases interchain interaction.Graphical abstractImage 1
       
  • WAXS/SAXS study of plastic deformation instabilities and lamellae
           fragmentation in polyethylene
    • Abstract: Publication date: Available online 2 June 2019Source: PolymerAuthor(s): Zbigniew Bartczak, Alina Vozniak The influence of the topology of the amorphous phase on deformation instabilities, leading to kinking and to fragmentation of lamellae is discussed. Samples of polyethylene of diverse structure were deformed in the plane-strain compression. The accompanying structural changes were analyzed using DSC, WAXS and SAXS.Several deformation instabilities occur at various true strains. At e = 0.3–0.4 lamellae oriented specifically along the loading direction undergo microbuckling instability, leading to cooperative kinking. This transition manifests as the second macroscopic yield. For a given layers stiffness the microbuckling depends on the ratio of the amorphous and crystalline thickness.At e = 0.6–1.0 the lamellae fragmentation due to the localization of crystallographic slip was observed, relatively weak at e = 0.6, but extensive at e = 1. Fragmentation is initiated by stress concentrations at the crystal-amorphous interface due to stretched ‘stress transmitter’ chains ST. Consequently, the critical strain of fragmentation depends inversely on the ST fraction at the interface – when it is low the stress concentrations grow stronger, prompting an earlier slip localization and subsequent lamellae fragmentation. Extensive fragmentation reduces deformation constraints and allows the formation of a new crystal ordering along the flow direction.Graphical abstractImage 1
       
  • Synthesis and characterization of post-sulfonated poly(arylene ether
           sulfone) membranes for potential applications in water desalination
    • Abstract: Publication date: Available online 1 June 2019Source: PolymerAuthor(s): Shreya Roy Choudhury, Ozma Lane, Dana Kazerooni, Gurtej S. Narang, Eui Soung Jang, Benny D. Freeman, John J. Lesko, J.S. Riffle This study focuses on post-sulfonated polysulfone membranes for potential applications in desalination by reverse osmosis or electrodialysis. A series of controlled molecular weight (5000 and 10,000 g/mol) polysulfones containing hydroquinone and their high molecular weight linear counterparts were synthesized using post-sulfonation of pre-formed polymers under mild conditions. The sulfonic acid groups were substituted on only the hydroquinone units. Amine terminated oligomers were crosslinked with a tetrafunctional epoxy molecule under suitable conditions to form membranes whereas the linear high molecular weight polymers were cast directly to form films with chain entanglements. Fixed charge concentrations of the membranes based on linear copolymers increased from 3.94 to 5.14 meq/mL when the ion exchange capacity was decreased from 1.30 to 0.88 meq/g. The fixed charge concentration of the networks cast from the 5000 g/mol oligomers increased from 4.04 to 6.23 meq/mL with a decrease in the ion exchange capacity from 1.51 to 0.90 meq/g.Graphical abstractImage 1
       
  • Copolymers containing two types of reactive groups: New compatibilizer for
           immiscible PLLA/PA11 polymer blends
    • Abstract: Publication date: Available online 1 June 2019Source: PolymerAuthor(s): Xin Yang, Hengti Wang, Jiali Chen, Zhiang Fu, Xuewen Zhao, Yongjin Li While reactive compatibilization has been widely used, both the compatibilization efficiency and the varieties still need further enhancements. Herein, we demonstrated a novel “Dual-reactive compatibilization” strategy using a compatibilizer containing bifunctional groups. It was shown that the compatibilizer containing two types of reactive groups shows higher compatibilization efficiency as compared with traditional compatibilizer with only one type of reactive groups. Specifically, a series of poly(styrene-co-(glycidyl methacrylate)-co-(maleic anhydride)) ternary copolymers (SGM) containing both reactive epoxide groups and maleic anhydride groups were synthesized and then incorporated into the immiscible poly(amide 11)/poly(l-lactic acid) (PA11/PLLA) blend. The terminal amino groups of PA11 are ready to react with the maleic anhydride groups of the SGM while the carboxyl groups of PLLA react with the epoxide groups of SGM. Double-grafted copolymers with both PA11 and PLLA chains were in-situ formed and located along the PA11-PLLA interface, in which the grafted PLLA chains were buried in PLLA phase while the grafted PA11 chains were immersed in PA11 phase. Thus the compatibility of PA11/PLLA was significantly improved. In addition, the effect of SGM structure on compatibilization efficiency was investigated. The PA11/PLLA (50/50) blends with 3 wt % specific compatibilizer (P(S93-G5-M2)) show the elongation at break and tensile strength of 411% and 57.9 MPa, respectively, the highest values reported so far for the blends. This work provides a new strategy to compatibilize immiscible polymer blends (especially the blends of engineering plastics containing reactive groups). Moreover, the novel bifunctional reactive compatibilizers are also ready for large-scale industrial applications.Graphical abstractImage 1
       
  • Internal structure and mechanical property of an anisotropic hydrogel with
           electrostatic repulsion between nanosheets
    • Abstract: Publication date: 26 August 2019Source: Polymer, Volume 177Author(s): Koki Sano, Naoki Igarashi, Yuka Onuma Arazoe, Yasuhiro Ishida, Yasuo Ebina, Takayoshi Sasaki, Takaaki Hikima, Takuzo Aida We recently developed a mechanically anisotropic hydrogel with a large internal electrostatic repulsion. The hydrogel is embedded with negatively charged titanate nanosheets that are cofacially oriented by a magnetic field. Because of the anisotropic electrostatic repulsion between the nanosheets, this hydrogel exhibits a large elastic modulus when compressed orthogonal to the nanosheet plane. In this paper, we systematically investigate how the intensity of the electrostatic repulsion affects the internal structure and mechanical property of this anisotropic hydrogel, where the free-ion concentration in the hydrogel medium was the key parameter for moderating the electrostatic repulsion due to its screening effect. With gradually changing the free-ion concentration in the hydrogel, nanoscopic arrangement and mesoscopic domain structure of the nanosheets were characterized by two-dimensional small-angle X-ray scattering (2D SAXS) and confocal laser scanning microscopy (CLSM), respectively. Furthermore, an anisotropic mechanical property of the hydrogel was evaluated by compression test. These results reveal that extensive deionization of the hydrogel medium and the resultant maximization of the electrostatic repulsion induces the nanosheets to adopt a monodomain lamellar structure that occupies the whole space of the hydrogel, thereby enhancing the mechanical anisotropy of the hydrogel.Graphical abstractImage 1
       
  • Arc-bridge Polydimethylsiloxane Grafted Graphene Incorporation into
           Quaternized Poly(styrene-b-isobutylene-b-styrene) for Construction of
           Anion Exchange Membranes
    • Abstract: Publication date: Available online 31 May 2019Source: PolymerAuthor(s): Zhao-Hua Mo, Yi-Xian Wu A novel robust poly(styrene-b-isobutylene-b-styrene) (SIBS)-based anion exchange membrane (AEM) could be achieved via quaternization and cross-linking reaction of chloromethylated SIBS with amines in the presence of graphene sheets grafted with polydimethylsiloxane arc-bridges (G-g-Arc PDMS). The resulting cross-linked QSIBS/G-g-Arc PDMS composite membranes exhibit significantly high ion conductivity (σ) and dynamic mechanical properties, marked by low methanol permeability, together with improved chemical stability. The σ of composite AEM with 0.25 wt% of graphene loading reached remarkably to 1.81 × 10-2 S cm-1 at 60 °C, compared to that (1.15 × 10-2 S cm-1) of QSIBS. This membrane also behaves high storage modulus of 236 MPa even at 150 °C, while Nafion 115 lost its modulus at 150 °C. The homogeneous dispersion of G-g-Arc PDMS in QSIBS matrix leads to a great decrease in methanol permeability to 3.81 × 10-7 cm2 s-1, which is much lower than that of Nafion 115.Graphical abstractImage 10000
       
  • Thermo-responsive micelles prepared from brush-like block copolymers of
           proline- and oligo(lactide)-functionalized norbornenes
    • Abstract: Publication date: Available online 30 May 2019Source: PolymerAuthor(s): Sutthira Sutthasupa, Kajornsak Faungnawakij, Kenneth B. Wagener, Fumio Sanda Thermo-responsive micelles were prepared from brush-like block copolymers of proline-derived norbornene and macromonomers bearing oligo(lactide) groups. The brush-like polymers with moderate molecular weights were synthesized by the ring-opening metathesis block copolymerization of a proline-functionalized norbornene (1) with norbornene macromonomers bearing oligo(lactide) groups using Umicore M31 as a catalyst. The proline-functionalized polynorbornene [poly(1)] exhibited the lower critical solution temperature (LCST) at 18 °C. Phase separation was reversible on heating and cooling without hysteresis. Poly(1) featured amphiphilic character, it self-assembled to form micelles in water at temperatures below the LCST, and aggregation of micelles was observed above the LCST. The LCST of the block copolymers increased with increasing percentage of the branched oligo(lactide) component, suggesting that the phase transition temperatures are tunable with respect to the monomer composition. The block copolymers self-assembled into micelles below the LCST, and further aggregated into larger particles, presumably due to dehydration at the corona, at temperatures above the LCST. The block copolymers also showed the potential to self-assemble into a variety of shapes determined by the amphiphilic balance of the block components.Graphical abstractImage 1
       
  • Ion transport, polarization and electro-responsive elelctrorheological
           
    • Abstract: Publication date: Available online 30 May 2019Source: PolymerAuthor(s): Yang Liu, Jia Zhao, Fang He, Chen Zheng, Qi Lei, Xiaopeng Zhao, Jianbo Yin Self-crosslinked bis(imidazolium)-based poly(ionic liquid)s (PILs) containing different counterions (P[C2DVIM][X], X = BF4−, PF6−, TfO−, TFSI−) are synthesized and the influence of counterions on electro-responsive electrorheological (ER) effect is studied in order to understand the structure-property relationship of crosslinked PIL-based ER system. It is found that the size and type of counterions have a significant influence on ER effect. As the size increases, the ER effect decreases (i.e. BF4− > PF6− > TfO− > TFSI−). Different from the linear PIL-based ER system, however, the P[C2DVIM]X with inorganic counterions shows stronger ER effect compared to P[C2DVIM]X with organic counterions. Meanwhile, the influence of counterions on temperature dependence of ER effect of the crosslinked PIL system is also different from the linear PIL system. By dielectric spectroscopy and X-ray scattering measurements, the mechanism behind the influence is analyzed. It demonstrates that, different from linear PIL system, the ionic aggregation is largely weakened in P[C2DVIM]X and the transport of mobile counterions and interfacial polarization are mainly dominated by the mesh size of crosslinking network. This should be responsible for the different dependence of ER effect on the size and type of counterions between self-crosslinked and linear PIL systems.Graphical abstractDifferent from linear poly(ionic liquid) system, self-crosslinked poly(ionic liquid)s with inorganic counterions show stronger ER effect compared to P[C2DVIM]X with organic counterions (i.e. BF4− > PF6− > TfO− > TFSI−). This is related to the fact that, instead of ionic aggregation, the mesh size of crosslinked network dominates ion transport and interfacial polarization of crosslinked poly(ionic liquid)s.Image 1
       
  • Transition mechanisms of Three-Dimensional Nanostructures Formed from
           Geometrically Constraining (AB) f star block copolymers
    • Abstract: Publication date: Available online 29 May 2019Source: PolymerAuthor(s): Zhanwei Shao, Di Zhang, Weiguo Hu, Yuci Xu, Weihua Li The self-assembly behavior of (AB)f star copolymers under a cylindrical confinement has been investigated using self-consistent field theory. Aiming to study the influence of the pore diameter on the order-order transitions as volume fraction varies, the phase diagram with respect to the volume fraction and the pore size is constructed. An interesting transition sequence of ordered nanostructures, H1A→P2A→L2A→ P3CB→H3CB, is predicted, which is corresponding to the phase transition of C→ G→L→G→C in bulk. Notably, this transition sequence is universal for both linear (AB diblock and BAB triblock) and star-like (AB)f diblock copolymer. In particular, we explore the formation mechanism of helical nanostructures as the volume fraction increases, where the P phase plays an important role in forming helical structures as an intermediate nanostructure. Finally, we construct the two-dimensional phase diagram, including pore size and volume fraction, of (AB)f star-like block under confinement at different number of arms, where P nanostructures was found to surrounded by other nanophases suggesting the importance of P nanostructure in the transition sequence.Graphical abstractWe, for the first time, identified the volume fraction independent phase transition sequence under cylindrical confinement at the full volume fraction space, that is, H1A→P2A→L2A→ P3CB→H3CB, which is corresponding to the phase transition of C→ G→L→G→C in bulk. This transition sequence is universal for both linear (AB diblock and BAB triblock) and star-like (AB)f diblock copolymer. The explored phase transition sequence under confinement is helpful to understand the transition mechanism of these nanostructures.Image 1
       
  • Synthesis of two-patch particles with controlled patch size via
           nonequilibrium solidification of droplets on rods
    • Abstract: Publication date: Available online 29 May 2019Source: PolymerAuthor(s): Zameer Hussain Shah, Xinnan Xu, Shuo Wang, Yurou Li, Yi Chen, Hongying Shan, Yongxiang Gao Nucleation and growth of droplets onto seed particles and subsequent solidification is an emerging technique for fabrication of complex colloids with controlled particle morphology and chemical makeup. The technique is often implemented at or near equilibrium, where the final composite particle structure is determined by the equilibrium contact angles of the droplets on the seed particles. Here, we apply the technique out of equilibrium, utilizing the rich and intriguing morphologies emerged as a droplet is triggered to dewet on a rod along the free energy minimization pathway. Specifically, 3-trimethoxysilyl propyl methacrylate (TPM) droplets were nucleated and grown onto silica rods. Upon dewetting, the droplets undergo a series of morphology changes, starting from engulfing the rods, contracting to the center, moving sideways to finally being fully separated from the rods. Composite patchy particles of controlled configurations were achieved by stimulating a fast photopolymerization of the TPM droplets at desired stages of the morphology evolution. Through seed surface functionalization, the patches can be decorated by either the hydroxyl or the amine group, which are used to create fluorescently-patterned patchy particles. Combining with surface evolver simulations, we demonstrate that nonequilibrium solidification of droplets on rods can be used to synthesize two-patch particles with a larger range of control over the patch size than its equilibrium counterpart.Graphical abstractImage 1
       
  • Selective 2,4-dichlorophenoxyacetic acid optosensor employing a
           polyethersulfone nanofiber-coated fluorescent molecularly imprinted
           polymer
    • Abstract: Publication date: Available online 28 May 2019Source: PolymerAuthor(s): Nargess Yousefi Limaee, Shohre Rouhani, Mohammad Ebrahim Olya, Farhood Najafi In the present study, a fluorescent optosensor containing a molecularly imprinted polymer in combination with electrospinning was employed for selective recognition of 2,4-dichlorophenoxyacetic acid (2,4-D). Free radical polymerization was carried out on the surface of polyethersulfone (PES) nanofibers as a substrate using a monomer, initiator, template and a polymerizable 1,8-naphthalimide derivative as the fluorogenic monomer. PES nanofiber@fluorescent molecularly imprinted polymer (PES nanofiber@FMIP) was produced by means of UV curing. The magnetic PES nanofiber@FMIP was developed in the same manner as the magnetic Fe3O4 nanoparticles were exerted in the electrospinning of the PES nanofiber. The imprinting factor (IF) was considered 1.97 as a selective character of PES nanofiber@FMIP versus PES nanofiber@FNIP. The developed sensor was able to selectively determine 2,4-D in a linear range of 1 × 10−7-1 × 10−3 M with limit of detection (LOD) of 1.01 × 10−8 M. The results confirmed that PES nanofiber@FMIP was satisfactorily able to determine trace concentrations of 2,4-D.Graphical abstractImage 1
       
  • Tensile deformation of artificial muscles: annealed nylon 6 lines
    • Abstract: Publication date: Available online 28 May 2019Source: PolymerAuthor(s): Yi-Wei Huang, Wen-Shin Lee, Fuqian Yang, Sanboh LeeIn this work, we study the tensile deformation of chicken muscle fibers and the temperature dependence of the tensile deformation of non-twisted nylon 6 lines and twisted nylon 6 (artificial muscles). Both the non-twisted nylon 6 lines and twisted nylon 6 are annealed at different temperatures of 150, 175, 190 and 200 ºC. The chicken muscle fibers under tensile loading exhibit four deformation stages with the tensile load being a linear function of the elongation in each stage. The largest Young’s modulus (the slope of the load versus the elongation curve) occurs at stage III. For the tensile deformation of the annealed non-twisted nylon 6 lines, the tensile load is proportional to the elongation. For the tensile deformation of the twisted nylon 6 (artificial muscles), there exist three stages with the tensile loading being a linear function of the elongation in stages I and III. The Young’s modulus calculated from the load-elongation curves decreases with the increase of the testing temperature. For the testing conditions used in this work, the tensile deformation eventually leads to the fracture of both the chicken muscle fibers and the annealed non-twisted nylon 6 lines. The fracture stress of the annealed non-twisted nylon 6 lines decreases with the increase of the testing temperature.Graphical abstractImage 1026
       
  • Ratiometric thermochromism in europium-containing conjugated polymer
    • Abstract: Publication date: Available online 28 May 2019Source: PolymerAuthor(s): Denis A. Turchetti, Alisson J. Santana, Luís G.T.A. Duarte, Teresa D.Z. Atvars, Raquel A. Domingues, Leni Akcelrud Aiming the development of a nanothermometer, a new Type II metallopolymer consisting of a fluorene derivative polymer complexed with europium ions is introduced, as a material with good solubility in common organic solvents and easy film formation. The structural and photophysical properties are discussed focusing on the observed ratiometric thermochromism behavior in solid state. For comparison purposes, the same structure without the complexed ions (LaPPS75) and a model compound simulating the complexed sites (LaPPS75 M) were used. The ratiometric luminescent temperature shows an operational range between 260 and 380 K with a maximum relative thermal sensitivity of 3.29% K−1 at 380 K.Graphical abstractImage 1
       
  • Investigation on the Growth of Snowflake-shaped Poly(L-Lactic Acid)
           Crystal by in-situ high-pressure microscope
    • Abstract: Publication date: Available online 28 May 2019Source: PolymerAuthor(s): Lei Zhang, Guoqun Zhao, Guilong Wang Crystallization of polymer film is a widely concerned condensed matter phenomenon directly determining the film properties and performances. However, challenging on understanding of the crystal growth process of polymer thin film still remains. Here, we developed an in-situ high-pressure observing system to record the crystal growth process of Poly(L-Lactic Acid) (PLLA) film in pressurized CO2 environment with different film thicknesses, molecular weights, temperatures and CO2 pressures. The preliminary stage of morphological evolution of snowflake-shaped crystal was recorded for the first time. Based on the morphological feature and microscopic structure, we found that the snowflake-shaped crystal with six main branches is constructed by multilayer rhombic terrace crystal originated from screw dislocation, and the six main branches are not formed at the same time. Two of them are preferentially formed on the long-axis directions of rhombic crystal, while the other four main branches are subsequently formed. The subsequently formed branches root from twin crystal induced from self-generated concentration field. The growth process of snowflake-shaped PLLA crystal is quite different from that of snowflake-shaped H2O crystal, but still meets the self-similarity principle and iterative generation principle of the fractal theory.Graphical abstractImage 10979
       
  • Evaluation of toughness and failure mode of PA6/mSEBS/PS ternary blends
           with an oil-extended viscoelastic controlled interface
    • Abstract: Publication date: Available online 28 May 2019Source: PolymerAuthor(s): Akira Ishigami, Shotaro Nishitsuji, Takashi Kurose, Hiroshi Ito Here, the physical properties of maleic-anhydride-modified styrene–ethylene–butylene–styrene copolymer (mSEBS) were controlled by adding paraffin oil; mSEBS formed the interface between polyamide 6 (PA6) and polystyrene (PS). Adding 50 wt% paraffinic oil to mSEBS enabled the reduction of the glass transition temperature (Tg) of the ethylene-butylene block and PS block. Change in Tg increased with the decreasing molecular weight of paraffin oil, indicating that the physical properties of mSEBS can be controlled. In this study, PA6/mSEBS binary blends and PA6/mSEBS/PS ternary blends were prepared using high-shear kneading process. In the ternary blends, mSEBS forms a core-shell structure containing PS segment. In the PA6/mSEBS binary blends, the maximum notched Izod impact strength was 25.0 kJ/m2, and in the ternary blend its value was more than 60.0 kJ/m2, revealing significantly increased impact strength. The fracture surface of the binary blend exhibited the occurrence and expansion of many voids. In case of ternary blends, large plastic deformation was confirmed. Result of dynamic mechanical analysis (DMA) revealed a large loss tangent (tan δ) from −90 to −25 °C in the ternary blend, unlike in neat PA6 or the binary blends. The flexible mSEBS sandwiched between PA6 and PS in the core-shell structure preferentially deformed during deformation, which revealed that its characteristic relaxation behavior was activated. These results suggest that controlling the physical properties of the interface in a higher-order structure of a polymer blend may enable the efficient expression of the interfacial material's function.Graphical abstractImage 1075
       
  • On complex structure of local free volume in bond fluctuation model of
           polymer matrix
    • Abstract: Publication date: Available online 28 May 2019Source: PolymerAuthor(s): Wojciech Radosz, RafaÅ. Orlik, Grzegorz Pawlik, Antoni C. MituÅ Complex dynamics in model polymer-based host-guest systems is ascribed to jamming effects resulting from inhomogeneous dynamics of local free volume in polymer matrix. As a first step towards quantification of this assumption we study the local free volume in static configurations in Monte Carlo Bond Fluctuation Model (BFM), using specially devised local free volume parameter V. Statistical analysis, including various correlation functions and probabilistic distributions, yields a quantitative characterization of a typical equilibrium local volume configuration V(r→) on large, intermediate and local scales. Two types of spatial organizations of local free volume are found and characterized: a liquid-like, constrained by steric interactions, and local voids nearly free of monomers. Those voids form large scale-free clusters with power-law distribution of sizes and complex fractal structure with fractal dimension dependent on cluster's size. The emerging physical picture offers a promising starting point for the characterization of inhomogeneous dynamics of local free volume in BFM and of guest molecules embedded in local volume mosaic states of BFM.Graphical abstractImage 1
       
  • Biobased thermosetting cellular blends: Exploiting the ecological
           advantage of epoxidized soybean oil in structural foams
    • Abstract: Publication date: Available online 27 May 2019Source: PolymerAuthor(s): Shubh Agnihotri, Srishti Shukla, Sai Aditya Pradeep, Srikanth Pilla In this study, the effect of epoxidized soybean oil (ESO) on the thermomechanical properties of foams based on epoxidized pine oil (EPO) was investigated. To obtain homogeneity in microstructure, an in-house developed, delayed addition approach was adopted for foaming compositions with polymethylhydrosiloxane (PMHS) while varying ESO content from 10% to 50%. The resulting foams were characterized with respect to microstructure, mechanical and thermal properties. The influence of rheology of blend compositions before gelation on the cell morphology was examined and a prospective approach was proposed for optimality in cell size. Although pure ESO did not cure at room temperature, blending with EPO facilitated processing the foams at room temperature, thereby curtailing the overall energy input in commercially manufacturing such composite systems. The behavior of foams under compressive loading was studied, and the compressive strength was observed to exhibit a decrease from 5.24 to 1.13 MPa with increase in ESO content. The nature of collapse plateau however suggested an increase in the fraction of load supported by the fluid in this region. This juxtaposed with a decrease in foam density deviated from Rehkopf's evaluation of load distribution between polymer and fluid. The foams were shown to exhibit high thermal stability, which increased from 182 to 208 °C with the amount of ESO present in the matrix.Graphical abstractImage 1
       
  • Accelerated ultraviolet aging of structural and luminescent properties of
           the ureasil-polyether hybrid materials U-PEO:Eu3+ and U-PPO:Eu3+
    • Abstract: Publication date: Available online 27 May 2019Source: PolymerAuthor(s): Gustavo Palácio, Damien Boyer, Sandrine Therias, Sandra H. Pulcinelli, Rachid Mahiou, Geneviève Chadeyron, Celso V. Santilli In this paper, we evaluate the role played by the polyether type and chain length on the complexation of Eu3+ by the urea group of siloxane-polyether organic-inorganic hybrid materials based on polyethylene oxide (U-PEO, mw = 1900 g mol−1) and polypropylene oxide (U-PPO, mw = 230, 2000, and 4000 g mol−1). Investigation was made of the effect of the photooxidation of the PEO and PPO chains, induced by artificially accelerated ultraviolet aging (λ ≥ 300 nm), with the decomplexation of Eu3+ from the urea-polyether array. Fourier transform infrared (FTIR) and photoluminescence (PL) spectra evidenced loss of the ligand-to-metal charge transfer (LMCT) when the Eu3+ cations were unable to disrupt the strong hydrogen-bonded urea/urea aggregates formed using shorter U-PPO chains (230 g mol−1) or semicrystalline U-PEO (1900 g mol−1). FTIR analysis showed that formate was the main photoproduct formed continuously during the artificial ultraviolet aging of U-PEO (1900 g mol−1) and U-PPO (2000 g mol−1), with concomitant decreases of Eu3+ complexed to urea bridges, spatially correlated siloxane nodes, and the Judd-Ofelt parameter Ω2 (R). The kinetics of all these parameters were described by exponential laws with comparable time constants, evidencing the sensitivity of the Eu3+ photoluminescence to the elimination/formation of the hydrogen-bonded urea-polyether array during the photooxidation of PPO chains. In the case of U-PEO:Eu3+, different time constant values were observed, indicating the existence of a faster process governed by the facilitated transport of the oxidative species through the amorphous moieties of the semicrystalline U-PEO. This sensitivity of structural and PL properties arising from the photoinduced degradation of ureasil-polyether films can be exploited in the fabrication of new transparent, flexible, and biocompatible UV dosimeters and sensors.Graphical abstractOrganic-Inorganic Hybrid (OIH) materials photoluminescence properties of lanthanide dopants combined with structural modifications induced by artificial ultraviolet aging.Image 1
       
  • Photo-stable cross-linked micron bead with functionalized quantum via
           suspension polymerization for color conversion
    • Abstract: Publication date: Available online 24 May 2019Source: PolymerAuthor(s): Changmin Lee, Eunhee Nam, Heeyeop Chae Acrylate groups were introduced on quantum dots (QD) via ligand exchange followed by nucleophilic reaction. The QDs were then polymerized with other multi-functional acrylic monomers in this study. Two acrylate groups were introduced at the end of an elongated ligand and the ligands with two acrylate groups were fully coordinated on the entire surface of the QD. This ligand modification scheme made the QDs highly reactive and also compatible with common organic solvents. No decrease in the quantum yield of the QDs was observed after ligand modification and the adduction reaction. The acrylate functional groups in the QDs were verified by 1H NMR and FT-IR. The prepared QDs with a terminal acrylate group were reacted with trimethylolpropane triacrylate and 1,6-hexanediol diacrylate to form micrometer scale beads via suspension polymerization. The diameter of the spherical beads was in the range of 80–150 μm and QDs 13 nm in diameter were found to be evenly dispersed in the polymer beads. The QD-polymer beads were applied to color conversion layers (CCL) on a blue light emitting diode (LED). The QD-polymer beads showed a 50% reduction over 72 h from the initial optical efficiency, while the QD embedded in the PMMA matrix (QD-PMMA) was reduced by 50% for 14 h.Graphical abstractImage 1
       
  • Adjustable self-assembly in
           polystyrene-block-poly(4-vinylpyridine) dip-coated thin films
    • Abstract: Publication date: Available online 23 May 2019Source: PolymerAuthor(s): Magdalena Konefał, Alexander Zhigunov, Ewa Pavlova, Peter Černoch, Ognen Pop-Georgievski, Milena Špírková This work studies the influence of dip-coating parameters on self-assembly in ultra-thin films of asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymers from a 1-chloropentane solution using a combination of several experimental techniques. Small-Angle X-ray Scattering, Atomic Force Microscopy, Grazing Incidence Small Angle X-ray Scattering and Transmission Electron Microscopy were used to characterize the fabricated films. We have shown a facile fabrication route to smooth films with a wide range of thicknesses. Arranged domains of P4VP oriented perpendicularly to the substrate were observed. The domain sizes and spacing varied in the range from 13 up to 35 nm and from 39 to 115 nm, respectively.Graphical abstractImage 1
       
  • Construction of master yield stress curves for polycarbonate: A
           coarse-grained molecular dynamics study
    • Abstract: Publication date: Available online 22 May 2019Source: PolymerAuthor(s): Atsushi Kubo, Jan-Michael Albina, Yoshitaka Umeno A coarse-grained particle model was developed for the simulation of deformations in polycarbonate. Coarse-grained molecular dynamics simulations of uniaxial and multiaxial deformations are carried out to determine the critical yield stress for various strain rates. From the calculated values, a master curve of the yield stress as a function of the strain rate is built at 300 K. It is found that the predicted results and experimental values are aligned on the same curve and can be described by a simple Cowper-Symonds relation. Furthermore, using the Williams, Landel and Ferry equation, a master curve is built to predict the yield stress at finite temperatures. By investigating additional deformation modes, two supplementary master curves are built at 300 K: one for the void nucleation and one for the shear yielding.Graphical abstractImage 1
       
  • Network reorganization in cross-linked polymer/silica composites based on
           exchangeable dynamic covalent carbon–carbon bonds
    • Abstract: Publication date: Available online 22 May 2019Source: PolymerAuthor(s): Takahiro Kosuge, Daisuke Aoki, Hideyuki Otsuka Diarylbibenzofuranone (DABBF), which contains an exchangeable dynamic covalent carbon–carbon bond was introduced into the polymer or silica domains of two series of polymer/silica composites with a network structure in order to investigate the correlation between the structural reorganization and the location of the DABBF units in these polymer/silica composites. The thermally induced structural reorganization behavior of the two polymer/silica composites was investigated by optical microscopy, dynamic mechanical analysis, and variable-temperature electron paramagnetic resonance spectroscopy. The thus obtained results revealed that the cross-linked polymer/silica composites that contain DABBF units in the polymer domain exhibit network reorganization, and that the efficiency of the network reorganization increases with the molecular weight between the cross-linking points composed of silica domains. Conversely, the cross-linked composite that contains the DABBF units in the silica domains does not show a network reorganization, as the densely cross-linked silica structure prevents the bond exchange reactions of the DABBF units. In their entirety, these results clearly indicate that the incorporation of dynamic covalent linkages in the high mobile polymer domain of cross-linked polymers is advantageous for structural reorganization, which affords a new guiding principle for the design of dynamic-covalent-chemistry-based materials.Graphical abstractImage 1
       
  • A versatile room-temperature method for the preparation of customized
           fluorescent non-conjugated polymer dots
    • Abstract: Publication date: Available online 16 May 2019Source: PolymerAuthor(s): Lorenzo Vallan, Esteban P. Urriolabeitia, Ana M. Benito, Wolfgang K. Maser We present a general procedure for the synthesis and in situ functionalization of highly fluorescent non-conjugated polymer dots, by exploiting the room-temperature carbodiimide-mediated condensation between citric acid and amines. The versatility of this method is proved by the preparation and characterization of a broad set of fluorescent nanoparticles with customized polymer structures and functional groups.Graphical abstractImage 1
       
 
 
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