Novel semi-alicyclic polyimide membranes: Synthesis, characterization, and gas separation properties Polymer (IF 3.483) Pub Date : 2018-07-18 Chae-Young Park, Eun-Hee Kim, Jong Hak Kim, Young Moo Lee, Jeong-Hoon Kim
To develop membrane materials for gas separation, a series of semi-alicyclic polyimides was synthesized using one-step thermal solution imidization from an alicyclic dianhydride with non-planar twisted structure, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and five aromatic diamines. All synthesized polyimides exhibited amorphous structures and superior thermal stability, with high glass transition temperatures (242–288 °C) withstanding high operation temperature and pressure. They also showed excellent solubility in many polar organic solvents commonly used in the fabrication of gas separation membranes. The gas permeation properties of the polyimide membranes were measured for six representative gases (H2, CO2, O2, CO, N2, and CH4). The gas permeabilities and selectivities of polyimide membranes were significantly influenced by the chemical structure of the diamines, which could be explained reasonably by the kinetic diameter of gases, the fractional free volumes and d-spacing values of the polyimides. Two DOCDA-based polyimides also showed very high selectivities for H2/CH4 and CO2/CH4 and slightly low permeabilities for H2 and CO2, which performances were comparable to the commercial polyimide materials, P84® and Matrimid® used in gas separation field.
Self-healing, reprocessing and sealing abilities of polysulfide-based polyurethane Polymer (IF 3.483) Pub Date : 2018-07-18 Wentong Gao, Mengyao Bie, Yiwu Quan, Jinyan Zhu, Wanqing Zhang
Polyurethanes are known for their satisfactory mechanical strength, which is highly desired for various applications. Poly(ethyl formal disulfide)-based materials have excellent self-healing ability because of containing abundant exchangeable disulfide bonds, while their strength is relatively low (< 0.8 MPa). Combining the advantages of the two materials, in this article, we synthesized self-healable polysulfide-based polyurethanes with a tensile strength of 2.62−5.80 MPa. After healing at 75 °C for 24 h or 100 °C for 4 h, the tensile strength of a fully cut optimized sample (PSPU-15) recovered to 90.8 and 93.1% of the original value 2.62 MPa, respectively, with the damaged incision disappearing and the sealing integrity fully recovered. Furthermore, the sample PSPU-15 possessed good reprocessing ability, retaining the tensile strength of 2.66−2.40 MPa after repeated processing. These outcomes indicated that polysulfide-based polyurethane is an attractive paradigm towards sustainable industrial applications.
Salt-inactive hydrophobic association hydrogels with fatigue resistant and self-healing properties Polymer (IF 3.483) Pub Date : 2018-07-17 Jiajun Xu, Xiuyan Ren, Guanghui Gao
Traditional hydrophobic association (HA) hydrogels can obtain excellent mechanical properties in the presence of anionic surfactants. However, such surfactants are sensitive to salt solutions, resulting in large fluctuation of mechanical properties for hydrogels. Here, a combined surfactant consisting of anionic surfactants (sodium dodecyl sulfate, SDS) and amphoteric surfactants (dodecyl dimethyl betaine, BS-12) was successfully introduced into HA hydrogels as stable physical crosslinking points. The resulting SDS/BS-12-HA hydrogels exhibited high tensile stress up to about 700 kPa. Moreover, the hydrogels demonstrated salt-inactive, self-healing and fatigue resistance properties owing to their unique dynamic and reversible physical crosslinking structure. Therefore, it's envisioned that this work may open a new method to develop a soft salt-inactive material with stable and excellent mechanical properties for extending the application range of hydrogels.
Comparison of the effects of post-spinning drawing and wet stretching on regenerated silk fibers produced through straining flow spinning Polymer (IF 3.483) Pub Date : 2018-07-17 Rodrigo Madurga, Alfonso M. Gañán-Calvo, Gustavo R. Plaza, José Miguel Atienza, Gustavo V. Guinea, Manuel Elices, Patricia A. López, Rafael Daza, Daniel González-Nieto, José Pérez-Rigueiro
Straining Flow Spinning is a versatile and robust spinning technique for the production of regenerated silkworm silk fibers using mild chemistries. However, reaching high values of tensile strength and strain at breaking requires a step of wet-stretching in water, which limits scalability and the practical usage of the technique. Here, we show that adding a post-spinning drawing step to the procedure improves the performance of the fibers, and allows the development of a scalable process. It is also shown that the properties of the fiber can be tuned by varying the parameters of the post-spinning step. Finally, equivalence is established between the discrete wet-stretching process and the continuous post-spinning drawing step.
Excellent Thermal Stability P(BeA-co-MMA) Microcapsules with High Thermal Energy Storage Capacity Polymer (IF 3.483) Pub Date : 2018-07-17 Yuchen Mao, Jin Gong, Meifang Zhu, Hiroshi Ito
Low thermal stability and the shortage of core leakage strongly limit the application of conventional energy storage microcapsules. This study focuses on a novel strategy to develop a new phase change material with excellent thermal durability without core leakage. The new phase change materials is a P(BeA-co-MMA) copolymer microcapsule with crystalline n-alkane side chains. Under the protection of polymer main chains as the shell or skeleton structure on a nano-scale, the crystalline side chains as the core will no longer suffer loss and will maintain stablity in use. The chemical composition, inner homogeneous structure, thermoregulation properties, crystalline behaviour and thermal stability are discussed. The P(BeA-co-MMA) microcapsules provide energy storage capacity in the temperature range of 48–62 °C with the highest enthalpy of 105.1 J·g–1. The 5% weight loss temperature (T5%) is more than 315 °C, which is high enough to withstand the general polymer processing temperature to open the possibility of developing energy storage modified fibre and polymer materials as functional fillers.
Fracture mechanism of high impact strength polypropylene containing carbon nanotubes Polymer (IF 3.483) Pub Date : 2018-07-17 Po-Hsiang Wang, Sourangsu Sarkar, Prabhakar Gulgunje, Nikhil Verghese, Satish Kumar
In our earlier contribution, it was shown that with the addition of 1 wt% functionalized multiwall carbon nanotube (f-MWNT), an unprecedented 152% increase in PP impact strength without a significant loss in stiffness and ductility can be achieved. In context of these observations, this work examined the impact fracture mechanism of such PP/f-MWNT nanocomposite, in which the PP interphase was tailored by the same co-solvent solution process. The nanotube-matrix stress transfer efficacy in PP/f-MWNT as compared to that of PP/pristine MWNT (p-MWNT) was determined by Raman spectroscopy. The calculated interfacial shear strength (τi) is 17.8 MPa in PP/f-MWNT and 2.2 MPa in PP/p-MWNT, suggesting improved matrix-CNT adhesion in the former. This strong interfacial adhesion allows CNTs to bridge the opening crack, absorb fracture energy and promote local plastic deformation of the polymer matrix. Such process was demonstrated using SEM fractography where breakage/pull out of the CNTs, microcracks, and the intensive fibril formation accompanied with the extension of the PP matrix were captured at the impact fracture surface. Both the interfacial shear strength and the SEM fractography supported the hypothesis that better matrix-CNT adhesion can be achieved through interphase engineering.
Study on phase transition behavior and lamellar orientation of uniaxially stretched poly(ʟ-lactide) / cellulose nanocrystal-graft-poly(ᴅ-lactide) blend Polymer (IF 3.483) Pub Date : 2018-07-17 Selvaraj Nagarajan, Jian Hu, Hao Wu, Yongxin Duan, Jianming Zhang
Towards the development of high-performance green composites, the surface functionalized cellulose nanocrystals (CNC) have been widely used as reinforcement along with biopolymer. In our previous work, it has been demonstrated that CNC grafted with PDLA (CNC-g-PDLA) could improve the crystal nucleation density and heat distraction ability of PLLA matrix via the PLLA/PDLA stereocomplex interaction. Herein, to understand the role of CNC-g-PDLA on the deformation behavior of PLLA/CNC-g-PDLA nanocomposites, the melt-quenched PLLA/CNC-g-PDLA nanocomposite was uniaxially stretched at 160 °C with various draw ratios. The stretched PLLA/CNC-g-PDLA composites allow us to discriminate the crystal transformation and crystal orientation of three individual components in the composites, that is, (i) PLLA matrix, (ii) PLLA/PDLA stereocomplex existed as interfacial phase, and (iii) CNC reinforcement. The results indicate that PLLA α′ and PLLA/PDLA stereocomplex crystals (βC) appear at the initial stage of drawing process. The disordered α′ transforms to ordered α and β forms gradually with increasing in draw ratio, whereas βC-crystals keep almost unchanged during the whole drawing process. The calculation on orientation function of various crystals suggests that the lamellaes of α form have the largest orientation degree along the stretching axis. Meanwhile,CNC nanoparticles and the βC crystals form the nano-dimensional shish kebab structure during stretching and present relatively low orientation. This study provides the physical insight to guide the preparation of high performance PLLA nanocomposites with hierarchical crystal and orientation structure.
Examining the nature of the network formation during epoxy polymerization initiated using ionic liquids Polymer (IF 3.483) Pub Date : 2018-07-17 Fiona C. Binks, Gabriel Cavalli, Michael Henningsen, Brendan J. Howlin, Ian Hamerton
A commercial diglycidyl ether of bisphenol A monomer (BaxxoresTM ER 2200, eew 182 g/mole) is thermally polymerized in the presence of an ionic liquid, 1-ethyl-3-methylimidazolium acetate at a variety of loadings (5-45 wt %). The loss modulus data for cured samples containing 5 wt % initiator display at least two thermal transitions and the highest storage modulus occurs in the sample that has been cured for the shortest time at the lowest temperature. Samples that are exposed to higher temperatures (140, 150 °C) yield more heterogenous networks, whereas following exposure to a much shorter/lower temperature cure schedule (80 °C) exhibits a considerably higher damping ability than the other samples, coupled with a lower glass transition temperature. Differential scanning calorimetry reveals that the latter sample achieves a conversion of 95 %, while crosslink densities for the DGEBA samples containing 5 wt % and 15 wt % are respectively 9.5 x 10-3 mol. dm-3 and 1.2 x 10-3 mol. dm-3 (when cured to 80 °C) and 2.0 x 10-2 mol. dm-3 and 2.4 x 10-3 mol. dm-3 (when cured to 140 °C).
Synthesis of diblock copolymer nano-assemblies: Comparison between PISA and micellization Polymer (IF 3.483) Pub Date : 2018-07-17 Habib Khan, Mengjiao Cao, Wenfeng Duan, Tengyuan Ying, Wangqing Zhang
RAFT dispersion polymerization following the formulation of polymerization induced self-assembly (PISA) and micellization of pre-prepared amphiphilic block copolymers in block-selective solvents are generally used to prepare block copolymer nano-assemblies. Herein, we make a comparison between these two methods by employing two typical block copolymers of poly(acrylic acid)-block-polystyrene (PAA-b-PS) and poly(ethylene glycol)-block-polystyrene (PEG-b-PS). It is found that the block copolymer nano-assemblies prepared by these two methods are similar with each other when the solvophilic block is relatively long and the solvophobic block is relatively short. Otherwise, the block copolymer nano-assemblies by these two methods are different. The possible reasons leading to the difference between PISA and micellization are discussed, and the kinetic factors including temperature, polymer concentration and solvent are ascribed. It is thought that the present study is helpful to clarify how the kinetic factors beyond the block copolymer itself affecting block copolymer morphology.
Designer poly(urea-siloxane) microspheres with controlled modulus and size: Synthesis, morphology, and nanoscale stiffness by AFM Polymer (IF 3.483) Pub Date : 2018-07-17 Hubert Gojzewski, Jagoda Obszarska, Agnes Harlay, Mark A. Hempenius, G. Julius Vancso
Crosslinked poly(urea-siloxane) (PUS) copolymer microspheres with diameters ranging from 0.8 to 1.8 μm with diameter polydispersity indices between 1.15 and 1.60 were synthesized in one-step precipitation polymerization in water-acetone solvent mixtures at room temperature. The spheres were obtained using aminopropyl-terminated siloxanes, isophorone diisocyanate and a tetrafunctional isocyanate crosslinker, employing a systematically varied molar ratio. The length of the siloxanes was controlled to obtain spheres with pre-determined Young's modulus values. Phase separation between soft disiloxane/poly(dimethylsiloxane) segments and hard isophorone bisurea units was observed with an excellent special resolution of ∼5 nm using atomic force microscopy (AFM). AFM mapping of the Young's modulus was achieved utilizing the PeakForce Quantitative Nanomechanical Mapping (QNM) mode. This AFM method allowed us to also measure the values of elasticity moduli of individual microspheres, ranging from 200 to 900 MPa. The microspheres can be used as filler to fine-tune the properties of composite materials, particularly with regard to elasticity. The hydrophobicity was also varied as indicated by water contact angle values between 122° - 132°. These features open the possibility of preparing designer composites for a range of applications from coatings to the biomedical field.
Porous carbon prepared from polyacrylonitrile for lithium-sulfur battery cathodes using phase inversion technique Polymer (IF 3.483) Pub Date : 2018-07-17 Soumyadip Choudhury, Dieter Fischer, Peter Formanek, Frank Simon, Manfred Stamm, Leonid Ionov
In this paper, a time and resource efficient way of preparing porous carbon cathode for lithium-sulfur batteries with superior cycle stability has been demonstrated. In this simple work, we used commercially available polymer as carbon source and non-solvent mixture as porogen or pore former. The cathode has been fabricated by using polyacrylonitrile as base polymer via phase inversion route. By this technique, a highly porous substrate material is generated by dipping a semi-gelled film of polyacrylonitrile in non-solvent mixture. After oxidative crosslinking followed by pyrolysis under inert atmosphere results a highly porous nitrogen doped carbon material, which was further hybridized with sulfur via melt diffusion of elemental sulfur. This cathode material shows although relatively low specific capacity (Cycle 1: ca. 1050 mAh/gsulfur, cycle 500: ca. 400 mAh/gsulfur), but excellent cycle stability over 500 charging-discharging cycles is displayed.
Diphenylsilane-containing linear and rigid whole aromatic poly(azomethine)s. Structural and physical characterization Polymer (IF 3.483) Pub Date : 2018-07-17 A. Tundidor-Camba, C.M. González-Henríquez, M.A. Sarabia-Vallejos, L.H. Tagle, P.A. Sobarzo, A. González, R.A. Hauyón, A.P. Mariman, C.A. Terraza
Six new whole aromatic poly(azomethine)s with different rigidity were prepared from three diamines and two dialdehydes, all of them containing a diphenylsilane moiety as a central structural element. Two amines containing biphenyl moieties were obtained for the first time. Thus, the synthesized polymers contain two silicon atoms in the repeat unit, where methyl and/or phenyl groups bonded to them, complete the tetra-valence of the heteroatom. The new materials were structurally characterized by means of FT-IR, solid NMR and elemental analysis. Solubility was tested in several organic solvents at room temperature and 40 °C and the inherent viscosity was determined. GPC analysis showed oligomeric chains of five repetitive units for the tested samples. Additionally, thermal behavior was studied by TGA and DSC analysis, by evidencing materials highly stable and rigid. Band gaps values ranging between 2.71 and 3.14 eV were obtained from UV/Vis and DRS analysis. The spin-coating technique was used to prepare films from soluble samples in NMP and their thicknesses were determined by the ellipsometric method. From these samples, and using AFM and four-point techniques, the effect of the annealing time on the roughness and conductivity of the films was studied. In accordance with the appropriate thermal and conductivity properties of the new silylated materials (which has a whole aromatic structure), could be proposed as an alternative for applications in the optoelectronics field.
Microscopic Theory of Heterogeneous Phase Inversion in Rubber/Plastic Blends Polymer (IF 3.483) Pub Date : 2018-07-17 Zhaoyang Wei, Nanying Ning, Ming Tian, Liqun Zhang, Jianguo Mi
Despite many investigations, phase inversion in rubber/plastic blends and its origin are far from being understood. Here we focus on the heterogeneous phase inversion in partially miscible blend of polyolefin elastomer (POE) and polypropylene (PP) using the classical density functional approach. We have shown that the blend decomposes into the POE-rich and PP-rich phases on the surfaces of POE or PP domains. For example, the free energy barriers and critical sizes of the POE-rich droplets on the two surfaces obviously decrease compared to the analogous values in the homogeneous nucleation. These values can be further reduced after introduction of nanoparticles, which act as the compatibilizer, improving morphology and final properties of the blend. These results indicate different phase inversion mechanisms in the blend, and can explain why different sizes of nanoparticles can observed in experiments.
Controlling the properties of radiation-synthesized thermoresponsive oligoether methacrylate hydrogels by varying the monomer side-chain length; self-composite network containing crystalline phase Polymer (IF 3.483) Pub Date : 2018-07-17 Krzysztof Piechocki, Marcin Kozanecki, Slawomir Kadlubowski, Barbara Pacholczyk-Sienicka, Piotr Ulanski, Tadeusz Biela
A series of thermo-responsive hydrogels have been synthesized by radiation-induced crosslinking polymerization in bulk based on; oligoether methacrylates (OEGMAs) of side chain lengths of 2–19 EG; monomer units. Side chain lengths have been shown to have a pronounced; effect on synthesis parameters (monomers of longer side chains are more; easily crosslinked, and the inert atmosphere promotes crosslinking more; than air) and hydrogel properties (the thermal stability of obtained; networks and their swelling capacities, as well as the temperature of; Volume Phase Transition (VPT), increase with increasing oligoether side; group length, while the VPT becomes less narrow). Networks based on; oligoether methacrylates of sufficiently long side chains (over 7 monomer; units) are capable of partial crystallization, forming self-composites, and the crystalline phase is chemically linked to a continuous, coherent; polymer network.
Analysis of the effect of block copolymers on interfacial tension in immiscible polymer blends Polymer (IF 3.483) Pub Date : 2018-07-17 Ivan Fortelný, Josef Jůza
Simple theoretical models show that concentration of a compatibilizing A-B block copolymer at the interface between the phases of A and B homopolymers in immiscible polymer blends increases with increasing chain length of copolymers or homopolymers. Copolymers with block lengths comparable to chain length of the blend components reduce interfacial tension most efficiently. Distribution of the block copolymer between the interface and the bulk phases is studied assuming that it is controlled by the rules of equilibrium thermodynamics. Analysis is based on Leibler's mean field theory and its modification by Noolandi. The analysis shows that the distribution of the copolymer between the interface and the bulk phases changes in a broad range depending on the system parameters. Substantial part of the added copolymer can be localized at the interface in contrast to assumptions used in previous analyses.
Carboxylated multiwalled carbon nanotubes effect on dynamic mechanical behavior of soft films composed of multilayer polymer structure Polymer (IF 3.483) Pub Date : 2018-07-17 Farzad Zahedi, Iraj Amiri Amrae
Dynamic mechanical properties due to incorporation of carboxylated multiwalled carbon nanotubes into three-layer polymer structure, with high damping property, via in situ emulsion polymerization and also blending are studied in detail. Using of storage modulus, loss modulus and damping behavior obtained from the DMA was investigated the manner of carboxylated MWCNTs into and onto the three-layer polymer structure. It was observed that different morphology and topology were formed using these two manufacturing methods. Also, it was observed that dynamic mechanical and damping properties are due to complex and multifunctional parameters such as adhesion, constrained chains, molecular optimum mobility between polymer and nanotubes.
Effect of solvent selectivity on supramolecular assemblies of block copolymer by solvent-vapor annealing Polymer (IF 3.483) Pub Date : 2018-07-17 Eunhye Kim, Sungmin Park, Young-Soo Han, Tae-Hwan Kim
Nanoparticles with well-ordered structures have attracted great attention recently due to its potential application, including data storage media, microelectronics and sensors. Herein, we report a strategy of the periodic arrays of iron oxide nanoparticle with supramolecular thin films. The thin films of PS-b-P2VP/FAA supramolecules were solvent-vapor annealed with mixed solvent-vapor condition of toluene: ethanol: water = 9: 1: 0.06 in volumetric ratio. The supramolecular thin film exhibits the structural change of disorder – vertical cylinder – vertical lamellae – mixture (cylinder and lamellae) - cylindrical morphology triggered by the addition of small amount of water due to the change of the solvent selectivity with major block depending on time, leading to the periodic arrays of iron oxide nanoparticle. We expect that this result can provide key information to fabricate the self-assembled naostructure of block copolymers by using the solvent-vapor processing without complicated procedures.
Synthesis, characterization of chiral poly(ferrocenyl-schiff base) iron(II) complexes/RGO composites with enhanced microwave absorption properties Polymer (IF 3.483) Pub Date : 2018-07-17 Chongbo Liu, Lin Li, Zhang Xiang, Wei-Ya Chen, Z. John Zhang, Yuancheng Qin, Dezhi Chen
Chiral poly(ferrocenyl-Schiff Bases) iron(II) complexes (CPSC)/Reduced graphene oxide (RGO) composites with excellent microwave absorption properties have been successfully prepared. The structures of poly(ferrocenyl-Schiff Bases) and their iron(II) complexes were characterized with IR, MS, HNMR, GPC, elemental analysis, etc. The morphology of CPSC and their composite materials were studied through SEM and TEM analysis. The conductivity, optical activity, electromagnetic parameter and microwave absorption properties of composite materials were also studied in details. The results show that chiral composites own much better microwave absorption properties and wider bandwidth compared to corresponding achiral composites. The maximum RL of chiral CPSC/RGO composite (CM-PL1B) reaches at −52.6 dB at 10.0 GHz with a thickness of 2.5 mm, and the bandwidth of RL less than −10 dB can reach up to 4.6 GHz (from 11.2 to 15.8 GHz), the remarkably enhanced microwave absorption properties are also discussed at length.
Structure characterization of UV-curing PEG-b-PPG-b-PEG dimethacrylate cross-linked network Polymer (IF 3.483) Pub Date : 2018-04-06 Enmin Wang, Abed Hasheminasab, Yuanhao Guo, Mark D. Soucek, Miko Cakmak
The molecular structure of a series of newly developed ultraviolet (UV) curable electrical contact stabilization materials, which contain polyethylene glycol (PEG)-block-polypropylene glycol (PPG)-block-polyethylene glycol (PEG) capped with methacrylate functional groups on both ends as the reactive oligomers and a methacrylated PEG as the reactive diluent was studied in detail. The effects of reactive diluents, including functionalities and compositions were investigated via a combination of dynamic mechanical analysis, differential scanning calorimetry, FT-IR spectroscopy and wide angle X-ray diffraction. All the films exhibit completely amorphous state at room temperature regardless of the composition or thermal history. However, a small amount of PPPDI molecular chains undergo crystallization upon slow cooling. This crystallization is completely inhibited when mixed with di-functional reactive diluents, owing to the high cross-link density. The introduction of mono-functional reactive diluents restricts but not completely prevents the crystallization process, which causes the resulting films to be difficult to crystallize to lower crystallinity levels. On the other hand, adding non-reactive diluents transforms the resulting films to become a fast-crystallizing material, as a result of the low cross-link density and a large portion of unreacted oligomers along with the unreactive component. Additionally, the degree of heterogeneity for the cross-linked networks is generally increased by the addition of reactive diluents. The molecular structures of PEG-b-PPG-b-PEG dimethacrylate cross-linked networks as well as mixed with different types of reactive diluents at both room temperature and crystallizing temperature were proposed.
High performance liquid crystalline physical gels prepared by side chain liquid crystalline polymers Polymer (IF 3.483) Pub Date : 2018-04-09 Jianhang Zhao, Yongjie Yuan, Lei Chen, Ye Li, Hailiang Zhang
Liquid crystalline physical gels (LCPGs) with stable mechanical properties and fast electro-optical response properties were prepared through the self-assembly of side chain liquid crystalline polymers (SCLCPs) with different spacer length poly [ω-4′-cyano-(1, 1′-biphenyl)] acrylate (PmACB, m is the spacer length of SCLCP, m = 0, 2, 4) as gelators in a nematic liquid crystal, 4-pentyl-4′-cyanobiphenyl (5CB). The gel-sol phase transition temperature (TGS), micro morphology, mechanical properties and electro-optical properties of LCPGs (SCLCPs/5CB) were systematically studied. The results show that only P0ACB can form stable liquid crystalline physical gels in 5CB and show excellent thermal stability, good self-supporting ability and fast electro-optical response properties. The TGS of 6 wt% P0ACB/5CB gel is 192 °C, and it also showed stable mechanical properties, its storage modulus is about 1.0 × 104 Pa. The threshold voltage (Vth) and saturation voltage (Vsat) of P0ACB/5CB gel with 3 wt% concentration are 0.29 V μm−1and 3.906 V μm−1 respectively, and the off state response time is only 6.748 ms. Moreover, the addition of the polymer does not affect the electro-optical response of the LCPGs.
The effects of functional nanofillers on the reaction kinetics, microstructure, thermal and mechanical properties of water blown rigid polyurethane foams Polymer (IF 3.483) Pub Date : 2018-07-12 Mercedes Santiago-Calvo, Josías Tirado-Mediavilla, José Luis Ruiz-Herrero, Miguel Ángel Rodríguez-Pérez, Fernando Villafañe
The use of functional nanofillers to improve the properties of rigid polyurethane (PU) foams has caused the need for a better understanding of how these nanofillers modify the reaction kinetic of the PU system. In this study, different nanoclays and nanosilicas are used as functional nanofillers. Analysis of the kinetic data obtained by in-situ FTIR spectroscopy monitoring allows to correlate the isocyanate consumption with the type of nanoparticles. The quantification of urethane and urea, obtained by deconvolution of the carbonyl region absorptions, enables to follow the blowing and gelling reactions during the foaming process. These reactions are correlated to the nature of the chemical groups present on the surface of the nanoparticles added. In addition, the effect of the modification of the reaction kinetics on the density, cellular structure, thermal conductivity and mechanical properties is herein discussed.
Rouse dynamics in PEO-PPO-PEO block-copolymers in aqueous solution as observed through fast field-cycling NMR relaxometry Polymer (IF 3.483) Pub Date : 2018-07-12 Carla C. Fraenza, Carlos Mattea, Germán D. Farrher, Amín Ordikhani-Seyedlar, Siegfried Stapf, Esteban Anoardo
We present a proton fast field-cycling (FFC) NMR relaxometry study of the molecular dynamics in three different deuterated water-dispersed triblock copolymers of ethylene oxide (EO) and propylene oxide (PO):EO80PO27EO80(F68), EO141PO44EO141 (F108), and EO101PO56EO101(F127). Independently of the phase and molecular arrangement, bi-exponential decays of the magnetization during the spin-lattice relaxation process could be observed for F127, while mono-exponential decays were measured for F68 and F108. This fact has been attributed to the relative ratio of PEO and PPO protons for each case. In F127, each component of the magnetization decay could be associated with a particular block of the co-polymer. A direct consequence of this fact is the independent characterization of the molecular dynamics of each block. It was found that the dominant relaxation mechanism can be attributed to the Rouse model, and it seems to be independent on whether the molecules are incorporated into a micelle, or as individual unimers in the aqueous solution. The experimental results and the provided explanation are consistent with entanglement-free self-assembled structures, and a fast exchange of unimers between the micellar structure and the solvent. This particular feature was also investigated in F68 and F108, although for these cases a mono-exponential decay of the magnetization was observed. NMR relaxometry results are complemented with other relaxation experiments in the rotating frame, NMR spectroscopy and atomic-force microscopy.
Competition and miscibility of isodimorphism and their effects on band spherulites and mechanical properties of poly(butylene succinate-co-cis-butene succinate) unsaturated aliphatic copolyesters Polymer (IF 3.483) Pub Date : 2018-07-11 Yang Yu, Zhiyong Wei, Liuchun Zheng, Chenhao Jin, Xuefei Leng, Yang Li
Unsaturated copolyesters poly(butylene succinate-co-cis-butene succinate) (P(BS-co-cBS)) were the first time prepared by polycondensation in combination with stannous octoate as catalyst and 4-methoxyphenol as radical inhibitor, achieving linear random copolyesters with a number-average molecular weight up to 38.2 kg/mol. The cis-2-butene-1, 4-diol used in this work showed a peculiarity of no isomerization or cross-linking side reaction even at high reaction temperatures, due to the high chemical stability of the unconjugated cis-double bond. Isodimorphic behavior between butylene succinate (BS) and cis-butane succinate (cBS) in P(BS-co-cBS) was evidenced by DSC and WAXD analyses. Then, the competition and miscibility of isodimorphism between BS and cBS units were further investigated by thermodynamic analyses. The significant discrepancy in competition and miscibility between BS and cBS units from conformational geometry demonstrated unique physicochemical properties and structure-properties relationships in such system of unsaturated copolyesters. A great impact of competition and miscibility on band spherulites and mechanical properties of the copolyesters was observed and discussed. In conclusion, our work here not only clarifies the effect of cis-double bond on isodimorphism in the unsaturated copolyesters, but also gives an insight into the mechanism of how the competition and miscibility regulates their physical properties.
In situ generation of a self-dispersed β-nucleating agent with increased nucleation efficiency in isotactic polypropylene Polymer (IF 3.483) Pub Date : 2018-07-11 Shicheng Zhao, Wei Qin, Zhong Xin, Shuai Zhou, Hanzhang Gong, Yeming Ni, Ke Zhang
Addition of a β-nucleating agent (β-NA) is the most effective method of preparing β-nucleated isotactic polypropylene (β-iPP); however, the poor dispersion and agglomeration of β-NAs limit nucleation efficiency. To solve this problem, a self-dispersing β-NA strategy was developed based on in situ preparation of β-NA (instead of pre-addition) during the processing of iPP. Zinc adipate (ZnAA), a typical β-NA, was chosen; self-dispersed ZnAA (ZnAA(IS)) was prepared in situ from its reaction precursors adipic acid (AA) and zinc oxide (ZnO) during extrusion of iPP. In situ preparation of ZnAA(IS) led to a significantly higher nucleation efficiency than pre-addition of ZnAA. The β-crystal content (kβ value) of nucleated iPP prepared with ZnAA(IS) reached 0.99, significantly higher than iPP prepared with ZnAA. Moreover, the impact strength of 0.1 wt % ZnAA(IS)/iPP composites was nearly 5.3-fold higher than neat iPP with a net gain in reinforcement (157%) compared to pre-addition of ZnAA. To explain these phenomena, we proposed mechanism for the self-dispersion of β-NA in the context of in situ generation of β-NA during iPP processing; the mechanism was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Polarized Optical Microscopy (POM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) data. Therefore, this strategy and method of preparing β-NA in situ offers unique advantages that will advance the production and application of β-iPP. Furthermore, this strategy could potentially be extended to solve issues of poor dispersion and agglomeration for other additives.
Acceleration of crystal transformation from crystal form II to form I in Polybutene-1 induced by nanoparticles Polymer (IF 3.483) Pub Date : 2018-07-11 Xing-Xing Zhang, Yan-Kai Li, Zhao-Yan Sun
The influence of nanofillers on the crystal transformation from crystal form II to form I of isotactic polybutene-1(PB-1) was investigated by differential scanning calorimetry (DSC), in situ wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. Two types of silicate clay both having one-dimensional structure, halloysite nanotube (HNT) and palygorskite (PGS), were used as nanofillers of PB-1. PGS accelerates the transformation from crystal form II to I for PB-1 more efficiently than HNT, which is attributed to the lattice match of crystal structure between PGS and form I as confirmed by the WAXD and SAXS tests. Moreover, hydrophobically modified clays MPGS and MHNT were used to improve the miscibility between nanoparticle and PB-1. However, transformation kinetics study indicates that the acceleration effect of MPGS is greatly decreased due to the shield of lattice match although the miscibility of the composites is improved, while that of MHNT is increased due to the improvement of miscibility. These results provide direct evidence that the existence of crystallographic relationships is another important factor to accelerate the crystal transformation from form II to I in PB-1.
Low-temperature sintering of stereocomplex-type polylactide nascent powder: The role of optical purity in directing the chain interdiffusion and cocrystallization across the particle interfaces Polymer (IF 3.483) Pub Date : 2018-07-11 Dongyu Bai, Xingyuan Diao, Yilong Ju, Huili Liu, Hongwei Bai, Qin Zhang, Qiang Fu
Recently, we proposed a novel strategy for fabricating high-performance stereocomplex-type polylactide (SC-PLA) products through low-temperature (180–210 °C, lower than the melting temperature of SC crystallites) sintering from its nascent powder, without serious thermal degradation involved in the conventional melt processing at higher temperatures. During the sintering, some poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) chains from adjacent powdery particles can interdiffuse across the interfaces and subsequently co-crystallize into new SC crystallites capable of welding the interfaces. The interfacial strength is dominated by the content of the newly-formed SC crystallites, however, the fast cocrystallization of PLLA/PDLA chains could hinder their sufficient interdiffusion at the interfaces and thus only limited interface-localized SC crystallites could be formed. In this work, we attempt to substantially promote the chain interdiffusion via depressing the cocrystallization rate. To do this, SC-PLA nascent powders with different optical purities of the lactate units were prepared, and the role of optical purity in directing the chain interdiffusion and cocrystallization has been investigated. Very interestingly, we demonstrate that decreasing optical purity (from 99.5 to 96%) is favorable for the formation of numerous SC crystallites at the interfaces because the lowering of cocrystallization rate enables more PLLA/PDLA chains to interdiffuse sufficiently before their cocrystallization. As a result, SC-PLA products with superior heat resistance have been fabricated by the sintering of low-optical-purity SC-PLA powder. These fascinating findings could not only provide new understanding on the low-temperature sintering mechanism of SC-PLA powders but also greatly expand the possibilities for the fabrication of SC-PLA products with superb properties.
Superior comprehensive performance of a rigid-rod poly(hydroxy-p-phenylenebenzobisoxazole) fiber Polymer (IF 3.483) Pub Date : 2018-07-05 Jianting Zhang, Ningren Jin, Jianrong Gao
The novel poly(hydroxy-p-phenylenebenzobisoxazole) (HPBO) was synthesized by different polymerization routes, including hydroxy-orderly distributed polymer (ord-HPBO) and hydroxy-randomly distributed polymer (ran-HPBO). Surface elemental composition, thermal stability, intrinsic viscosity, UV resistance, surface morphology, mechanical and interfacial properties of HPBO fiber were investigated. ATR-FTIR and EDS spectrums identify the formation of mono-hydroxyl modified polymer. Excellent thermal stability (up to 600 °C), mechanical properties (tensile strength of 4.32 GPa, modulus of 169.7 GPa) and rheological spinnability of ran-HPBO-AS via HD self-polymerization route were obtained. Meanwhile, the SEM after UV irradiation indicated that the photostability of HPBO is better than PBO. The interfacial shear strength (IFSS) between HPBO-AS fiber and epoxy resin is 21.7 MPa, 87.1% higher than that of PBO-AS fiber. Comparing different HPBO synthesis routes, the self-polymerization of HD salt route is believed to be a feasible route for industrial production and the ran-HPBO is expected to become a new generation of high-performance fiber.
Wet spun polyacrylontrile-based hollow fibers by blending with alkali lignin Polymer (IF 3.483) Pub Date : 2018-07-05 Bing Zhang, Chunxiang Lu, Yaodong Liu, Pucha Zhou
Alkali lignin, a by-product of commercialized paper making process, is an abundant and environmental-friendly material. In this paper, polyacrylontrile (PAN) -based hollow fiber was fabricated by one-step wet-spinning technique through blending with alkali lignin at different ratios. The phase diagram of the blends was determined by titration method. When alkali lignin is added into the PAN solution, the clouding points move away from polymer-DMSO axis, and miscibility gap increases. The phase separation of PAN was slowed down by mixing with alkali lignin which resulted in the formation of hollow structure and promoted the pore formation in the wall. This work clearly explains the roles that alkali lignin plays in the system consisting of polymer, solvent and nonsolvent, and provides a feasible method to produce PAN-based hollow fibers.
Oxygen diffusivity and permeation through polymers at elevated temperature Polymer (IF 3.483) Pub Date : 2018-07-05 Mathew C. Celina, Adam Quintana
Oxygen permeability (P), diffusivity (D) and solubility (S) properties are representative of gaseous diffusion in polymers and required for the understanding of polymer physics driven phenomena as well as the quantification of mass transport or polymer degradation processes when diffusion limited oxidation effects result in spatially dependent oxidation behavior. Precise P, D, S characterization data for O2 in polymeric materials at elevated temperatures have not been reported due to instrumental challenges and competitive reactively driven oxygen loss (oxidation reactions), although estimations have been accomplished from indirect measurements of oxidation depths when analyzed with theoretical degradation models. This study offers an overview on experimental approaches which have been applied to the characterization of a range of thin polymer films. As an overview, the O2 permeation features of three epoxy thermo-set materials, polyimides (Kapton and bismaleimides), and polypropylene for 25–140 °C were investigated with time-dependent flux measurements and yield permeation data which so far have not been available in the literature. Arrhenius plots of P for two epoxies (828/D230 and 828/D400) show the influence of the glass transition temperature, and intriguingly a transition originates mostly through noticeable changes in S but not D. Multiple material behaviors demonstrating the influence of reactive oxygen loss are discussed. Polymer oxidation chemistry will often interfere with physical permeation measurements at elevated temperatures, in conflict with perhaps the expectation for simple non-reactive O2 transport. Misleading data may result unless the underlying reactive oxidative loss is considered and compensated for, or permeation data are compared at multiple O2 partial pressures to validate non-reactive experimental conditions.
Wet stable and mechanically robust cellulose nanofibrils (CNF) based hydrogel Polymer (IF 3.483) Pub Date : 2018-07-05 Muhammad R. Hossen, Nayereh Dadoo, David G. Holomakoff, Aimee Co, William M. Gramlich, Michael D. Mason
Freeze dried, highly porous materials made from cellulose nanofibrils (CNF) hydrogels are capable of absorbing and storing a significant quantity of liquid inside their 3D structure, with total absorption capacity increasing linearly with porosity. One of the challenges of freeze dried high porosity CNF gels is their propensity to break down rapidly in aqueous environments. Here we explore a method to overcome this deficiency by incorporating methacrylate functionalized carboxymethyl cellulose (MetCMC) into the CNF system followed by UV irradiation leading to crosslinking of the methacrylate groups of MetCMC. The resultant polymer composite matrix successfully maintains a robust 3D structure, without collapsing, even when rewetted and stored in water. When freeze dried, the CNF-MetCMC composite maintains its size and shape whereas air drying induces significant shrinkage. In contrast, air dried CNF-MetCMC hydrogels swell when rewetted. Swelling and shrinkage of CNF-MetCMC hydrogels were tuned by controlling the ratio between CNF and MetCMC in the composite. The crosslinking between the methacrylate groups of MetCMC also enhances the dry and wet modulus of CNF-MetCMC gels significantly. We invoke a simple model involving a balance between hydrogen bonding and crosslinking to explain these data.
Microphase structure of polyurethane-polyurea copolymers as revealed by solid-state NMR: Effect of molecular architecture Polymer (IF 3.483) Pub Date : 2018-07-05 Maxim V. Mokeev, Stepan A. Ostanin, Natalia N. Saprykina, Vjacheslav V. Zuev
1H spin-diffusion solid-state NMR, in combination with other techniques, was utilized to investigate the effect of molecular architecture, solubility parameter of hard and soft segments, and their length on the domain size, interphase thickness and degree of phase separation in polyurethane-ureas based on oligomeric 4,4′-diisicyanate diphenylmethane, methylene-bis-(2-chloroaniline) and polyols based on polyethylene oxide, polypropylene oxide and polybutadiene with different length. Polyurethane-ureas based on polyethylene oxide soft blocks did not form rigid domains as a result of absence of microphase separation. The domain sizes of the hard segments in polyurethane-ureas under study practically did not show any dependence on their composition, but interphase thicknesses are higher for systems based on polybutadiene soft blocks. This indicates that the degree of phase separation depends strongly not only on the binary thermodynamic interaction between hard and soft segments in polyurethane-ureas, but is also influenced by their molecular architectures in the experimental temperature range.
Reduced physical aging rates of polylactide in polystyrene/polylactide multilayer films from fast scanning calorimetry Polymer (IF 3.483) Pub Date : 2018-07-05 Xavier Monnier, Samira Fernandes Nassar, Sandra Domenek, Alain Guinault, Cyrille Sollogoub, Eric Dargent, Nicolas Delpouve
The physical aging behavior of amorphous polylactide constrained against polystyrene in layers of 300 nm, thanks to the layer–multiplying co–extrusion process, was investigated by fast–scanning calorimetry (FSC). By cooling down the sample from the liquid state to the glassy one at very fast scanning rates, it was possible to investigate the structural relaxation of the polymer glass at high temperatures for which the time needed to reach the equilibrium was shortened. Therefore it was possible to perform the study of physical aging in experimental conditions providing an expanded view of the structural relaxation for short aging times. Taking benefit of this property, it was highlighted that the aging kinetics of polylactide occurred significantly slower in the multilayer film, in comparison with a bulk amorphous film. The process of recovery in the multilayer system was found to occur at similar rates, or even slower, than in a three–layer film in which polylactide reached its maximum extent of crystallinity. This was attributed to mobility hindrance that might be inherent to the extrusion conditions or associated with the presence of capped interfaces with polystyrene.
Entanglement dynamics in ultra-high molecular weight polyethylene as revealed by dielectric spectroscopy Polymer (IF 3.483) Pub Date : 2018-07-06 Stavros X. Drakopoulos, Georgios C. Psarras, Giuseppe Forte, Ignacio Martin-Fabiani, Sara Ronca
With the help of Broadband Dielectric Spectroscopy, it has been possible to study the molecular dynamics of disentangled Ultra High Molecular Weight Polyethylene in a wide temperature and frequency range. Catalytic ashes of aluminum oxide act as dielectric probes, allowing the identification of five different processes: an αc-process due to movements in the crystalline phase, two γ-processes attributed to amorphous chain portions close to the crystalline lamellae, and two β-processes that we have attributed to the disentangled and entangled amorphous phases. The entanglement formation has been followed by isothermal runs and a model that predicts the energy spent to form entanglements as a function of time and temperature is thereby proposed. This model allowed us to calculate the associated activation energy of the entanglement process.Our work advances further the understanding of entanglement dynamics of ultra-high molecular weight polymers, and the proposed model could prove useful to describe other similar processes such as cross-linking.
Zirconium-chitosan hydrogel beads for removal of boron from aqueous solutions Polymer (IF 3.483) Pub Date : 2018-07-06 Joanna Kluczka, Małgorzata Gnus, Alicja Kazek-Kęsik, Gabriela Dudek
In this study, zirconium(IV)-chitosan (Zr-CTS) hydrogel beads were synthesized for boron(III) removal. Zr-CTS was characterized by a series of experimental techniques, including SEM, XRD and FTIR. Kinetic, isotherm, and thermodynamic investigations were employed to understand the adsorption behavior. It was found that boron removal is a pH-dependent process, having the highest performance at pH 6–7. It was also shown that the process of boron adsorption follows the pseudo-second-order kinetic model and is dependent on Zr(IV) content in hydrogel beads, achieving the maximum adsorption capacity of 24.5 mg/g. Thermodynamic constants demonstrated a feasible, spontaneous, and endothermic adsorption. Boron removal by Zr-CTS was found to occur through the adsorption of boron species on the surface of amorphous zirconium hydroxide via complexation mechanism. The results indicated that due to its efficiency in removing boron, good regeneration capacity and convenient form, Zr-CTS might be considered as a promising adsorbent for water purification.
Thin film mechanical characterization of UV-curing acrylate systems Polymer (IF 3.483) Pub Date : 2018-07-06 R. Anastasio, E.E.L. Maassen, R. Cardinaels, G.W.M. Peters, L.C.A. van Breemen
This study presents the mechanical characterization of UV-curing acrylate systems. UV-curable polymers are commonly used in the stereolithography (SLA) technique to build multi-layered objects. Typically, the mechanical properties of the 3D-printed product are affected by the intrinsic material heterogeneity along the sample thickness. To understand what determines this heterogeneity, single layers of UV-curable polymer are characterized and the effect of process conditions on the mechanical properties is studied. Micro-compression experiments are carried out to determine the intrinsic mechanical properties which are representative of one single UV-cured layer. To determine the right conditions to generate maximally-cured micropillars, the evolution with irradiation time of monomer conversion, glass-transition temperature and yield stress has first been studied. Thereto, micrometer-sized pillars and dog-bone shaped samples have been prepared via UV-curing. Micro-compression measurements on maximally-cured micropillars are performed to study possible size effects. The results reveal that with decreasing pillar size, the yield stress decreases. Tensile measurements are performed on dog-bone shaped samples which have been processed in the same way as compared to the compression samples. These tensile tests show higher yield stress values when compared with compression tests. This size effect can be attributed to the rinsing with acetone during the sample preparation that leads to a removal of monomer from the crosslinked network. As a consequence, in the real 3D-printing process, the mechanical properties will depend on the feature size. In conclusion, a method is presented to determine the mechanical properties of one single layer of material used in the rapid-prototyping SLA process. The experimental procedure we adopted requires only a few millilitres of material and, therefore, is well suited for screening materials under real SLA process conditions.
Mechanical response of double-network gels with dynamic bonds under multi-cycle deformation Polymer (IF 3.483) Pub Date : 2018-07-06 A.D. Drozdov, J. deClaville Christiansen
Mechanical behavior of double-network (DN) gels with covalent and non-covalent bonds under multi-cycle loading depends strongly on time, strain rate and deformation program. A model is developed for the viscoelastic and viscoplastic responses of a polymer network with permanent and temporary junctions. Viscoelasticity is modeled as breakage and reformation of temporary bonds driven by thermal fluctuations. Viscoplasticity is treated as sliding of permanent junctions with respect to their initial positions in the network. Slippage occurs when a junction becomes unbalanced due to transition of a chain linked by this junction from its active state into the dangling state. Analysis of observations in tensile tests with various strain rates, relaxation tests, loading-unloading tests, and multi-cycle tests with various deformation programs on a series of DN gels shows that the experimental stress–strain diagrams are described correctly by the governing equations, material parameters evolve consistently with experimental conditions, and predictions of the model are in quantitative (where sufficient data are provided) and qualitative agreement with experimental data. In particular, numerical simulation demonstrates the ability of the model to describe the Mullins effect in DN gels.
Synthesis of polyaniline/graphene/MoS2 nanocomposite for high performance supercapacitor electrode Polymer (IF 3.483) Pub Date : 2018-07-04 Shatrudhan Palsaniya, Harshal B. Nemade, Ashok Kumar Dasmahapatra
Conducting polymers are usually good candidates for electrode materials of supercapacitors in spite of their lower cyclic stability, which can further be improved by combining with suitable nanofillers. In this work, we report the synthesis of nanocomposites of polyaniline (PANI), with equal weight% of graphene (G) and MoS2, prepared via in-situ oxidative polymerization of PANI, along with PANI-G binary nanocomposites. The morphological analysis confirms the formation of well-dispersed composite materials, and the ternary composite appears to be an interlayered structure of graphene and MoS2, encapsulating the PANI nanorods. As a result, the ternary composite exhibits an excellent supercapacitance behavior, suitable for energy storage applications as revealed by an enhanced cyclic stability. The ternary composite PANI-G-MoS2 symmetric electrode measurement exhibits a remarkably high specific capacitance (Cs, 142.30 F g−1) over binary composites under galvanostatic charge-discharge (GCD) cycles. The improved cyclic stability has contributed significantly in recovering the capacitance retention as high as 98.11% in comparison with pure PANI (∼40%) and binary composites (∼60–96%). Further, PANI-G-MoS2 symmetric electrode (viz., based on two electrode measurement) exhibits a high energy density (2.65 Wh kg−1) at a power density of 119.21 W kg−1, which is attributed to the high charge transport phenomenon occurs at the interfacial region between electrodes and electrolyte.
Effect of the incorporation of an Ag nanoparticle interlayer on the photovoltaic performance of green bulk heterojunction water-soluble polythiophene solar cells Polymer (IF 3.483) Pub Date : 2018-07-04 Massimiliano Lanzi, Elisabetta Salatelli, Loris Giorgini, Martina Marinelli, Filippo Pierini
Two water-soluble regioregular poly(3-alkylthiophene)s, incorporating aminic groups at the end of the side chains, have been synthesized using a post-polymerization functionalization procedure on a ω-bromine substituted polyalkylthiophene. The high solubility of the obtained polymers in water allowed for the preparation of “green” bulk heterojunction solar cells which reached a power conversion efficiency of 4.85% when PC61BM was used as electron-acceptor material. Improved optical absorption and photocurrent have been obtained by interposing a layer of Ag nanoparticles between the buffer and the photoactive layer, leading to a final power conversion efficiency of 5.51%.
Determination of phase specific localization of carbon black in ternary rubber blends: a macroscopic approach by Fourier transform infrared spectroscopy (FTIR) Polymer (IF 3.483) Pub Date : 2018-07-04 A.D. Sarma, H.H. Le, A. Das, S. Wießner, K.W. Stöckelhuber, A.K. Bhowmick, G. Heinrich
The phase specific localization of the reinforcing fillers like carbon black (CB), which has been known to influence the physical and mechanical performance of the rubber blends, can be determined by different characterization techniques, however, only for binary rubber blends. They have been failed so far when applied for more complicated systems like filled ternary rubber blends. In the present work we introduced a new technique using the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) with germanium crystal for characterization of the specific localization of CB in a ternary blend of solution styrene butadiene rubber (SBR), butadiene rubber (BR) and natural rubber (NR). It is the first time we could follow the change of the amount of CB localized in each phase of this blend along the mixing time. CB firstly is incorporated into the NR phase and then it obviously migrates from the NR phase to the SBR phase as a function of mixing time that corresponds very well with the theoretical prediction based on the Z-model using the surface tension values of the filler and rubber blend components. The interaction between CB rubber components can be qualitatively proved by the shift of the FTIR peak. Thermogravimetric analysis (TGA) was used to support the results obtained by the FTIR method. The study was further extended to follow the CB distribution in multi-step mixing.
Novel composite proton exchange membrane with long-range proton transfer channels constructed by synergistic effect between acid and base functionalized graphene oxide Polymer (IF 3.483) Pub Date : 2018-07-03 Yumin Huang, Tao Cheng, Xuechun Zhang, Wenluan Zhang, Xiaobo Liu
In this work, two different functionalized graphene oxide (GO), sulfonic acid functionalized GO (SGO) and amino functionalized GO (NGO), were synthesized and incorporated into the sulfonated poly(arylene ether nitrile) (SPEN) by single doping and codoping. It was found that the codoping of SGO and NGO contributed to the enhancement of proton exchange membrane performance. These two functionalized GO as fillers were uniformly dispersed in SPEN matrix and their synergistic effect created the long-range proton transfer channels along fillers/SPEN matrix interfaces. Meanwhile, acid-base pairs which was induced by strong interfacial interactions between fillers and SPEN matrix provided new and low-energy-barrier pathways for proton hopping, facilitating the proton conduction via Grotthuss mechanism. Among all the membranes, the codoped S/N-3 composite membrane exhibited the highest proton conductivity (0.064 S·cm−1 at 20 °C and 0.21 S·cm−1 at 80 °C). Besides, it was endowed with unprecedented dimensional stability, especially in high temperature (just 12.75% at 80 °C). Also, low methanol permeability was conferred owing to methanol trapping effect of two functionalized GO. Furthermore, S/N-3 composite membrane showed a superior selectivity of 4.48 × 105 S cm−3 s, which was nearly 10 times of that of commercialized Nafion 117. Our investigation provides a new strategy on the design of high performance composite membranes for applications of PEMs and other related fields.
Synergistic conductivity increase in polypyrrole/molybdenum disulfide composite Polymer (IF 3.483) Pub Date : 2018-07-03 Udit Acharya, Patrycja Bober, Miroslava Trchová, Alexander Zhigunov, Jaroslav Stejskal, Jiří Pfleger
Polypyrrole/molybdenum disulfide (PPy/MoS2) composites were synthesized by in-situ chemical polymerization of pyrrole in the presence of MoS2 flakes. The conductivity of the composite with a moderate content of PPy (15–30 wt%) reached 13 S cm−1, which is markedly higher than the conductivity of both the pristine PPy and MoS2, 1 and 10−6 S cm−1, respectively. The improved conductivity was explained by a formation of ordered thin PPy films with high conductivity at the MoS2 surface. At higher pyrrole content, globular PPy was formed in the bulk of the composite resulting in an increase of a disordered polymer fraction, and the conductivity decreased. The composite conductivity is thus controlled not only by content of PPy but also by the proportions between ordered and disordered PPy phases. The structural and morphological characterization of composite materials is based on Fourier-transform infrared and Raman spectroscopies, wide-angle X-ray diffraction, and scanning and transmission electron microscopies. The charge-carrier transport in the composites fits the Mott variable-range hopping mechanism.
Development of new nonlinear optical polymers based on epoxy- amine oligomers with Bi-chromophore fragments in the side chain Polymer (IF 3.483) Pub Date : 2018-07-03 Gulshat N. Nazmieva, Tatiana А. Vakhonina, Nataliya V. Ivanova, Anastasiya V. Sharipova, Olga D. Fominykh, Maxim A. Smirnov, Marina Yu Balakina, Oleg G. Sinyashin
For the first time bichromophore nonlinear optically active compounds, 3,5-bis [2- (N-ethyl-4- (4′-nitrophenylazo) anilino) ethoxy] benzyl alcohol, DF1, and 3,5-bis [6- (N-methyl-4- (4′-nitrophenylazo) anilino) hexaoxy] benzyl alcohol, DF2, have been synthesized. The synthesis of the epoxy-amine oligomers containing DF1 and DF2 dendritic fragments in the side chain was preceded by molecular design which demonstrated that the hexyl groups, binding the chromophores to the branching center in DF2, are able to provide greater mobility of the chromophores compared to the ethyl groups in DF1, thus determining the preference of the former from the viewpoint of NLO activity. Bi-chromophore compounds were introduced into the side chain of epoxy amine oligomers using the esterification reaction under mild conditions by the Steglich method. As a result, oligomers OAB-DF1 (Tg = 122 °C) and OAB-DF2 (Tg = 107 °C) were obtained with good yields, the degree of functionalization was 60 mol% and 45 mol%, respectively. The values of the NLO coefficients, d33, were measured by second harmonic generation technique; they are equal to 29 pm/V for OAB-DF1 and 40 pm/V for OAB-DF2.
An improved visco-hyperelastic model charactering the electromechanical behaviour of dielectric polymers Polymer (IF 3.483) Pub Date : 2018-07-03 Mengzhou Chang, Zhenqing Wang, Wenyan Liang
Dielectric polymers can achieve large, reliable deformation in response to an external electric field and have attracted significant interest as actuators and transducers. The electromechanical performance depends on the interaction between the visco-hyperelastic behaviour of materials and the Maxwell stress caused by the electric field. However, the mechanisms of complex structures, such as a surface-treated and filler-reinforced space system, are still not completely understood. A mechanical model for evaluating the surface effect and electromechanical performance is first proposed on the basis of visco-hyperelastic theory and statistical mechanics. Then, several factors affecting the geometry and material properties of complex structures are quantitatively investigated. The model will contribute to the development of dielectric polymers because its theoretical predictions are in agreement with existing experimental data.
1,4-Diketo-pyrrolo[3,4-c]pyrroles (DPPs) based insoluble polymer films with lactam hydrogens as renewable fluoride anion chemosensor Polymer (IF 3.483) Pub Date : 2018-07-04 Haichang Zhang, Kun Yang, Chao Chen, Yanhui Wang, Zhenzhen Zhang, Liangliang Tang, Qikun Sun, Shanfeng Xue, Wenjun Yang
Manipulating the sub-units of conjugated co-polymers was a convenient and promising strategy for developing novel functional materials. Here a soluble alternating copolymer (P-Boc) consisted of 9,9-dialkylfluorene and 1,4-diketo-2,5-di(t-butoxycarbonyl)-3,6-diphenyl-pyrrolo[3,4-c]-pyrrole was designed and synthesized. Heating the spin-coated P-Boc film could afford an insoluble polymer film (P-2H) with multiple lactam hydrogen units by the removal of the t-butoxycarbonyl groups. Unlike the small molecules with lactam hydrogen, the P-2H film was insoluble and exhibited the remarkable naked-eye visible color change and a new long-wavelength absorption band in the fluoride anion-containing organic solution. The naked-eye visible and spectroscopic detection limits for fluoride anion were ∼10−6 and ∼10−8 M, respectively. Moreover, the fluoride anions bonded with P-2H film could be easily removed by immersing in acidic solutions, and the resulting P-2H film could again probe fluoride anion. Energy dispersive X-ray spectroscopy analysis indicated that most lactam units in P-2H film could bond fluoride anions and the bonded fluoride anions could be removed quantitatively. These results demonstrated that P-2H was not only an efficient and renewable fluoride anion chemosensor but also might become a promising fluoride anion extractor.
A new recyclable crosslinked polymer combined polyurethane and epoxy resin Polymer (IF 3.483) Pub Date : 2018-07-02 Yong-Jin Peng, Xin He, Qiang Wu, Ping-Chuan Sun, Chang-Jun Wang, Xue-Zheng Liu
First polymer nanofiber of electrospun immobilized molybdenum complex on bio-iron oxide based on polyvinyl alcohol for green oxidation of alcohols Polymer (IF 3.483) Pub Date : 2018-07-02 Sedighe Abbaspour Noghi, Atena Naeimi, Hooshang Hamidian
Programmable electro-optical performances in a dual-frequency liquid crystals / polymer composite system Polymer (IF 3.483) Pub Date : 2018-07-02 Xiao Liang, Mei Chen, Shumeng Guo, Xiao Wang, Shuaifeng Zhang, Lanying Zhang, Huai Yang
Thermosets derived from diallyl-containing main-chain type benzoxazine polymers Polymer (IF 3.483) Pub Date : 2018-07-02 Chien-Han Chen, Ching Hsuan Lin, Tung I. Wong, Meng Wei Wang, Tzong Yuan Juang
Cationic scavenging by polyaniline: Boon or bane from synthesis point of view of its nanocomposites Polymer (IF 3.483) Pub Date : 2018-07-02 Vipin Kumar, Siwat Manomaisantiphap, Kouhei Takahashi, Teruya Goto, Natsuki Tsushima, Tatsuhiro Takahashi, Tomohiro Yokozeki
Shell of amphiphilic molecular bottlebrush matters as unimolecular micelle Polymer (IF 3.483) Pub Date : 2018-06-30 Yi Chen, Houbo Zhou, Ziyang Sun, Huaan Li, Huahua Huang, Lixin Liu, Yongming Chen
UV-mediated synthesis of pNIPAM-crosslinked double-network alginate hydrogels: Enhanced mechanical and shape-memory properties by metal ions and temperature Polymer (IF 3.483) Pub Date : 2018-06-30 Eun Jung Choi, Seonggyun Ha, Jookyeong Lee, Thathan Premkumar, Changsik Song
Development of hybrid magnetorheological elastomers by 3D printing Polymer (IF 3.483) Pub Date : 2018-06-29 A.K. Bastola, M. Paudel, L. Li
High-performance polyimide copolymer fibers derived from 5-anino-2-(2-hydroxy-4-aminobenzene)-benzoxazole: Preparation, structure and properties Polymer (IF 3.483) Pub Date : 2018-06-29 Xuemin Dai, Feng Bao, Long Jiao, Haibo Yao, Xiangling Ji, Xuepeng Qiu, Yongfeng Men
Photo-curable acrylate polyurethane as efficient composite membrane for CO2 separation Polymer (IF 3.483) Pub Date : 2018-06-27 Hossein Molavi, Akbar Shojaei, Seyyed Abbas Mousavi
Surface-initiated RAFT polymerization from vapor-based polymer coatings Polymer (IF 3.483) Pub Date : 2018-06-27 Gowthamy Venkidasubramonian, Domenic Kratzer, Vanessa Trouillet, Nicolas Zydziak, Matthias Franzreb, Leonie Barner, Joerg Lahann
Form II to I transformation of polybutene-1 and copolymer of butane-1 and ethylene: A role of amorphous phase Polymer (IF 3.483) Pub Date : 2018-06-27 Chang Liu, Zhijie Zhang, Shaoyong Huang, Quan Chen
Synthesis and characterization of sustainable polyurethane foams based on polyhydroxyls with different terminal groups Polymer (IF 3.483) Pub Date : 2018-06-28 M. Stanzione, V. Russo, M. Oliviero, L. Verdolotti, A. Sorrentino, M. Di Serio, R. Tesser, S. Iannace, M. Lavorgna
Ultrahigh oxygen permeability of chemically-modified membranes of novel (co)polyacetylenes having a photodegradative backbone and crosslinkable side chains Polymer (IF 3.483) Pub Date : 2018-06-28 Mingyu Zhang, Toshiki Aoki, Lijia Liu, Jianjun Wang, Masahiro Teraguchi, Takashi Kaneko
Multilevel structure analysis of polyimide fibers with different chemical constitutions Polymer (IF 3.483) Pub Date : 2018-06-26 Huanyu Lei, Mengying Zhang, Hongqing Niu, Shengli Qi, Guofeng Tian, Dezhen Wu
Chemistry, polymer dynamics and mechanical properties of a two-part polyurethane elastomer during and after crosslinking. Part II: Moist conditions Polymer (IF 3.483) Pub Date : 2018-06-26 Bettina Zimmer, Christophe Nies, Christian Schmitt, Cristo Paulo, Wulff Possart
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