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Polymer
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ISSN (Print) 0032-3861 - ISSN (Online) 0032-3861
Published by Elsevier Homepage  [3206 journals]
  • Corrigendum to “Comparing the sorption kinetics of
           polytetrafluoroethylene processed either by extrusion or spark plasma
           sintering” [Polymer 190 (2020) 1–15/122192]
    • Abstract: Publication date: 27 March 2020Source: Polymer, Volume 192Author(s): Ilham Elaboudi, Ahmed Mdarhri, Christian Brosseau, Ali Nourdine, Mourad Rzaizi, Laurent Servant
       
  • Gasochromic response of optical sensing platform integrated with
           polyaniline and poly(3,4-ethylenedioxythiophene) exposed to NH3 gas
    • Abstract: Publication date: Available online 22 February 2020Source: PolymerAuthor(s): Abdul Hadi Ismail, Nor Akmar Mohd Yahya, Mohd Adzir Mahdi, Mohd Hanif Yaacob, Yusran SulaimanThe optical NH3 gas sensing performance of polyaniline (PANI) and poly(3,4-ethylenedioxythiophene (PEDOT) in the form of bilayers and copolymers was analysed in this study. The order of the bilayers and the presence of acid dopant on the fabrication of the sensing platform produced different absorbance responses upon exposure to NH3 gas. The limit of detection of the bilayer (PANI(aq.)/PEDOT(aq.)) was 7.86 ppm which is under the threshold limit value of NH3, with response and recovery times of 2.33 min and 46.8 s, respectively. The gasochromic behaviour of PANI and PEDOT during the adsorption of NH3 gas was closely related to the changes in the oxidation state which have simultaneously altered the colour intensity of the respective sensing layer.Graphical abstractImage 104
       
  • Structural and light driven molecular engineering in photochromic polymers
    • Abstract: Publication date: Available online 22 February 2020Source: PolymerAuthor(s): Adam Szukalski, Aleksandra Korbut, Ewelina OrtylLight driven properties and remote control modulation in organic materials is still a challenging subject. Optical data storage has revolutionized modern technology. According to increasing interest of more advanced and better-controlled systems composed of the organic materials, photochromic polymers take significant part of still desired objective. In this contribution, we demonstrate two novel single-component macromolecular photo-responsive systems, characterized by optical Kerr effect (OKE) experiment. Productive and fully reversible all-optical switching can be easily obtained with utilization of thin polymeric film. An employed 30 cycles of remote controlled light driven (de)activation refractive index anisotropy (Δn) demonstrate efficient optical modulation. Importantly, two copolymers structures intentionally varying slightly in the chemical construction characterize significantly different nonlinear optical (NLO) response. The output Δn signal, enclosing kinetics, magnification, reversibility and stability can be easily controlled by applying molecular engineering concerning chemical architecture of the photo-responsive system. We present herein the photoisomerization studies and nonlinear optical spectroscopic analysis considering OKE phenomenon and obtained parameters, including photoinduced birefringence and 3rd order NLO susceptibility. Aforementioned approach allowed to construct organic-based device dedicated to the future utilization in opto-electronics and photonics as effective optical modulator or switch.Graphical abstractImage 1
       
  • Investigating the atmospheric pressure plasma jet modification of a
           photo-crosslinkable hydrogel
    • Abstract: Publication date: Available online 21 February 2020Source: PolymerAuthor(s): Inès Hamouda, Cédric Labay, Maria Pau Ginebra, Erwan Nicol, Cristina CanalAtmospheric pressure plasma jets (APPJ) have great potential in wound healing, bacterial disinfection and in cancer therapy. Recent studies pointed out that hydrogels can be used as screens during APPJ treatment, or even be used as reservoirs for reactive oxygen and nitrogen species generated by APPJ in liquids. Thus, novel applications are emerging for hydrogels which deserve fundamental exploration of the possible modifications undergone by the polymers in solution due to the reactivity with plasmas. Here we investigate the possible modifications occurred by APPJ treatment of an amphiphilic poly(ethylene oxide)-based triblock copolymer (tPEO) photo-crosslinkable hydrogel. While APPJ treatments lead to a certain degradation of the self-assembly of the polymeric chains at low concentrations (2 g/L), the polymeric chains are unaffected by APPJ and the hydrogel forming ability is kept. APPJ treatments induced a pre-crosslinking of the network with an increase of the mechanical properties of the hydrogel. Overall, the small modifications induced allow thinking of polymer solutions with hydrogel forming ability a new platform for several applications related to plasma medicine, and thus, with potential in different therapies.Graphical abstractImage 1
       
  • Crystallization and melting of poly(butylene terephthalate) and
           poly(ethylene terephthalate) investigated by fast-scan chip calorimetry
           and small angle X-ray scattering
    • Abstract: Publication date: Available online 20 February 2020Source: PolymerAuthor(s): Akihiko Toda, Ken Taguchi, Koji Nozaki, Xinchao Guan, Wenbing Hu, Yoshitomo Furushima, Christoph SchickThe crystallization and melting behaviors of poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) were examined by Hoffman-Weeks (H–W), Gibbs-Thomson (G-T), and thermal Gibbs-Thomson (t-G-T) plots constructed by using fast-scan calorimetry and small-angle X-ray scattering. With PBT and PET, neither an H–W nor a G-T plot could be utilized for the determination of the equilibrium melting point (TM0) of chain-extended infinite-size crystals. The thermal Gibbs-Thomson plot utilizes the change in the melting point and the heat of fusion of chain-folded crystals during the secondary stage of isothermal crystallization. TM0 was determined from a t-G-T plot, and the results were in good agreement with the literature values for PBT and PET. G-T and t-G-T plots suggested a temperature-dependent folding surface free energy (σe), as has been proposed by Hoffman et al. The σe values obtained with G-T and t-G-T plots support the consistency of the analysis.Graphical abstractImage 1
       
  • Anisotropic thermoresponsive hydrogels by mechanical force orientation of
           clay nanosheets
    • Abstract: Publication date: Available online 20 February 2020Source: PolymerAuthor(s): Lie Chen, Qingshan Wu, Jianqi Zhang, Tianyi Zhao, Xu Jin, Mingjie LiuHydrogels have drawn great attentions in the past two decades due to their excellent biocompatibility and multi stimuli responsiveness, which have a wide range of applications in the field related to tissue engineering, sensor and biomedicine. However, conventional artificial hydrogels are usually isotropic in structure with random crosslinking of polymer chains. To imitate the well-defined hierarchical structures ranging from the molecular scale to macroscopic scale like biological soft tissues in hydrogels. Herein, an anisotropic thermoresponsive hydrogel was reported via a linear remolding of highly stretchable clay-PNIPAm nanocomposite hydrogel by a secondary crosslinking. The as-prepared hydrogel shows anisotropic mechanical performance and can deformed anisotropically in response to temperature change. Besides, the oriented structures of clay nanosheets and polymer network that contribute to understand the anisotropic mechanism of SC-hydrogel was investigated. The special functions of current SC-hydrogel suggest that it may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, sensors, and biological materials.Graphical abstractImage 1
       
  • Reprocessable polybenzoxazine thermosets crosslinked by mussel-inspired
           catechol-Fe3+ coordination bonds
    • Abstract: Publication date: Available online 19 February 2020Source: PolymerAuthor(s): Youjun He, Sheng Gao, Chanchira Jubsilp, Sarawut Rimdusit, Zaijun LuThe traditional thermosets cannot be reprocessed, which causes serious environmental pollution and resource waste. The catechol-Fe3+ coordination bonds existing in marine mussel byssal cuticle provide a reversible crosslinking structure for reprocessable thermosets. A reprocessable polybenzoxazine thermoset (PBOZ-dopa45-Fe3+) by catechol-Fe3+ coordination bonds was synthesized successfully based on mussel-inspired chemistry and benzoxazine chemistry. Firstly, benzoxazine monomers containing carboxyl groups were synthesized. Secondly, polybenzoxazine with carboxyl groups was obtained through thermal ring-opening polymerization. And then catechol groups were grafted onto the pendant groups of polybenzoxazine. Finally, the reprocessable polybenzoxazine was obtained by catechol groups coordinating with Fe3+. The structure of polybenzoxazine was characterized by NMR, FTIR and SEC measurements. The formation of reversible crosslinked network composed of catechol-Fe3+ coordination bonds is confirmed by UV–Vis absorbances, system color changes, and dissolution states in methanol solutions of different pH. Reprocessing experiments indicate that the reversible catechol-Fe3+ coordination bonds endow remarkable reprocessability of cured resin. Dynamic mechanical measurements and thermogravimetric measurements show that the PBOZ-dopa45-Fe3+ can still maintain excellent thermal properties. Cross-linking by catechol-Fe3+ coordination bonds provides a new way for the preparation of reprocessable thermosets.Graphical abstractImage 1
       
  • The low resistance and high sensitivity in stretchable electrode assembled
           by liquid-phase exfoliated graphene
    • Abstract: Publication date: Available online 19 February 2020Source: PolymerAuthor(s): Yunfei Zhu, Hongyun Chen, Lixiang Jiang, Lixin Xu, Huijian YeFlexible electrodes have been extensively investigated to fulfill the development of highly advanced human interaction electronics. It's still a challenge to develop the conductive film for the scalable device with low resistance under large deformation. In this work, we reported a stretchable conductive layer on elastomer substrates assembled by few-layer graphene, which was exfoliated in the low-boiling organic solvent with assistance of hyperbranched copolymer as stabilizer that was adsorbed on the nanosheets via CH-π non-covalent connections. The relative resistance change of graphene film is 117% as the mechanical strain reaches 35%, which retains high conductivity under tensile operation. The resistance of the graphene electrode is dependent on the overlapping of the nanosheets during the deformation, in which the slipping of nanosheets is due to the lubricant effect of the hyperbranched segments acting as dynamic CH-π interactions. This work highlights a general strategy of the stretchable conductive film for the flexible electronics, and sheds a light on the conduction mechanism for the graphene film during large deformation.Graphical abstractHere we reported a stretchable conductive layer on elastomer substrates assembled by few-layer graphene, which was exfoliated in the low-boiling organic solvent with assistance of hyperbranched copolymer as stabilizer that was adsorbed on the nanosheets via CH-π non-covalent connections. The relative resistance change of graphene film is 117% as the mechanical strain reaches 35%, which retains high conductivity under tensile operation. The resistance of the graphene electrode is dependent on the overlapping of the nanosheets during the deformation, in which the slipping of nanosheets is due to the lubricant effect of the hyperbranched segments acting as dynamic CH-π interactions.Image 1
       
  • Visible-light Induced Synthesis of Biocompatible Porous Polymers from
           Oligocarbonatedimethacrylate (OСM-2) in the Presence of Dialkyl
           Phthalates
    • Abstract: Publication date: Available online 18 February 2020Source: PolymerAuthor(s): V.V. Yudin, R.S. Kovylin, M.A. Baten'kin, T.I. Kulikova, S.A. Chesnokov, I.L. Fedushkin, M.N. Egorikhina, Y.P. Rubtsova, I.N. Charykova, S.G. Mlyavykh, D.Ya. AleynikPolymer monoliths containing open interconnected pores were synthesized by a visible-light induced polymerization of oligocarbonatedimethacrylate (OCM-2) in the presence of dialkylphthalates (C6H4[C(O)OR]2, R = C2H5, n-C4H9, n-C8H17 and n-C9H19) as porogenic agent. A closeness of the refractive indices of the forming polymer and dialkylphthalates provides for the formation of transparent porous monoliths, thus making manufacture of thick porous polymeric materials using visible light possible. The porous polymers derived from OCM-2 can sorb water and benzene. The filling of pores by water increases with an increase of a number of carbon atoms in the ester groups from 0.65 for diethyl phthalate to 1.0 for dinonyl phthalate. Experimentally defined value of Hildebrand solubility parameter δ for poly-OCM-2 is 24.9 MPa1/2. A closeness of the solubility parameters of the polymer (δp) and porogenic agent (δs) guarantees the porous architecture of the polymer formed. The porous polymeric materials have been studied in vitro using a culture of human dermal fibroblasts (HDF) of four passages. The MTT test (MTT is 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) has shown that the materials are not cytotoxic. During long-term cultivation of the cells on the material surface a pronounced cell adhesion as well as cell viability and proliferative activity have been detected.Graphical abstractImage 10106
       
  • Structure and properties of silk fibroin aerogels prepared by non-alkali
           degumming process
    • Abstract: Publication date: Available online 18 February 2020Source: PolymerAuthor(s): Haiwei Yang, Zongqian Wang, Mingrong Wang, Changlong LiSilk fibroin aerogel generally suffers from weak mechanical properties, which limits its application in the high-performance materials. Hence, we develop a non-alkali urea degumming strategy for the raw silk to impove the mechanical properties of silk fibroin aerogel. The silk fibroin aerogel with a low density of 13.43 ± 0.77 mg/cm3 was fabricated successfully via silk fibroin dissolution, dilution and freeze-drying. We systematically analyze the solution properties of silk fibroin prepared via alkali degumming and non-alkali degumming. Meanwhile, the morphology and structure of aerogel are characterized by scanning electron microscopy, X-ray diffraction spectroscopy and Gaussian multi-peaks-fiting technique of infrared spectrum. Moreover, we investigate the effects of non-alkali degumming method on the mechanical properties and thermal stability of aerogels. The results manifest that the non-alkali urea degumming process reduces damage to silk fibroin, leading to the stable three-dimensional skeleton structure of the prepared aerogels. Furthermore, compared with the silk fibroin aerogel prepared by alkali degumming, the silk fibroin aerogel prepared by non-alkali degumming has higher crystallinity and content of β-sheet structure, resulting in the better mechanical properties and thermal stability. This work may pave the way for the fabrication of silk fibroin aerogel materials with high mechanical properties.Graphical abstractImage 10047
       
  • One-Pot Synthesis of polymeric LiPON
    • Abstract: Publication date: Available online 17 February 2020Source: PolymerAuthor(s): Gideon Abels, Ingo Bardenhagen, Julian SchwenzelLithium metal is a promising anode material for high energy lithium ion batteries due to its high specific capacity. Inherent difficulties such as the chemical reactivity and dendrite growth during cycling have kept it from being operational in energy storage systems so far. One approach to overcome these challenges is the use of a stable interlayer on top of the lithium. The glassy solid-state electrolyte lithium phosphorus oxynitride (LiPON) is a promising candidate to achieve this. However, it is prepared by a time and energy consuming physical vapor deposition technique. As an alternative to this, we developed the synthesis of a modified polyphosphazene having a similar chemical formula as the glassy LiPON which allows for a large scale application of such a stable interface with an easier and cheaper processing. Following a two-step one pot synthesis starting from poly(dichlorophosphazene), this polymeric LiPON could be successfully isolated and showed solubility in different solvents which distinguishes it clearly from sputtered LiPON.Graphical abstractImage 1071957
       
  • Photo-induced topological self-reorganization and self-growth of polymer
           based on dynamic reversible aromatic pinacol units
    • Abstract: Publication date: Available online 17 February 2020Source: PolymerAuthor(s): Yuan Li, Ze Ping Zhang, Wei Jie Mo, Min Zhi Rong, Ming Qiu Zhang, Dong LiuCrosslinked polyurethane containing aromatic pinacol units as novel reversible C–C bonds provider is synthesized. For the first time, photo-induced topological self-reorganization through the reversible C–C bonds leads to the transformation of micro-phase separation structure, realizing improvement of the tensile strength and failure strain from 23 MPa to 34 MPa and from 1205% to 1695%, respectively. In contrast, mechanical properties of the reference sample without pinacol moieties decrease sharply after the same UV irradiation. Internal structural variations are analyzed in detail by equilibrium swelling experiment, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), small angle neutron scattering (SANS) and positron annihilation lifetime spectroscopy (PALS). Moreover, the carbon radicals generated from homolysis of the aromatic pinacol are found to be able to further initiate polymerization of vinyl monomers, which helps to achieve crack healing, surface self-growth and formation of semi-interpenetrating polymer networks. This kind of macromolecular initiator-embedded polymer could re-initiate polymerization when the surface arrays are wiped away to expose the fresh underlying aromatic pinacol units. It is believed that the outcomes may enrich and expand the applications of dynamic covalent polymers.Graphical abstractImage 1
       
  • Fractal analysis of the formation process and morphologies of
           hyaluronan/chitosan nanofilms in layer-by-layer assembly
    • Abstract: Publication date: Available online 15 February 2020Source: PolymerAuthor(s): J. Hernandez-Montelongo, V.F. Nascimento, R. Hernández-Montelongo, M.M. Beppu, M.A. CottaIn the last decade, hyaluronan (HA, polyanion) and chitosan (CHI, polycation) biopolymers have been assembled by layer-by-layer (LbL) for the synthesis of antibacterial coatings. As electrostatic interactions are the main driving force for the formation of LbL films, pH and ionic strength (IS) are important critical variables of synthesis. In this context, we used surface fractal analysis of HA/CHI films to characterize the growth process for different bilayers obtained with two pH (5 and 3) and IS values (0 and 0.1 M NaCl). Our results showed that the HA/CHI assembling is mainly affected by changes in the pH than IS. Fractal dimension (Df) of pH 5 series presented values ∼2.2, indicating that irregularities from the initial random adsorption process are minimized. However, when pH decreased to 3, Df increases up to ∼2.5, suggesting a transition to diffusion-limited aggregation.Graphical abstractImage 1
       
  • Novel nano-patterned structures of mixed hairy nanoparticles in single
           layer
    • Abstract: Publication date: Available online 15 February 2020Source: PolymerAuthor(s): Niboqia Zhang, Linxiuzi Yu, Yan-Chun Li, Hong Liu, Zhong-Yuan LuTethering mixed homo/diblock polymer chains on the nanoparticles (NPs) imposes simultaneous enthalpic and entropic influences on their self-assembly. In the aggregation of these NPs, the chain distribution is strongly influenced by the neighboring NPs. Therefore, the so-called mutual templating of the NPs is the main reason for the formation of the exotic self-assembly structures of grafted chains. In this study, by using dissipative particle dynamics simulations, we design three representative mixed hairy nanoparticles (MHNPs) systems and investigate their microphase separation process during solvent evaporation. The minimal model for the MHNP is grafting two types of incompatible (A and B) homopolymer chains on the same graft-site with uniform distribution on the NP surface. Based on the minimal model, adding a C block at the free end of both A and B blocks facilitates the investigation of the influence of chain composition on microphase separation structures. In the third model, we change the B chain in the minimal model into a BC diblock copolymer chain to study the influence of chain mismatch on the formation of nano-patterns. By comparing the microphase structures and their formation processes, we can find that wedge-shaped nanostructures appear in specific range of interparticle distances (D) due to mutual templating; adding another block will terminate the mutual templating effect and results in the wedge-shaped nanostructures attaching to the NP surface surrounded by the ring structure formed by outer block C; for the systems with chain mismatch, apertures with six-fold symmetry appear in the monolayer film formed by MHNPs when D is large enough. These findings facilitate the design and fabrication of advanced functional materials with ordered structures on the nanoparticle level.Graphical abstractGraphical abstract for this article
       
  • Polyaniline as an On−Off−On bright green fluorescent probe: Solvent
           directed synthesis, characterization and recognition of chromium through
           the inner filter effect
    • Abstract: Publication date: Available online 15 February 2020Source: PolymerAuthor(s): Sumana Pal, Debiprasad Roy, Nandagopal Bar, Shreyashi Chowdhury, Pranesh ChowdhuryBright green fluorescent polyaniline (FPANI) has been synthesized to develop efficient inner filter effect pair (probe-anylate). The synthesized FPANI have dual emissive peaks (blue and green) depending on excitation wavelength. But the green fluorescence intensity is prominent and significantly bright having quantum yield in the order of 0.17. Solvent directs the quality of the probe (FPANI) in terms of molecular weight, physical appearance and optical properties. An analytical method has been developed to recognize trace level of chromium and lead simultaneously and selectively using On-Off-On characteristics of the synthesized FPANI. Cr(VI) switches ‘On’ to ‘Off’ mode of the probe due to inner filter effect, while Pb(II) brings back green fluorescence (‘On’ mode) from non-fluorescent one (‘Off’ mode) through quantitative chemical interaction with chromium.Graphical abstractImage 1
       
  • Formation and Stabilization of Crystal Nuclei in Isotactic Polybutene-1
           Aged below Glass Transition Temperature
    • Abstract: Publication date: Available online 14 February 2020Source: PolymerAuthor(s): Peiru Liu, Yanhu Xue, Yongfeng MenAbstractAging of glassy isotactic polybutene-1 (iPB-1) below the glass transition temperature (Tg) leads to remarkable acceleration of the subsequent isothermal crystallization due to the promotion of crystal nuclei. The formation and development of crystal nuclei during aging below Tg and during heating to the crystallization temperature have been probed by fast scanning chip calorimetry. The size and stability of the crystal nuclei change with the aging time. A short aging below Tg can only induce nuclei with small sizes which can grow into bigger stable one during the heating process above Tg if the heating rate is not high enough. With a prolonged aging time below Tg, bigger stable nuclei can also be developed, and its number increases till reaches a maximum value. These results suggest that noncooperative local motions rather than cooperative segmental motions in glassy iPB-1 are responsible to the formation of crystal nuclei during aging below Tg.
       
  • Effect of temperature on the viscoelastic damage behaviour of
           nanoparticle/epoxy nanocomposites: Constitutive modelling and experimental
           validation
    • Abstract: Publication date: 16 March 2020Source: Polymer, Volume 191Author(s): Robin Unger, Behrouz Arash, Wibke Exner, Raimund RolfesThe accurate prediction of the complex material response of nanoparticle/epoxy nanocomposites for thermomechanical load cases is of great interest for engineering applications. In the present work, three main contributions with respect to multi-scale modelling of the viscoelastic damage behaviour of nanocomposites are presented. Firstly, a constitutive model for the viscoelastic damage behaviour at finite temperatures below the glass-transition temperature is proposed. The constitutive model captures the main characteristics of the material response including the non-linear hyperelasticity, softening behaviour and the effect of temperature. Secondly, the material model is calibrated using purely experimental results to evaluate the best capability of the model in reproducing the stress–strain response at different strain rates and temperatures. The calibrated model predicts the material behaviour across a range of nanoparticle weight fractions with good agreement with experimental results. Finally, a combined approach of experimental testing and molecular simulations is proposed to identify the parameters of the constitutive model. This study shows that the proposed simulation-based framework can be used to significantly reduce the number of experimental tests required for identification of material parameters without a significant loss of accuracy in the material response prediction. The predictive capability of the atomistically calibrated constitutive model is validated, with additional experimental results not used within the parameter identification, in terms of an accurate representation of the viscoelastic damage behaviour of nanoparticle/epoxy nanocomposites at finite temperatures. The present study underlines the capabilities of numerical molecular simulations intended for the characterisation of material properties with respect to physically based constitutive modelling and multi-scale approaches.Graphical abstractGraphical abstract for this article
       
  • Isothermal step thickening in a long-spaced aliphatic polyester
    • Abstract: Publication date: Available online 14 February 2020Source: PolymerAuthor(s): Stephanie F. Marxsen, Manuel Häuβler, Stefan Mecking, Rufina G. AlamoDiscontinuous lamellar thickening has been found at the isothermal crystallization temperatures of a long-spaced aliphatic polyester (PE-48,48) synthesized via polycondensation of the diol and diacid. The isothermal step thickening is characterized by a discrete increase in melting temperature with increasing crystallization time and an increase in heat of fusion of the high melting peak at the expense of the low melting peak. The increase in crystal thickness, quantified by SAXS, is consistent with a straightening of the chains at the basal surfaces of the lamellae to complete a full repeat of the crystalline layer. The increase in thickness and decrease in surface energy are associated with the sudden increase in crystal melting. The isothermal thickening follows a logarithmic dependence of time with a rate that increases with temperature. The thickening process is thermally activated and follows Arrhenius behavior with an activation energy of 238 ± 4 kJ/mol.Graphical abstractImage 1
       
  • Recrystallization of Biaxially Oriented Polyethylene Film from Partially
           Melted State within Crystallite Networks
    • Abstract: Publication date: Available online 14 February 2020Source: PolymerAuthor(s): Minqiao Ren, Yujing Tang, Dali Gao, Yueming Ren, Xuerong Yao, Hongwei Shi, Taoyi Zhang, Changjiang WuRecrystallization behavior and the final crystallite orientation of biaxially oriented polyethylene (BOPE) film from different melted states have been studied by using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD), respectively. WAXD result shows that two kinds of crystallites (1 and 2) with different orientations are aligned around the transverse direction (TD) of the film plane. When BOPE film is annealed in the temperature range of 110∼125 oC, the residual crystallites 1 are still aligned along the TD, while the residual crystallites 2 are gradually rotated and aligned along the machine direction (MD). Recrystallization of BOPE film from the partially melted states is enhanced and the maximum crystallization peak shifts to higher temperature by 7 °C. The newly formed crystallites after recrystallization are aligned along the TD and MD, respectively. When annealing temperature attains to 128 oC, a trace amount of residual crystallites 1 persists along the TD. The newly formed crystallites after recrystallization are also aligned the TD. When the storing temperature range is in 130∼150 oC, the melt memory effect occurs in BOPE film, and it influences crystallization kinetics and the crystallite orientation.Graphical abstractTop: Variation of the crystallization peak temperature (Tc,peak) as a function of the storing temperature (Ts) for BOPE film.Bottom: (a) X-ray pole figure of (200) crystal plane of BOPE film.(b)X-ray pole figure of (200) crystal plane of BOPE film annealed at 125 oC for 5 min and then cooled down to 25 oC.Image 104
       
  • Prediction of glass transition temperature and Young's modulus of an
           inaccessible polymer substrate in changing environment
    • Abstract: Publication date: Available online 13 February 2020Source: PolymerAuthor(s): Payel Bandyopadhyay, Mrinal Dwivedi, Hariharan Krishnaswamy, Pijush GhoshPolymer bi-layer systems are often exposed to different environmental service conditions which can potentially alter the mechanical properties as it approaches the glass transition temperature of an inaccessible substrate. However, since the substrate is inaccessible, it is difficult to measure or quantify the changes in these properties while in use. A methodology has been proposed in this work for prediction of glass transition temperature and Young's modulus of an inaccessible substrate in a bilayer system. The composite mechanical property of a bi-layer system is a function of the mechanical properties of coating, substrate and the depth at which it is measured. In the present work, poly-Methylmethacrylate (PMMA) coating of ∼890 nm is deposited on epoxy substrate. Nanoindentation experiments are conducted at different temperatures on the bi-layer system as well as on bulk PMMA. Finite element analysis has been used to obtain the material dependency of stress distribution coefficient (α) for deconvoluting the modulus of the substrate. The methodology developed by the present authors can predict the glass transition temperature as well the magnitudes of Young's modulus of an inaccessible substrate reasonably well.Graphical abstractImage 1
       
  • Phase-selective conductivity enhancement and cooperativity length in
           PLLA/TPU nanocomposite blends with carboxylated carbon nanotubes
    • Abstract: Publication date: Available online 13 February 2020Source: PolymerAuthor(s): Sofia Valenti, Omid Yousefzade, Jordi Puiggali, Roberto MacovezTransmission electron microscopy, temperature-modulated differential scanning calorimetry, and broadband dielectric spectroscopy were employed to characterize ternary nanocomposites consisting of carboxylated carbon nanotubes (CNT) dispersed in a blend of two immiscible polymers, poly(L,lactide) (PLLA) and thermoplastic polyurethane (TPU). The nanocomposite blends were obtained by melt-compounding of PLLA and TPU in the presence of 0.2 wt-% CNT, either in the presence or absence of a Joncryl® ADR chain extender for PLLA, leading to reactive and non-reactive melt mixed samples. In both cases, the binary PLLA/TPU blend is characterized by phase separation into submicron TPU droplets dispersed in the PLLA matrix, and displays two separate glass transition temperatures. The carbon nanotubes are present either inside the TPU phase (samples obtained without chain extender), or at their boundaries (reactive-melt mixed samples). The effect of the sub-micron confinement of the TPU component is to decrease the cooperativity length of the primary segmental relaxation of this polymer, which is accentuated by the presence of the CNT fillers. Depending on the type of sample, five or six distinct relaxations are observed by means of dielectric spectroscopy, which we are able to assign to different dielectric phenomena. Our dielectric data show that the CNT fillers do not contribute directly to the long-range charge transport in the nanocomposite blends, consistent with the nanocomposites morphology, but rather result in a shift of the Maxwell-Wagner-Sillars space-charge frequency associated with charge accumulation at the PLLA/TPU boundary. Such shift testifies to a selective conductivity enhancement of the TPU phase due to the filler.Graphical abstractImage 1
       
  • Kinetic and thermodynamic parameters guiding the localization of
           regioselectively modified kaolin platelets into a PS/PA6 co-continuous
           blend
    • Abstract: Publication date: Available online 12 February 2020Source: PolymerAuthor(s): Aurélie Taguet, Belkacem Otazaghine, Marcos BatistellaThis article highlights the role of kinetic and thermodynamic parameters on the localization of modified kaolin platelets into a high interfacial tension co-continuous PS/PA6 blend after extrusion, injection molding and annealing. Three kinds of copolymers were synthesized and grafted on kaolin: poly(styrene-co-(methacryloyloxy)methyl phosphonic acid) copolymer (P(S-co-MAPC1(OH)2)), polystyrene terminated 3-(mercaptopropyl)triethoxysilane, (ETS-PS) and poly(styrene-co-3-methacryloxypropyltrimethoxysilane) copolymer, (P(S-co-MPS)). Those copolymers were distinguished by (1) the nature of their functional groups (phosphonic acid that reacts only with aluminol groups or alkoxysilane that reacts with both silanol and aluminol groups), (2) the amount of functional groups and (3) their molecular weights. After functionalization the kaolin samples (K1, K2 and K3, respectively) were analyzed by FTIR, TGA and Py-GC/MS to evaluate the grafting. It was shown that P(S-co-MAPC1(OH)2) and P(S-co-MPS) copolymers grafted on kaolin led to highly anisotropic K1 and K3 kaolin platelets, respectively. Then, 50/50/5 PS/PA6/Ki samples (i = 0 to 3) were processed as follows: (1) kaolin platelets were dispersed (via solvent cast) into the PS phase. Then, (2) PS + kaolin were melt mixed by microcompounder with PA6, then (3) the PS/PA6/Ki were injection molded into disks and finally (4) they were annealed (via dynamic or quiescent annealing). Thanks to the high shear rate and longtime of mixing during extrusion (microcompounder), all the kaolin platelets (unmodified K, K1, K2 and K3) crossed the interface and were localized in the PA6 phase. All Ki kaolin stayed in the PA6 phase during injection. However, after annealing (quiescent or dynamic), the localization of the nanoplatelets was guided by thermodynamic parameters, and SEM analysis revealed the segregation of K1 and K3 kaolin platelets at the polymers interface, with a high tendency to impede polymer phases coalescence. Hence, modified K1 and K3 kaolin are promising compatibilizing agents for a co-continuous PS/PA6 blend.Graphical abstractImage 1
       
  • Transient swelling behaviour of dual stimuli sensitive nanocomposite
           hydrogels
    • Abstract: Publication date: Available online 12 February 2020Source: PolymerAuthor(s): Saeed Mousazadeh, Mehrdad KokabiSmart nanocomposite hydrogels can undergo large deformation under external stimuli. Several coupled physical processes simultaneously affect the transient swelling behaviour of pH and temperature-sensitive hydrogels. Besides, the hydrogel properties change in response to the external stimuli in the presence of nanoparticles, which affect its transient deformation and swelling behaviour. This work focused on transient swelling modeling of pH and temperature-sensitive polymer/clay nanocomposite hydrogels. The time-dependent processes were considered simultaneously with material properties updating in each time-step during the finite element procedure. A set of experiments was designed to evaluate the numerical solving results in the free and constrained swelling conditions. The results illustrate that the proposed developed model successfully predicts the transient swelling behaviour of pH and temperature-sensitive either for hydrogels or nanocomposite hydrogel counterparts, which can offer a guideline to the abundant usage of these soft materials.Graphical abstractImage 1
       
  • Synthesis of an oxygen-permeable block copolymer with catechol groups and
           its application in polymer-ceramic pressure-sensitive paint
    • Abstract: Publication date: Available online 11 February 2020Source: PolymerAuthor(s): Makoto Obata, Kouta Yamai, Masaki Takahashi, Shintaro Ueno, Hiroya Ogura, Yasuhiro EgamiAn oxygen-permeable block copolymer, poly(2,2,2-trifluoroethyl-co-isobutyl methacrylate)-b-poly(N-acryloyldopamine) (FEM-b-PDOPA), in which the PDOPA segment acts as an adhesive section to attach TiO2 nanoparticles, was successfully synthesized via RAFT polymerization followed by a post-polymerization modification with dopamine. Conjugates of FEM-b-PDOPA with TiO2 nanoparticles were prepared by mixing them in chloroform and methanol. IR and solid-state CP-MAS 13C NMR spectroscopies clearly indicated the presence of FEM on the TiO2 nanoparticles. Thermogravimetric analysis of the resulting nanoparticles indicated that FEM-b-PDOPA, rather than FEM alone, was tightly bound to the TiO2 nanoparticles, and that the weight fraction was 2.5 wt%. Polymer-ceramic pressure-sensitive paint was prepared by mixing a luminescent dye, FEM, and TiO2 treated with either FEM-b-PDOPA or native TiO2. In comparison with the coating prepared using native TiO2, the pretreatment of TiO2 with FEM-b-PDOPA effectively reduced the photodegradation of the luminescent dye without deterioration in pressure and temperature sensitivity or dynamic response performance.Graphical abstractegi10BDQD6QZSL
       
  • Studying the mechanism of biodiesel acting as an environmental stress
           cracking agent with polyethylenes
    • Abstract: Publication date: Available online 11 February 2020Source: PolymerAuthor(s): A.K. Saad, H.A. Abdulhussain, F.P.C. Gomes, J. Vlachopoulos, M.R. ThompsonThis paper focuses on understanding the compatibility of biodiesel with different grades of polyethylene, specifically examining the environmental stress cracking ability of biodiesel. Traditional testing methods were coupled with a nondestructive ultrasonic testing method to investigate the modes of interaction by biodiesel with the polymer. The mechanism of failure was studied by gravimetric analysis and infrared spectroscopy to monitor fluid absorption in the notched and bent specimens while attenuation in the higher harmonics of an emitted acoustic pulse followed internal stresses. The ultrasonic technique offered a unique opportunity to link fuel penetration with microstructural changes prior to visible fracturing. Analysis of the mechanism was aided by the color of the fuel showing that cracking was preceded by highly localized absorption around the notch of the specimen, whereas resin grades with apparent immunity to cracking experienced uniform absorption over the whole body of a specimen.Graphical abstractGraphical abstract for this article
       
  • A fast response, large deformation, excellent mechanical pH-responsive
           polyacrylonitrile/polyimide bilayer film
    • Abstract: Publication date: Available online 10 February 2020Source: PolymerAuthor(s): Xu Wang, Chengyong He, Longbo Luo, Daiqiang Chen, Xiangyang Liu, Jiaqiang QinHere, we demonstrated pH responsive polyacrylonitrile/polyimide (PAN/PI) bilayer films with fast response, large deformation and excellent mechanical properties obtained by vertical-phase-separation. These films with concave/convex interface were composed by modified PAN (m-PAN) layer with nitrogen heterocyclic structure (pyridine ring) acting as responsive layer and PI as supporting layer. Attributing to the nitrogen heterocyclic structure being able to complex proton, m-PAN layer shows an acid-swelling behavior, exhibiting a completely different responsive behavior compared with traditional PAN responsive materials which are all of the alkali-swelling. The pH-induced bend and straight reciprocating motion occurs periodically with fast speed in acid and alkali solution alternatively, and the movement speed and size depend on the content of m-PAN, the pH value, the load and the relative stiffness and thickness of the two layers. Due to the excellent mechanical property of PI supporting layer, response strength of m-PAN and interface between PI and m-PAN, this soft polymer film actuator exhibited a tensile strength of 74 MPa and acted as an actuator for driving a high weight load of 1600 times its own weight.Graphical abstractA pH responsive polyacrylonitrile/polyimide (PAN/PI) bilayer actuator with fast response, large deformation and excellent mechanical properties obtained by vertical-phase-separation. Attributing to the nitrogen heterocyclic structure being able to become a complex proton, m-PAN layer shows an acid-swelling behavior, exhibiting a completely different responsive behavior compared with traditional PAN responsive materials which are all of the alkali-swelling.Image 1
       
  • Effects of sulfonate incorporation and structural isomerism on physical
           and gas transport properties of soluble sulfonated polyimides
    • Abstract: Publication date: Available online 10 February 2020Source: PolymerAuthor(s): Dajie Zhang, Jong Geun Seong, Won Hee Lee, Shinji Ando, Yinhua Wan, Young Moo Lee, Yongbing ZhuangThis study presents the effects of sulfonate incorporation and structural isomerism of soluble sulfonated polyimides (SPIs) for potential membrane applications. The fluorinated dianhydride (6FDA) and three commercially sulfonated diamines, 2,4,6-trimethyl-3,5-diaminobenzenesulfonic acid (tDSA), 2,5-diaminobenzenesulfonic acid (pDSA), and 2,4-diaminobenzenesulfonic acid (mDSA), were used to synthesize SPIs in a one-step polycondensation. The SPIs are soluble in common organic solvents and have good mechanical properties as represented by tensile strength of 88.4–115.8 MPa and elongation at break of 10.3–15.2%. The resulting SPI membranes exhibit low dielectric constants (∼2.61) and linear thermal expansion coefficients (CTE) ranging from 54.6 to 71.7 ppm/K. These SPI membranes have fractional free volume (FFV) of 0.119–0.148. The sulfonation incorporation induced closer inter-chain packing, smaller FFV, larger CTE, higher average refractive indices (nav), better transparency and higher ideal selectivities for almost all gas pairs for their membranes. The para-linked TEA-pSPI membrane exhibited a larger inter-chain d-spacing, larger FFV, larger CTE, smaller nav and slightly higher permeability coefficients than the corresponding meta-linked TEA-mSPI membrane. This study guides molecular architecture for improving particular membrane performance by introducing sulfonation groups as well as adjusting either para- or meta-linkages into polymeric main chains.Graphical abstractImage 1
       
  • Toughened carbon-fiber reinforced epoxy via isophorone diisocyanate amine
           surface modification
    • Abstract: Publication date: Available online 10 February 2020Source: PolymerAuthor(s): Thomas L. AttardSurface modification of a carbon-fiber reinforced epoxy (CF/E) via isophorone diisocyanate amine (IDA) is investigated. The covalently bonded IDA, engendering a microscopically thin layer (2 μm–50 μm wide), is an exchange chemical reaction after topically spraying polyurea moieties (isocyanate and amine groups) to curing epoxy, composed of amine and epoxide groups reacting for tc hours (h). Quasi-static nanoindentation, uniaxial tension and uniaxial compression testing reveal that the chemical bond feature of the tunable IDA surface, conceived at low tc, markedly improves damage tolerance in brittle CF/E by significantly supplementing the energy-release rate (fracture toughness). Compression tests revealed that energy absorption and deflection ductility of IDA-modified CF/E, i.e., C-IDA, and prepared at tc = 0 h, are two and five times greater relative to C-IDA at tc = 0.5 h. Tension tests revealed that energy absorption and deflection ductility of C-IDA at tc = 0 h are 150% and 50% greater than C-IDA at tc = 24 h. Micromechanical properties of the IDA reaction include a uniquely distributed reduced elastic modulus (Er), bounded by moduli of pure epoxy and polyurea overspray. The results, in combination with atomic force microscopy (AFM) and non-negative matrix factorization (NMF), validate a link between IDA chemistry and mechanical energy transferability. Manifested as damage localization, fractograph analysis confirms existence of this link, where bridging of individual damage events in CF/E is markedly reduced.Graphical abstractImage 1
       
  • PVP-SiO2 and PVP-TiO2 hybrid films for dielectric gate applications in
           CdS-based thin film transistors
    • Abstract: Publication date: Available online 10 February 2020Source: PolymerAuthor(s): M.S. de Urquijo-Ventura, M.G. Syamala Rao, S. Meraz-Davila, J.A Torres- Ochoa, M.A. Quevedo-Lopez, R. Ramirez-BonWe report a simple solution process to deposit organic-inorganic poly (vinyl phenol) (PVP)–SiO2 and PVP-TiO2 hybrid films. The spin dropped hybrid films were prepared at low-temperature and their main properties were studied by TGA, FE-SEM, AFM, FTIR, XPS and contact angle measurements. The results show that the surface of the PVP-SiO2 and PVP-TiO2 hybrid films is smooth with very low surface roughness of 0.25 and 0.51 nm, and surface energy of 48.4 and 40.1 mJ/m2, respectively. The electrical properties of the hybrid films, measured on MIM devices, show low leakage current density under 10−7 A/cm2 and dielectric constant of 5 and 4.6 at 1 kHz, respectively. The hybrid films were used as gate dielectric in solution-processed CdS thin film transistors (TFTs), showing diverse performance. The CdS/PVP-SiO2 devices showed high mobility of 18 cm2/V, on/off current ratio of 104, low threshold voltage of 0.6 V and subthreshold swing of 0.25 V/dec. Whereas, the corresponding values for the CdS/PVP-TiO2 ones were 0.45 cm2/V, 104, 1.9 V and 1.25 V/dec, respectively. The lower electrical performance of the CdS/PVP-TiO2 devices was attributed to the mismatching surface energies between the surfaces of the dielectric and semiconductor layers, and to the influence of a large number of trapped charges at this interface.Graphical abstractImage 1
       
  • Effect of molecular weight to the structure of nanocellular foams: Phase
           separation approach
    • Abstract: Publication date: Available online 10 February 2020Source: PolymerAuthor(s): Shu-Kai Yeh, Zong-En Liao, Keng-Chuan Wang, Yu-Ting Ho, Vania Kurniawan, Po-Chih Tseng, Tien-Wen TsengNanocellular foam is one of the most exciting research areas in foam research. Creating nanocellular foams of high expansion ratio with a cell size lower than 100 nm is still a challenge. In this study, poly(methyl methacrylate) (PMMA) of three different molecular weights, namely PMMA-H, PMMA-M, and PMMA-L, were foamed using the two-step solid-state foaming method to create nanocellular foams. The results showed that the molecular weight of PMMA is one of the critical factors that affect the preparation of PMMA nanofoam. Open-cell nanocellular foams with a cell size of approximately 30–40 nm and cell density of 1016 cells/cm3 were successfully prepared using PMMA-H. The relative density of the foam is between 0.25 and 0.41. Qualitative phase diagrams were created based on saturating temperature, foaming temperature, and molecular weights. Phase separation theory may explain the formation of closed- or open-cell foam with spinodal decomposition contributing to nanosized open cell structure.Graphical abstractImage 1
       
  • The merging mechanisms of poly(3-hexylthiophene) domains revealed through
           scanning tunneling microscopy and molecular dynamics simulations
    • Abstract: Publication date: Available online 9 February 2020Source: PolymerAuthor(s): Jin-Kuo Li, Ming-Yue Shao, Zhi-Yong Yang, Olga GuskovaHerein, we in situ track the merging processes of poly(3-hexylthiophene) (P3HT) domains physisorbed onto graphite while keeping the domain structures clearly resolved through scanning tunneling microscopy (STM). The domain shape-fixed, amoeba/worm-like and bridge-mediated merging mechanisms are revealed. In the domain shape-fixed diffusion, the moving domains obey the principle of the non-continuous random walks. Both diffusive and ballistic-like dynamics are disclosed. Additionally, the asymmetrical domains may show anisotropic movements. In the amoeba-like style, the pseudopodia are formed and changed stochastically while in the worm-like style two permanent parts (head and body) of the domains are formed prior movement and kept fixed in the motions. Finally, the integration of two domains is called a bridge-mediated one, if a small domain is bound to a bigger one directly through a dynamic bridge. The molecular dynamics simulations support the experimental findings of P3HT domain movements and rotations on the graphite surface.Graphical abstractImage 1
       
  • Effects of ethyl-L-glutamated and phenylalanine ratio/sequence on the
           
    • Abstract: Publication date: Available online 9 February 2020Source: PolymerAuthor(s): Dianliang Zhang, Desheng Qi, Jiayu Wang, Shuangjiang Yu, Chaoliang He, Mingxiao DengInjectable hydrogels have attracted great research interest for the delivery drugs and recruitment of cells to promote tissue regeneration. In this work, a series of the amino acid based methoxy-poly (ethylene glycol)-b-(poly (γ-ethyl-L-glutamate-co/b-L-phenylalanine) block copolymers (mPEG-b-P (ELG-co/b-Phe)s) with similar block chain length, but different proportion and sequence of γ-ethyl-L-glutamate (ELG) and L-phenylalanine (Phe) arrangements were prepared through ring-opening polymerization method. The influence of the ratio and sequence structures of mPEG-b-P (ELG-co/b-Phe)s on their thermosensitive aqueous gelation behaviors were investigated in detail. The results showed that the obtained polymers showned higher modulus (G’) and lower critical gelation temperature with higher proportion of L-phenylalanine. However, the physical properties start to deteriorate as the copolymers have a large number of phenylalanine groups. To clarify this phenomenon, the analysis of secondary structure with circular dichroism (CD) and fourier transform infrared (FTIR) spectrum showed that random coil reached a higher percentage as incorporated phenylalanine groups increased. On the other hand, the polymers with different sequence and similar compositions exhibited divergence due to the influence of random coil conformation. In addition, the good biocompatibility of mPEG-b-P (ELG-co-Phe)s were observed in vitro and in vivo. The copolymers have the potential to be used as thermo-sensitive injectable hydrogels for biomedical applications.Graphical abstractThe proportion and sequence of γ-ethyl-L-glutamate and L-phenylalanine influenced the secondary structure, sol-to-gel transition behaviour and mechanical property of methoxy-poly (ethylene glycol)-b-(poly (γ-ethyl-L-glutamate-co/b-L-phenylalanine) block copolymers.Image 1
       
  • Development of a continuous manufacturing process for self-reinforced
           composites using multi-step highly drawn polypropylene tapes
    • Abstract: Publication date: Available online 9 February 2020Source: PolymerAuthor(s): Dong Woo Kim, Yoon Sang Kim, Yong Chae Jung, Seong Yun Kim, Jong Man Song, Minkook Kim, Jaewoo KimDespite the benefits of recycling, impact resistance, and lightweightness, polypropylene (PP) self-reinforced composites (SRCs) still suffer from a lack of research, especially in continuous manufacturing processes. Herein we report a comprehensive study, from the four-step high-ratio drawing of PP-tapes to the continuous manufacturing of SRCs. The mechanical properties of the PP-tape depend strongly on the final draw ratio with the intermediate drawing history having a negligible effect. Mechanical improvements accompany increases in melting temperature and crystallinity, and a decrease in density. PP-SRC was manufactured by continuous double-belt pressing, with optimum performance attained when processed with a 87-148-80 (°C) temperature profile. Structural integrity was not attained at lower temperatures due to poor impregnation, whereas higher temperatures degraded the mechanical properties of the PP-SRC by relaxing the highly drawn PP-tapes. Finally, an analytical approach based on micro-computed tomography, PP-tape relaxation, and rule-of-mixture calculations led to accurate predictions of experimental moduli.Graphical abstractImage 1
       
  • TransPoly: A theoretical model to quantify the dynamics of water transfer
           through nanostructured polymer films
    • Abstract: Publication date: Available online 7 February 2020Source: PolymerAuthor(s): Giana Almeida, Sandra Domenek, Patrick PerréMass transfer of penetrants is among the most important physical properties of polymer films to properly ensure function during service. In the case of interaction between penetrants and polymer, non-Fickian diffusion can be observed. This phenomenon is described by numerous reports and a few models have been proposed. Nevertheless, few of them quantify Fickian and non-Fickian behaviour using parameters with clear physical meaning. The present work develops a new non-Fickian mass transport model: TransPoly (Transfer through Polymers). Based on coupled heat and mass transfer, it accounts for simultaneous Fickian transport and molecular relaxation. This model is applied to data of water vapour mass transfer in nanocomposites of polylactide and cellulose nanocrystals. The contribution of the non-Fickian mass transfer on water vapour sorption is highlighted. TransPoly can be applied to several kinds of polymers and used for prediction purposes once the parameters are determined on a learning database.Graphical abstractGraphical abstract for this article
       
  • Multiscale analysis of viscoelastic properties, topography and internal
           structure of a biodegradable thermo-responsive shape memory polyurethane
    • Abstract: Publication date: Available online 7 February 2020Source: PolymerAuthor(s): Marcin K. Heljak, Adrian Chlanda, Wojciech Swieszkowski, Monika BilIn this paper, the effect of the temperature on viscoelastic properties of the thermo-responsive biodegradable shape memory polyurethane (SMPU) is presented. Comprehensive micro and nano mechanical and morphological studies were performed to assess the behavior of the considered material in the form of 3D-printed fibers. For this purpose, specimen’s topography, nano-mechanical and macro-mechanical characterization of the material were carried out. Data obtained from the temperature-dependent AFM indentation test was used to quantify nanoscale viscoelastic properties of the investigated material. Power-law rheology (PLR) was chosen as constitutive viscoelastic relaxation model describing behavior of the investigated material at different temperatures. Topography and phase contrast studies done in the nanoscale exposed bi-phasic structure of heated SMPU polymer - soft and hard domains corresponding with structural composition of the material were detected. The applied fitting procedure enabled for the identification of the viscoelastic properties of the revealed phases identified as the hard and the soft domains.Graphical abstractImage 109
       
  • The effect of temperature and pressure on polycaprolactone morphology
    • Abstract: Publication date: Available online 7 February 2020Source: PolymerAuthor(s): Cameron Baptista, Aharon Azagury, Hyeseon Shin, Christopher M. Baker, Eileen Ly, Rachel Lee, Edith MathiowitzThe morphology and melting behavior of poly(ε-caprolactone) (PCL) processed at varying pressure-temperature-time conditions (2000–20,000 lbf, 22–70 °C, and 5–15 min) were studied using polarized light microscopy (PLM), differential scanning calorimetry (DSC), and X-Ray diffraction (XRD). Samples processed well below the melting region at 22 °C displayed minimal to no birefringent properties, with broadened crystalline XRD scattering patterns, indicative of plastic crystal mesophase morphology. Plastic crystal quantity was shown to gradually increase from 16% to 30% with processing pressure increasing from 2000 lbf to 20,000 lbf. The mechanism of this formation is thought to be the result of crystal disorganization upon plastic deformation, related to the low-energy barrier slip-planes in the crystalline structure. With sufficient chain mobility achieved at higher processing temperatures (50 °C and 60 °C), samples displayed broad birefringent strokes under PLM and were characterized by XRD scattering patterns of broad anisotropic arcs around the equator of the 2D azimuthal pattern, which are indicative of condis crystal mesophase orientation. As opposed to plastic crystal, the condis crystal quantities showed no correlation with increased pressure, ranging between 28% and 40% as processing pressure increased. The additional chain mobility at these temperatures is thought to enable the mesophase to orient radially (normal to the direction of the external load), allowing the transition from plastic crystal to condis crystal. Thus, this paper reports the formation of four distinct morphologies upon processing PCL namely; crystalline, condis crystal mesophase, plastic crystal mesophase, and amorphous.Graphical abstractImage 1
       
  • POSS enhanced 3D graphene - Polyimide film for atomic oxygen endurance in
           Low Earth Orbit space environment
    • Abstract: Publication date: Available online 7 February 2020Source: PolymerAuthor(s): Ranjana Shivakumar, Asaf Bolker, Siu Hon Tsang, Nurit Atar, Ronen Verker, Irina Gouzman, Mor Hala, Nehora Moshe, Alexandra Jones, Eitan Grossman, Timothy K. Minton, Edwin Hang Tong TeoRecently, 3D-graphene infused polyimide (3DC/PI) films have shown to be an effective protection coating for electrostatic discharge in spacecraft. However, these films are not suitable for Low Earth Orbit (LEO) due to atomic oxygen (AO) erosion. Here, we used Polyhedral Oligomeric Silsesquioxane (POSS) to enhance the AO durability of 3D-C/PI films. Three different ways of adding POSS to the composite films were studied with ground-based AO exposure. For all infusion approaches, their electrical conductivity behaviour is well preserved and the presence of POSS results in reduced AO erosion yield. Of all the methods studied here, incorporating POSS directly into PI results in the lowest erosion yield of 4.67 × 10−25 cm3/O-atom (one order of magnitude lower than that of Kapton). Adding POSS to PI, extends the durability of the composite film beyond 10 years, making it an ideal protective material for long term mission in LEO.Graphical abstractImage 1
       
  • Effects of zinc oxide filler on the curing and mechanical response of
           alkyd coatings
    • Abstract: Publication date: Available online 7 February 2020Source: PolymerAuthor(s): Lauren F. Sturdy, Madeleine S. Wright, Alexander Yee, Francesca Casadio, Katherine T. Faber, Kenneth R. ShullThe mechanical properties of an alkyd resin filled with zinc oxide pigment were studied at different concentrations over a wide range of time scales using dynamic mechanical analysis, quartz crystal rheometry and nanoindentation. The motivation for this work stems from the interest in accessing the long-term properties of paint coatings by studying the mechanical properties of historic paints. In this foundational work, we compare three different modalities of mechanical measurements and systematically determine the effect of pigment filler loading on the measured properties. Quantitative agreement between the methods is obtained when the characteristic time scales of each of the methods is taken into account. While nanoindentation is the technique most readily applied to historic paint samples, the rheometric quartz crystal microbalance (rheo-QCM) is the best suited for obtaining mechanistic information from measurements of paint properties over time, provided that appropriate thin-film samples can be produced. In these studies we find that ZnO increases the rate of oxidation of the alkyd during the initial stages of cure by an amount that depends on the ZnO content.Graphical abstractGraphical abstract for this article
       
  • Development of Elastic Recovering 4-methyl-1-pentene/Propylene Copolymer
    • Abstract: Publication date: Available online 6 February 2020Source: PolymerAuthor(s): Masahiko Okamoto, Kazuki Mita, Takayuki Uekusa, Mikihito Takenaka, Mitsuhiro ShibayamaABSTRACTWe investigated the solid structures and mechanism of the rubber elastic behavior of 4-methyl-1-pentene / propylene random copolymers (PMPCs), which were prepared using metallocene catalyst, by time-resolved wide-angle X-ray diffraction and small-angle X-ray scattering measurements. PMPC becomes an amorphous polymer and exhibits rubber elasticity in the propylene content (PC) ranging from 28 mol% to 75 mol%. However, the amorphous structure and the elastic recovery largely differ depending on PC. PMPC with PC = 75 mol% had an amorphous structure similar to that of polypropylene and developed rubber elasticity. This was because of the entropic elastic behavior caused by entanglements of polymer chains in a manner that was same as that in amorphous polymers. On the other hand, PMPCs with PC = 28 and 40 mol% had unique amorphous structures. The structures had high elastic recovery because of the interactions between molecular chains and the inhomogeneous structure. These phenomena are presumed to occur because the two structures were responsible for the reversible deformation, thereby exhibiting excellent rubber elasticity.Graphical abstractImage 1049117
       
  • High barrier biosourced polyester from dimethyl
           [2,2′-bifuran]-5,5′-dicarboxylate
    • Abstract: Publication date: Available online 6 February 2020Source: PolymerAuthor(s): H. Eliot Edling, Hua Sun, Edward Paschke, David A. Schiraldi, James M. Tanko, Mark Paradzinsky, S. Richard TurnerPoly (ethylene 2,2′-bifuran-5,5′dicarboxylate) (PEBF) is a new biosourced polyester recently reported to have significant enhancement of oxygen barrier properties and glass transition temperature when compared to poly (ethylene terephthalate). We report herein our independent studies on the polymerization and properties of this new polyester. Our findings are contrasted to an earlier report. While the Tg of 106–108 °C was confirmed to be consistent with the early data, we observed crystallization on both cooling and heating cycles in the DSC which were not previously observed, higher tensile elongation to break values, and significantly lower oxygen permeabilities compared to the earlier report. Preliminary uniaxial orientation experiments indicate that this polymer is a good candidate for biaxial orientation processing. We discovered that both the monomer, dimethyl-2,2′-bifuran-5,5′-dicarboxylate (BFE), and the polymer are subject to thermal oxidation which was explored with cyclic voltammetry on the monomer. Experiments with added antioxidant during the polycondensation show marked reduction in the thermal oxidation as observed by color reduction and enhanced stability to melt processing.Graphical abstractImage 1
       
  • Thermal expansion of semi-crystalline polymers: Anisotropic thermal strain
           and crystallite orientation
    • Abstract: Publication date: Available online 5 February 2020Source: PolymerAuthor(s): Esther Ramakers-van Dorp, Bernhard Möginger, Berenika HausnerovaPerformance demands on injection- and blow-molded parts are steadily increasing. As a dimensional stability depends largely on shrinkage and warpage during/after processing, the process-induced changes should be taken into account in a mold design. To predict shrinkage, this study introduces an approach to model the thermal expansion based on an elementary volume unit cell consisting of stacked crystalline and amorphous layers. Its validation is performed with the help of the thermal expansions of injection- and blow-molded polyethylene parts measured with respect to the process directions by a dynamic mechanical analyzer in a tension mode. Differential scanning calorimetry measurements are carried out to obtain crystallinity as a function of temperature of the PE parts as an input parameter to calculate the thermal expansion. The additional utilization of the phase specific coefficients of thermal expansion (CTE) and Young's moduli taken from literature for the model showed that the measured thermal expansion lies between the calculated ultimate coefficient of thermal expansion. To adjust the ultimate CTE, the process-dependent tilting and rotation angles are fitted, and it seems that relaxation processes at elevated temperatures (which are not considered in the model yet) cause a deviation. Thus, the model yields a good agreement with the measured data up to a temperature of 70 °C.Graphical abstractImage 1
       
  • Simulation of tensile modulus of polymer carbon nanotubes nanocomposites
           in the case of incomplete interfacial bonding between polymer matrix and
           carbon nanotubes by critical interfacial parameters
    • Abstract: Publication date: Available online 5 February 2020Source: PolymerAuthor(s): Yasser Zare, Kyong Yop RheeIn this paper, we correlate the minimum length of carbon nanotubes (CNTs) vital for operative stress transferring between polymer matrix and nanoparticles (Lc) to the critical interfacial shear modulus between polymer and CNTs (Gc) and the interfacial shear modulus (Gi) in the case of imperfect interfacial adhesion between polymer and carbon nanotubes (CNTs). Both “Gc” and “Gi” define the effective aspect ratio and volume fraction of CNTs in nanocomposites. Moreover, the developed Hui-Shia model investigates the roles of “Lc”, “Gc” and “Gi” in the tensile modulus of nanocomposites. The impacts of various parameters on the “Lc” and effective terms are highlighted. Furthermore, the experimental results of modulus for several samples and the influences of all parameters on the modulus evaluate the developed model. The accurate agreement between experimental and theoretical results as well as the correct roles of all parameters in the modulus supports the current approach. There is a direct relationship between the modulus of nanocomposites and “Lc”. Low “Gc” and high “Gi” as well as thin and long CNTs positively control the “Lc” and effective terms producing a high modulus for nanocomposites.Graphical abstractImage 100505
       
  • In silico study of bio-based epoxy precursors for sustainable and
           renewable thermosets
    • Abstract: Publication date: Available online 4 February 2020Source: PolymerAuthor(s): Baris DemirAbstractA computational approach was developed to examine thermo-mechanical properties of experimentally investigated bio-based precursors for making sustainable resins. Molecular dynamics simulations were utilised to generate and test resin samples. Divanillyl alcohol derived epoxy monomers with different functionalities, diglycidylether of divanillyl alcohol (DiGEDVA), triglycidylether of divanillyl alcohol (TriGEDVA), and tetraglycidyl of divanillyl alcohol (TetraGEDVA) cross-linked with cyclo-aliphatic diamine (IPDA) were used to generate three-dimensional polymer networks. Influence of the functionality of bio-derived epoxy monomer on the network formation was investigated. The thermal properties such as glass transition temperature and coefficients of linear thermal expansion were predicted. In addition, the mechanical performance of the resins was evaluated by testing the cross-linked resins under tensile and shear deformation. Young’s and shear moduli were predicted and explained based on the network analysis (e.g. the percentage of monomers partly reacted or completely reacted). Here, a completely reproducible and reliable computational protocol is provided to design, test and tune bio-based epoxy monomers for future’s sustainable thermoset polymers.
       
  • Effects of naphthoxy side groups on functionalities of linear
           polyphosphazenes: Fluorescence, ion response and degradability
    • Abstract: Publication date: Available online 3 February 2020Source: PolymerAuthor(s): Shaojun Wu, Husitu Lin, Shuangkun Zhang, Wei Liu, Jianjun Liu, Zhanpeng Wu, Dezhen WuPolyphosphazenes with different substitution rates of β-naphthoxy side groups are synthesized through ring opening polymerization of hexachlorocyclotriphosphazene (HCCP), subsequent nucleophilic substitution by β-naphthol in organic solutions. The concentration and solvent effects, ions response, solid-state fluorescence and degradability of these polymers are investigated. It is found that the peaks in excitation spectra redshift with the increase of polymer concentration, and gradually stronger interaction of polymer molecules results in different concentration effects at λex = 300 nm and λex = 355 nm, respectively. It demonstrates that the fluorescence intensity of polymer solution enhance by increasing the polarity of solvents, and iron ions could quench fluorescence of polymer solutions. Moreover, the fluorescence intensities of polyphosphazenes containing β-naphthoxy side groups in solid-state is stronger than those in solution. The highest fluorescence intensities of those in both solid and solution is those polymers with 90% substitution rate of naphthoxy side groups. However, the polymers with lower substitution rate of naphthoxy side groups are degradable easily in acid medium.Graphical abstractImage 1
       
  • Fluorescence microscopy tracking of dyes, nanoparticles and quantum dots
           during growth of polymer spherulites
    • Abstract: Publication date: Available online 3 February 2020Source: PolymerAuthor(s): Shu-Gui Yang, Hui-Jie Xie, Hina Saba, Liliana Cseh, Goran UngarThe distribution of additives and nanoparticles in a semicrystalline polymer is largely dependent on the complex hierarchical polymer morphology and the kinetics of its development. Here we show by in-situ fluorescence microscopy (FM), coupled with polarized optical and scanning electron microscopy, that a substantial fraction of the additive (Nile Red, NR) and even NR-labelled silica nanoparticles (NP) and quantum dots (QD) was pushed ahead of the growing spherulites during melt-crystallization. For the 35 and 200 nm NPs this was unexpected because their diffusion rate based on Stokes-Einstein equation should have been 2–3 orders of magnitude slower than the rate at which spherulites were growing. Another surprising finding was that much of the initially rejected NR and some QDs subsequently re-entered the spherulites through back-diffusion, posing the question why they were then rejected in the first place. The excessive initial rejection of NR and QDs and the unexpectedly rapid migration of NPs are both explained by the additive preferentially filling and being carried along by the polymer depletion zone in the melt ahead of the growing spherulite, and the high negative pressure in these zones. The effectiveness of FM in detecting minute cracks and cavities is also demonstrated. The results also show that the most severe clustering of additives occurs where spherulites did not nucleate, a problem preventable by the addition of nucleating agent.Graphical abstractImage 1
       
  • Design of high impact thermal plastic polymer composites with balanced
           toughness and rigidity: Toughening with core-shell rubber modifier
    • Abstract: Publication date: Available online 31 January 2020Source: PolymerAuthor(s): Fushi Li, Yunbao Gao, Yue Zhang, Wei JiangIt is different from one phase impact modifier such as ethylene-propylene rubber (EPR), ethylene-propylene-diene monomer copolymer (EPDM), polyolefin elastomer (POE) et al., that the core-shell rubber particles constructed by a hard core and a soft shell is a typical two phases impact modifier. They have been successfully and widely introduced to toughen polymers by melt blending or alloying in reactor. However, an important but unclear question is how to obtain the high impact thermal plastic polymer composites with less rigidity loss by optimizing the structure and the properties of the core and shell phases. To answer this question, we develop the model from one phase modifier to two phases modifier and make a quantitative calculation in this study and obtain the following results: (1) In order to obtain the high impact polymer composites with low rigidity loss, the modulus of the core should be as higher and the modulus of shell should be as lower as they can; (2) Comparing to one phase impact modifier, core-shell rubber particles toughened polymer composites can have less rigidity loss. The lowest modulus loss for the high impact PP can decrease from 26.1% for one phase modifier, to 13.5% for the core-shell modifier with PE core, and to 5.4% for the core-shell modifier with PP core; (3) The impurity, i.e. the rubber shell contains homo PP or PE and the core contains EPR, leads to the increase of the rigidity loss for the high impact PP alloys in reactor.Graphical abstractImage 1
       
  • Semiconducting Small Molecule/Polymer Blends for Organic Transistors
    • Abstract: Publication date: Available online 25 January 2020Source: PolymerAuthor(s): Li-Hui Chou, Yaena Na, Chung-Hyoi Park, Min Soo Park, Itaru Osaka, Felix Sunjoo Kim, Cheng-Liang LiuABSTRACTOrganic thin-film transistors (OTFTs) are expected to play a key role in future printed electronics. As a promising candidate for numerous commercial applications and next-generation electronics, organic small molecule/polymer blend systems have attracted significant interest. Herein, recent developments and progress in polymer blends based on small molecule semiconductors and polymers for OTFTs are discussed with a focus on device operation, solution processing, phase separation, and semiconductor blend system morphologies. The blends exhibit promising characteristics, combining the high charge-carrier mobility of small molecules, solution-based processability of polymers, and unique morphological features of their blends. Both insulating and conjugated polymers are separately reviewed to discuss the effects of polymeric components on the charge transport properties, film quality, and morphology. The outlook for this field along with future opportunities and challenges are also discussed.Graphical abstractImage 10743
       
 
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