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Journal Cover Polymer
  [SJR: 1.188]   [H-I: 197]   [154 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0032-3861
   Published by Elsevier Homepage  [3043 journals]
  • Interplay of microphase separation, crystallization and liquid crystalline
           ordering in crystalline/liquid crystalline block copolymers
    • Authors: Zaizai Tong; Junyi Zhou; Rui-Yang Wang; Jun-Ting Xu
      Pages: 1 - 9
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Zaizai Tong, Junyi Zhou, Rui-Yang Wang, Jun-Ting Xu
      A series of liquid crystalline/crystalline block copolymers (BCPs) containing poly(methacrylate) block with liquid crystalline (LC) azobenzene moieties in the side chains (PMMAzo) and crystalline block poly( l -lactide) (PLLA) were prepared. The interplay of microphase separation, crystallization and LC ordering in these BCPs was investigated. It is revealed that microphase separation between two blocks is favorable to the LC ordering, which is attributed to the enhanced local concentration of LC moieties in PMMAzo microdomains. For a similar reason, crystallization of PLLA can intensify microphase separation thus facilitate LC ordering of PMMAzo. PLLA crystallization may also stabilize the LC structure, leading to phase transition temperatures of the BCPs higher than that of PMMAzo homopolymer. On the other hand, the LC ordering can conversely affect crystallization of PLLA. The crystallizability of PLLA is weakened by the chemically linked PMMAzo block. The special PLLA ε-crystals, which are usually formed in the presence of organic solvents, are unexpectedly observed under suitable conditions.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.071
      Issue No: Vol. 130 (2017)
       
  • Barrier, mechanical and conductive properties of polycaprolactam
           nanocomposites containing carbon-based particles: Effect of the kind of
           particle
    • Authors: Rodrigo Méndez; Benjamin Constant; Cristhian Garzon; Muhammad Nisar; Sônia Marlí Bohrz Nachtigall; Raúl Quijada
      Pages: 10 - 16
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Rodrigo Méndez, Benjamin Constant, Cristhian Garzon, Muhammad Nisar, Sônia Marlí Bohrz Nachtigall, Raúl Quijada
      In this study, polycaprolactam (PA6) nanocomposites with thermally reduced graphene oxide (TrGO) and carbon nanotubes (CNTs) were prepared by melt blending with the aim of obtaining films with improvements in permeability (oxygen and water vapor), mechanical properties and electrical conductivity. The permeability to water vapor and oxygen of the nanocomposites containing TrGO significantly decreased with increasing filler load due to a more tortuous path to gas permeation. For CNT nanocomposites, low barrier properties were found. The tensile tests showed similar behavior in both cases, with somewhat higher elastic modulus for TrGO compounds. CNT gave higher electrical conductivity to polyamide with lower percolation threshold; however this conductivity reached a constant value around 10 wt% of filler. The conductivity of TrGO nanocomposites was lower, probably due to the presence of impurities in its structure; however, the property increased up to 15 wt% of filler load without evidence of stabilization at this concentration.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.063
      Issue No: Vol. 130 (2017)
       
  • Unprecedented dependence of stiffness parameters and crystallinity on
           comonomer content in rapidly cooled propylene-co-1-pentene copolymers
    • Authors: Alberto García-Peñas; José M. Gómez-Elvira; Vicente Lorenzo; Ernesto Pérez; María L. Cerrada
      Pages: 17 - 25
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Alberto García-Peñas, José M. Gómez-Elvira, Vicente Lorenzo, Ernesto Pérez, María L. Cerrada
      A thorough evaluation of the mechanical behavior exhibited by fast crystallized propylene-1-pentene copolymers, synthesized in a broad range of 1-pentene compositions, is here described. Different mechanical magnitudes derived from loading, creep and unloading processes in depth sensing indentation measurements are correlated to structural features. Several ordered forms are able to be developed applying a fast cooling processing at the composition interval analyzed in these propylene-1-pentene copolymers. Moreover, either a single polymorph or distinct ratios of two crystalline lattices can be obtained, depending on comonomer content. Crystallinity as well as the type of existing crystallites play a critical role in the value of those mechanical magnitudes. An uncommon dependence of either crystallinity or stiffness on 1-pentene content is observed in these copolymers, associated with their capability of crystallizing in the trigonal form.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.10.006
      Issue No: Vol. 130 (2017)
       
  • Synthesis and structure – property relationship of biobased
           poly(butylene 2,5-furanoate) – block – (dimerized fatty acid)
           copolymers
    • Authors: Magdalena Kwiatkowska; Inez Kowalczyk; Konrad Kwiatkowski; Anna Szymczyk; Roman Jędrzejewski
      Pages: 26 - 38
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Magdalena Kwiatkowska, Inez Kowalczyk, Konrad Kwiatkowski, Anna Szymczyk, Roman Jędrzejewski
      A series of poly(butylene 2,5-furanoate) – block – (dimerized fatty acid) (PBF-b-FAD) copolymers were successfully synthesized from 2,5-furandicarboxylic acid (FDCA), 1,4-butanediol (1,4-BD), and dimerized fatty acid diol (FADD) via a polycondensation in melt under the relatively mild process conditions and a reasonable excess of diol. The copolymers with different PBF to FAD segment ratio were characterized in regard of their chemical composition, microstructure, thermal transitions and stability as well as the mechanical performance. Some results were also discussed in relation to terephthalic acid based PBT-b-FAD copolymers, synthesized under the same experimental procedure. A detailed analysis of PBF homopolymer confirmed its relatively high molecular weight, semicrystalline structure, and in consequence a very good mechanical performance. In turn an incorporation of FADD amorphous segments between PBF blocks resulted in multiblocked structure with the ester group links and the real composition very close to those calculated theoretically. Although the specific furan ring architecture disturbs the macromolecules symmetry, thus the crystallization process, the PBF-b-FAD copolymers, varying in between 20 and 80 wt% of the rigid segments, reveal the heterogeneous microstructure. And the phase separation may be enhanced by the annealing above Tcc. In consequence the furan-aromatic copolyesters combine a variety of physical properties (also the elastomeric behavior), tunable by both PBF to FAD ratio and the thermal treatment, with a good processability. They are also characterized by almost twice higher level of the tensile stress and E modulus when compared to previously reported PTF-b-FADD copolymers. Considering the soon commercialization of bio-1,4-butanodiol the presented materials have also a potential to be synthesized as fully bio-based.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.10.009
      Issue No: Vol. 130 (2017)
       
  • Pulsed laser studies of cationic reactive surfactant radical propagation
           kinetics
    • Authors: Thomas R. Rooney; Anna Chovancová; Igor Lacík; Robin A. Hutchinson
      Pages: 39 - 49
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Thomas R. Rooney, Anna Chovancová, Igor Lacík, Robin A. Hutchinson
      Pulsed laser polymerization coupled with size exclusion chromatography (PLP-SEC) was implemented to study the micellar radical homopropagation kinetics of cationic surfmer, polycaprolactone choline iodide ester methacrylate (PCLnChMA with n = 2 average polyester units), at concentrations of 5, 10, and 20 wt% in aqueous solutions at 25, 50, 70, and 85 °C. PCL2ChMA can propagate in both aqueous and compartmentalized phases, with the relative importance of the two reaction loci changing with temperature. As the corresponding saturated macromonomer concentration, [M], inside the growing polymeric micelles cannot be easily determined, only the product of propagation rate coefficient (k p) and [M] are measured by PLP-SEC; at 25 °C, a minimum k p of 863 ± 95 L mol−1 s−1 is estimated assuming bulk [M]. (Macro)monomer composition drifts for batch acrylamide (AM)/PCLnChMA micellar copolymerizations in D2O at 50 °C are well represented by the apparent reactivity ratios r AM = 0.31 ± 0.03 and r PCL3ChMA = 8.79 ± 0.38.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.064
      Issue No: Vol. 130 (2017)
       
  • pH-responsive polyampholytic hybrid Janus nanoparticles
    • Authors: Panagiotis G. Falireas; Maria Vamvakaki
      Pages: 50 - 60
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Panagiotis G. Falireas, Maria Vamvakaki
      Polyampholytic hybrid Janus nanoparticles comprising an inorganic silica core and a shell consisting of compartmentalized poly(acrylic acid) and poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) grafted polymer chains have been prepared. The synthesis of the nanoparticles was accomplished via a multi-step process commenced by a styrene/methanol Pickering emulsion using amine-functionalized silica nanoparticles (D = 100 nm) as the stabilizer, followed by the free radical polymerization of the styrene droplets to obtain silica nanoparticle stabilized polystyrene colloidosomes. Two different polymers, poly(tert-butyl acrylate) poly(t-BA) and PDMAEMA, were grown from the opposite sides of initiator-modified Janus silica nanoparticles by a two-step surface-initiated atom transfer radical polymerization (ATRP). Following acid hydrolysis of the t-butyl ester groups, the polyampholytic bicomponent particles were obtained. The asymmetric polymer decoration of the silica nanoparticles was verified by scanning electron microscopy, whereas the aqueous solution properties of the hybrid nanoparticles were investigated by potentiometric titration, zeta-potential measurements and dynamic light scattering. Studies on the size of the polyampholytic nanoparticles as a function of the solution pH revealed the presence of individual Janus nanoparticles with a symmetric V-shape change in their size signifying the absence of interparticle aggregation upon ionization of the compartmentalized oppositely charged polyelectrolyte chains.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.068
      Issue No: Vol. 130 (2017)
       
  • Deep red aggregation-induced CPL emission behavior of four-component
           tunable AIE-active chiral polymers via two FRET pairs mechanism
    • Authors: Ziyu Wang; Yayun Fang; Xingyu Tao; Yuxiang Wang; Yiwu Quan; Shuwei Zhang; Yixiang Cheng
      Pages: 61 - 67
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Ziyu Wang, Yayun Fang, Xingyu Tao, Yuxiang Wang, Yiwu Quan, Shuwei Zhang, Yixiang Cheng
      Two four-component chiral polymers with two Förster resonance energy transfer (FRET) pairs incorporating chiral 1,1′-binaphthyl, 4,7- di(thiophen-2-yl)-2,1,3-benzothiadiazole (DTBT), tetraphenylethene (TPE) and fluorene moieties were designed and synthesized via one-pot two-step of Pd-catalyzed Sonogashira reaction and Suzuki reaction by changing different ratios of DTBT chromophore and AIE-active TPE group. Both chiral polymers exhibit large Stokes shift (257 nm) and tunable red aggregation-induced emission (AIE) response behavior via two intramolecular FRET pairs by changing excitation wavelength. Interestingly, the chiral polymer with lower ratio of DTBT (P-1) shows obvious aggregation-induced circularly polarized luminescence (AICPL) emission signals in deep red region (around 650 nm) and higher g lum, which can reach as high as ±2.0 × 10-3 in THF-H2O mixtures.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.072
      Issue No: Vol. 130 (2017)
       
  • Facile preparation of degradable thermoresponsive polymers as
           biomaterials: Thermoresponsive polymers prepared by radical polymerization
           degrade to water-soluble oligomers
    • Authors: Syuuhei Komatsu; Taka-Aki Asoh; Ryo Ishihara; Akihiko Kikuchi
      Pages: 68 - 73
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Syuuhei Komatsu, Taka-Aki Asoh, Ryo Ishihara, Akihiko Kikuchi
      A novel thermoresponsive and biodegradable polymer, poly(MDO-co-HEA), was prepared by radical copolymerization of 2-methylene-1,3-dioxepane (MDO) and a hydrophilic vinyl monomer, 2-hydroxyethyl acrylate (HEA), in dimethylsulfoxide (DMSO), varying feed monomer compositions. Poly(MDO-co-HEA) showed lower critical solution temperature (LCST)-type phase separation in aqueous medium, forming coacervate droplets into which low molecular weight hydrophobic molecules could be loaded above the LCST. The LCST could be controlled not only by the chemical compositions of the hydrophobic MDO and hydrophilic HEA in the polymer chains, but also by ion and polymer concentration. Degradation tests in aqueous media indicated that poly(MDO-co-HEA) was converted into hydrophilic oligomers by hydrolysis of the ester groups in the polymer backbone. The facile preparation poly(MDO-co-HEA) are valuable for use in functional biomedical materials, such as base of drug delivery carrier and cell culture scaffold instead of non-degradable stimuli-responsive polymer.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.073
      Issue No: Vol. 130 (2017)
       
  • Size-dependent linear rheology of silica filled poly(2-vinylpyridine)
    • Authors: Yihu Song; Qiang Zheng
      Pages: 74 - 78
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Yihu Song, Qiang Zheng
      Nanoparticles reinforcement of polymers has been of great interest to researchers for the better part of a century. However, researchers are in confusion in describing the role of filler network. Herein we report a framework to solve both reinforcement and dissipation of nanocomposites with respect to strain amplification effect of dynamically retarded bulk polymer phase and jamming of nanoparticles in the filler phase, disclosing a new mechanism differing from previously established ones. We show how the viscoelastic filler phase impacts on the terminal flow of the matrix. Our finding, which counters the conventional understandings of nanoparticles reinforcement, provides a unique description of linear rheology of nanocomposites comprised by fillers of different sizes and polymers of different molecular weights.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.070
      Issue No: Vol. 130 (2017)
       
  • Effect of solvent induced dielectric property modulation of poly(methyl
           methacrylate) insulator on the electrical and photosensing behaviour of
           p-channel organic transistors
    • Authors: D. Panigrahi; S. Kumar; A. Dhar
      Pages: 79 - 87
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): D. Panigrahi, S. Kumar, A. Dhar
      We have investigated the influence of solvent dipole moment on the dielectric properties of poly(methyl methacrylate) (PMMA) gate dielectric and unravel its effect on the OFET performance, environmental stability, and photosensitivity. The device performance improved substantially upon the use of high dipole moment solvents, however, it was also observed that such solvents can exacerbate the operational stability of the transistors. A detailed investigation of polymer bulk and surface properties revealed that the choice of solvents can strongly influence its micro-molecular structure, dipolar orientation and surface chemical composition which consequently, affect the device performance and stability by controlling the leakage characteristics, capacitance density, trap formation mechanism and charge trapping behaviour at dielectric/semiconductor interface. This report illustrates the requirement of proper solvent selection to achieve high electrical performance as well as long term operational stability. Our study also demonstrates that low dipole moment solvents are more favourable in transistors for photo-detection applications.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.065
      Issue No: Vol. 130 (2017)
       
  • Comparison of two coarse-grained models of cis-polyisoprene with and
           without pressure correction
    • Authors: Takahiro Ohkuma; Kurt Kremer
      Pages: 88 - 101
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Takahiro Ohkuma, Kurt Kremer
      We investigate two coarse-grained models of a cis-polyisoprene melt. The bonded interactions which are used in both models are derived by Boltzmann inversion of the probability distributions of the bonded variables in a single chain simulation. The non-bonded interactions are derived by an iterative Boltzmann inversion method in the melt state with pressure correction in a model and without in the other model. In our mapping rule, two or three carbons are grouped into coarse-grained beads. The trade-off relationship between pressure and compressibility is observed in the coarse-grained models. Since the relaxation dynamics of the coarse-grained models are accelerated by the smoothed potentials, single numerical factors are introduced to rescale the time scale of the coarse-grained models, respectively. The factors of the two models are in the same order but the model with pressure correction displays larger acceleration than the other. It is found that the stress relaxation function near equilibrium and the nonlinear viscosity under steady shear are essentially the same between the two coarse-grained models in the rescaled time scales despite of their different equilibrium pressures. We also study the dependency of the rescaling factors on the chain length of the polymer. The rescaling factors increase with increasing the chain length and exponentially saturates to certain values around 100 monomers in chains.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.09.062
      Issue No: Vol. 130 (2017)
       
  • Effect of monomer sequence distribution on the CO2-philicity of
           a well-defined ternary copolymer: Poly(vinyl acetate-co-vinyl
           butyrate-co-vinyl butyl ether)
    • Authors: Zewen Zhu; Yongfei Zhang; Wei Jiang; Lu Sun; Lixin Dai; Gang Zhang; Jun Tang
      Pages: 102 - 111
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Zewen Zhu, Yongfei Zhang, Wei Jiang, Lu Sun, Lixin Dai, Gang Zhang, Jun Tang
      The work aims to interpret the phase behavior of multi-polymers in super critical CO2 via a spatially dependent structural parameter, the monomer sequence distribution, rather than traditional statistical factors. Well-defined statistical copolymers based on three CO2-philic monomers, vinyl acetate, vinyl butyrate and vinyl butyl ether, were synthesized with reversible addition-fragmentation chain transfer free-radical polymerization by combining their kinetic behaviors and pairwise reactivity ratios into the Alfrey–Goldfinger–Skeist model. The corresponding cloud point pressures become nonlinear with the polymer composition and possess upper critical solution pressure behavior. Additionally, their diad and triad monomer sequence distributions were calculated by simple theoretical arithmetic. While analyzing the cloud point pressure measurements, we found that both the differences in composition and symmetrical structure of the monomer triads could impact the CO2-philicity of triads, which were close to the properties of the products, and thus, the variations in the triad sequence distribution could reasonably predict the phase behavior of the products.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.09.050
      Issue No: Vol. 130 (2017)
       
  • Swelling behaviors of proton exchange membranes in alcohols
    • Authors: Young Don Yi; Young Chan Bae
      Pages: 112 - 123
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Young Don Yi, Young Chan Bae
      Swelling behaviors of physically crosslinked polymer membranes were observed in water and alcohols across a wide range of temperatures. Swelling of proton exchange membranes (PEM) was related to specific interactions at lower temperature. In average swelling ratio (SR) analysis, more hydrophobic PEMs showed lower expansion in water and methanol (MeOH), but higher SRs in other alcohols. The average SR was highest for MeOH and decreased as the carbon number increased. When hydrogen bonding is strongest, more hydrophobic PEMs had higher SRs in alcohols with more carbon. The total volume changes in alcohols was highest in MeOH and decreased as the carbon number increased. At high temperature, a PEM with flexible structure showed higher total volume change. A new equation based on Flory-Rehner's theory was proposed to describe the swelling behavior of PEMs. The new equation had fewer parameters and better represented the experimental volume expansion data than previous models.
      Graphical abstract image

      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.09.069
      Issue No: Vol. 130 (2017)
       
  • Synthesis of graphene oxide/poly(3,4–ethylenedioxythiophene)
           composites by Fenton's reagent
    • Authors: Lorena Carrasco–Valenzuela; E. Armando Zaragoza–Contreras; Alejandro Vega–Rios
      Pages: 124 - 134
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Lorena Carrasco–Valenzuela, E. Armando Zaragoza–Contreras, Alejandro Vega–Rios
      Graphene oxide/poly(3,4–ethylenedioxythiophene) composites were synthesized through Fenton's reaction. The synthesis was performed using graphene oxide intercalated with iron (III) chloride and hydrogen peroxide. Then, in situ polymerization of 3,4–ethylenedioxythiophene monomer via Fenton's reaction on graphene oxide was accomplished. The composites exhibit a matrix growth of poly(3,4–ethylenedioxythiophene) chains on and around the graphene oxide layers presenting π−π interactions between both materials. The electroactivity and optical properties of the composite were increased. The intercalation of iron (III) chloride is demonstrated through X–ray diffraction as the interlayer distance of the graphene oxide sheets increased with the addition of the compound. Transmission electron microscopy analysis was carried out to establish that the polymer matrix was growing around the layers. The Fourier transform infrared spectroscopy measurements were implemented as a complementary technique for Raman to confirm the possibility of a π–π interaction. The materials show a maximum fluorescence emission at 480 and 530 nm. Properties were measured to establish the presumable application in hybrid solar cells, due to the absorption of the composite in the UV and near–IR region in a range of 210–350 nm and 700–800 nm. The composites exhibited a matrix growth of conducting polymer chains on and around the graphene oxide layers presenting red–ox states with a potential application as a counter electrode.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.013
      Issue No: Vol. 130 (2017)
       
  • Polytriphenylamine derivative with enhanced electrochemical performance as
           the organic cathode material for rechargeable batteries
    • Authors: Jiaqi Xiong; Zhi Wei; Tao Xu; Yang Zhang; Chuanxi Xiong; Lijie Dong
      Pages: 135 - 142
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Jiaqi Xiong, Zhi Wei, Tao Xu, Yang Zhang, Chuanxi Xiong, Lijie Dong
      A novel polytriphenylamine derivative, poly(4-carbamoyl-N,N-diphenylaniline-2,2,5,5-tetramethyl-pyrrolin-1-oxyl) (PTPA-PO) has been synthesized and utilized for the fabrication of the cathode material for organic rechargeable batteries for the first time. The molecular structure, morphology, and electrochemical performance of the obtained polymers were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), cyclic voltammetry (CV), respectively. Additionally, the charge-discharge performance of the obtained polymers as cathode material were explored by galvanostatic charge-discharge tests. As a result, compared with PTPA, the as-prepared polymer presented an enhanced discharge capacity of 134.5 mAh·g−1 with two well-defined plateaus. Besides, the PTPA-PO, as the cathode material, exhibited an improved rate performance and remained above 90% of the initial capacity over 100 cycles. These outstanding electrochemical performances were attributed to the combination of the conducting polymer PTPA and the radical pendant PO together with the novel linear molecular structure, which not only provided a two-electron redox process, but also enhanced the charge carrier transportation along the polymer chain.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.004
      Issue No: Vol. 130 (2017)
       
  • Single-phase block copolymers by cross-metathesis of 1,4-cis-polybutadiene
           and 1,4-cis-polyisoprene
    • Authors: Simona Daniele; Annaluisa Mariconda; Gaetano Guerra; Pasquale Longo; Luca Giannini
      Pages: 143 - 149
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Simona Daniele, Annaluisa Mariconda, Gaetano Guerra, Pasquale Longo, Luca Giannini
      Macromolecular Cross-Metathesis (MCM) reactions on commercial Polybutadiene (PBD) and Polyisoprene (PIP) homopolymers, in the presence of first generation Grubbs and Hoveyda-Grubbs catalysts, are reported. 13C-NMR resonances of butadiene(B)/isoprene(I) heterosequences show block-copolymer formation, with blocks longer than a hundred monomer units, even for long reaction times. DSC scans of MCM products show that, with MCM time, PBD crystallinity progressively disappears while the well separated Tg of the two homopolymers merge to an intermediate single Tg. This indicates that PBD and PIP blocks are completely miscible when their lengths are reduced to a few hundred units. 13C NMR spectra also show that, for the considered MCM process, double bond isomerizations are definitely more frequent than heterosequence formations.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.008
      Issue No: Vol. 130 (2017)
       
  • FT-IR studies of factors affecting the diffusivity of oligo (oxyethylene)
           fatty acid ester in PE films: Effect of temperature, ethylene oxide chain
           length and base resin type
    • Authors: Yuanyuan Zhou; Lei Hou; Hongyu Chen; Rudi Steenbakkers; Kalyan Sehanobish; Peiyi Wu; Qing Shi
      Pages: 150 - 160
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Yuanyuan Zhou, Lei Hou, Hongyu Chen, Rudi Steenbakkers, Kalyan Sehanobish, Peiyi Wu, Qing Shi
      A migration kinetics study of a series of oligo (oxyethylene) fatty acid esters of various chain lengths in polyethylene film was studied using Fourier transform infrared (FT-IR) spectroscopy. Diffusion coefficients ( D ) were determined as a function of temperature, ethylene oxide (EO) chain length and base resin type. The activation energy of diffusion ( E a ) for each oligo (oxyethylene) fatty acid ester was determined using the Arrhenius plot of D dependence on inverse temperature. The correlation between obtained D and the number-averaged molecular weight M n of oligo (oxyethylene) fatty acid ester was described well by a power law expression ( D = b M n − a ), and the parameters a and b were determined from experimental data. Two other models, which have the form of an Eyring expression, were derived to express the effects of temperature and EO chain length on the diffusion process of oligo (oxyethylene) fatty acid esters. Diffusivity of oligo (oxyethylene) fatty acid ester in linear low density polyethylene (LLDPE) was higher than in high density polyethylene (HDPE) and low density polyethylene (LDPE).
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.001
      Issue No: Vol. 130 (2017)
       
  • Anisotropic nanoparticles as templates for the crystalline structure of an
           injection-molded isotactic polypropylene/TiO2 nanocomposite
    • Authors: Peng Zhang; Tobias Kraus
      Pages: 161 - 169
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Peng Zhang, Tobias Kraus
      We study the molecular origins of anisotropy in a semicrystalline polymer nanocomposite that is caused by aligned, elongated filler nanoparticles. Our study is based on spatially resolved 2D WAXS/SAXS data that indicates the arrangement of molecules, lamellae, and filler particles in the composite. Isotactic polypropylene (IPP) samples filled with anisotropic TiO2 nanoparticles were prepared by injection molding. The nanocomposite contained IPP crystals with preferential alignment, while neat IPP formed crystals with random orientation under the same preparation conditions. We studied the mechanism through which anisotropic TiO2 nanoparticles change the molecular assembly in the polymer melt and cause preferential alignment. Our hypothesis is that shear forces during injection molding align the long axis of the nanoparticles parallel to the melt flow direction, and the particles align the adjacent IPP molecules. The aligned IPP molecules in the melt then serve as nuclei in crystal growth during solidification. This templating increases the elastic modulus compared to that of neat IPP.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.09.067
      Issue No: Vol. 130 (2017)
       
  • Poly(methylhydrosiloxane) networks of different structure and content of
           Si-H groups: Physicochemical properties and transformation into silicon
           oxycarbide ceramics
    • Authors: Monika Wójcik-Bania; Agnieszka Łącz; Anna Nyczyk-Malinowska; Magdalena Hasik
      Pages: 170 - 181
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Monika Wójcik-Bania, Agnieszka Łącz, Anna Nyczyk-Malinowska, Magdalena Hasik
      In the work, poly(methylhydrosiloxane) was cross-linked by three vinylsiloxanes differing in molecular structure and functionality, i.e. linear difunctional ViMMVi, branched tetrafunctional Q(MVi)4 and cyclic tetrafunctional D4 Vi. The cross-linking process was conducted at three molar ratios of Si-H to Si-CH=CH2 groups in order to obtain different amounts of unreacted Si-H groups in the systems. As established by swelling measurements, the applied cross-linker and molar ratio of reactive groups show the influence on the average cross-linking densities of the studied systems. Conducted thermal investigations allowed to conclude that the amount of Si-H groups present in the system affects the number of decomposition steps of the studied networks. The results of thermal studies of the cross-linked samples were complemented by FTIR and XRD analyses of the residues formed after pyrolysis of the cross-linked products conducted at different temperatures in the range between 200 and 1000 °C in Ar atmosphere. The presence of the free carbon phase in the obtained silicon oxycarbide materials was confirmed by Raman spectroscopy.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.020
      Issue No: Vol. 130 (2017)
       
  • Synthesis and characterization of a microporous 6FDA-polyimide made from a
           novel carbocyclic pseudo Tröger's base diamine: Effect of bicyclic
           bridge on gas transport properties
    • Authors: Mahmoud A. Abdulhamid; Xiaohua Ma; Xiaohe Miao; Ingo Pinnau
      Pages: 182 - 190
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Mahmoud A. Abdulhamid, Xiaohua Ma, Xiaohe Miao, Ingo Pinnau
      A newly designed carbocyclic pseudo Tröger's base diamine (CTB) monomer, 2,8-dimethyl-3,9-diamino-5,6,11,12-tetrahydro-5,11-methanodibenzo[a,e][8]annulene (CTBDA) and its isomeric analogue 2,8-dimethyl-(1,7)(4,10)(3,9)-diamino-5,6,11,12-tetrahydro-5,11-methanodibenzo[a,e][8]annulene (iCTBDA), were designed for the synthesis of microporous 6FDA-based polyimides (6FDA-CTBDA and 6FDA-iCTBDA). Both polyimides were soluble, exhibited excellent thermal stability of ∼490 °C, and had high surface areas of 587 m2 g−1 (6FDA-CTBDA) and 562 m2 g−1 (6FDA-iCTBDA). A 6FDA-based polyimide derived from 4,10-dimethyl-3,9-diamino-6H,12H-5,11-methanodibenzo[b,f][1,5]-diazocine (6FDA-TBDA) was made for comparison to investigate the effects of the basic tertiary nitrogen functionality in the Tröger's base diamine on the polymer properties relative to the carbocyclic 6FDA-CTBDA analogue. 6FDA-TBDA displayed lower gas permeabilities but moderately higher gas-pair permselectivities than 6FDA-CTBDA. The enhanced permselectivity of 6FDA-TBDA resulted exclusively from higher diffusion-based selectivity. Direct gas sorption measurements demonstrated that the basicity in the Tröger's base bridge moiety enhanced the sorption capacity of CO2 only slightly and had no effect on the CO2/CH4 solubility selectivity in 6FDA-TBDA vs. 6FDA-CTBDA.
      Graphical abstract image

      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.017
      Issue No: Vol. 130 (2017)
       
  • Stress transfer in nanocomposites enabled by poly(methyl methacrylate)
           wrapping of carbon nanotubes
    • Authors: Amir A. Bakhtiary Davijani; Huibin Chang; H. Clive Liu; Jeffrey Luo; Satish Kumar
      Pages: 191 - 198
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Amir A. Bakhtiary Davijani, Huibin Chang, H. Clive Liu, Jeffrey Luo, Satish Kumar
      Good dispersion and interfacial interaction of carbon nanotubes in polymer matrices are important to effectively achieve mechanical reinforcement in nanocomposites. Previously, it was shown that poly(methyl methacrylate) (PMMA) helically wraps around single wall carbon nanotubes (SWNTs), and thus prevents SWNT bundling. In this work, influence of PMMA-wrapped SWNTs on tensile properties of PMMA/SWNT composites and stress transfer from the matrix to the nanotubes were studied. The tensile modulus and tensile strength of the PMMA-wrapped SWNT nanocomposite buckypapers made by vacuum filtration are 5.9 and 3.7 times that of the SWNT buckypaper without PMMA wrapping, respectively. Stress transfer in SWNTs was determined by monitoring G′ Raman band shift during nanocomposite film tensile deformation. Results showed that during tensile deformation, PMMA-wrapped SWNTs in the nanocomposite buckypapers experienced up to 1 GPa stress, while negligible stress was observed in the SWNT buckypaper without PMMA wrapping. Solvent-cast nanocomposite films under tensile deformation, and with SWNT loading between 0.1 and 10 wt%, PMMA-wrapped SWNTs experience stress as high as 3.1 GPa, while nanocomposites made without PMMA wrapping experience only about half of this stress value. The improved tensile properties are a result of improved CNT dispersion and enhanced interfacial stress transfer achieved via PMMA wrapping of SWNTs. A new Raman band peak was observed at 2276 cm−1 in PMMA-wrapped nanocomposites. Dynamic mechanical properties of various nanocomposites were also studied and reported.
      Graphical abstract image

      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.002
      Issue No: Vol. 130 (2017)
       
  • Synthesis of poly(butylene terephthalate)-block-poly(ethylene
           oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) multiblock
           terpolymers via a facile PROP method
    • Authors: Minzhi Zhang; Jiali Gu; Xiang Zhu; Lingfeng Gao; Xiaohong Li; Xiaoming Yang; Yingfeng Tu; Christopher Y. Li
      Pages: 199 - 208
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Minzhi Zhang, Jiali Gu, Xiang Zhu, Lingfeng Gao, Xiaohong Li, Xiaoming Yang, Yingfeng Tu, Christopher Y. Li
      We present here the application of in situ cascade polycondensation-coupling ring-opening polymerization (PROP) method for the facile synthesis of a series of three-component poly(butylene terephthalate)-block-poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) multiblock terpolymers (PBT-b-PEO-b-PPO-b-PEO-b-PBT)n, using cyclic oligo(butylene terephthalate)s (COBTs) as monomers and dihydroxyl end-functional PEO-b-PPO-b-PEO (EPE) as macroinitiator. The structure details of these copolymers were characterized by 1H-1H gCOSY and 1H-13C gHSQC NMR spectra. With the assignment of multiblock chain ends, block segmental ends and corresponding groups for each segment, the number-average molecular weights for multiblock terpolymers and each block segment were estimated by the quantitative 1H NMR spectra. Polymerization kinetics studies confirm the PROP mechanism. With crystalline PBT and PEO segments, the multiblock terpolymers are double-crystalline polymers, where the melting point and crystallinity of PBT and PEO segments increase with corresponding PBT and PEO content, respectively. The covalent linking of PBT segments with PEO segments leads to the confined crystallization environment for both blocks, where a strong depression on melting point of PEO crystals was observed, which becomes amorphous at an EPE triblock content of 50%. TEM and SAXS results show interesting lamella-like microphase separation morphologies in these multiblock terpolymers.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.010
      Issue No: Vol. 130 (2017)
       
  • Orientation of polymer chains in spherulites of poly(ethylene oxide)-urea
           inclusion compounds
    • Authors: Yang Gao; Shu-Fang Yao; Hai-Mu Ye; Bao-Hua Guo; Jun Xu
      Pages: 209 - 217
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Yang Gao, Shu-Fang Yao, Hai-Mu Ye, Bao-Hua Guo, Jun Xu
      Orientation of polymer chains in the spherulites of polymer-small molecule inclusion compounds (IC) is an interesting issue. Two kinds of spherulite morphologies were observed in the metastable β phase of poly(ethylene oxide) (PEO)/urea IC under the same isothermal crystallization temperature. Via polarized micro-Fourier transform infrared spectroscopy and two-dimensional wide angle X-ray diffraction technique, we found that PEO chains in the two morphologies oriented differently: one along the radius and the other along the tangential direction of the spherulites. The β IC spherulites with polymer chains along the radial direction crystallized directly from melt. In contrast, the metastable spherulites with polymer chain oriented along the tangential direction among the preformed urea crystals. The phase transition from the metastable β spherulites to the stable α IC during heating was examined as well. For the both types of spherulites of the β IC, the conversion rate along polymer chain direction was lower than that perpendicular to the polymer chain. After phase transition, the orientations of PEO chains almost did not change. The two types of morphologies with different orientations of β IC crystals in the spherulites can be attributed to the competitive nucleation behavior of the β PEO-urea IC and pure urea crystals, which varies with the EO/urea molar ratio in the mixture melt. With the increasing EO/urea molar ratio, the fastest growth direction of β IC will change from the direction along the PEO chain to that normal to the PEO chain. Namely, the polymer/small molecule molar ratio has profound effect on the growth behavior of the β phase IC crystals.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.025
      Issue No: Vol. 130 (2017)
       
  • Retrieving the original appearance of polyhedral oligomeric
           silsesquioxane-based porous polymers
    • Authors: Dengxu Wang; Ruixue Sun; Shengyu Feng; Wensi Li; Hongzhi Liu
      Pages: 218 - 229
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Dengxu Wang, Ruixue Sun, Shengyu Feng, Wensi Li, Hongzhi Liu
      A class of polyhedral oligomeric silsesquioxane (POSS)-based porous polymers containing typical π-conjugated units, including biphenyl, tetrahedral silicon-centered units and tetraphenylethene, have been prepared by Heck reactions of octavinylsilsesquioxane (OVS) with the corresponding brominated monomers. Two sets of reaction conditions were employed to retrieve their original appearance. These materials exhibit tunable appearance with the colors from dark colors to various colors and the physical forms from coarse powders with irregular shape particles to fine powders with relatively uniform solid spheres by altering the reaction conditions from method A to method B. It is found that the variation of appearance leads to the alteration of the fluorescence from nearly no fluorescence to bright fluorescence. Considering the conjugated feature of these polymers, we speculate that these polymers were afforded as their original appearance by method B. This finding could explain the unexpected phenomenon that many conjugated porous polymers exhibit no or very low fluorescence despite of their π-conjugated structures, that is, their real appearance may be covered by the residuals in the networks. Thus, researchers should deliberately consider the material's appearance when preparing fluorescent porous polymers. Additionally, samples with fine powders show excellent dispersion stability in solvents, which is beneficial for the use of these materials in solution processable methodologies such as spin-coating. Furthermore, these materials show efficient fluorescence quenching for nitrobenzene vapour in thin films, thereby indicating their potential application as sensing agents for the detection of explosives.
      Graphical abstract image

      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.021
      Issue No: Vol. 130 (2017)
       
  • A multi-mechanism model for large-strain thermomechanical behavior of
           polyurethane shape memory polymer
    • Authors: A.F. Saleeb; S.H. Natsheh; J.S. Owusu-Danquah
      Pages: 230 - 241
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): A.F. Saleeb, S.H. Natsheh, J.S. Owusu-Danquah
      The physical mechanisms underlining the unique shape memory behavior in polymers differ greatly from those in intermetallics. However, phenomenologically, both material systems exhibit pseudoplasticity and superelasticity. This provides the main motivation for the present work, in which a recently-developed multi-mechanism model, previously used successfully for intermetallics is extended to capture the thermomechanical responses of a polyurethane-polyester-polyol material having a glass temperature of 55 °C. To this end, nine different tensile test cases were considered, including engineering strains up to 200%, stress changes up to 120 MPa, temperature range from 35 °C to 75 °C, as well as cyclic isothermal and non-isothermal behaviors. The model results were found to be in excellent agreement with the experiments. Additionally, investigations were carried out to provide macromolecular connection of the model inelastic state variables, as well as study its loading-mode and loading-rate sensitivities.

      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.003
      Issue No: Vol. 130 (2017)
       
  • Linear minority chain in a star brush: The coil-to-flower transition
    • Authors: Alexey A. Polotsky; Alexander D. Kazakov; Tatiana M. Birshtein
      Pages: 242 - 249
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Alexey A. Polotsky, Alexander D. Kazakov, Tatiana M. Birshtein
      Conformational transition in a single “minority” linear polymer chain inserted into a polymer brush made of arm-grafted chemically identical stars (star brush) is studied theoretically. It is shown that the chain can undergo a transition between conformations of the grafted coil and the “flower” consisting of a strongly stretched “stem” passing through the brush and the coil-like “head” on the top of the brush. The coil-to-flower transition can be provoked by changing internal parameters of the system (the chain length or the brush grafting density) or external conditions (the solvent strength). At sparse grafting, the coil-to-flower transition occurs continuously as a second-order-like phase transition, whereas at moderate and high grafting density, when the brush has a “two-layer” structure, the transition has the features of the first order phase transition. This opens a route for designing “molecular switches” based on a linear chain inserted in a star brush.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.005
      Issue No: Vol. 130 (2017)
       
  • Synthesis of novel optically active
           poly(thiophenyleneethynylenephenylene)s. Effects of chirality competition
           and cooperation at the side chains on higher order structures
    • Authors: Yu Miyagi; Yoshinori Otaki; Yuki Takahashi; Fumio Sanda
      Pages: 250 - 257
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Yu Miyagi, Yoshinori Otaki, Yuki Takahashi, Fumio Sanda
      Novel poly(thiophenyleneethynylenephenylene)s having optically inactive/active amide groups were synthesized by the Sonoghashira-Hagihara coupling polymerization of 3-substituted 2,5-dibromothiophene 1 with 1-substituted 3,5-diethynylbenzenes 2N, 2R, 2S derived from glycine and d-/ʟ-alanines. Poly(1–2S) exhibited an intense Cotton effect based on negative exciton chirality at 405 and 366 nm. On the other hand, poly(1–2N) exhibited a Cotton effect similar to that of poly(1–2S) but weaker, and poly(1–2R) exhibited a weak Cotton effect based on positive exciton chirality. The chiral secondary structures of the polymers were dependent on chirality cooperation and chirality competition of the side chains. The trend of the circular dichroism (CD) signs and intensities of the polymers can be explained by the concepts of “chiral cooperation” and “chiral competition” between the optically active thiophene unit and optically inactive/active phenylene unit. These polymers formed aggregate structures with increasing MeOH content of CHCl3/MeOH mixed solvents, with accompanying decrease of the UV–vis absorptions and photoluminescence (PL) intensities.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.09.014
      Issue No: Vol. 130 (2017)
       
  • Ductile polymer-based films with ultrahigh permittivity and low dielectric
           loss
    • Authors: Ming-Sheng Zheng; Jun-Wei Zha; Yu Yang; Chao-Qun Li; Peng Han; Chao-He Hu; Yong-Qiang Wen; Zhi-Min Dang
      Pages: 258 - 266
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Ming-Sheng Zheng, Jun-Wei Zha, Yu Yang, Chao-Qun Li, Peng Han, Chao-He Hu, Yong-Qiang Wen, Zhi-Min Dang
      High-permittivity (high-k) materials play a key role in advanced electronics and electrical power systems. How to prepare the flexible material with high permittivity and low dielectric loss turns out to be a hard work due to the essential low permittivity of polymers. In this work, a kind of ductile polymer-based composites was fabricated by incorporating ionic liquids into polymer matrices. The optimized permittivity of composite with 50 wt% ionic liquid reached up to 3.3 × 104, while the dielectric loss was as low as 0.65. The temperature dependence of dielectric properties was also investigated, and a high permittivity as well as low dielectric loss at 100 Hz of about 2.0 × 104 and 0.23 were achieved at 80 °C, respectively. Furthermore, the study reveals that the dielectric loss peaks of the composite films can be affected by the content of ionic liquid, temperature even the size of ions. In short, the finding indicates that the addition of ionic liquids into polymers provides a big opportunity to improve dielectric properties of polymer materials.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.026
      Issue No: Vol. 130 (2017)
       
  • Growth of polymer brushes by “grafting from” via ATRP –
           Monte Carlo simulations
    • Authors: Piotr Polanowski; Krzysztof Hałagan; Joanna Pietrasik; Jeremiasz K. Jeszka; Krzysztof Matyjaszewski
      Pages: 267 - 279
      Abstract: Publication date: 9 November 2017
      Source:Polymer, Volume 130
      Author(s): Piotr Polanowski, Krzysztof Hałagan, Joanna Pietrasik, Jeremiasz K. Jeszka, Krzysztof Matyjaszewski
      The growth of polymer brushes from flat surfaces via a grafting-from approach by atom transfer radical polymerization (ATRP) was simulated using a Monte Carlo method, the dynamic lattice liquid (DLL) model, under athermal conditions. Sets of probabilities representing reactions participating in ATRP or overall ATRP reaction probability were implemented in the simulation model. The later corresponds to the ATRP system in which statistically less than one monomer is attached to the chain end during its active period. Dense and moderately dense brushes with degrees of polymerization 45–150 were studied assuming various polymerization rates. It was determined that chain length distribution strongly depends on the reaction probability and grafting density (GD). For dense brushes (GD = 0.3–0.6) the dispersity was comparable with the experimental results only for the lowest probabilities used (p = 2 × 10−5). For GD = 0.1 and in the presence of free chains 10 or even 100 times higher probabilities gave satisfactory results. If polymerization rate was too high, two groups of chains could be distinguished: slowly growing short chains, the ends of which were close to the flat surface, where monomer concentration was lower and quickly growing long chains with the ends far from the surface, where monomer concentrations were higher. The relationship between experimental parameters of ATRP and parameters used in the simulations are discussed.
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      PubDate: 2017-10-18T04:18:22Z
      DOI: 10.1016/j.polymer.2017.10.011
      Issue No: Vol. 130 (2017)
       
  • Insight into the influence of OA-Fe3O4 nanoparticles on the morphology and
           scCO2 batch-foaming behavior of cocontinuous LLDPE/PS immiscible blends at
           semi-solid state
    • Authors: Guangchun Zhang; Shaofeng Zhang; Jian Qiu; Zhiwei Jiang; Haiping Xing; Minggang Li; Tao Tang
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Guangchun Zhang, Shaofeng Zhang, Jian Qiu, Zhiwei Jiang, Haiping Xing, Minggang Li, Tao Tang
      The influence of oleic acid modified Fe3O4 (OA-Fe3O4) nanoparticles on the morphology and foaming behavior of cocontinuous linear low density polyethylene/polystyrene (LLDPE/PS) immiscible blends (60/40 by weight) was studied. The morphology observation showed that the addition of nanofillers resulted in the increased dispersion degree of both LLDPE and PS components and even the transformation of phase structure from cocontinuous structure to sea-island structure, when enough amounts of nanoparticles were added. Meanwhile the introduction of enough amounts of OA-Fe3O4 nanoparticles effectively enhanced the foaming ability of LLDPE/PS blend at semi-solid state during scCO2 batch foaming. The mechanism analysis for the change of foaming behavior showed that the improved foaming capacity resulted from the change of the phase structure of LLDPE/PS blends and heterogeneous nucleation of OA-Fe3O4 nanofillers. Sorption and desorption measurements showed that the addition of OA-Fe3O4 nanoparticles in the LLDPE/PS blend increased the solubility of CO2, and the presence of enough amount of OA-Fe3O4 decreased the desorption rate of CO2 in the initial period of depressurization process, which are beneficial to cell nucleation and growth. Furthermore, it was found that the melt behavior and crystalline properties of LLDPE/PS blends were not the key factors to improved foaming behavior of the blends in the presence of OA-Fe3O4 nanoparticles.
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      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.053
      Issue No: Vol. 129 (2017)
       
  • Organic dispersion of polyaniline and single-walled carbon nanotubes and
           polyblends with poly(methyl methacrylate)
    • Authors: Thomas Farrell; Kan Wang; Cheng-Wei Lin; Richard B. Kaner
      Pages: 1 - 4
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Thomas Farrell, Kan Wang, Cheng-Wei Lin, Richard B. Kaner
      Traditionally, in situ polymerization has been used to make polymer-carbon nanotube composites. Here, we report a simple method of mixing polyaniline with single-walled carbon nanotubes in a variety of organic solvents via ultrasonication. The maximum loading fraction of SWCNTs in the composites is determined by the conformation of the polyaniline chains. The type of solvent used has the greatest influence on the conformation of the polyaniline chains. Furthermore, the composites can be easily blended with poly(methyl methacrylate) (PMMA), to form polyblends. The electrical conductivities and transparencies of the polyblend films are reported.
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      PubDate: 2017-09-27T11:21:19Z
      DOI: 10.1016/j.polymer.2017.09.032
      Issue No: Vol. 129 (2017)
       
  • Polycarbonates derived from propylene oxide, CO2, and 4-vinyl cyclohexene
           oxides terpolymerization catalyzed by bifunctional salcyCoIIINO3 complex
           and its post-polymerization modification
    • Authors: Hongye Zhang; Binyuan Liu; Huining Ding; Junwu Chen; Zhongyu Duan
      Pages: 5 - 11
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Hongye Zhang, Binyuan Liu, Huining Ding, Junwu Chen, Zhongyu Duan
      Terpolymerizations of CO2, propylene oxide (PO), and 4-vinyl cyclohexene oxide (VCHO) were successfully catalyzed by a single cobalt(III) complex of a salen-type ligand bearing one quaternary ammonium salt on the five-position of each aromatic ring. The influences of various reaction conditions such as molar ratio of the monomers, reaction time and reaction temperature on the terpolymerization progress were investigated. The resulting terpolymers showed only one thermolysis peak and one adjustable glass-transition temperature (T g) dependable on vinyl cyclohexene carbonate (VCHC) unit content with the relationship of “T g (°C) = 64 × F Vinyl + 39”. Furthermore, the epoxy group was incorporated by oxidation of vinyl group of PVCHC units and the cyclic carbonate (CC) functional group was achieved by reaction of CO2 with epoxy-functionalized terpolymer. The linear dependencies of the T g on the mole fractions ratio of pendent epoxy and CC groups on the poly(cyclohexene carbonate) main chain were also observed. Notably, the T g of fully CC-functionalized PCHC was up to 196 °C, which was the highest T g of CO2-based polycarbonate reported at the absence of cross-linked structure.
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      PubDate: 2017-09-27T11:21:19Z
      DOI: 10.1016/j.polymer.2017.09.033
      Issue No: Vol. 129 (2017)
       
  • Reactive supramolecular filler for elastomer reinforcement
    • Authors: Xin Tan; Yihong Zhao; Mengsha Qian; Gary R. Hamed; Li Jia
      Pages: 12 - 20
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Xin Tan, Yihong Zhao, Mengsha Qian, Gary R. Hamed, Li Jia
      A reactive amphiphile, SA1, which comprises a mercaptodecyl oleophilic tail and a β-alanine oleophobic moiety, has been introduced to serve as the building block for supramolecular filler. At least a fraction of SA1 reacts in situ during mechanically mixing and vulcanization with SBR via thiol-ene reaction. Some oxidative dimerization also concomitantly occurs to give DSA1. The chemical coupling between SA1 and SBR results in drastically improved filler domain dispersion. Short fibrous crystalline domains, which are likely composed of SA1, SA1 grafted to SBR, and DSA1, less than 10 nm in width and a few tens to one hundred nanometers in length are observed by TEM. The filler domains are evenly distributed in the SBR. In contrast, the simple filler PA1 forms large irregular aggregates on the length scale of hundreds of nanometers. The improved filler dispersion and filler-rubber interaction allow effective energy dissipation and result in significantly improved mechanical properties. A solution-mixing method proves feasible for mixing SA1 and SBR and actually has resulted in better mechanical properties than the mechanical mixing method. Since the conventional mechanical mixing method for rubber compounding is highly energy-intensive, avoidance of the mechanical mixing method is another practical advantage for the novel strategy of supramolecular reinforcement.
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      PubDate: 2017-09-27T11:21:19Z
      DOI: 10.1016/j.polymer.2017.09.024
      Issue No: Vol. 129 (2017)
       
  • Prediction of resin textural properties by vinyl/divinyl copolymerization
           modeling
    • Authors: Leandro G. Aguiar; Juliana O.V. Moura; Thiago R. Theodoro; Turibio G.S. Neto; Vinícius M.P. Lopes; Joslaine R. Dias
      Pages: 21 - 31
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Leandro G. Aguiar, Juliana O.V. Moura, Thiago R. Theodoro, Turibio G.S. Neto, Vinícius M.P. Lopes, Joslaine R. Dias
      The production of polymeric resins through free-radical copolymerization is an interesting procedure from an economic standpoint; however, its mathematical representation is of great complexity. In the present study, modeling tools were used to describe the copolymerization of styrene with ethylene glycol dimethacrylate (EGDMA) beyond the gel point. Balance of species and sequences, method of moments, and numerical fractionation technique were applied in the model's kinetic description. Diffusion effects were also taken into account. The concept of elementary gel structures (EGSs) was used in order to predict textural properties of polymer particles, such as specific surface area and swollen gel volume. Suspension copolymerizations were carried out in the presence of toluene/heptane mixtures, and data on these reactions were used to assess the model's predictability. Reactivity parameters showed similarities to styrene/divinylbenzene systems. Agreement between the model and experimental data improved when diffusion effects were considered. The fitted apparent coiling factors for dry particles were found in the range of 0.368–0.406, and a linear correlation was obtained between this parameter and toluene fraction (a good solvent), being consistent with the pore formation phenomenon.
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      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.042
      Issue No: Vol. 129 (2017)
       
  • A pseudo-thermodynamic description of dispersion for nanocomposites
    • Authors: Yan Jin; Gregory Beaucage; Karsten Vogtt; Hanqiu Jiang; Vikram Kuppa; Jay Kim; Jan Ilavsky; Mindaugas Rackaitis; Andrew Mulderig; Kabir Rishi; Vishak Narayanan
      Pages: 32 - 43
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Yan Jin, Gregory Beaucage, Karsten Vogtt, Hanqiu Jiang, Vikram Kuppa, Jay Kim, Jan Ilavsky, Mindaugas Rackaitis, Andrew Mulderig, Kabir Rishi, Vishak Narayanan
      Dispersion in polymer nanocomposites is determined by the kinetics of mixing and chemical affinity. Compounds like reinforcing filler/elastomer blends display some similarity to colloidal solutions in that the filler particles are close to randomly dispersed through processing. It is attractive to apply a pseudo-thermodynamic approach taking advantage of this analogy between the kinetics of mixing for polymer compounds and thermally driven dispersion for colloids. In order to demonstrate this pseudo-thermodynamic approach, two polybutadienes and one polyisoprene were milled with three carbon blacks and two silicas. These samples were examined using small-angle x-ray scattering as a function of filler concentration to determine a pseudo-second order virial coefficient, A 2 , which is used as an indicator for compatibility of the filler and polymer. It is found that A 2 follows the expected behavior with lower values for smaller primary particles indicating that smaller particles are more difficult to mix. A 2 is analogous to the excluded volume and long-range interaction potential for non-equilibrated nanocomposites. The measured values of A 2 can be used to specify repulsive interaction potentials for coarse grain DPD simulations of filler/elastomer systems. In addition, new methods to quantify the filler percolation threshold and filler mesh size as a function of filler concentration are obtained. The results represent a new approach to understanding and predicting dispersion in polymer nanocomposites based on a thermodynamic analogy.
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      PubDate: 2017-09-27T11:21:19Z
      DOI: 10.1016/j.polymer.2017.09.040
      Issue No: Vol. 129 (2017)
       
  • Nanorheology of poly - and monodispersed polymer brushes under oscillatory
           flow as models of epithelial cancerous and healthy cell brushes
    • Authors: J.D. Hernández Velázquez; S. Mejía-Rosales; A. Gama Goicochea
      Pages: 44 - 56
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): J.D. Hernández Velázquez, S. Mejía-Rosales, A. Gama Goicochea
      In this work we study the rheology of polymeric brushes at the nanoscale interacting with an explicitly included atomic force microscopy (AFM) tip, using dissipative particle dynamics simulations, as models for pericellular brushes on epithelial cells. Two types of cells brushes are modeled: normal cells, whose surface is covered by brushes of uniform length, and cancer cells, which are covered by brushes of non-uniform length. To study their rheology, an external oscillatory shear acting on the surface of the model cells is applied, at two values of stiffness of the chains that conform the brushes. Properties such as viscosity, the coefficient of friction and interfacial tension are reported as profiles along the direction normal to the surface of the cell and are found to depend on the amplitude of the external oscillatory shear. Additionally, it was found that the mean thickness of the brush decreases with increasing amplitude of the external motion. Moreover, it is noteworthy that the properties of the uniform brush are qualitatively different from those of the polydispersed one when the oscillatory shear acts on the sample. It is argued that these differences arise from the collective effect of the chains that conform the brushes. These results illustrate the usefulness of applying physical methods such as AFM in studies of diagnosis and characterization of cancer cells.
      Graphical abstract image

      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.046
      Issue No: Vol. 129 (2017)
       
  • Polymerization-induced self-assembly of acrylonitrile via ICAR ATRP
    • Authors: Guowei Wang; Zongyu Wang; Bongjoon Lee; Rui Yuan; Zhao Lu; Jiajun Yan; Xiangcheng Pan; Yang Song; Michael R. Bockstaller; Krzysztof Matyjaszewski
      Pages: 57 - 67
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Guowei Wang, Zongyu Wang, Bongjoon Lee, Rui Yuan, Zhao Lu, Jiajun Yan, Xiangcheng Pan, Yang Song, Michael R. Bockstaller, Krzysztof Matyjaszewski
      Polymerization-induced self-assembly (PISA) has attracted growing interest as facile fabrication process of polymer-based nanomaterials. However, PISA of acrylonitrile (AN) by atom transfer radical polymerization (ATRP) has remained an outstanding challenge due to the high activity of AN and poor solubility of polyacrylonitrile (PAN) in AN monomer. Here the application of PISA by using an initiators for continuous activator regeneration (ICAR) ATRP for the synthesis of PAN-based nano-objects is demonstrated. A highly active ATRP macroinitiator, methoxy-poly(ethylene oxide) 2-bromo-2-phenylacetate (mPEO-BPA) was synthesized by esterification and used also as a stabilizer. The molecular weight of the macroinitiator was found to determine the structure of self-assembled nano-objects. The high molecular macroinitiator (mPEO113-BPA) formed nano-objects with spherical or worm-like morphology, while the lower molecular weight analogue (mPEO45-BPA) resulted in precipitation in most cases due to insufficient stabilization of the nano-objects.
      Graphical abstract image

      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.029
      Issue No: Vol. 129 (2017)
       
  • Rheology in shear and elongation and dielectric spectroscopy of
           polystyrene-block-poly(4-vinylpyridine) diblock copolymers
    • Authors: Tarek Kollmetz; Prokopios Georgopanos; Ulrich A. Handge
      Pages: 68 - 82
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Tarek Kollmetz, Prokopios Georgopanos, Ulrich A. Handge
      We elucidate the influence of composition (weight ratios of 89/11, 76/24 and 49/51) and morphology (spherical, cylindrical and lamellar) on the dielectric and viscoelastic properties in shear and elongation of anionically synthesized polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymers in the microphase-separated state. The temperature dependence of the response in both experiments is compared. The analysis of the linear regime shows the appearance of composition (superposition of moduli) and interfacial effects caused by microphase separation (low frequency shoulder, plateau and ω 1 / 2 regime for dynamic moduli and Maxwell-Wagner-Sillars polarization in dielectric experiments). In shear and extensional flows with a constant deformation rate, a pronounced strain-softening behavior in case of a cylindrical and a lamellar morphology appears. For a high weight fraction of the majority phase and a spherical morphology, respectively, strain-softening is observed to a lesser extent. Consequently, strain-softening of diblock copolymer melts can be tuned by the weight/volume ratio of the two blocks.
      Graphical abstract image

      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.031
      Issue No: Vol. 129 (2017)
       
  • Simultaneous step-growth and chain-growth cationic polymerization of
           styrenic monomers bearing carbazolyl groups
    • Authors: Irina V. Vasilenko; Aliaksei A. Vaitusionak; Jurgita Sutaite; Ausra Tomkeviciene; Jolita Ostrauskaite; Juozas V. Grazulevicius; Sergei V. Kostjuk
      Pages: 83 - 91
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Irina V. Vasilenko, Aliaksei A. Vaitusionak, Jurgita Sutaite, Ausra Tomkeviciene, Jolita Ostrauskaite, Juozas V. Grazulevicius, Sergei V. Kostjuk
      Cationic polymerization of two styrene derivatives containing carbazole moiety with different linking topology, 9-(4-vinylphenyl)carbazole (M1) and 3-(4-vinylphenyl)-9-ethylcarbazole (M2), using 1-chloro-1-phenylethane (PhEtCl)/SnCl4 initiating system has been investigated. It was shown that polymerization of M1, which is characterized by higher electron density on the carbon at the 3 position of carbazolyl group than on vinyl group, proceeds predominantly via step-growth (SG) pathway through addition of protonated monomer/oligomers to 3-position of carbazolyl group (electrophilic aromatic substitution). On the contrary, M2, in which 3-position of carbazolyl group is protected via introduction of 4-vinylphenyl group, polymerized predominantly via chain-growth (CG) pathway through addition of carbocation to double bond of monomer. The polymers synthesized via SG mechanism showed different photophysical characteristics in comparison with corresponding monomer, while in case of polymers prepared via CG mechanism the polymer and monomer have the same absorption and fluorescence profiles.
      Graphical abstract image

      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.036
      Issue No: Vol. 129 (2017)
       
  • A molecular dynamics-based analysis of the influence of strain-rate and
           temperature on the mechanical strength of PPTA crystallites
    • Authors: Brian Mercer; Edward Zywicz; Panayiotis Papadopoulos
      Pages: 92 - 104
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Brian Mercer, Edward Zywicz, Panayiotis Papadopoulos
      Molecular dynamic simulations are used to quantify how the mechanical behavior of PPTA crystallites, the fundamental building blocks of aramid fibers such as Kevlar®, depend on strain-rate, temperature, and crystallite size. The (axial) crystallite elastic modulus is found to be independent of strain-rate and decreases with increasing temperature. The crystallite failure strain increases with increasing strain rate and decreases with increasing temperature and crystallite size. These observations are consistent with crystallite failure being driven by stress-assisted thermal fluctuations of bonds within PPTA crystallites and the concepts of the kinetic theory of fracture. Appealing to reliability theory, a model is proposed that predicts the onset of both primary and secondary bond failure within a crystallite as of function of strain rate, temperature, and crystallite size. The model is parameterized using bond failure data from constant strain-rate molecular dynamic strain-to-failure simulations and is used to compute the activation volume, activation energy, and frequency for both primary and secondary bond ruptures.
      Graphical abstract image

      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.037
      Issue No: Vol. 129 (2017)
       
  • Comparison of chain-growth polymerization in solution versus on surface
           using reactive coarse-grained simulations
    • Authors: Binghui Deng; Edmund F. Palermo; Yunfeng Shi
      Pages: 105 - 116
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Binghui Deng, Edmund F. Palermo, Yunfeng Shi
      We developed a reactive coarse-grained model for chain-growth polymerization to study the chain length distribution of polymers grafted from a surface as compared to those grown in solution. The surface-initiated polymer chains exhibit a markedly broader distribution of chain lengths (larger dispersity) and slower chain growth kinetics as compared to the solution phase process. Two key factors that cause deviation from ideal grafting are identified: (1) the formation of chain “loops” with both termini attached to the substrate via recombination and (2) the “starvation” effect, in which the live chain ends of short polymers are sterically shielded from monomers by the presence of longer neighboring chains. Both effects are markedly amplified with increasing initiator surface density, thus limiting the density of high molecular weight chains grafted from the surface. Whereas the “loop” effect is absent in systems that are very strictly “living” (no termination), the starvation effect is likely operative in most real systems. Taken together, these results suggest a theoretical limit on the density of polymer brushes that can form on surfaces by a “grafting-from” technique, based on the kinetics of the chain-growth polymerization process.
      Graphical abstract image

      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.048
      Issue No: Vol. 129 (2017)
       
  • Chain mobility, secondary relaxation, and oxygen transport in
           terephthalate copolyesters with rigid and flexible cyclic diols
    • Authors: Krishnan A. Iyer
      Pages: 117 - 126
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Krishnan A. Iyer
      High glass transition temperature (T g) polyesters based on cycloaliphatic diols such as 1,4-cyclohexanedimethanol (CHDM) and 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD) have attracted significant interest as bisphenol-A replacement. Whereas most literature reports focus on synthetic approaches, the present study investigates in depth various structure-property relationships in CHDM- and TMCD-containing novel copolyesters. Significant enhancements in T g and increases in fragility are observed with the incorporation of bulky CHDM and rigid TMCD as comonomers. Substantial increase in oxygen permeability is measured with the incorporation of CHDM from 14.3 for poly(ethylene terephthalate) to 52.6 cc-mil/100in2.day.atm (SPU) for poly(1,4-cyclohexyldimethylene terephthalate). When 35 mol% CHDM is replaced by TMCD as comonomer, the value further increases to 137.0 SPU. In the case of CHDM-containing polyesters, improvements in both sub-T g molecular mobility (due to additional chair-to-boat transformations) and fractional free volume (FFV) result in an increase in oxygen diffusion. On the other hand, substituting 35 mol% CHDM with more rigid TMCD yields a suppressed β-relaxation. In particular, CHDM-based copolyesters follow a linear correlation between the strength of β-relaxation and diffusivity whereas the TMCD-based copolyester exhibits a significantly positive deviation from the correlation. Therefore, the much higher FFV in TMCD-containing polyester plays a more important role in determining oxygen transport through such polymer. Finally, we demonstrate that copolyesters based on CHDM and TMCD display significantly enhanced resistance to moisture-induced plasticization and the competing penetrant effect.
      Graphical abstract image

      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.049
      Issue No: Vol. 129 (2017)
       
  • Effect of anisotropic thermal expansion on the torsional actuation of
           twist oriented polymer fibres
    • Authors: Shazed Aziz; Sina Naficy; Javad Foroughi; Hugh R. Brown; Geoffrey M. Spinks
      Pages: 127 - 134
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Shazed Aziz, Sina Naficy, Javad Foroughi, Hugh R. Brown, Geoffrey M. Spinks
      Torsional actuation of twisted polymer fibres is the basis for high performance tensile actuation when these fibres are formed into coils. The thermally-induced torsional actuation of twisted polyamide-6 fibres can be predicted by a single helix approximation when the measured diameter and length direction thermal expansion coefficients are known. The single helix model illustrates the sensitivity of the magnitude of torsional actuation to the volume expansion anisotropy for a given volume change. The applicability of the model has been further assessed by investigating three polymer fibres that display different thermal expansion anisotropies. Commercially available polyethylene, polypropylene and polyamide-6 fibres were twisted to the maximum extent without coiling and then heat treated to fix the twisted structure. Heating the twisted fibres between 26 and 62 °C resulted in a partial untwist which was reversed during cooling. The single-helix model of the twisted fibres was used to accurately predict the torsional stroke based on the measured fibre length and diameter change during heating. Comparative torsional stroke of twisted polyamide-6, polyethylene and polypropylene was explained in terms of materials thermo-physical properties. Generated blocked torques was also correctly predicted by the single-helix model when combined with the measured fibre torsional stiffness. Variances between torsional stiffnesses were found to be dependent of different anisotropic thermal properties of tested fibres.
      Graphical abstract image

      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.052
      Issue No: Vol. 129 (2017)
       
  • Functional polyethylene with regularly distributed ester pendants via
           ring-opening metathesis polymerization of ester functionalized
           cyclopentene: Synthesis and characterization
    • Authors: Shaofei Song; Zhenyan Xing; Zhenmei Cheng; Zhisheng Fu; Junting Xu; Zhiqiang Fan
      Pages: 135 - 143
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Shaofei Song, Zhenyan Xing, Zhenmei Cheng, Zhisheng Fu, Junting Xu, Zhiqiang Fan
      A new series of functional polyethylene (PE) with ester pendant (−COOR, R = methyl, ethyl, n-propyl, n-butyl, n-octyl, n-dodecyl, n-tetradecyl and n-hexadecyl) on every five main chain carbons were prepared via ring-opening metathesis polymerization (ROMP) of COOR functionalized cyclopentene catalyzed by a ruthenium-based catalyst and subsequent hydrogenation of the ROMP products. High monomer conversions (70–80%) were achieved in all the ROMP reactions. Chain structure, molecular weight and molecular weight distribution (MWD) of the ROMP products and hydrogenated polymers were characterized by 1H, 13C NMR and GPC, which showed regular distribution of the COOR pendants along the main chain, moderate molecular weight and narrow MWD. Thermal properties and side chain crystallization behaviors of the functional PEs were investigated by differential scanning calorimetry (DSC). Glass transition temperature (T g) of the polymer decreased for nearly 30 °C when R of the pendant COOR was enlarged from methyl to n-octyl, and the new polymers showed lower melting temperature (T m), higher side chain crystallinity (X c) and more precise side chain lamellar crystal thickness (l c) as compared with corresponding polyacrylates carrying the same side alkyl. The new polymers exhibited moderate thermal stability.
      Graphical abstract image

      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.057
      Issue No: Vol. 129 (2017)
       
  • Synthesis and characterization of Ag NPs templated via polymerization
           induced self-assembly
    • Authors: Yaoming Zhang; Paulina Filipczak; Guping He; Grzegorz Nowaczyk; Lukasz Witczak; Wojciech Raj; Marcin Kozanecki; Krzysztof Matyjaszewski; Joanna Pietrasik
      Pages: 144 - 150
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Yaoming Zhang, Paulina Filipczak, Guping He, Grzegorz Nowaczyk, Lukasz Witczak, Wojciech Raj, Marcin Kozanecki, Krzysztof Matyjaszewski, Joanna Pietrasik
      Spherical poly(acrylic acid)-block-polystyrene (PAA-b-PS) nano-objects were prepared via polymerization induced self-assembly (PISA) and used as templates for the synthesis of silver nanoparticles (Ag NPs). The PAA shells on the spheres acted as templates for the formation of immobilized Ag NPs by loading Ag + ions followed by reduction. The templates covered with discrete Ag NPs showed surface-enhanced Raman spectroscopy (SERS) effect as substrates for adenine detection and high catalytic activity for reduction of 4-nitrophenol to 4-aminophenol.
      Graphical abstract image

      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.047
      Issue No: Vol. 129 (2017)
       
  • Dynamical modeling and experimental aspects of multi-responsive
           hydroxy-functional methacrylate-based gels with tunable swelling induced
           by multivalent ions
    • Authors: Nermin Orakdogen; Berran Sanay
      Pages: 151 - 168
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Nermin Orakdogen, Berran Sanay
      Novel materials displaying multi-responsive property were developed by forming crosslinked copolymer systems that exhibit distinct temperature, pH and salt-sensitivity independently. An investigation of the mechanical properties of a novel multi-responsive poly(hydroxypropyl methacrylate) (PHPMA)-based hydrogel system was carried out with two major objectives. First was to study the effect of various preparation conditions; reaction temperature, comonomer content on the elasticity as well as on the absorbency of resulting hydroxy-functional methacrylate-based gels and the second was to interpret their water uptake data by various kinetic models. Experiments were conducted to characterize the equilibrium swelling and temperature/pH-dependent phase transitions of PHPMA-based copolymeric gels prepared by radical crosslinking copolymerization in aqueous solution with tetraethyleneglycol dimethacrylate (TEGDMA) as crosslinker. The aqueous equilibrium swelling properties of PHPMA hydrogels and cryogels containing methacrylate-based comonomer were described using N,N-dimethylaminopropyl methacrylate (DMAEMA) having weakly basic cationic groups. For PHPMA-based copolymeric hydrogels, the scaling laws relating the optimum preparation conditions with the crosslinking density N and the swelling degree q v were derived. Dynamic kinetics profiles were evaluated to outline the swelling/deswelling response of the resulting hydrogels and cryogels which presents useful information when designing specific applications that pursue or require the absorption of pH-sensitive or ionic-strength-sensitive molecules.
      Graphical abstract image

      PubDate: 2017-10-05T05:56:39Z
      DOI: 10.1016/j.polymer.2017.09.051
      Issue No: Vol. 129 (2017)
       
  • Conductive network formation and destruction in polypropylene/carbon
           nanotube composites via crystal control using supercritical carbon dioxide
           
    • Authors: Yasamin Kazemi; Adel Ramezani Kakroodi; Sai Wang; Aboutaleb Ameli; Tobin Filleter; Petra Pötschke; Chul B. Park
      Pages: 179 - 188
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Yasamin Kazemi, Adel Ramezani Kakroodi, Sai Wang, Aboutaleb Ameli, Tobin Filleter, Petra Pötschke, Chul B. Park
      This study reports on the effects of the matrix's crystal type (α or γ crystal) and chain mobility on the electrical properties of polypropylene (PP)/carbon nanotube (CNT) composites. Isothermal crystallization of the composites was performed at various temperatures and under atmospheric and elevated pressures with supercritical carbon dioxide (scCO2). Remarkably, experimental results indicated that the composites' isothermal annealing at 150 °C under a supercritical carbon dioxide (scCO2) pressure of 31 MPa reduced their percolation threshold by nearly 50%, via the formation of a significant amount of γ crystals. On the other hand, isothermal annealing of PP/CNT at 135 °C under the scCO2 conditions destructed the conductive network via promoting heterogeneous nucleation of α crystals on the CNT surface. Consequently, this led to a desirable combination of a high dielectric permittivity of ε' = 58.0 and a low dielectric loss of tan δ = 0.2 of PP/1.0 wt% CNT composites at a frequency of 100 Hz.
      Graphical abstract image

      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.056
      Issue No: Vol. 129 (2017)
       
  • Modeling induction period of polymer crystallization
    • Authors: Hiroshi Yokota; Toshihiro Kawakatsu
      Pages: 189 - 200
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Hiroshi Yokota, Toshihiro Kawakatsu
      We study the possibility of the spinodal decomposition in the induction period of the polymer crystallization. This phenomenon was first reported in an X-ray scattering experiment, and has still been controversial due to various experiments and theories that support or deny the phenomenon. In this article, we explain the condition for the spinodal decomposition to occur in polymer melts by deriving a Ginzburg-Landau model of the free energy as a functional of the density and the orientation of the segments, where we introduce the excluded volume and the nematic interactions through a combination of the random phase approximation and the transfer matrix for the polymer conformation. We show that, upon elimination of the degrees of freedom of the orientation, the nematic interaction reduces to an effective attraction whose strength increases with the stiffness of the polymer chain. Such an attraction induces spinodal decomposition especially for stiff polymer chain case.
      Graphical abstract image

      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.022
      Issue No: Vol. 129 (2017)
       
  • Thermal conductivity of graphene oxide-enhanced polyvinyl alcohol
           composites depending on molecular interaction
    • Authors: Sunnam Kim; Jumpei Shimazu; Tuyoshi Fukaminato; Tomonari Ogata; Seiji Kurihara
      Pages: 201 - 206
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Sunnam Kim, Jumpei Shimazu, Tuyoshi Fukaminato, Tomonari Ogata, Seiji Kurihara
      Graphene oxide (GO) synthesized from graphite via oxidation and exfoliation is a graphene-like single-layer sheet with numerous oxygen groups and defects on the basal plane. In this study, GO is added as a filler in the polyvinyl alcohol (PVA) matrix for the purpose of improving thermal conductivity. GO is well dispersed in PVA aqueous solution, and GO/PVA composite films are easily prepared with various GO contents. The thermal conductivities of the polymer composites investigated in terms of GO content concentration, GO degree of oxidation, PVA degree of polymerization, and silica-bead packing in the GO/PVA composite. On the basis of phonon mean free path, the effect of oxygen groups in GO is discussed in relation to crystallinity of PVA and molecular interaction between GO and PVA. In addition, the phonon conductive path along the direction of thickness in the GO/PVA composite film is achieved via silica-bead packing.
      Graphical abstract image

      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.055
      Issue No: Vol. 129 (2017)
       
  • Nanoscale chemical imaging of a deuterium-labeled polyolefin copolymer in
           a polyolefin blend by atomic force microscopy-infrared spectroscopy
    • Authors: Mark A. Rickard; Gregory F. Meyers; Brian M. Habersberger; Carl W. Reinhardt; Jamie J. Stanley
      Pages: 247 - 251
      Abstract: Publication date: 27 October 2017
      Source:Polymer, Volume 129
      Author(s): Mark A. Rickard, Gregory F. Meyers, Brian M. Habersberger, Carl W. Reinhardt, Jamie J. Stanley
      A combination of atomic force microscopy-infrared spectroscopy (AFM-IR) and a deuterium-labeled ethylene-propylene (EP) copolymer enables direct nanoscale chemical imaging of all three components in a polyethylene/polypropylene/ethylene-propylene copolymer blend for the first time. AFM-IR is a hybrid technique that provides the spatial resolution of AFM with the chemical selectivity of IR. Deuterium labeling of the EP copolymer enables it to be distinguished from the blend components. This combination enables chemical imaging of all components in the polyolefin blend at a spatial resolution (∼50 nm) that far exceeds conventional Fourier-transform infrared and Raman microscopy, which are limited by the diffraction of light. AFM-IR spectra and images of the C-D stretch in the polyolefin blend definitively establish that the deuterium-labeled EP copolymer is dispersed in the polyethylene matrix. This strategy is broadly applicable to other types of polymer blends that contain chemically-similar components.
      Graphical abstract image

      PubDate: 2017-10-11T16:58:09Z
      DOI: 10.1016/j.polymer.2017.09.045
      Issue No: Vol. 129 (2017)
       
 
 
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