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All issues / Volume 9 (2015) / Issue 6 (June)

Added function – Added value: Multifunctional high-performance composites
A. Bismarck
Vol. 9., No.6., Pages 489-489, 2015
DOI: 10.3144/expresspolymlett.2015.46
This is an editorial article. It has no abstract.
An excellent ozone-resistant polymethylvinylsiloxane coating on natural rubber by thiol-ene click chemistry
N. Y. Ning, Z. P. Zheng, L. Q. Zhang, M. Tian
Vol. 9., No.6., Pages 490-495, 2015
DOI: 10.3144/expresspolymlett.2015.47
Natural rubber (NR) as renewable resource is a kind of cheap and versatile elastomer. A disadvantage of NR is that the ozone resistance is not good, which needs to be improved for its wider application. In this study, polymethylvinylsiloxane (PMVS) coating on natural rubber (NR) was realized for the first time by using thiol-ene click reaction under UV irradiation, simultaniously realizing the fast crosslinking of PMVS layer and the covalent crosslinking between PMVS layer and NR layer. As a result, a good interphase adhesion between PMVS coating and NR was obtained. The coating of the crosslinked PMVS layer on NR resulted in an obvious increase in the ozone resistance of NR. Our study provides a new and high efficient strategy to prepare elastomer materials with good ozone resistance.
Low band-gap polymers incorporating benzotriazole and 5,6-dialkoxy-benzothiadiazole as solution processable electrochromic materials
W. T. Neo, Q. Ye, X. Wang, H. Yan, J. Xu
Vol. 9., No.6., Pages 496-508, 2015
DOI: 10.3144/expresspolymlett.2015.48
Two series of donor-acceptor type conjugated polymers bearing benzotriazole or 5,6-dialkoxy-benzothiadiazole as acceptors unit are synthesized via Stille coupling. The optical, electrochemical, spectroelectrochemical characterizations and theoretical calculations are carried out. The polymers display excellent solubility in common organic solvents upon the introduction of long aliphatic side chains. The electrochromic performances of the polymers are also studied. Upon oxidation, the polymers switch from magenta or blue to a transmissive light blue state. In particular, respectable optical contrasts of about 44 and 40% are obtained in the visible and near infrared (NIR) region respectively for P2. The polymers also reveal fast switching of about from one second to a few seconds. In addition, P2 exhibits a high coloration efficiency of 518 and 561 cm2/C in the visible and NIR region respectively. The promising electrochromic behaviour of these polymers, together with the enhanced solubility will allow large-scale processing and advancement towards real applications.
Enhanced thermal and mechanical properties of poly(trimethylene terephthalate-block-poly(tetramethylene oxide) segmented copolymer based hybrid nanocomposites prepared by in situ polymerization via synergy effect between SWCNTs and graphene nanoplatelets
S. Paszkiewicz, A. Szymczyk, K. Livanov, H. D. Wagner, Z. Roslaniec
Vol. 9., No.6., Pages 509-524, 2015
DOI: 10.3144/expresspolymlett.2015.49
Graphene nanoplatelets/single walled carbon nanotubes/poly(trimethylene terephthalate-block-poly(tetramethylene oxide) segmented copolymer (GNP/SWCNT/PTT-PTMO) hybrid nanocomposites were synthesized via in situ polymerization. A remarkable synergistic effect between GNPs and SWCNTs on improving thermal and mechanical properties of nanocomposites based on segmented block copolymers was observed. Heterogeneous structure of the PTT-PTMO allowed for a better and more uniform distribution of both types of nanoparticles and stabilized the structure in question. This enabled us to observe a so-called ‘synergistic effect’, caused by the use of mixture of carbon nanotubes and graphene nanopletelets, on the enhancement of thermal and mechanical properties of the obtained polymer. In order to ascertain the influence of mentioned carbon nanostructures on the nano-phase-separated structure of the synthesized PTT-PTMO block copolymers, differential scanning calorimetric (DSC) and dynamic mechanical thermoanalysis (DMTA) measurements were performed. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images of the PTTPTMO nanocomposites displayed that hybrid nanofillers exhibited better distribution and compatibility than SWCNTs and GNPs did individually. The tensile modulus of 0.5SWCNT/0.1GNP/PTT-PTMO composites was 68% higher than that of the PTT-PTMO alone, compared to only a 10 and 28% increase in tensile modulus for 0.3GNP/PTT-PTMO and 0.3SWCNT/PTT-PTMO composites respectively (the highest concentration when single nanofiller was added).
Effect of annealing and UV-radiation time over micropore architecture of self-assembled block copolymer thin film
G. del C. Pizarro, O. G. Marambio, M. Jeria-Orell, C. M. Gonzalez-Henriquez, M. Sarabia-Vallejos, K. E. Geckeler
Vol. 9., No.6., Pages 525-535, 2015
DOI: 10.3144/expresspolymlett.2015.50
Block copolymers have been recognized as versatile materials to prepare nanoporous polymer films or membranes, but their potential has not been completely explored. This study focuses on the formation and characterization of nanoporous polymer films based on poly(styrene)-block-(methylmethacrylate/methacrylic acid); (PS-b-MMA/MAA) were obtained through atom transfer radical polymerization (ATRP), by using two different protocols: annealing and annealingirradiation; for improving the formation of microporous surface. The composition, crystallinity and structural order of the films were studied by Raman spectroscopy. The film polymer thickness was obtained through very high resolution ellipsometry (VHRE). Finally, atomic force microcopy (AFM) and scanning electron microscopy (SEM) techniques were used to detect changes in the porous-structure. These results show that the morphological properties of the block copolymer were affected via the modification of two variables, UV-radiation time and annealing. SEM and AFM micrographs showed that the morphology exhibit a porous ordered structure. Contact angle measurement suggests additional interactions between hydrophilic functional groups that influence the film wettability.
Combined main-chain/side-chain ionic liquid crystalline polymer based on ‘jacketing’ effect: Design, synthesis, supra-molecular self-assembly and photophysical properties
L. Weng, H. L. Xie, C. G. Arges, J. Tang, G. Q. Zhong, H. L. Zhang, E. Q. Chen
Vol. 9., No.6., Pages 536-553, 2015
DOI: 10.3144/expresspolymlett.2015.51
Reasonably fabricating ordered structures of ionic polymers is very important for the development of novel functional materials. By combining the ions and liquid cry stalline polymer, we successfully designed and synthesized a series of novel combined main-chain/side-chain ionic liquid crystalline polymer (MCSC-ILCPs) containing imidazolium groups and different counter-anions, poly (2,5-bis{[6-(4-butoxy-4'-imidazolium biphenyl)hexyl]oxycarbonyl}styrene salts) poly(BImBHCS-X) with the following types of counter-anions (Br¯, BF4¯, PF6¯ and TFSI¯). Combined technologies confirmed the chemical structures of the monomers and polymers with imidazolium cation and different counter-anions. Differential scanning calorimetry (DSC), polarized light microscopy (PLM) and one- and two-dimensional wide-angle X-ray diffraction (1D and 2D WAXD) results illustrated that the LC structures and the transitions of ordered structures depended on the nature of the counter-anion employed. The polymers with Br¯ and BF4¯ counter-anions exhibited smectic A (SmA) LC behavior below the isotropic temperature. The another one, poly(BImBHCS–TFSI) with the large volume of the TFSI¯ anion destroyed the packing of the LC ordered structure resulting in an amorphous structure. The photophysical properties of the polymers prepared can be adjusted by tuning the ionic interaction of the polymers by switching the counter-anion.
Evaluation of pH-sensitive poly(2-hydroxyethyl methacrylate-co-2-(diisopropylamino)ethyl methacrylate) copolymers as drug delivery systems for potential applications in ophthalmic therapies/ocular delivery of drugs
P. A. Faccia, F. M. Pardini, J. I. Amalvy
Vol. 9., No.6., Pages 554-566, 2015
DOI: 10.3144/expresspolymlett.2015.52
Smart polymers like pH sensitive systems can improve different pharmacological treatment. In this work the behavior of copolymers containing 2-hydroxyethyl methacrylate (HEMA) with different proportions of 2-(diisopropylamino) ethyl methacrylate (DPA) and different amounts of cross-linker agent, ethylene glycol dimethacrylate (EGDMA) are evaluated as pH-sensitive drug delivery systems for potential application in ophthalmic therapies. A detailed characterization of the pH-responsive behavior was performed by swelling studies and scanning electron microscopy (SEM) analysis. Drug loading and release studies at different pH values were evaluated using Rhodamine 6G (Rh6G) as a model drug. The interaction between Rh6G and hydrogels was studied by Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The results show that the presence of DPA in the copolymers confers pH-responsive properties to the polymer, as noted in swelling and SEM studies, when the pH decreases below 7.40 the swelling degree increases and a porous morphology is observed. The apparent pKa of copolymers was estimated between 6.80 and 7.17 depending on the composition. The amount of Rh6G loaded depends mainly on the medium pH and the interaction between the drug and the copolymers, observed by SEM and FTIR spectrum. The release of Rh6G of copolymers p(HEMA/DPA) show a normal Fickian or anomalous diffusion behavior at different pH values, depending on the HEMA/DPA ratio.
Effect of bisphenol-A on the structures and properties of phthalonitrile-based resin containing benzoxazine
M. Z. Xu, K. Jia, X. B. Liu
Vol. 9., No.6., Pages 567-581, 2015
DOI: 10.3144/expresspolymlett.2015.53
Phthalonitrile and benzoxazine have been considered as high-performance materials in the field of heterocyclic chemistry. The polymerization of phthalonitrile and benzoxazine accelerated by active phenolic hydroxyl has attracted wide interests. In this work, self-promoted polymerization behavior and processability of phthalonitrile containing benzoxazine (BA-ph) with bisphenol-A (BPA) were investigated. Results revealed that BA-ph/BPA exhibited representative doublestage curing behaviors corresponding to the ring-opening polymerization of benzoxazine rings and ring-formation polymerization of nitrile groups. Compared with that of BA-ph, processability of BA-ph/BPA was improved and could be tuned by varying BPA contents, processing temperature and time. Then BA-ph/BPA/glass fiber (GF) composite laminates were prepared. In comparison with that of BA-ph/GF laminates (542 MPa and 25.8 GPa), the flexural strength and modulus were up to 789 MPa and 23.6 GPa, respectively. Moreover, double Tgs were observed at temperature around 200~300°C and 300~380°C, indicating microphase separation during the polymerization of oxazine rings and nitrile groups, confirmed by the scanning electron microscopic (SEM) images. Thermal stabilities demonstrated that all BA-ph/BPA/GF composites exhibited high T10% up to 510°C. The systematic study of BA-ph/BPA system could enrich our knowledge on phthalonitrile-based resins in industrial applications, especially in the areas which require excellent mechanical properties and high temperature resistance.
Published by:

Budapest University of Technology and Economics,
Faculty of Mechanical Engineering, Department of Polymer Engineering