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Polymer
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0032-3861
Published by Elsevier Homepage  [3181 journals]
  • Waterborne polyurethane nanocomposite reinforced with amine intercalated
           α-zirconium phosphate - study of thermal and mechanical properties
    • Abstract: Publication date: Available online 14 November 2019Source: PolymerAuthor(s): Manoj B. Kale, Nidhin Divakaran, Suhail Mubarak, Duraisami Dhamodharan, T. Senthil, Lixin Wu The in situ polymerization scheme was chose to introduce the amine intercalated α-zirconium phosphate (fZrP) in the waterborne polyurethane (WPU). The α-ZrP (ZrP) was prepared by refluxing zirconyl chloride octahydrate and then amine intercalated using ethylenediamine. The nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and thermo gravimetric analysis. The fZrP was introduced in the WPU with the known filler content of 0.1, 0.5 and 1 wt%, respectively. The prepared WPU/fZrP nanocomposites films have shown better mechanical, thermal and water resistance properties compared to the neat WPU and unmodified ZrP nanocomposites. The tensile strength of WPU filled with 1 wt% fZrP was increased by 57.09 % against the WPU filled with 1 wt% unmodified ZrP. The thermal properties of the WPU showed increasing performance with the increasing fZrP content. The incorporation of fZrP in the WPU increased the thermal conductivity from 0.1777 W/m.K for virgin WPU and 0.2969 W/m.K for WPU/fZrP (1 wt%). The water resistance performance of the WPU was also improved with the increasing filler content. The results portray that the α-ZrP nanoplates can be an additive material to improve the thermo-mechanical performance of polymers.Graphical abstractImage 10323
       
  • Novel Reinforcement Behavior in Nanofilled Natural Rubber (NR) /
           Butadiene-acrylonitrile Rubber (NBR) Blends: Filling-Polymer Network and
           Supernanosphere
    • Abstract: Publication date: Available online 14 November 2019Source: PolymerAuthor(s): Tinghui Han, Selvaraj Nagarajan, Hongying Zhao, Chong Sun, Shipeng Wen, Suhe Zhao, Shugao Zhao, Liqun Zhang It is worthy to understand the reinforcement of nanoparticle in rubber blends in application prospect because of its dispersion and distribution. The dielectric and mechanical methods were used to study the reinforcement impact of the carbon black (CB) in NR/NBR blends, based on the percolation and reinforcement theories. Results indicated that the CB aggregates had dispersed in NBR phase and the reinforcement effect was dependent on both CB concentration and the rubber blend ratio. It has been observed that the CB particles diffused and filling in the NBR reinforcement network at 50:50 ratio of NR/NBR blend, CB particles assembled as supernanosphere at 70:30 ratio and CB particles wrapped/covered supernanosphere at 90:10 ratio. The highest elongation at break was observed in 90:10 ratio of NR/NBR.The new observations are conducive to providing guidelines for producing high mechanical performance and low conductivity percolation threshold elastomers via a maturely industrial method for a wide range of application.Graphical abstractImage 103059
       
  • Single nozzle electrospinning of encapsulated epoxy and mercaptan in PAN
           for self-healing application
    • Abstract: Publication date: Available online 14 November 2019Source: PolymerAuthor(s): Sayed Ali Mirmohammad Sadeghi, Sedighe Borhani, Ali Zadhoush, Mohammad Dinari In this research, two types of core-shell nanofibers, epoxy-polyacrylonitrile (PAN) and mercaptan-PAN were successfully fabricated using single nozzle electrospinning. Fourier transform infrared spectroscopy (FTIR) analysis showed absence of chemical reaction between the encapsulated epoxy or mercaptan and PAN. Moreover, transmittance electron microscopy (TEM) images proved that the encapsulated epoxy and mercaptan were uniformly distributed within core of the nanofibers. Hybrid core-shell nanofibers mat was produced through twin electrospinning of epoxy-PAN and mercaptan-PAN on the same collector. Solidification of released core materials leads to repair a damaged area which could be used in epoxy composites for self-healing application. Degree of curing of epoxy resin was obtained to be 0.7 at 10 °C, proving that the dual component healing agent, epoxy and mercaptan is a suitable self-healing system in sub-room temperature. This research shows that solubility parameter of the materials plays a major role in the formation mechanism of core-shell nanofibers.Graphical abstractImage 108254
       
  • Preparation of printable double-network hydrogels with rapid self-healing
           and high elasticity based on hyaluronic acid for controlled drug release
    • Abstract: Publication date: Available online 14 November 2019Source: PolymerAuthor(s): Yang Qiao, Shichao Xu, Tianzhe Zhu, Nan Tang, Xuejian Bai, Chunming Zheng On account of the features about computer-accurate control, the technology of 3D printing has a broad future for developing customized ergonomic biomedical materials. Herein, a printable dual-network hydrogel for drug delivery was designed. The acrylamide-modified hyaluronic acid was mixed with folic acid and Fe3+ at first. With the formation of metal-carboxylate coordination bonds, the first layer of physical crosslinking network (HFF) was formed, followed by performing the spectral analysis and rheology measurements to verify the bonding. The second layer of PAM network was then polymerized by ultraviolet radiation, with high elasticity and fatigue resistance to satisfy its application as a wound dressing. Furthermore, acetylsalicylic acid (Asa) was used as a drug model resulted in a pH responsiveness of the prepared hydrogels with the sustained drug releasing behavior over 300 h. These results signified the potential application of this self-healing hydrogel with good mechanical properties in regenerative medicine.Graphical abstractImage 1
       
  • Reinforced and toughened PP/PS composites prepared by Fused Filament
           Fabrication (FFF) with in-situ microfibril and shish-kebab structure
    • Abstract: Publication date: Available online 14 November 2019Source: PolymerAuthor(s): Yixin Jiang, Junjie Wu, Jie Leng, Ludwig Cardon, Jie Zhang In this work, in-situ microfibrillar composites (MFC) of polypropylene (PP)/polystyrene (PS) were produced by Fused Filament Fabrication (FFF) with a self-designed build platform. Due to the high shearing and stretching effect during the FFF process, PS phase underwent a large deformation. A large number of PS microfibrils could be observed in the samples. Meanwhile the molecular chain of PP was also stretched and arranged along the flow direction in the 3D Printing process. Finally, microfibrils, shish-kebab and hybrid shish-kebab crystal structures can be found and they make contributions to the mechanical performance. This work confirms the applicability of semi-crystalline polymer in FFF technology and discusses the development of phase morphology and crystalline morphology during printing. These obtained results will provide new ideas for broadening the amount of available materials and the application fields of FFF samples.Graphical abstractImage 1
       
  • Enhanced thermal stability, toughness, and electrical conductivity of
           carbon nanotube-reinforced biodegradable poly(lactic acid)/poly(ethylene
           oxide) blend-based nanocomposites
    • Abstract: Publication date: Available online 14 November 2019Source: PolymerAuthor(s): Kartik Behera, Yen-Hsiang Chang, Mithilesh Yadav, Fang-Chyou Chiu Carbon nanotube (CNT) was incorporated into the miscible poly(lactic acid)/poly(ethylene oxide) (PLA/PEO) blend to successfully fabricate biodegradable nanocomposites. Scanning electron microscope images revealed the well dispersion of as-received CNT within the blend through the melt-mixing process. Thermogravimetric analysis showed that the CNT significantly improved the thermal stability of the blend (up to 68 °C increase at 3-phr CNT addition compared to the blend at 10 wt% loss) in air. Differential scanning calorimetry data showed the nucleation effect of CNT on the crystallization of individual PLA and PEO; the presence of CNT increased the melting temperature of PLA crystals. Measurement of rheological behavior confirmed the formation of CNT (pseudo-)network structure in the composites. The impact strength of the composite with 3-phr CNT loading was three times higher than that of the blend. The electrical resistivity of the blend reduced by up to nine orders of magnitude at 3-phr CNT loading. The electrical and rheological percolation thresholds were both achieved at 1-phr CNT loading for the nanocomposites.Graphical abstractImage 1
       
  • Quantitative predictions of maximum strain storage in shape memory
           polymers (SMP)
    • Abstract: Publication date: Available online 14 November 2019Source: PolymerAuthor(s): Chris C. Hornat, Marlies Nijemeisland, Michele Senardi, Ying Yang, Christian Pattyn, Sybrand van der Zwaag, Marek W. Urban Shape memory polymers (SMPs) are dynamic materials able to recover previously defined shapes when activated by external stimuli. The most common stimulus is thermal energy applied near thermal transitions in polymers, such as glass transition (Tg) and melting (Tm) temperatures. The magnitude of the geometrical changes as well as the amount of force and energy that a SMP can output are critical properties for many applications. While typically deformation steps in the shape memory cycles (SMC) are performed at temperatures well above thermal transitions used to activate shape changes, significantly greater amounts of strain, stress, and mechanical energy can be stored in Tg-based SMPs when deformed near their Tg. Since maximum shape memory storage capacity can be appraised by evaluating the viscoelastic length transitions (VLTs) in a single dynamic mechanical analysis (DMA) experiment, this study correlates VLTs with the measured storage capacities obtained from stress-strain experiments for a broad range of well-defined crosslinked acrylates, epoxies, and polyurethanes. This systematic approach allows for assessment of crosslink/junction density (νj), viscoelasticity, and chemical composition effects on maximum deformability, and enables predictions of the magnitude of shape memory properties across a wide variety of polymers. These studies demonstrate that the maximum storable strain (ε-storemax) can be accurately predicted using junction density (νj) and shape memory factor (SMF), the latter accounting for the contribution of chemical makeup.Graphical abstractImage 1
       
  • Study on the Degradation Behavior and Mechanism of Poly(lactic acid)
           Modification by Ferric Chloride
    • Abstract: Publication date: Available online 12 November 2019Source: PolymerAuthor(s): Xiaolong Li, Shang Gong, Le Yang, Feng Zhang, Lijin Xie, Zhu Luo, Xiaosong Xia, Jun Wang A kind of poly(lactic acid) (PLA) material with rapid degradation capacity was prepared with ferric chloride (FeCl3), it’s degradation rate was more than 10 times higher than that of pure PLA. FeCl3 forms stable chemical bonds with C and O, which weakens the ester bond and leads to rapid degradation of PLA immensely. The degradation process of modified PLA is greatly accelerated because the presence of Fe3+ facilitates the first step of the degradation process. The thermal stability of the modified materials decreased greatly, and the PLA changed from a higher crystalline polymer to an almost non-crystalline polymer with increasing FeCl3 content, which enhanced the degradation rate due to the reduced intermolecular force. In terms of the degradation performance, the modified materials containing 2.95 phr FeCl3 possessed the best comprehensive performance.Graphical abstractImage 107960The degradation behavior of modified samples and pure PLA in alkali solution. (The red box indicates that the state has not changed since that day.)
       
  • Crystallization-driven microstructure changes during microphase separation
           for environment-friendly thermoplastic triblock copolymer elastomers
    • Abstract: Publication date: Available online 12 November 2019Source: PolymerAuthor(s): Shuangshuang Ding, Chu Fang, Xuehui Wang, Zhigang Wang A study on the crystallization-driven microstructure changes during microphase separation for a series of high transparent semicrystalline thermoplastic triblock copolymer elastomers (TBCPEs), polylactide-b-polyisoprene-b-polylactide (PLA-b-PI-b-PLA) was conducted in this work. A series of PLA-b-PI-b-PLA TBCPEs with different molecular masses of PI midblock and same molecular mass of PLA end blocks were synthesized. Differential scanning calorimetry was applied to demonstrate the microphase separation and crystallization behaviors of these samples. Small-angle X-ray scattering and ultra-small-angle X-ray scattering techniques were employed to investigate the different microphase-separated structures between solvent-cast and melt quenched PLA-b-PI-b-PLA films. It was disclosed that crystallization of the PLA end blocks could obviously enlarge the interdomain distance if the microphase-separated structures in PLA-b-PI-b-PLA took lamella or cylinder formats, while much less effect was noticed if the structures took sphere format. Wide-angle X-ray diffraction measurement demonstrated that PLA end blocks in PLA-b-PI-b-PLA could crystallize and eventually form α-form crystals with relatively high crystallinity values. The α-form crystals stay clear with high transparency even with high crystallinity values, because the initially formed microphase-separated structures could confine crystallization of PLA end blocks, preventing the growth of any large PLA crystals eventually.Graphical abstractImage 1
       
  • Study on thermal behavior of regenerated micro-crystalline cellulose
           containing slight amount of water induced by hydrogen-bonds transformation
           
    • Abstract: Publication date: Available online 11 November 2019Source: PolymerAuthor(s): Wenhao Li, Jian Hu, Li Cheng, Long Chen, Lijuan Zhou, Jianming Zhang, Yuan Yuan Cellulose exhibit an excellent ability to adsorb water because of its strong hydrophilicity. The effect of water present in natural cellulose on the structure and thermal property has been paid attention. However, the influence is not clear on the cellulose after regeneration, in the process of which a large amount of water is usually used. In the present study, two important thermal behavior of water-loss and oxidation respectively in the temperature range of 20–165 °C and 165–300 °C was identified in the heating process of the regenerated microcrystalline cellulose (MCC) with the water content of 2.4 wt%. By using perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy combined with generalized 2D correlation spectroscopy (2DCOS), the successive changes in the physical loss of water, the initial inter- and intrachain H-bonds weakening, and the formation of the weak/free H-bonds are illustrated during the first process. While continuous development of the weak/free H-bonds network and the transition from the OH groups within H-bonds to the C=O group are closely linked in the subsequent oxidation process. Furthermore, it is found that a higher crystallinity and a lower water-content can be obtained in the sample after high-temperature annealing. Thus prepared MCC go through the same two stages but with high-temperature shift of ca. 10 °C. The structural changes in H-bonds correlated to the thermal behavior mentioned above exhibit a high-temperature shift correspondingly. Temperature-dependent WAXD spectra reveals that the higher thermal stability of the sample is contributed from the structural regularity and the high crystallinity of the regenerated cellulose II improved by decreased water content. Our results indicate that water existence should be considered in the process of the preparation and industrialization of cellulose.Graphical abstractImage 1
       
  • Polypyrrole nanospheres@graphene aerogel with high specific surface area,
           compressibility, and proper water wettability prepared in
           dimethylformamide-dependent environment
    • Abstract: Publication date: Available online 11 November 2019Source: PolymerAuthor(s): Erhui Zhang, Weifeng Liu, Qi Liang, Xuguang Liu, Zongbin Zhao, Yongzhen Yang A polar functionalization modification is put forward to prepare polypyrrole nanospheres@graphene aerogel (PPys@GA) with high specific surface area, compressibility, and proper water wettability. Polarity of mixed solutions is regulated by controlling the volume ratio of H2O to N,N-dimethylformamide (DMF) to realize better dispersion of graphite oxide (GO), while PPys prepared by weak oxidant (FeCl2/H2O2) own excellent water wettability and can be easily adsorbed on GO sheets to restrain the aggregation of graphene sheets during the reduction self-assembly process more efficiently than PPys synthesized using strong oxidants. The finally resultant PPys@GA enjoys the advantages of high specific surface area (686 m2 g−1), ultralow density (7.8 mg cm−3), high Young's modulus (45.33 kPa) as well as proper wettability (a contact angle of 86°). And such excellent comprehensive properties for PPys@GA outperform many of their counterparts, which qualifies PPys@GA acting as a promising candidate for extensive applications such as adsorption, catalysis, sensors and energy storage materials.Graphical abstractImage 1
       
  • Infusion of graphene quantum dots to modulate thermal conductivity and
           dynamic mechanical properties of polymers
    • Abstract: Publication date: Available online 11 November 2019Source: PolymerAuthor(s): Joel R. Seibert, Özgür Keleş, Jun Wang, Folarin Erogbogbo Graphene quantum dots are small fragments of graphene that may be advantageous to transferring properties to polymers because of their small size, molecular like interactions, surface chemistry and ability to overcome dispersibility challenges in composite formation. Here, we begin the first thermal conductivity study with graphene quantum dots by revealing the thermal and mechanical properties of composites made by infusing graphene quantum dots into epoxy. We found that graphene quantum dots that have the capability to improve the toughness of epoxy by 260%, increase the thermal conductivity by 144%, increase the glass transition temperature by 10%, increase the storage modulus by 9%, and decrease damping by 45%. We anticipate graphene quantum dots infusion to be a starting point for creating more sophisticated polymer composites.Graphical abstractImage 1
       
  • Fabrication of Poly(butylene succinate) phosphorus-containing ionomers
           microcellular foams with significantly improved thermal conductivity and
           compressive strength
    • Abstract: Publication date: Available online 9 November 2019Source: PolymerAuthor(s): Ke Ru, Shuidong Zhang, Xiangfang Peng, Junsheng Wang, Huaqiao Peng Biodegradable microcellular foams with high comprehensive performances were highly desired for many applications. Differed from previous researches, poly(butylene succinate) ionomer (PBSI) foams fabricated by supercritical CO2 were promising for yielding high thermal conductivity and compressive feature. Novel PBSIs microcellular foams with different phosphorus-containing ionic group (PCIG) content (FPBSIs-K) were fabricated in the study. Then, the relationships between the structure and properties, including thermal conductivity, compressive strength and thermal safety of FPBSIs-K were investigated. Strikingly, owing to the physical cross linking by PCIG aggregation, the significant increases in the melt strength generated stronger surface tension and orientation force. Consequently, FPBSI7.5-K (7.5 wt% PCIG content) achieved about 100% closed cell structure, and high orientation for cells. Compared with those of PBS foams, FPBSI7.5-K achieved 10-folds, 9-folds and 5-folds increases in char yield, thermal conductivity and compressive strength, and their values were 15.4%, 315 mW/mk and 3.5 MPa, respectively. The mechanism for FPBSIs-K with significant improvements in thermal conductivity and compressive strength were proposed. Moreover, the incorporation of PCIG promoted FPBSIs-K to form a stable char layer and inhibit the release of combustible gaseous pyrolysis products. This work inspired to develop high-performances biodegradable microcellular foams for environment protection, lightweight structural materials and fire safety.
       
  • Effect of solvent aromaticity on poly(9,9-dioctylfluorene) (PFO) chain
           solution behavior and film condensed state structure
    • Abstract: Publication date: Available online 9 November 2019Source: PolymerAuthor(s): Bin Liu, Hao Zhang, Jiaxuan Ren, Tengning Ma, Mengna Yu, Linghai Xie, Dan Lu Solvent media is crucial to the dynamic evolution process of conjugated polymer condensed state structures from solution state to film. Especially, aromatic solvent can arouse strong π-π interaction with conjugated polymer backbone. Poly(9,9-dioctylfluorene) (PFO) is a classic hairy-rod conjugated polymer. Chlorobenzene (CB) and toluene (Tol) were used as aromatic solvents, while tetrahydrofuran (THF) and chloroform (CF) were used as non-aromatic solvents. It was firstly found that PFO chain solution behaviors were closely connected to solvent aromaticity with broad concentration range from 0.005 mg/mL to 5 mg/mL. Owing to the bigger chain exclude volume in CB and Tol solvents, in dilute solution with PFO concentration ≤ 0.7 mg/mL, PFO single chains adopted more extended and rigid chain conformation than those in THF and CF solvents, thus, needed conjugated length of β conformation could be easily achieved, and β conformation could be firstly formed; PFO solution concentration increased to ≥ 1 mg/mL, chain aggregation began formation, but aggregation sizes were larger meanwhile chain packing density decreased according to the fractal dimension parameter df; Until PFO solution concentration increased to ≥ 3 mg/mL, only β conformation characteristic peaks began appearance in the all PL spectra. The different solution state behaviors directly affect film condensed structures. A fiber and ordered structure formed in films from CB and Tol solvents, meanwhile circular sheet and short rod-like morphology formed in films from THF and CF solvents, respectively. Solvent effect is significant not only to deeply understand the physical essence both condensed state structure formation and photoelectric performance enhancement but also to well control conjugated polymer condensed state structure to achieve photoelectric devices with high efficiency and stability.Graphical abstractImage 1
       
  • Self-healing thiol-ene networks based on cyclodextrin-adamantane
           host-guest interactions
    • Abstract: Publication date: Available online 9 November 2019Source: PolymerAuthor(s): Riku Muroi, Kaito Sugane, Mitsuhiro Shibata The reactions of β-cyclodextrin, pentaerythritol propoxylate and 1-adamantanecarboxylic acid with allyl bromide in the presence of basic salts generated their allylated products (ACD, APEP and AAd, respectively). The thiol-ene photopolymerizations of these allylated compounds and pentaerythritol tetrakis(3-mercaptopropionate) (S4P) produced thiol-ene network films (ACD-S4P, ACD-APEP-S4P, ACD-AAd-S4P, APEP-AAd-S4P and ACD-APEP-AAd-S4P). The FT-IR and gel fraction measurements of the photo-cured films revealed that almost all the thiol and allyl groups were consumed, and polymer networks were certainly formed. Glass transition temperatures (0.5 and 0.3 °C) of ACD-S4P and ACD-AAd-S4P were higher than those (−9 to −15 °C) of other films incorporating APEP. The tensile strength and modulus of ACD-S4P were much higher than those of the films incorporating APEP or AAd. Only the films incorporating both ACD and AAd possessed the self-healing property. ACD-AAd-S4P showed a higher tensile strength and modulus than ACD-APEP-AAd-S4P did. ACD-AAd-S4P was healed twice at 80 °C and only once at room temperature. ACD-APEP-AAd-S4P was healed only once at 80 °C. The maximum healing efficiency was 85% for tensile modulus of ACD-AAd-S4P.Graphical abstractImage 1
       
  • Fluorinated Polycarbonate Photoresists with Adjustable Double Bond Density
           for Electro-optic Switch Applications by Directly Written Method
    • Abstract: Publication date: Available online 9 November 2019Source: PolymerAuthor(s): Shuxiang Ding, Chunxue Wang, Zuosen Shi, Xiaoyu Shi, Zhenzhen Cai, Changming Chen, Zhanchen Cui A series of fluorinated polycarbonates (AF-3OH-PC MAs) terminated by different proportions of acrylate group were synthesized and directly used as photoresist materials. The materials can directly form a cross-linked film under UV light and initiator conditions without the addition of small molecular crosslinkers. The thermal stability (Td up to 416 ˚C), the absorption at 1550 nm is almost zero and electro-optical stabilities ( after 80 °C for 200 h, the r33 remains 91% of the initial value) are significantly improved since the small molecular crosslinkers were not added. The propagation and insertion loss of the device were measured by a cut-back method to be only 0.66 dB/cm and 1 dB, respectively. It may be possible to have an enlightening effect on preparing electro-optical switches with better performance.Graphical abstractImage 10136
       
  • Nucleation theory of polymer crystallization with conformation entropy
    • Abstract: Publication date: Available online 9 November 2019Source: PolymerAuthor(s): Hiroshi Yokota, Toshihiro Kawakatsu Based on classical nucleation theory, we propose a couple of theoretical models for the nucleation of polymer crystallization, i.e. one for a single chain system (Model S) and the other for a multi-chain system (Model M). In these models, we assume that the nucleus is composed of tails, loops and a cylindrical ordered region, and we evaluate the conformation entropy explicitly by introducing a transfer matrix. Using these two models, we evaluate the occurrence probability of critical nucleus as a function of the polymer chain stiffness. We found that the critical nucleus in Model M is easier to occur than in Model S because, for semi-flexible chains, the nucleus in Model M can grow by adding a new polymer chain into the nucleus rather than to diminish the loop and tail parts as in the case of Model S.Graphical abstractImage 1
       
  • Kinetic Theory of A2+B3+B2 type
           hyperbranched polymerization
    • Abstract: Publication date: Available online 9 November 2019Source: PolymerAuthor(s): Tongfan Hao, Zhiping Zhou, Deyue YanAbstrasctThe kinetics of the hyperbranched polymerization with A2, B3 and B2 monomer has been developed in this work. The analytical expressions of the size distribution function and the various molecular parameters of the resulting hyperbranched polymers were derived. Compared with A2+B3 type hyperbranched polymerization, with the addition of B2 type monomer in the reaction system, the gel range moves in smaller value and a narrower interval of the initial functional ratio (α), i.e. initial ratio of B to A group in respective B3 and A2 monomer. At a specified feed ratio α, the addition of B2 monomer can enhance the critical conversion of A groups and reduce that of B groups as well. The addition of linear B2 monomer in reaction system can significantly reduce the degree of branching and improve the number-average degree of polymerization for the products obtained. In this way, according to the theoretical research in this work, molecular structure and parameters can be effectively designed by choosing the appropriate feed ratio of monomers for the hyperbranched polymerization of A2+B3+B2 type.Graphical abstractImage 10770
       
  • Thermal annealing induced formation of polymeric nanopillars of asymmetric
           bottlebrush block copolymers
    • Abstract: Publication date: Available online 8 November 2019Source: PolymerAuthor(s): Qian Wang, Fan Wu, Longfei Luo, Zhihao Shen, Xing-He Fan Polyhedral polymeric particles are desirable for various applications, but the fabrication is limited due to thermodynamic favorability of sphere formation. Herein, we employed a new strategy to prepare anisotropic nanopillars by thermally annealing bottlebrush block copolymers (BBCPs) with geometric asymmetry. Screw nut-like assembly and hexagonal nanopillars are formed after thermal annealing at 50 °C and 60 °C, respectively, which is rare in self-assembly of block copolymers. The shape transformation of the particles is thermodynamically driven, while the formation of hexagonal nanopillars is mainly attributed to entropic origin (the molecular geometry of the BBCP). This work provides a new strategy to prepare nanomaterials with noval structures.Graphical abstractImage 1
       
  • Formation and growth of cavities in tensile deformation of
           Poly(ε-caprolactone) and its miscible blends
    • Abstract: Publication date: Available online 8 November 2019Source: PolymerAuthor(s): Zhiyong Jiang, Tao Liao, Ran Chen, Yongfeng Men Microstructural development of poly(ε-caprolactone) (PCL) and its miscible blends with poly(vinyl methyl ether) (PVME) and poly(styrene-co-acrylonitrile) (SAN) were investigated as a function of strain in the process of uniaxial stretching using in situ synchrotron ultrasmall- and small-angle X-ray scattering (USAXS and SAXS) techniques. The addition of amorphous polymer SAN gives rise to a distinct reduction in the entanglement density of the amorphous phase of PCL, whereas an introduction of PVME does not affect the entanglement density in the blend. At small strains, the initial cavities in pure PCL are oriented perpendicular to the drawing direction, while the cavities at the onset of their formation are oriented along the extensional direction for the PCL/PVME blend. Nevertheless, no cavity scattering is observed in PCL/SAN blend during the process of tensile deformation. These results confirm that the cavitation is directly linked to the lamellar crystallites with their orientation parallel to the drawing direction at small extension ratios. For the two cavitated samples, the volume fraction of cavities was assessed from the integrated scattering intensity based on a three phase model. A critical stress value, above which the lamellar mosaic blocks begin to be pulled apart and the cavitation just sets in, was found to be nearly constant at around 15 MPa. Furthermore, the dimensions of cavities were evaluated at different deformations via direct cylinder model fitting to the USAXS patterns. The height of cavities is much larger than the long spacing of lamellar stacks even at the early stages of cavity formation, which indicates the cavities emanating from the lamellae into several amorphous phases at small elongations. Analysis of the SAXS patterns shows an independence of lamellar long spacing on the sample composition at large strains, which strongly supports the deformation scheme of stress-induced fragmentation and recrystallization.Graphical abstractImage 1
       
  • Influence of Poly(Vinylidene fluoride) on photovoltaic performance of
           interfacially engineered band gap modulated P3TAA-co-P3HT perovskite solar
           cell at ambient condition
    • Abstract: Publication date: Available online 8 November 2019Source: PolymerAuthor(s): Arnab Shit, Pousali Chal, Sanjoy Mondal, Arun K. Nandi Recently, mixing of foreign polymers with perovskite increases light absorption yielding a large increase of power conversion efficiency (PCE) and also increasing longevity of perovskite solar cells (PSCs). The previous studies are limited at dry or at very low humid conditions. Here, for practical use, we report a new series of poly(vinylidene fluoride) (PVDF)-perovskite (MAPbI3) hybrid solar cells made from different PVDF concentrations e.g. 0.0, 0.25, 0.5, 1.0, 2.5, 5.0 mg/ml, and are designated as H1, H2, H3, H4, H5, and H6, respectively. The average grain size, measured from SEM images of MAPbI3 (312 ± 91 nm) has decreased with increasing PVDF concentration showing a minimum (215 ± 43 nm) for H5 sample. UV–Vis absorption spectra show the highest absorption for H5 sample for all the wavelengths. The intensities and width of X-ray diffraction peaks increase in the hybrids (H3 and H5) from pristine perovskite indicating increase of crystallinity and crystalline size. We have used an interfacially engineered, band gap modulated poly(3-thiophene acetic acid)–co-poly(3-hexyl thiohene) P3TTA - co - P3HT, with 43 mol% P3TAA content as hole transporting material (HTM) and TiO2 as electron transporting material (ETM) to fabricate the cell. The PCE, measured on illumination with a light of one sun at ambient condition (humidity 75–85%, temperature 30 °C), is 12% for H5 PSC, highest reported so far, and it is 20% higher from pristine PSC. The incident photon to current conversion efficiency (IPCE) data exhibit strong absorption in the broad range 300–800 nm showing a maximum IPCE value of 84%. Impedance spectral data indicate that lifetime of photo-generated charges are highest (48.4 m s) explaining the highest PCE value for H5-PSC compared to other hybrids. The longevity of the H5-PSC is significantly (54%) higher than PSC made with pristine perovskite measured and stored under identical ambient condition.Graphical abstractImage 1
       
  • PAA-b-PPO-b-PAA triblock copolymers with enhanced phase separation and
           inverse order-to-order phase transition upon increasing temperature
    • Abstract: Publication date: Available online 8 November 2019Source: PolymerAuthor(s): Chao Lv, Ruiyang Wang, Jia Gao, Ning Ding, Shunni Dong, Jingjing Nie, Junting Xu, Binyang Du Enhanced phase separation and inverse order-to-order phase transition with increasing temperature was observed for a series of poly (acrylic acid)-b-poly (propylene oxide)-b-poly (acrylic acid) triblock copolymers with various block lengths by temperature-variable synchrotron small-angle X-ray scattering (SAXS). This abnormal phase behavior was attributed to the change of hydrogen (H)-bonding interaction in block copolymers upon increasing temperature and theoretically explained from thermodynamic viewpoint. The temperature-dependent FTIR analysis revealed that increasing temperature led to the weakening of overall H-bonding interactions and the increase of free CO and C–O–C groups. The Flory-Huggins interaction parameter χ of PAA and PPO blocks was positive and increased with increasing temperature as determined from the SAXS profiles of disordered block copolymer. The thermodynamic calculation indicated that the increase of ΔH was larger than the decrease of –TΔS with increasing temperature because of the relatively large value of χ, leading to the increase of overall ΔGmix and hence the enhanced phase separation at higher temperature.Graphical abstractImage 1
       
  • Bamboo-like nanostructures prepared using template-based wetting methods:
           Molecular arrangements of polyimide and carbon tubes in cylindrical
           nanopores
    • Abstract: Publication date: Available online 8 November 2019Source: PolymerAuthor(s): Yi-Hsuan Tu, Chih-Ting Liu, Chien-Wei Chu, Hung-Chieh He, Chun-Wei Chang, Jiun-Tai Chen With excellent mechanical and physical properties, polyimides (PIs) possess diverse applications in different fields. PI-based materials can also be converted to carbon materials by high temperature carbonization processes. The fabrication and properties of PI-based nanomaterials and corresponding carbon nanomaterials, however, have been less investigated, especially the packing behaviors of the polymer chains. In this work, we study the fabrication and characterization of PI nanostructures using the solution wetting (SW) method and the solvent-annealing-induced nanowetting in templates (SAINT) method. Poly(amic acid) (PAA) tubes are first prepared using anodic aluminum oxide (AAO) membranes. After thermal imidization and carbonization processes, PI and carbon tubes can be obtained, respectively. Bamboo-like structures are also observed in the tubes, which can be attributed to the Marangoni effect induced by the gradient of the surface tensions during the solvent evaporation process. Moreover, the laser Raman micro-spectroscopy results show that the packing behaviors of the polymer chains in the nanostructures prepared by the SAINT method are better than those prepared by the SW method, indicating that the solvent annealing process can improve the chain packing while assisting the infiltration of polymer chains in the nanopores.Graphical abstractImage 1
       
  • Unusual thickness relaxation of spin-coated polystyrene ultrathin films in
           the glassy state
    • Abstract: Publication date: Available online 7 November 2019Source: PolymerAuthor(s): Chunming Yang, Isao Takahashi Relaxation in the thickness of ultrathin polystyrene films (thickness 
       
  • Transformation from form II to form I accelerated by oriented lamellae in
           Polybutene-1
    • Abstract: Publication date: Available online 7 November 2019Source: PolymerAuthor(s): Jinlong Chen, Binghua Wang, Taicheng Sun, Jianwei Xu, Jingbo Chen, Bin Zhang Promoting the transformation from Form II to Form I in polybutene-1 (PB-1) is deemed to be crucial and demanded for commercial applications. The mechanism of phase transition is previously described in terms of thermal or mechanical stress applied between the crystalline and amorphous regions. Here, we find that the structural feature of lamellae, such as lamellar orientation, can also be a vital factor to facilitate the transition process. In-situ X-ray measurement allows us to observe a power-law decrease of the induction time of Form I, ti, with increasing the degree of orientation of (200) plane of initial Form II crystallites, f(200): ti ∼ f −1 (200). By comparison with the randomly oriented lamellae, the well-defined oriented lamellae perpendicular to the flow direction are in favor of shortening the ti. The acceleration of this phase transition may be due to more tie molecules distributed in the oriented lamellae increasing the probability of the formation of Form I nuclei.Graphical abstractImage 1
       
  • Distribution of water states within Poly(HEMA-co-HPMA)-based
           hydrogels
    • Abstract: Publication date: Available online 7 November 2019Source: PolymerAuthor(s): Sara Abasi, Ryan Davis, Daria Anna Podstawczyk, Anthony Guiseppi-Elie The distribution of water states within hydrogels is implicated in their biotechnical performance. Formulated synthetic hydrogels based on poly(2-hydroxyethylmethacrylate-co-N-(2-hydroxypropyl) methacrylamide) [poly(HEMA-co-HPMA)] of varying cross-linker concentration and monomer mole ratio were studied for their degree of hydration and water distribution. Cross-linker concentrations of 0.1, 0.5, 1.0, and 3.0 mol% tetraethylene glycol diacrylate (TEGDA) were studied when the HEMA:HPMA mole ratios were selected to be 1:0 and 4:1. Additionally, the cross-linker concentration of 1.0 mol% TEGDA was studied in detail when the HEMA:HPMA ratio was selected to be 1:1. The degree of hydration was determined by gravimetry. The distribution among water states was determined from Gaussian deconvolution of the DSC thermograms and use of ΔHf(T) for T 
       
  • Phase separation and performance of polyethersulfone/cellulose
           nanocrystals membranes
    • Abstract: Publication date: Available online 6 November 2019Source: PolymerAuthor(s): Fatemeh Lessan, Mohammad Karimi, Jose Leobardo Bañuelos, Reza Foudazi We investigate the effect of cellulose nanocrystals (CNC) as a hydrophilic nanoparticle on the characteristics of polyethersulfone (PES) based membranes. The membranes are fabricated using typical nonsolvent induced phase separation (NIPS) method. We study the radius of gyration and aggregation of PES in dimethylformamide in the presence of CNC, the rheological behavior of dope dispersions, and the morphology, permeability, irreversible fouling, MWCO, ζ-potential, water contact angle and mechanical properties of final membranes. Small-angle X-ray scattering analysis show that high CNC and water concentrations lead a transition from mass fractal to surface fractal scattering. Addition of CNC into the PES solution induces the formation of an interconnected polymer network, yet excess CNC loading eventually results in a heterogeneous composite with diminished mechanical properties. Additionally, an increase in the viscosity and elasticity of the dope dispersions is observed in the presence of CNC, which changes the morphology of the final membranes. The CNC concentration up to 1.5 wt% increases the water permeability of membrane while retaining the same dye rejection and fouling resistance as the neat one. The enhanced performance of PES/CNC membrane is related to the rheological properties and phase separation behavior of the cast dispersion. The results of water contact angle analysis confirm the higher wettability of the CNC filled membranes. Incorporation of up the 2 wt % CNC leads to a higher strength but lower ductility in comparison to the neat PES membrane.Graphical abstractImage 1
       
  • Molecular dynamics simulation of amorphous polyethylene (PE) under cyclic
           tensile-compressive loading below the glass transition temperature
    • Abstract: Publication date: Available online 5 November 2019Source: PolymerAuthor(s): Qiang Bao, Zhenyu Yang, Zixing Lu The intensive applications of polymer in many engineering composites have imposed an urgent need on the understanding of the mechanical behavior and deformation mechanism of the polymer under cyclic loading. This paper presents the results of a numerical study on the behavior of amorphous polyethylene (PE) subjected to cyclic tensile and compressive loads using molecular dynamics (MD) simulations, based on a united-atom approach. The effects of polymer chain length, the number of chains and strain rates are studied at first. Hysteresis loops, as well as visco-elastoplastic of PE under cyclic loading predicted by MD simulations are qualitatively in agreement with previous experiments. Three distinct hysteresis loops observed in successive loading-unloading reveal the contribution of elasticity, viscosity and plasticity under different loading strains, respectively. The rubber-like recovery behavior of PE at low temperature is attributed to that the mobility of molecular chains is constrained at low temperature. Energy analysis shows that the van der Waals energy and dihedral angle energy are considered to be the primary factors that affects the cyclic behavior of PE.Graphical abstractImage 1094
       
  • Dewetting behavior of self-assembled films of polystyrene-b-poly(methyl
           methacrylate) induced by solvent vapor annealing
    • Abstract: Publication date: Available online 5 November 2019Source: PolymerAuthor(s): Jintao Zuo, Gangyao Wen, Kun You We once studied the dewetting behaviors of spin-coated and Langmuir−Blodgett (LB) films of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) induced by solvent vapor annealing (SVA), and revealed the different contact degrees between hydrophilic PMMA blocks and the substrate in the above two kinds of films. In this work, the dewetting behavior of self-assembled films of PS-b-PMMA induced by SVA was studied for the first time. Effects of copolymer composition, solution concentration, and SVA time were systematically considered. With the increase of SVA time, continuous flat self-assembled films undergo complicated progresses including the formation of bicontinuous or holed structures, the formation of droplets, and the periodic increase and decrease of droplet sizes. The periodic evolutions of droplet sizes in the self-assembled films are similar to those in our previous LB films but different from their single evolutions in the spin-coated films. It indicates that the former two kinds of films have good contact degrees between PMMA blocks and the substrate. Furthermore, the contact degrees in the self-assembled films are better than those in the LB films. In our current minds, the contact degrees are mainly related to the length of hydrophilic blocks and their parallel/vertical segment ratio to the substrate.Graphical abstractImage 108925
       
  • Reactive splicing compatibilization of immiscible polymer blends:
           Compatibilizer synthesis in the melt state and compatibilizer architecture
           effects
    • Abstract: Publication date: Available online 2 November 2019Source: PolymerAuthor(s): Bin Wei, Qingqing Lin, Xin Zheng, Xiaoying Gu, Li Zhao, Jianchun Li, Yongjin Li Reactive compatibilization is an effective method to improve the compatibility of immiscible polymer blends. The in-situ-formed graft/block copolymers should be thermodynamically located at the interface to bridge the neighboring phases. Unfortunately, they are often pulled out of the interface because of the asymmetric molecular structures. Here, we propose a new strategy to compatibilize immiscible polymer blends called reactive splicing compatibilization. Poly (styrene-co-glycidyl methacrylate) (SG) with high glycidyl methacrylate (GMA) content is used as the reactive backbone chain. Both poly (l-lactic acid) (PLLA) and poly (butylene adipate-co-terephthalate) (PBAT) molecular chains can be easily grafted onto the SG main backbone by the reaction of the terminal carboxylic acid groups with the epoxide groups in the melt. Direct melt blending SG with PLLA and/or PBAT leads to reactive compatibilizers with various molecular architectures, which are used for subsequent compatibilization of PLLA/PBAT blends. It was found that the compatibilizer architecture significantly affects the compatibilization efficiency. The best compatibilization occurs with a reactive compatibilizer of SG-g-PBAT with the SG to PBAT weight ratio of 1:2. The compatibilized PLLA/PBAT (50/50 w/w) blend has precise co-continuous phase morphology with very few micelles. The blend exhibits extremely high Charpy notched impact strength of 90.2 kJ/m2 and tensile strength of 33.3 MPa. The principle of the facile splicing compatibilization strategy is highly applicable to many other immiscible blends with both components containing reactive groups.Graphical abstractWe report the splicing compatibilization strategy for immiscible polymer blends. The compatibilizer architecture effects on the compatiblization efficiency were investigated.Image 1
       
  • Covalent grafting of unfunctionalized pristine MWCNT with Nylon-6 by
           microwave assist in-situ polymerization
    • Abstract: Publication date: Available online 31 October 2019Source: PolymerAuthor(s): Roberto Yañez-Macias, Ernesto Hernández Hernández, Carlos A. Gallardo-Vega, Raquel Ledezma-Rodríguez, Ronald F. Ziolo, Yucundo Mendoza Tolentino, Salvador Fernández Tavizon, Carlos A. Avila-Orta, Zureima Garcia-Hernández, Pablo Gonzalez Morones Covalent grafting of nylon-6 (Ny-6) and pristine multi-walled carbon nanotubes (MWCNT-P) was performed in-situ via microwave assist polymerization (MAP) of ε-caprolactam and 6-aminocaproic acid at different power and time conditions. The results showed that the microwave dielectric heating of the MWCNT-P activates the nanotube vacancies to react with the amine group of 6-aminocaproic acid at 175 °C. When the reaction temperature reaches 230 °C, Ny-6 polymerization ensues, simultaneously, with insertion of Ny-6 chains on the amine-activated MWCNT to obtain a nanohybrid, MWCNT-Ny, with a grafted Ny-6 coating of 14 nm. The hybridization reaction therein affects the entire polymerization process and the molecular weight and yield of both the hybrid and Ny-6. Raman, XPS and electrical conductivity data for the MWCNT-Ny films show that the nanotube structure remains intact in the films which display an electrical surface conductivity range of 0.47–0.06 S/m. The compatibility and dispersion of the MWCNT-Ny nanohybrid in Ny-6, as observed by crystallization and fusion of the so-formed hybrid polymer nanocomposite, HPNC, exceed those obtained by conventional methods of preparation using ultrasound and functionalized nanotubes.Graphical abstractImage 1
       
  • Reexamination of the microphase separation in MDI and PTMG based
           polyurethane: Fast and continuous association/dissociation processes of
           hydrogen bonding
    • Abstract: Publication date: Available online 31 October 2019Source: PolymerAuthor(s): Zhengyang Kong, Qiang Tian, Ruoyu Zhang, Jingbo Yin, Lei Shi, Wu Bin Ying, Han Hu, Chenkai Yao, Kai Wang, Jin Zhu Microphase separation and hard segment packing in polyurethanes remain areas of active research interest in order to optimize their performances. In this work, a commercial thermoplastic polyetherurethane (1180A, BASF) is used as a model system to investigate the packing of hard segments during microphase separation. Although DSC studies show several transitions during heating and cooling, no crystal structure is detected by XRD. Nevertheless, these endothermic and exothermic peaks should belong to the complicate hard/soft segment interaction and related structures. Time and temperature dependent FTIR spectra prove fast hydrogen bonding association/dissociation phenomena in the current system. We infer that such fast process can induce loosely or irregular packing of hard segments during cooling. On the other hand, the continuous change of degree of microphase separation with temperature implies different hard domain structures and stabilities at different temperatures. At high temperature, only hard domains with large size and compactly packed segments can survive. This is because the thermodynamic stability of hard domains is decided by the strength of hydrogen bonding and the size of hard domain, similar with classical description of ‘nucleation’. Morphological information obtained by fitting the SAXS curves proves the validity of the above model. Moreover, the significant difference in mechanical properties before and after thermal treatment can be explained by the microstructure model.Graphical abstractImage 1
       
  • Ionic liquid copolymerized polyurethane membranes for pervaporation
           separation of benzene/cyclohexane mixtures
    • Abstract: Publication date: Available online 31 October 2019Source: PolymerAuthor(s): Tao Xi, Yingying Lu, Xinyu Ai, Lin Tang, Lulu Yao, Wentao Hao, Peng Cui Benzene and cyclohexane are both important raw materials in polymer chemical industry. However, they are hard to be separated via the traditional distilling methods. In this work, ionic liquid copolymerized waterborne polyurethane (IL-co-PU) membranes were proposed for the pervaporation separation of benzene/cyclohexane mixtures. The results, including swelling rate, diffusion coefficients, partial flux, permeance and selectivity, showed that the IL-co-PU membranes could preferentially absorb and transfer benzene molecules rather than cyclohexane. The ILs might have functioned as facilitated transporter in the membranes. The permeation flux and separation factor of the IL-co-PU membranes increased simultaneously with the increase of IL contents. That is, these membranes had no trade-off between permeability and selectivity, which most of the polymer membranes suffered. With consideration of the good performance and easy handling property of the IL-co-PU membranes, they are of great potential in pervaporation separation of benzene/cyclohexane mixtures.Graphical abstractImage 10948660
       
  • Driving the polymerization of PEDOT:PSS by means of a nanoporous template:
           Effects on the structure
    • Abstract: Publication date: Available online 30 October 2019Source: PolymerAuthor(s): Andrea Pinna, Maria Francesca Casula, Luca Pilia, Antonio Cappai, Claudio Melis, Pier Carlo Ricci, Carlo Maria Carbonaro Poly(3,4-ethylenedioxythiophene) (PEDOT) polymerization has been carried out both in a template-free environment and inside the nanopores of SBA-15 mesoporous silica. Comparing the two methods and the secondary doping of commercial PEDOT:PSS, we were able to study the structural effect of the templated polymerization via a multi-technique approach. We found that the confined polymerization favours a more linear configuration of the polymer chains, in a similar way to the well-known secondary doping with organic solvents. Moreover, comparison of computational and experimental results suggests that the PEDOT mean chain length is greater when the polymerization occurs in the nanoporous template, promoting the formation of a polymer with larger molecular weight and crystallinity.Graphical abstractImage 1
       
  • Confinement effect on spatio-temporal growth of spherulites from
           cellulose/ionic liquid solutions
    • Abstract: Publication date: Available online 30 October 2019Source: PolymerAuthor(s): Ashna Rajeev, Basavaraj Madivala G In this study, we investigate the growth kinetics and through-the width-distribution of polycrystalline morphologies developed in the confined microcrystalline cellulose (MCC)/1-allyl-3-methylimidazolium chloride (AmimCl) solution films at controlled temperature and humidity. Being an anti-solvent, the diffusion of moisture from the edges to the interior of the cellulose film causes the aggregation and rearrangement of cellulose molecules. When the confined films of thickness varying between 100 μm and 850 μm are incubated for over 25 days, different polycrystalline morphologies evolve. While a skin-transition-core morphological distribution is observed in the films of thickness ≥ 700 μm, interesting morphologies such as cylindrites, shish-kebab, deformed spherulites are observed in confined films of thickness ≤ 500 μm. The formation of concentric rings called terraces is also observed on the spherulites in highly confined films, signaling two dimensional (2-D) growth. The growth kinetics is observed to follow the classical Avrami theory. The Avrami exponent value, n, in the highly confined film (100 μm) is found to be close to 2, indicating 2-D growth.Graphical abstractImage 1
       
  • Single-chain conformation of carboxylated schizophyllan, a triple helical
           polysaccharide, in dilute alkaline aqueous solution
    • Abstract: Publication date: Available online 30 October 2019Source: PolymerAuthor(s): Yu Tomofuji, Kazuto Yoshiba, Bjørn E. Christensen, Ken Terao Synchrotron-radiation small-angle X-ray scattering measurements were carried out for a schizophyllan (SPG) sample with the weight-average molar mass Mw of 340 kg mol−1 and five carboxylated SPG (sclerox) samples with different degrees of substitution (DS) ranging from 0.18 to 0.45 in 200 mM aqueous NaOH including 10 mM NaCl to determine Mw, the second virial coefficient A2, the particle scattering function P(q), and the radius of gyration 〈S2〉. Positive A2 values indicated that this alkaline solvent was a good solvent for all polysaccharide samples investigated. The resultant Mw values (∼100 kg mol−1) were much smaller than that for the trimer in aqueous NaCl at neutral pH, indicating all SPG and sclerox samples dissolved as single chains in the alkaline solvent. Both P(q) and 〈S2〉 were consistently explained by the wormlike chain model. The obtained parameters were almost independent of DS. While the chain stiffness (12–18 nm) in terms of the Kuhn segment length or twice the persistence length was similar to those for the other single chain polysaccharides, the helix pitch per residue (0.1 nm) was quite smaller than the trimer state (0.3 nm). This shrunken main-chain helical structure is most likely due to hydrophobic interactions between helical main chain and side groups.Graphical abstractImage 1
       
  • Ionic liquid-based monolithic porous polymers as efficient flame retardant
           and thermal insulation materials
    • Abstract: Publication date: Available online 29 October 2019Source: PolymerAuthor(s): Zhaoqi Zhu, Huijuan Wei, Fei Wang, Hanxue Sun, Weidong Liang, An Li It remains very challenging to create porous materials with both good thermal insulation and flame retardancy for construction of energy-saving buildings. Herein, we report the first example of ionic liquid (IL)-based monolithic porous polymers as efficient flame retardant with good thermal insulation, which was synthesized by polymerization of vinyl tetrafluoroborate ionic liquid monomers with polydivinylbenzene (PDVB) as a crosslinker through a facile solvothermal synthesis followed by freeze drying (named as PDVB-BF4ILs). The PDVB-BF4ILs is mainly composed of mesopores with a pore sizes ranging from 8.8 to 20.3 nm. The PDVB-BF4ILs has a decomposition temperature of higher than 320 °C. The PDVB-BF4ILs show high thermal insulation with a low thermal conductivity (0.019W m−1 k−1) in air. Also, the PDVB-BF4ILs possesses excellent flame retardancy with a low peak heat released rate (139.3W g−1). Compared with porous PDVB, the pHRR of PDVB-BF4ILs was reduced by approximately 75%. Torch burn test implies that the PDVB-BF4ILs shows self-extinguishing behavior without generation of any melt dripping, indicating an excellent flame retardancy. Taking advantages of simple fabrication process, easily to be scaled-up, excellent thermal insulation and flame retardancy, such IL-based monolithic porous polymers may have great potential for real applications.Graphical abstractImage 1
       
  • Synthesis and Characterization of a highly crystalline
           benzotriazole-selenophene copolymer semiconductor
    • Abstract: Publication date: 5 December 2019Source: Polymer, Volume 184Author(s): Eunbyuel Lee, Woojin Shin, Onyu Bae, Felix Sunjoo Kim, Ye-Jin Hwang A new donor (D)-acceptor (A) type copolymer semiconductor based on benzotriazole and selenophene was designed and synthesized. The benzotriazole-selenophene copolymer (P(BTz-Se)) showed a highly crystalline lamellar packing structure with a lamellar interchain distance of 1.77 nm and large mean crystalline domain size of 17.26 nm. The average field-effect hole mobility of an as-cast P(BTz-Se) film was 2.93×10−4 cm2 V−1 s−1. After annealing the polymer film at 150 °C, a 55-fold enhanced average hole mobility (1.61×10−2 cm2 V−1 s−1) with high on/off current ratio (1.7×106) was observed. In addition to the great charge carrier mobility, P(BTz-Se) showed a narrow energy bandgap (1.69 eV) and broad optical absorption range with excellent absorption coefficient, suggesting that this copolymer semiconductor may also be a good electron donor in organic photovoltaic devices.Graphical abstractImage 1
       
  • Photopolymerization of acrylate resin and ceramic suspensions with
           benzylidene ketones under blue/green LED
    • Abstract: Publication date: 5 December 2019Source: Polymer, Volume 184Author(s): Hongyuan Fu, Yunzhao Qiu, Jian You, Tingting Hao, Bingfeng Fan, Jun Nie, Tao Wang Finding novel photoinitiators with photobleaching properties suitable for long-wavelength LED light sources is important for their potential use in the photocuring ceramic suspensions containing acrylate resin. Two D-π-A-π-D conjugated benzylidene ketones with visible light absorption (TPAK and CZK) were synthesized and evaluated as photoinitiators in the photocuring of acrylate resin and ceramic suspension under blue (460 nm)/green (520 nm) LED sources. Results showed that the two photoinitiators have high photoinitiating activity and can effectively produce thick-layer curing in acrylate resin and ceramic suspension due to their quick photobleaching properties under 460 nm and 520 nm LED light sources. The curing depth of the ceramic suspensions was measured as a function of the concentration of TPAK and CZK and the energy level of the LED light source. Jacob's equation was used to determine the critical energy Ec and depth sensitivity Dp of every suspension with different concentrations of benzylidene ketones.Graphical abstractImage 1
       
  • Highly thermally stable mesoporous Poly(cyanate ester) featuring
           double-decker–shaped polyhedral silsesquioxane framework
    • Abstract: Publication date: Available online 26 October 2019Source: PolymerAuthor(s): Wei-Cheng Chen, Mahmoud M.M. Ahmed, Chih-Feng Wang, Chih-Feng Huang, Shiao-Wei Kuo In this study we prepared cyanate ester–functionalized double-decker silsesquioxane (DDSQ) nanoparticles through a sequence of hydrosilylation of nadic anhydride (ND) with DDSQ and then treat with 4-aminophenol to provide DDSQ-ND-OH, and reaction with cyanogen bromide (BrCN) to form DDSQ-ND-OCN (a bis-phenyl cyanate ester DDSQ). After thermal curing of DDSQ-ND-OCN, we obtained mesoporous poly(cyanate ester) (PCE)/DDSQ frameworks that displayed high thermal stabilities and char yields since the inorganic DDSQ nanoparticles were dispersed in the PCE matrix homogeneously, as revealed using electron microscopy. Thermal polymerization at 210 °C provided a PCE/DDSQ framework having a thermal decomposition temperature (516 °C) and char yield (70 wt%); these values increased to 600 °C and 81 wt%, respectively, after thermal treatment at 420 °C. More interestingly, these mesoporous PCE/DDSQ frameworks displayed electrochemical properties better than those of other non-carbonized materials.Graphical abstractImage 1
       
  • Two-dimensional non-close-packed arrays of polystyrene microspheres
           prepared by controlling the size of polystyrene microspheres
    • Abstract: Publication date: Available online 26 October 2019Source: PolymerAuthor(s): Donghoi Kim, Dongsoo Jang, Hyunkyu Lee, Jeewoo Lim, Chinkyo Kim Randomly formed close-packed arrays of 3-μm-large polystyrene microspheres on a sapphire substrate by drop-casting were found to convert to two-dimensional non-close-packed ones when the microsphere-coated substrate was dipped into and taken out of a chloroform/ethanol mixed solution with specific volume fractions. The conversion was found to be associated with (1) the increased center-to-center distance between nearest neighboring microspheres caused by the increase in size and (2) the subsequently increased edge-to-edge distance between them caused by the decrease in size with their positions not much changed. The increase of microspheres in size was due to swelling by absorbing chloroform. The subsequent decrease of microspheres in size was due to deswelling caused by gradual change in the solvent environment during evaporation. The dependence of conversion from closed-packed arrays to non-close-packed ones on the volume fraction of each constituent was investigated. This type of conversion was found to occur readily on both sapphire and Si substrates.Graphical abstractImage 1
       
  • Aliphatic polyketones via cross-metathesis polymerization: Synthesis and
           post-polymerization modification
    • Abstract: Publication date: Available online 25 October 2019Source: PolymerAuthor(s): Fu-Rong Zeng, Jing Xu, Qi Xiong, Kai-Xuan Qin, Wei-Jun Xu, Yue-Xin Wang, Zan-Jiao Liu, Zi-Long Li, Zi-Chen Li Polyolefins attract considerable attention due to their vast consumption and wide application. In this study, cross-metathesis polymerization (CMP) is demonstrated to be an efficient and feasible method for the synthesis of aliphatic polyketones. The synthetic route features good yield, mild condition and easy operation. The success of CMP relies on the high cross-metathesis tendency between α-olefin and vinyl ketone units of monomer 2. Optimization of polymerization condition was conducted to generate unsaturated polyketone P0 (Mn,GPC = 14 kDa), and the results of kinetic study verified high efficiency and structural integrity of this system. Furthermore, post-polymerization modification of P0 by using thiol-Michael chemistry furnished functional polyketones P1–P6, and full conversion of the internal vinyl ketone groups of P0 was observed in each case. The pristine and functional polyketones P0–P6 were virtually soluble in most common organic solvents. In particular, hydrophobic and fluorescent polyketones (P5 and P6) were also obtained by this means. Therefore, this synthetic strategy shows promising future and exemplifies huge potential for the synthesis of a diverse range of functional polyketones.Graphical abstractImage 1
       
  • A simple and convenient route to synthesize novel hyperbranched Poly(amine
           ester) with multicolored fluorescence
    • Abstract: Publication date: Available online 4 September 2019Source: PolymerAuthor(s): Yuqun Du, Tian Bai, Hongxia Yan, Yan Zhao, Weixu Feng, Wanqing Li Multicolored fluorescence stemed from the nonconventional luminescent polymers without aromatic units is an interesting and meaningful property. So far, a few such polymers bearing multicolored fluorescence are reported; its species, however, are relatively little. Herein, we synthesized a kind of novel water-soluble hyperbranched poly(amine ester) (HPAE) via a straightforward transesterification polycondensation reaction using inexpensive and easily available chemicals. Intriguingly, the pure HPAE could emit blue, green and red luminescence when irradiated by different excitation wavelengths. The TEM result shows that the synergy effect of intra-/intermolecular hydrogen bonds and hydrophobic effect could induce the HPAE to self-assemble and form supramolecular HPAE in water. Such supramolecular HPAE further promote to form stronger through-space conjugation, thus which is favourable for the emission. In addition, the significant solvent and pH dependence profiles of luminescence intensity are also observed. In particular, the HPAE can be used to detect metal ions, and there is strong selective quenching in respect of Fe3+. Therefore, the HPAE show a potential probe for Fe3+.Graphical abstractImage 1
       
  • Crack propagation under static and dynamic boundary conditions
    • Abstract: Publication date: Available online 14 July 2019Source: PolymerAuthor(s): Yuko Aoyanagi, Ko Okumura Velocity jumps observed for crack propagation under a static boundary condition have been used as a controlling factor in developing tough rubbers. However, the static test requires many samples to detect the velocity jump. On the contrary, crack propagation performed under a dynamic boundary condition is timesaving and cost-effective in that it requires only a single sample to monitor the jump. In addition, recent experiments show that velocity jump occurs only in the dynamic test for certain materials, for which the velocity jump is hidden in the static test because of the effect of stress relaxation. Although the dynamic test is promising because of these advantages, the interrelation between the dynamic test and the more established static test has not been explored in the literature. Here, by using two simulation models, we elucidate this interrelation and clarify a universal condition for obtaining the same results from the two tests, which will be useful for designing the dynamic test.Graphical abstractImage 1
       
  • Miniaturized characterization of polymers: From Synthesis to rheological
           and mechanical properties in 30 mg
    • Abstract: Publication date: Available online 24 October 2019Source: PolymerAuthor(s): S. Petisco-Ferrero, R. Cardinaels, L.C.A. van Breemen The determination of rheological and mechanical material properties becomes a challenge when the availability of material is limited to a few (milli)grams. This miniaturized testing is hampered by the contradicting requirements of small sample sizes (and thus surface areas) and sufficiently large generated torques and forces. In this paper we provide a feasible methodology to determine the relevant material parameters in terms of processing and mechanical performance starting from 30 mg of material, using micropillars with a diameter of 1 mm. Complex viscosity in small amplitude oscillatory shear as the relevant parameter for thermoconformation processes is determined by means of eccentric rheometry. Herein, the sample is placed off-centered, which results in an increase in the generated torque without the need for increasing the size of the sample. By combining experimental data and numerical simulations, we show that the choice of the pillar aspect ratio is essential to maintain a homogeneous sample deformation and thus to extract correct rheological parameters. Values obtained with eccentric rheometry collapse with those obtained from standard rheometry. The intrinsic mechanical behavior is evaluated at room temperature and the yielding kinetics is studied. The methodology developed here can be extended to other systems and testing conditions, allowing a full material characterization in the liquid as well as in the solid state with only 30 mg of material.Graphical abstractImage 1
       
  • Unusual excitation wavelength tunable multiple fluorescence from
           organocyclo-phosphazene microspheres: Crosslinked structure-property
           relationship
    • Abstract: Publication date: Available online 24 October 2019Source: PolymerAuthor(s): Majid Basharat, Yasir Abbas, Wei Liu, Zahid Ali, Shuangkun Zhang, Wenqi Zou, Zhanpeng Wu, Dezhen Wu Herein, we reported the organocyclophosphazenes (OCP) microspheres with excitation wavelength tunable fluorescence (EWTF) emission by reacting hexachlorocyclotriphosphazene and 4,4′-methylenedianiline via one-pot facile method. The as-prepared microspheres exhibit blue (λλex 280 nm), green (λλex 365/420 nm) and red (λλex 546 nm) tunable fluorescence emissions in the ultraviolet (UV) and visible region. The microspheres have shown broadband semiconductors like absorptions in UV and visible regions indicate the multiple bandgaps in the microspheres. The role of the crosslinked structure and property demonstrated that stable interactions are conceivable in microspheres than branched polymer, which imparted EWTF property. This study explored the cyclotriphosphazene as a platform for the synthesis of EWTF materials, and their potential utilization in the full spectrum tunable fluorescence and other light related technologies.Graphical abstractImage 1
       
  • Interplay Between Chemical and Physical Aging in Diethanolamine Cured
           Diglycidyl Ether of Bisphenol-A (DGEBA) Epoxy
    • Abstract: Publication date: Available online 23 October 2019Source: PolymerAuthor(s): Gabriel K. Arechederra, John D. McCoy, Jamie M. Kropka Thermomechanical properties during isothermal aging of diethanolamine (DEA) cured diglycidyl ether of bisphenol-A (DGEBA) were tracked using uniaxial compression and differential scanning calorimetry. The epoxy was cured at 70°C for 24 hours, following standard procedure, and then aged at one of four temperatures, T: 55°C, 65°C, 76°C or 105°C. The initial glass transition of cured DGEBA/DEA was 70°C and increased proportionally with the logarithm of time indicating that additional crosslinks had formed. Similarly, the yield stress, σy, increased, by up to 80%, proportionally with the logarithm of aging time until approximately 600 hours. After that time period, the increase in σy slows significantly. Aging also narrowed the yield peak and increased the post-yield flow stress. The changes in σy due to physical aging were separated from those due to chemical aging by testing samples combining both physical and chemical aging and comparing the results to those from (only) chemically aged samples. The proposed method for separating out the physical contributions can be used to predict the mechanical changes due to physical aging in slowly chemically evolving materials. The aging data are also utilized along with data on σy as a function of strain rate for unaged material to generate a tentative expression for σy as a function of strain rate, aging time and temperature. The derivation of this expression requires only the common assumption that the rate of change of σy /T with respect to log(strain rate) is independent of temperature and of aging time.Graphical abstractImage 1057
       
  • Sustainable elastomer of triazolinedione-modified Eucommia ulmoides gum
           with enhanced elasticity and shape memory capability
    • Abstract: Publication date: Available online 23 October 2019Source: PolymerAuthor(s): Hengchen Zhang, Cuihong Ma, Ruyi Sun, Xiaojuan Liao, Jianhua Wu, Meiran Xie Sustainable Eucommia ulmoides gum (EUG) was a biomaterial with the molecular structure of trans-1,4-polyisoprene and poor elasticity, and was usually considered as a hard rubber with a limited applications in rubber products. Triazolinedione (TAD)-based Alder-ene reaction was used to modify EUG to precisely tune the mechanical properties and effectively improve the elasticity by reducing crystallinity, introducing urazole groups, and forming hydrogen bonds between EUG molecules. By adjusting TAD feed, the modified EUG could become an excellent tough elastomer with combined high strength, elongation, and toughness; or a unique rubber with superhigh elongation, low Young's modulus, and good elastic recovery rate. Furthermore, the modified EUG displayed enhanced shape memory capability with fast shape recovery speed, high cyclic shape recovery rate after 10-cycle deformations, and large shape memory recoverable deformation. Therefore, these elastomers may have extended applications in tires and smart materials.Graphical abstractImage 1
       
  • Probing the structural evolution in deformed isoprene rubber
by in situ
           synchrotron X-ray diffraction and atomic force microscopy
    • Abstract: Publication date: Available online 23 October 2019Source: PolymerAuthor(s): Shuquan Sun, Fengyan Hu, Thomas P. Russell, Dong Wang, Liqun Zhang Developing a better understanding of the structural evolution in deformed polymers is key to designing new materials and structures that achieve superior mechanical properties. Here, we used in situ synchrotron wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM) nanomechanical mapping (AFM-NM) to assess the strain-induced crystallization (SIC) and the associated structural evolution and mechanical properties of peroxide vulcanized isoprene rubber (IR) as a function of crosslink density (ν) and strain. The WAXD and AFM-NM results show agreement in the onset strain of SIC. Crystalline reflections appears in the WAXD while a nanofibrillar structure is found by AFM-NM. The higher ν, the smaller is the onset strain of a steep upturn in the stress-strain curves, the smaller is the onset strain of SIC, the higher is the crystallinity as evidenced in the WAXD, and the larger is the amount of nanofibrils seen by AFM-NM. Both WAXD and AFM-NM results show the SIC occurs rapidly at high strains while most chains remain in the amorphous state. The elastic modulus of the formed nanofibrils that range in diameter from several to a hundred nanometers, is two times higher than that of the amorphous regions. From the WAXD and AFM-NM results, a schematic model of structural evolution is proposed and used to illustrate the self-reinforcement mechanism in IR.Graphical abstractImage 1
       
  • Alkaline stability of model anion exchange membranes based on
           poly(phenylene oxide) (PPO) with grafted quaternary ammonium groups:
           Influence of the functionalization route
    • Abstract: Publication date: Available online 23 October 2019Source: PolymerAuthor(s): R.-A. Becerra-Arciniegas, R. Narducci, G. Ercolani, S. Antonaroli, E. Sgreccia, L. Pasquini, P. Knauth, M.L. Di Vona We study the effect of pendent methyl groups on the alkaline stability of model anion exchange polymers based on poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) with grafted trimethylammonium groups. The polymer backbone is modified varying the synthesis procedure: by the bromination route, the ionomeric ammonium groups are inserted on the structural methyl group of PPO (Br-PPO-TMA), while by the chloromethylation route the ammonium groups are attached in the ortho-position to the methyl group of PPO (Cl-PPO-TMA). The properties of the membranes are studied by NMR and FTIR spectroscopy, thermogravimetry, water uptake, mechanical tensile tests, small-angle X-ray scattering (SAXS) and impedance spectroscopy. SAXS analysis indicates a better nanophase separation for Cl-PPO-TMA, which is consistent with a slightly larger water uptake and ionic conductivity. The properties of the two polymers are also compared before and after the aging in 2 M NaOH at 80 °C for different times. The thermogravimetric analysis shows the loss of the ammonium groups and the backbone ether cleavage after the alkali treatments. The samples prepared by the bromination route show a higher stability of ionic conductivity, presumably due a reduced alkaline attack of the ammonium groups, although DFT calculations do not show major differences of thermodynamic and kinetic reaction parameters. After alkaline treatment, the mechanical properties are more degraded for the Br-PPO-TMA compound. The decreased mechanical properties can be attributed to a reduction of the average chain length of PPO by alkaline scission of the ether links. Both synthesis routes have advantages and disadvantages, but the higher reproducibility and the better mechanical properties of samples prepared by chloromethylation are considered preponderant benefits.Graphical abstractImage 1
       
  • Enhanced dielectric and electrical energy storage capability of polymers
           with combined azobenzene and triphenylamine side groups by ring-opening
           metathesis polymerization
    • Abstract: Publication date: Available online 22 October 2019Source: PolymerAuthor(s): Yu Zhu, Fengwang Ma, Cuihong Ma, Huijing Han, Ruyi Sun, Hui Peng, Meiran Xie Polymers with strong polar side groups of combined push-pull azobenzene and triphenylamine were synthesized by ring-opening metathesis polymerization, and exhibited excellent dielectric and energy storage properties mainly due to highly dipolar polarization. The dielectric constant of polymer containing one azobenzene group and one triphenylamine group was 13.5, which was enhanced to 15.7 when one azobenzene group and two triphenylamine groups were incorporated into polymer in virtue of its higher dipole density. Besides, the dielectric loss of polymers was lowered to 0.004–0.025, and the stored-energy density of polymer can reach up to 5.09 J cm−3 at electric field strength of 270 MV m−1 with good charge-discharge efficiency of 86.4%. Therefore, polymers are promising for dielectric and electrical energy storage applications.Graphical abstractImage 1
       
  • A Thermo-Responsive Random Copolymer of Poly(NIPAm-co-FMA) for
           Smart Textile Applications
    • Abstract: Publication date: Available online 22 October 2019Source: PolymerAuthor(s): Zih-Siang Huang, Jia-Wei Shiu, Tun-Fun Way, Syang-Peng Rwei A thermo-responsive random copolymer of poly(N-isopropylacrylamide-co-furfuryl methacrylate) (NF-10) has been fabricated and applied in Nylon fabrics for smart textile applications. The copolymer was synthesized by free radical copolymerization of N-isopropylacrylamide (NIPAm) and furfuryl methacrylate (FMA) using 2,2’-azobis(2-methylpropionitrile) (AIBN) initiator. The copolymer was characterized by 1H nuclear magnetic resonance (NMR), fourier-transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The fabrics were dipped in a solution which NF-10 mixed with bismaleimide (BMI) to form a Diels-Alder bonded cross-linked fabric (D-A fabric) through Diels-Alder reaction, as a covalent network structure that around the fibers of the fabrics. Additionally, D-A fabric has been provided the excellent washing fastness of 86% and controlled the pore sizes by the temperature of phase change of NF-10, investigating via scanning electron microscope (SEM) and pore size analyzer (PSA). Finally, PNIPAm-based copolymer exhibits the excellent performances, promising for the smart textile applications and commercialization in the future.Graphical abstractImage 108613
       
  • Revisiting Flow-Induced Crystallization of Polyethylene Inversely: An in
           situ Swelling SANS Study
    • Abstract: Publication date: Available online 22 October 2019Source: PolymerAuthor(s): Tingting Wang, Nan Tian, Jie Chen, Lizhao Huang, Guangai Sun, Jian Gong, Dong LiuABSTRACTThe inherent mechanisms of flow-induced crystallization (FIC), especially the amorphous formation, have been revisited inversely, via in situ swelling small angle neutron scattering (SANS). The neutron contrast between crystalline and amorphous phases of crosslinked high-density polyethylene was strengthened by deuterated o-xylene-d10. Thereby, the morphological evolutions and kinetics of various FIC samples (imposed initial strain: 0.6, 0.9, 1.4, and 2.3) during the swelling process were obtained simultaneously. The half time for swelling to reach equilibrium decreases from ca.39100 s to 4500 s for S0.0 to S2.3. Moreover, , the evolutions of the expanded long period (LP) are similar to the swelling kinetics. Interestingly, the increment LPt-LP1 increases monotonically from 1.55 nm to 4.32 nm. However, the expanding ratio (LPt/LP1) first increases from 1.05 to 1.13 for S0.0 to S1.4, then decreases to 1.11 for S2.3. Combining ex situ small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) results, current work demonstrates that both crystalline degree and different morphology contribute to the influences of swelling. It suggests that the generated amorphous networks triggered by different strain were endued with various inherent structure and characters, and the nature of amorphous phase can severely affect the swelling behavior.Graphical abstractImage 108
       
  • SU-8 inkjet patterning for microfabrication
    • Abstract: Publication date: Available online 22 October 2019Source: PolymerAuthor(s): R. Bernasconi, M. Costa Angeli, F. Mantica, D. Carniani, L. Magagnin Controlled SU-8 inkjet printing constitutes an attractive approach to realize electronic microstructures, MEMS, microfluidic devices or transducers. Indeed, inkjet printing is the most promising low-cost manufacturing process capable of depositing functional materials with high resolution, making this technique attractive for micrometric patterning. On the base of these premises, it's here presented the possibility to successfully print SU-8 complex patterned structures. Indeed, two different diluted SU-8 mixtures are successfully printed and a deep analysis on the effect of the physical parameters of the solvent is presented. The main challenges in SU-8 inkjet patterning are individuated and discussed through the evaluation of different shapes presenting critical printing aspects. In addition, some possible approaches to address such challenges are presented. Finally, the possibility to use inkjet printed SU-8 masks as templates for metal electrodeposition is demonstrated.Graphical abstractImage 1
       
  • Facile rare-earth triflate-catalyzed esterification of cellulose by
           carboxylic anhydrides under solvent-free conditions
    • Abstract: Publication date: Available online 21 October 2019Source: PolymerAuthor(s): Suzuka Takeuchi, Akinori Takasu We report here the facile rare-earth triflate-catalyzed esterification of cellulose by carboxylic anhydrides, including acetic anhydride, at room temperature under solvent-free conditions. As a model, D-glucose was peraceylated using only equimolar amounts of acetic anhydrides against hydroxyl groups to give the expected 1,2,3,4,6-pentaacetyl α-D-glucopyranoside (crude yield 98%, 68% yield after recrystallization) under solvent-free condition. In the case of powdery microcrystalline cellulose, acetylation proceeded both in the absence of pyridine and solvent to give peracetylated cellulose, even in the bulk. From 1H NMR measurements, the degree of substitution (DS) was 3.0 (100% acetylation) and we concluded that Sc(OTf)3-catalyzed solvent-free esterification of cellulose had taken place. The number-average molecular weight (Mn), calculated using the 1H NMR intensity ratio based on the anomeric proton in the reducing terminus, was 1.7 × 104 (repeating unit of pyranose unit: 56).Graphical abstractImage 1
       
  • l-lactide)-based+nanocomposites+with+different+layered+doubled+hydroxides+as+nanofiller&rft.title=Polymer&rft.issn=0032-3861&rft.date=&rft.volume=">Influence of interfaces on the crystallization behavior and the rigid
           amorphous phase of poly(l-lactide)-based nanocomposites with different
           layered doubled hydroxides as nanofiller
    • Abstract: Publication date: Available online 21 October 2019Source: PolymerAuthor(s): Jing Leng, Paulina Szymoniak, Nian-Jun Kang, De-Yi Wang, Andreas Wurm, Christoph Schick, Andreas Schönhals Based on the three-phase model of semi-crystalline polymers, we determined all phase fractions of the NiAl-LDH/PLLA nanocomposite in dependence on the concentration of the nanofiller. Moreover, the rigid amorphous fraction (RAF) was separated into the RAFcrystal and the RAFfiller unbiasedly. A detailed comparison to the related nanocomposite system MgAl-LDH/PLLA was made considering that Mg and Ni have different atomic weights. As a first result is was found that NiAl-LDH/PLLA displays a higher crystallization rate compared to MgAl-LDH/PLLA, which is related to the different morphologies of the two nanocomposite systems. For both systems RAFcrystal increases with increasing concentration of the nanofiller. This means in the case of the nanocomposite not each crystal produces the same amount of RAF, as often assumed. Also, RAFfiller increases with the concentration for both systems but in a different way. This is discussed considering again the different morphologies of both nanocomposites.Graphical abstractImage 1
       
  • Structural evolution of hard-elastic polyethylene cast film in
           temperature-strain space: An in-situ SAXS and WAXS study
    • Abstract: Publication date: Available online 19 October 2019Source: PolymerAuthor(s): Yuanfei Lin, Xueyu Li, Xiaowei Chen, Minfang An, Qianlei Zhang, Daoliang Wang, Wei Chen, Lei Sun, Panchao Yin, Lingpu Meng, Liangbin Li Hard-elastic polyethylene (HEPE) cast films are the key intermediate product for producing PE microporous membranes (dry process) used as separators in Lithium battery. The effects of temperatures on the deformation mechanisms of HEPE cast films are systematically studied with in-situ synchrotron radiation small- and wide-angle X-ray scattering (SAXS/WAXS) techniques during stretching in a wide temperature range from 25 to 135 °C. The structural evolutions and mechanical behaviors show three distinct features, which contribute to the rough divisions of the temperature space into three regions (I/II/III) with α-I relaxation temperature (TαI) and the onset melting temperature (Tonset) as the boundaries. On the basis of the evolutions of the structural parameters like long period (Lm), micro-strain (εm), orientation parameter (f200) and crystallinity (Xc), etc., lamellar separation is the main deformation mode in the linear elastic strain zone. And microphase separation of interlamellar amorphous, lamellar crystal slipping and melt-recrystallization are proposed to determinate the later non-linear mechanical behaviors in the three temperature regions, respectively. The full view of deformation mechanisms in the 2D temperature-strain space aids to deepen the understanding of the nonequilibrium structural evolutions in hard-elastic polyethylene films and guide the manufacture of high-performance microporous membranes with dry process.Graphical abstractImage 1
       
  • The role of mandrel rotation speed on morphology and mechanical properties
           of polyethylene pipes produced by rotational shear
    • Abstract: Publication date: Available online 19 October 2019Source: PolymerAuthor(s): Hao Yang, Xiehuai Luo, Kaizhi Shen, Yi Yuan, Qiang Fu, Xueqin Gao, Long Jiang Properties of plastic products depend on their microstructure and morphology. To improve the pressure rating (maximum pressure) of plastic pipes, a novel rotational shear system (RSS) was developed in this study to fabricate plastic pipes with enhanced hoop tensile strength through applying hoop shear on the pipes using a rotational mandrel. Morphology study results showed that different morphologies of the HDPE pipes were produced when the mandrel rotated at 5 rpm, 7.5 rpm, 10 rpm, 12.5 rpm and 15 rpm. The hoop tensile strength and heat resistance of the pipes were found to increase rapidly with the rotation speed and the properties peaked at 7.5 rpm. At this speed, the hoop tensile strength and Vicat softening temperature (VST) increased by about 338% and 26.8 °C, respectively. The axial tensile strength of the pipe was also slightly improved under this condition. The high mechanical and thermal performance of the pipe produced at 7.5 rpm was attributed to homogeneously distributed shish-kebab structures throughout the pipe wall.Graphical abstractImage 1
       
  • Graphene oxide: An effective ionic conductivity promoter for phosphoric
           acid-doped poly (vinyl alcohol) gel electrolytes
    • Abstract: Publication date: Available online 18 October 2019Source: PolymerAuthor(s): Saeideh Alipoori, M.M. Torkzadeh, M.H. Mohamadzadeh Moghadam, Saeedeh Mazinani, Seyed Hamed Aboutalebi, Farhad Sharif Recently, incorporation of nanomaterials into gel electrolytes has been used to improve the electrochemical performance of energy storage devices. Here, graphene oxide-based gel electrolyte samples were prepared by exploiting Poly (vinyl alcohol) as the polymer matrix and H₃PO₄ as ion producer. There has been a significant improvement in ionic conductivity by adding a small amount of graphene oxide, 0.05 wt % and 0.1 wt % for large-area graphene oxide and small-area graphene oxide which is 23.85 ± 0.23 and 29.21 ± 0.06 mS cm−1, respectively. The improvement may be attributed to the homogeneous distribution of graphene oxide, acting as an ionic conductivity promoter. Moreover, graphene oxide sheets with small area have lower bulk resistance as they can move easily through the gel with high amount of bound water, resulting in high ionic conductivity. Additionally, the GO containing gel has superior mechanical properties (tensile modulus of 2.77 ± 0.65 MPa and tensile strength of 8.33 ± 1.99 MPa) and high cyclic stability (retained 89% of initial specific capacitance after 2000 cycles) compared to the one without GO which makes it a potential candidate for use as gel electrolyte in flexible and wearable electronic gadgets.Graphical abstractImage 1
       
  • Investigation of the features of alternating copolymerization of
           1,1-bis(4-dimethylsilylphenyl)ethylene and isoprene modified with additive
           
    • Abstract: Publication date: Available online 17 October 2019Source: PolymerAuthor(s): Qingchi Ma, Li Han, Hongwei Ma, Pibo Liu, Heyu Shen, Lincan Yang, Chao Li, Xinyu Hao, Yang Li Alternating copolymers consisting of a kind of mild electron-withdrawing 1,1-diphenylethylene (DPE) derivative and di-olefins, such as 1,1-bis(4-dimethylsilylphenyl)ethylene (DPE-2SiH) and isoprene (Ip), were successfully synthesized via anionic copolymerization using N,N,N′,N′-tetramethylethylenediamine (TMEDA) as the modifier and benzene as the solvent. Two mild electron-withdrawing groups (binary -SiH) existed in this system. Therefore, the reaction activity of DPE-2SiH was higher than that of dimethyl-[4(1-phenylvinyl)phenyl]silane (DPE-SiH), and DPE-2SiH was expected to be an appropriate co-monomer for polymerization with dienes. The addition of TMEDA was found to not only control the resulting sequence but also regulate the contents of cis- and trans-structures in the Ip units. To further explore the mechanism of polymerizing DPE-2SiH and isoprene with and without the use of the TMEDA additive, the target samples were carefully characterized by SEC, 1H NMR and in situ 1H NMR. By examining the results, the apparent rate constants of DPE-2SiH and Ip without TMEDA were 1.19 × 10−3 min−1 and 1.29 × 10−2 min−1, respectively, while those of DPE-2SiH and Ip with TMEDA were 4.47 × 10−5 min−1 and 3.05 × 10−5 min−1, respectively. The reactivity ratios rIp of isoprene with and without TMEDA were also calculated by the least square method and found to be 0.65 and 4.21, respectively, which illustrates the mechanisms of the copolymerization of DPE-2SiH and isoprene. By investigating the mechanism of the copolymerization process, the sequence can be controlled the alternating copolymerization can be facilely realized in a nonpolar solvent through the use of TMEDA. The alternating copolymers using this method have great significance both to regulation method of the microstructure of isoprene units and to the industrial production of functionalized materials. Then the alternating copolymers of DPE-2SiH and Ip were also applied to synthesize centipede-shaped grafted poly(isoprene)s (PIps). For the existence of bilateral -SiH groups in the chain, hydrosilylation of -SiH and alkynyl groups was performed at room temperature to avoid the unexpected reaction of the -SiH and alkenyl groups from the PIp branches.Graphical abstractImage 1
       
  • Konjac glucomannan/kappa carrageenan interpenetrating network hydrogels
           with enhanced mechanical strength and excellent self-healing capability
    • Abstract: Publication date: Available online 16 October 2019Source: PolymerAuthor(s): Yulong Chen, Cunzhen Song, Yukai Lv, Xin Qian Konjac glucomannan (KGM) hydrogels have attracted considerable interest in many fields, such as drug delivery, tissue engineering, bio-medicine, and food processing, due to their good biocompatibility, biodegradability, gelation performance and security. However, KGM hydrogels prepared by traditional methods often exhibit poor mechanical properties, severely limiting their practical applications. To obtain hydrogels of excellent mechanical performance, a simple one-step method was developed. Through this method, KGM/kappa-carrageenan (KC) hydrogels of interpenetrating network (IPN) structure were prepared, where the chemical gel network was constructed via reaction between the KGM and borax and the physical network was built by introducing a KC component. Besides, the -OSO3−-groups on the KC chains will also interact with the hydroxyl groups on the KGM chains to form hydrogen bonds, effectively binding the two networks into a whole. We find that the tensile strength of the obtained IPN hydrogels can reach to 100.2 kPa. Since the second physical network structure is temperature sensitive and recoverable, the hydrogels obtained by our method are of excellent self-healing performance. Our results showed that the mechanical strength of the self-healed hydrogels can recover by 96.7% after heat treating at 60 °C for 30 min.Graphical abstractImage 106
       
  • Integrating transient and sacrificial bonds into biobased elastomers
           toward mechanical property enhancement and macroscopically responsive
           property
    • Abstract: Publication date: Available online 16 October 2019Source: PolymerAuthor(s): Bin Liu, Zhenghai Tang, Zhao Wang, Liqun Zhang, Baochun Guo The development of biobased polymers from renewable resources offers a solution to the growing environmental concerns and scarcity of fossil feedstock. The synthesized biobased polymers, especially for biobased elastomers, are mechanically weak, which greatly restricts their applications. In the present work, we demonstrate that the integration of transient and sacrificial quadruple H-bonding motifs into as-synthesized biobased elastomer can enhance the mechanical properties and bestow it with adaptive performance. Specially, the biobased elastomer was synthesized through melting poly-condensation using biobased di-acids and diols as the starting materials. The biobased elastomer is covalently crosslinked and grafted with ureido-pyrimidinone (UPy) containing acrylate through thiol-ene click reaction by using pentaerythritol tetra(3-mercaptopropionate) as the linkers. Under external load, UPy aggregations based on H-bonding can function as sacrificial units through reversible rupture and re-formation events, leading to significant improvements on the modulus and strength of the biobased elastomer while maintaining the extensibility. In addition, the dissociation and re-formation of H-bonding under thermal stimuli impart the elastomer with thermo-activated shape memory behavior.Graphical abstractThe incorporation of transient and sacrificial quadruple H-bonding motifs into bio-based elastomer that is synthesized from bio-based di-acids and diols can enhance the mechanical properties and bestow it with adaptive recovery.Image 1
       
  • Mixed ion-electron conducting PEO/PEDOT: PSS miscible blends with intense
           electrochromic response
    • Abstract: Publication date: Available online 15 October 2019Source: PolymerAuthor(s): Kuan Fu, Ruihua Lv, Bing Na, Shufen Zou, Rong Zeng, Bin Wang, Hesheng Liu Aqueous solution processable PEDOT: PSS is promising for electrochromic applications. However, dense morphology with few ion paths usually results in low optical contrast and slow electrochromic response. Herein, polyethylene oxide (PEO) was simply blended with PEDOT: PSS aqueous dispersion to promote ion diffusion and thus electrochromic performance. The PEO is miscible with PEDOT: PSS in the blends due to molecular interactions, corresponding to the increase in the grain size and the decrease in the melting point of the PEO component. The electrochemical activity of PEDOT chains in the blends is remarkably enhanced with the incorporation of 40 wt% PEO fraction, resulting in the significant change in the transmittance (64%) between oxidized and reduced states. Meanwhile, the response time is within 1 s for both coloring and bleaching, accompanied by a high coloration efficiency of 269.1 cm2/C.Graphical abstractImage 1
       
  • Sustainable approach towards enhancing thermal stability of bio-based
           polybenzoxazines
    • Abstract: Publication date: Available online 15 October 2019Source: PolymerAuthor(s): Pratibha Sharma, Pramit Dutta, Leena Nebhani The present work demonstrates a sustainable approach to develop hybrid bio-based polybenzoxazines with thermal performance compatible to the petro-based analogues. Bio-based phenols undergoes Mannich like condensation with 3-aminopropyl triethoxysilane (APTES) and paraformaldehyde in ethanol as reaction medium as well as under solvent-less condition. In comparison to the synthesis in the presence of solvent, the reaction completion time was significantly reduced through solvent-less approach thereby improving the sustainability of procedure. Benzoxazine monomers were structurally characterized using Fourier transform infrared spectroscopy (FT-IR), proton and carbon nuclear magnetic spectroscopy (1H, 13C NMR). The synthesised monomers undergo thermally accelerated ring opening polymerization which was evidenced using differential scanning calorimetry (DSC). Silane functionality in monomer is sensitive to moisture and can possibly alter curing profile of resins as well as processing with time. Rheological behavior of the resins after a rest period of 30 days at room temperature was investigated to ensure solvent-less processing. Contact angle measurements on the polybenzoxazine specimen were also performed to interpret the effect of generated siloxane linkages on the hydrophobicity of material. Thermal performance of the hybrid polybenzoxazines has been studied by thermogravimetric analysis (TGA) and results have been compared with the reported petro-based polybenzoxazines.Graphical abstractAn attempt has been made to sustainably enhance the thermal performance of bio-based polybenzoxazines via integrating silica network formed as a result of polymerization of benzoxazine monomers modified with silanes. Bio-based benzoxazine monomers have been synthesised using phenols of natural origin and amine functionalized silane under solvent-less conditions. Polybenzoxazine-silica network prepared using the bio-based monomers, exhibit high thermal stability and char yield.Image 1
       
  • Effect of surfactant assisted β-nucleating agent self-assembly on the
           crystallization of polypropylene
    • Abstract: Publication date: Available online 15 October 2019Source: PolymerAuthor(s): Chao Ding, Gao-Gao Wu, Ya Zhang, Yu Yang, Bo Yin, Ming-Bo Yang Agglomeration of β nucleating agent (β-NA) strongly affects the nucleating efficiency of β-NA and dispersion and self-assembly morphology are important factors for better properties of β-PP product. In this work, a nonionic surfactant was utilized to assist the self-assembly of β-NA as a special nucleating agent for the crystallization of polypropylene. The influence of nonionic surfactant on the self-assembly behavior, β nucleating ability , and dispersion status were investigated by polarized optical microscopy, differential scanning calorimetry and in-situ Fourier transform infrared spectroscopy and scanning electron microscope. The result suggested that surfactant assisted self-assembled β-NA exhibited higher β nucleating ability, longer needle-like frameworks , and better dispersion status. In-situ FTIR result showed that the surfactant accelerated the breaking up of intermolecular hydrogen bonds of β-NA, which may accelerate the β-NA dissolution. A model was proposed to explain the mechanism of surfactant assisted β-NA self-assembly. This work may have significant meaning in the regulation of β-NA self-assembly.Graphical abstractImage 10
       
  • Alkaline monomer for mechanical enhanced and self-healing hydrogels based
           on dynamic borate ester bonds
    • Abstract: Publication date: Available online 14 October 2019Source: PolymerAuthor(s): Fei Ji, Jinhui Li, Guoping Zhang, Wenjie Lan, Rong Sun, Ching-Ping Wong Hydrogels based on borate ester bonds enable fast, multiple repairs with their dynamically reversible covalent bonds at room temperature. However, these materials could only be healed with alkaline additives to control the pH values right now which results in the limited healing and mechanical performance. In this research, dimethylaminoethyl methacrylate (DMAEMA) is employed as an alkaline monomer and randomly copolymerize with N-methylol acrylamide (NAM) to form a mechanical enhanced and self-healing hydrogel at room temperature. The hydrogels exhibit a dramatic fracture stress of as much as 368 kPa and fracture strain of 542%. Besides, the anti-fatigue properties of the hydrogels (slight residual deformation after stretch-release cycles at strain of 200%) have been proved as well. Moreover, the as-prepared hydrogels successfully achieve 91% of the fracture stress recovery within 1 h at room temperature and 100% repair of the fracture strain after 24 h. At last, the healing mechanism has been discussed. This work provides a novel system for the borate ester bonds-based self-healing materials with improved healing and mechanical performance by the simple and efficient method which would expand the range of applications in smart materials.Graphical abstractImage 1
       
  • Mechanical, Toughness and Thermal properties of 2D Material- Reinforced
           Epoxy Composites
    • Abstract: Publication date: Available online 10 October 2019Source: PolymerAuthor(s): Sensen Han, Qingshi Meng, Zhe Qiu, Amr Osman, Rui Cai, Yin Yu, Tianqing Liu, Sherif Araby Developing epoxy composites with high thermal conductivity and excellent mechanical properties becomes imperative in electronic and aerospace industries. This study investigates and compares the effect of adding boron nitride (BN) sheets and graphene platelets (GnPs) on the mechanical properties and thermal conductivity of epoxy resin. The study shows that incorporation of BN or GnPs into epoxy matrix significantly enhanced both mechanical properties and thermal conductivity of epoxy composites. At fractions ranging 1−4 wt%, GnPs/epoxy composites provide higher Young’s modulus, fracture toughness (K1c) and critical stress energy release rate (G1c) compared to BN/epoxy composites. The thermal conductivity of the epoxy composites is up to the maximum of 0.33 Wm-1K-1 at 4 wt% of GnP loading, which is much higher than that of the composites filled with the same loading of BN (0.23 Wm-1K-1). The study emphasizes the importance of adding thin nanosheets (thickness 3-5 nm) at low loadings in developing epoxy composites to achieve desired mechanical and thermal properties.Graphical abstractThermal conductivity of epoxy/BN and epoxy/GnP composites.Image 1011506
       
  • Crystal self-nucleation in polyamide 11 of different semicrystalline
           morphology
    • Abstract: Publication date: Available online 7 October 2019Source: PolymerAuthor(s): Katalee Jariyavidyanont, Andreas Janke, René Androsch Self-nuclei supported recrystallization of the crystal-free melt of polyamide 11 (PA 11) of qualitatively different initial semicrystalline morphology, either containing nodular crystals or spherulitically grown lamellar crystals, has been investigated by fast scanning chip calorimetry, optical microscopy and atomic force microscopy. Melt-recrystallization of PA 11 initially containing a large number of nodules of high surface-to-volume ratio and strong coupling to the surrounding amorphous structure, as confirmed with the detection of significant amount of rigid amorphous fraction, is distinctly faster than melt-recrystallization of PA 11 initially containing lamellae and spherulites, caused by a lower number of self-nuclei in the latter system. Moreover, the temperature range of survival of self-nuclei above the respective melting temperature of nodular and lamellar crystals is larger for PA 11 initially containing nodules. The melt-residence time, within the assessable time-range before onset of melt-recrystallization, has no effect on the self-nuclei number. Enhanced self-nucleation in PA 11 containing nodules, compared to spherulitically crystallized PA 11, is suggested being caused by the distinctly larger initial number of individually grown crystals. A possible effect of the rigid amorphous fraction, forming during nodular crystallization, on hindering relaxation of the melt is discussed.Graphical abstractImage 1
       
 
 
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