bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal degradation behaviours of flame-retardant polycarbonate containing potassium diphenyl sulfonate and polymethylphenylsilsesquioxane
Authors: Wang Jiangbo , Xin Zhong 
Published: August 2014

AbstractPotassium diphenyl sulfonate (KSS) and polymethylphenyl silsesquioxane (PMPSQ) were proved to be effective flame retardants for PC by the LOI test and UL-94 measurements. The thermal degradation behaviours were investigated by TGA and flame-retardant mechanism of KSS/PMPSQ/PC system was studied by the kinetic analysis methods including Kissinger method and Flynn- Wall-Ozawa method. The results showed that the activation energies of flameretardant PC (FRPC) were lower than that of pure PC at lower degree of conversion, which indicated that the KSS and PMPSQ both promoted the thermal degradation of PC in the early and middle stages. Flynn-Wall-Ozawa method further revealed that the addition of the flame retardant PMPSQ increased the activation energy of FRPC thermal degradation in the final stage, which illustrated that the PMPSQ stabilized the char residues and improved the flame retardancy of FRPC in the thermal degradation. Therefore, the improved flame-retardant behaviours of KSS and PMPSQ on PC were achieved.
Block copolymerization of 2,2-dimethyltrimethylene carbonate with adipic anhydride catalyzed by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate)
Authors: Ling Jun , Ren Shijian , Shen Zhiquan 
Published: August 2014

AbstractTetrahydrofuran-soluble block copolymer of 2,2-dimethyltrimethylene carbonate with adipic anhydride [poly(DTC-b-AA)] containing 64.7/35.3 DTC/AA in molar ratio with Mn of 12.3 104 and Mw/Mn of 1.64 was synthesized by lanthanum tris(2,6-di-tert-butyl-4- methylphenolate) catalyst at 25 C in 32 min. The copolymer was characterized by SEC, 1H NMR and DSC. Copolymers with AA block from 8.5 % to 50.8 % were prepared by changing the solvent and feeding ratio of DTC/AA.
Synthesis of ATRP macroinitiator based on synthetic cis- 1,4-polyisoprene and its application for graft polymerization of MMA
Authors: Vayachuta Lapporn , Phinyocheep Pranee , Derouet Daniel , Pascual Sagrario 
Published: August 2014

AbstractModification of synthetic cis-1,4-polyisoprene (PI) into bromoalkylfunctionalized polyisoprene (PIBr), an ATRP macroinitiator, was investigated by two-step chemical reaction. The PI was partially epoxidized into epoxidized polyisoprene (EPI) using m-chloroperbenzoic acid, then the EPI was transformed into PIBr by reaction with 2-bromo-2-methylpropionic acid. The results from 1H NMR revealed that the addition product occurs in competition with epoxide ring rearrangement. The amount of bromoalkyl functionalized units was determined from 1H NMR spectra. The graft polymerization of MMA using ATRP technique from macroinitiator units in PIBr was investigated using three different ligands, i.e. N-(n-octyl)-2-pyridylmethanimine (NOPMI), N-(n-octadecyl)-2-pyridylmethanimine (NODPMI) and 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA), resulting in formation of graft copolymer of PI and PMMA. The PMMA grafts were successfully separated from the PI backbone using acidolysis for studying their number-average molecular weights (M̄̅̅n,SEC ) and polydispersity indexes (PDI). All of the ligands used give a increase of M̄̅̅n with MMA conversion. Comparing between 3 ligands, Cu(I)Br complexed with NOPMI shows first-order kinetic plot.
Preparation of ZnO/PMMA inorganic/organic composite microspheres via soap less emulsion polymerization
Authors: Ma Xiaokun , Tang Lanqin , Zhou Bing , Xia Yupeng , Lei Hong , Wang Zichen 
Published: August 2014

AbstractZnO/PMMA inorganic/organic composite microspheres were synthesized with a yield of 83 wt% via soap less emulsion polymerization. The hydrophobic ZnO nanoparticles were modified by oleic acid (OA), which could improve the compatibility between ZnO nanoparticles and methyl methacrylate (MMA) monomer in emulsion system. The existence of ZnO was indicated by the XRD characteristic peaks of the composite microshperes. The TEM micrographs showed that the morphology of the composite microspheres was uniform and ZnO nanoparticles could be encapsulated in the PMMA polymer microspheres. When the ZnO nanoparticles participated in the polymerization process, the surface morphology of composites microspheres changed from smooth to grooved which was characterized by FESEM. In addition, the fluorescence property of the ZnO/PMMA composites became stronger with the increasing amount of ZnO nanoparticles and the fluorescence absorption was stronger than that of pure ZnO.
Methacrylate copolymers with substituted azobenzene side groups: synthesis, characterization and photo-induced birefringence properties
Authors: Cao Haizhong , Zhu Jian , Zhang Wei , Chen Xinrong , Cheng Zhenping , Wu Jianhong , Zhu Xiulin 
Published: August 2014

AbstractWell-defined copolymer of methyl methacrylate (MMA) and 2-methylacrylic- acid-2-{ethyl-[4-(4-methoxy-phenylazo)-3-methyl-phenyl]-amino}-ethyl ester (MAMP) bearing pendent azobenzene groups, was synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT). Copolymers with different contents of azobenzene moieties, e. g. from 12 mol % to 100 mol %, were obtained by varying the feed molar ratios of MAMP and MMA. The reactivity ratios of these two monomers were measured and calculated via the modified Kelen- Tüdos method. Glass transition temperature of the copolymers was measured by differential scanning calorimetry (DSC). Photoinduced trans-cis isomerization of azobenzene moieties in the copolymer was studied at room temperature. Films cast from the functional copolymers were characterized by photo-induced birefringence and surface relief grating (SRG).
Microwave-assisted ring-opening polymerization of poly (glycolic acid-co-lactic acid) copolymers
Authors: Li Guang , Zhao Na , Bai Wei , Chen Dong Liang , Xiong Cheng Dong 
Published: August 2014

AbstractThe microwave-assisted synthesis of poly(glycolic acid-co-lactic acid) (PGLA) copolymers by ring-opening polymerization of glycolide (GA) and L-lactide (L-LA) was studied. The microwave irradiation time and feed ratios on the molecular weights, as well as the thermal properties of the copolymers were discussed. These copolymers were characterized by 1H-NMR, GPC and DSC. It was found that the largest molecular weight ([η]: 0.8745 dL/g) of PGLA5050 was obtained at the irradiation time of 5 min. The color of the copolymers changed from white to light brown, and the yield was higher with the extension of the irradiation time. The molar component ratio of GA in PGLA (FG) was higher than the initial GA feed ratio (nGA) in the raw materials. As the nGA content increased, the glass transition temperature (Tg) of the copolymers decreased and the melting temperature (Tm) of the copolymers increased.
Tuning of multicompartment micelles from cross-linkable ABC triblock copolymer with the addition of core-forming homopolymer
Authors: Yu Haizhou , Jiang Wei 
Published: August 2014

AbstractMulticompartment disks with bumpy edges could be synthesized controllably by dissolving a linear ABC amphiphilic triblock copolymer of polystyrene-b-polybutadiene-b-poly (2-vinylpridine) (PS440-b-PBd1020-b-P2VP114) in selective solvent mixtures of toluene and methanol. The disk size was controllable by the initial copolymer concentration. Diameter of the disks increased with the increase of the copolymer concentration. Interestingly, through adding a homo-PS to the system morphological transition took place from multicompartment disk with bumpy edges to sphere, and to hollow sphere with bumpy surfaces. Furthermore, the diameters of the hollow spheres increased with the increase of the homo-PS content, whereas the diameters of the hollows remained unchanged. Moreover, the PB block could be cross-linked by UV irradiation, stabilizing the preformed structure.
Development of synthetic extracellular bone matrix on poly(L-lactic acid) substrates via electrostatic selfassembly and biomimetic mineralization technologies
Authors: Tan Qinggang , Ren Jie , Chen Chu 
Published: August 2014

AbstractBiomimetic formation of extracellular matrix (ECM) like coatings on artificial biomaterials provides a promising route to gain bioactive materials for tissue engineering applications. Organic ECM is also a template for apatite mineralization in bone tissue. This study was aimed at designing a multilayer film containing an ECM-like molecule on biomaterial surfaces to direct apatite mineralization and to develop biomimetic biomaterials for bone tissue engineering. A multilayer film consisting of gelatin and poly(ethylenimine) molecules was formed on a poly(L-lactic acid) substrate via electrostatic self-assembly technique. Bonelike apatite coating was formed on the multilayer film modified poly(L-lactic acid) substrate in simulated body fluids (SBFs). The amount of forming apatite could be controlled by the Ca2+ and HPO4 2- concentrations in SBF and also through the mineralization time. Gelatin terminated multilayer film can induce the apatite formation with a weak orientation in the (002) plane and the apatite is similar in composition to the natural bone. The gelatin multilayer film/apatite composite coating may serve as a promising microenvironment for bone tissue formation and growth.
Synthesis and quaternization of nitroxide-terminated poly(4-vinylpyridine-co-acrylonitrile) macroinitiators and related diblock copolymers
Authors: Poláková Lenka , Lokaj Jan , Holler Petr , Starovoytova Larisa , Pekárek Michal , Štěpánek Petr 
Published: August 2014

AbstractNitroxide-terminated 4VP AN copolymers have been synthesized at 125 oC using an alkoxyamine (MAMA-SG1) as a unimolecular initiator. Their compositions were compared with those published for the conventional radical 4VP-AN copolymerization. To verify the initiation potential of the copolymers containing nitroxyl end groups, they were employed in chain extension with styrene (S). Both the prepared statistic copolymer macroinitiators and related diblock copolymers, poly(4VP-co-AN) and poly(4VP-co-AN)-block-poly(S), respectively, were quaternized with methyl iodide in N,N-dimethylformamide or methanol at ambient temperature. The size-exclusion chromatography and NMR were used for the characterization of the polymers; the completeness of the quaternization was checked by the IR spectrometry.
Miscibility and crystallization kinetics of poly(ε- caprolactone)/bezoxazine blends
Authors: Chiu Hsiu-Jung , Tsai Ruey-Shi , Huang Jieh-Ming 
Published: August 2014

Abstract The miscibility and crystallization kinetics of the blends of poly(e- caprolactone) (PCL) and bezoxazine (B-m) resin was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that PCL/B-m blends were miscible in the melt. Thus the blend exhibited a single glass transition temperature (Tg), which increased with increasing B-m composition and the crystal equilibrium temperature (Tmo) depressed with the addition of B-m from the Hoffman-Weeks equation analysis. The freezing crystallization temperature (Tfc) for the nonisothermal crystallization on the cooling process, and the spherulitic growth and overall crystallization rates of PCL for the isothermal crystallization were depressed with the addition of B-m component, attributing it to the dilution of PCL concentration due to the addition of B-m.
Essential work of fracture study on thermoplastic polyolefin filled with silicon carbide nanoparticles
Authors: Liao Cheng Zhu , Tjong Sie Chin 
Published: August 2014

AbstractThermoplastic polyolefin (TPO) containing 70 wt% polypropylene and 30 wt% styrene-ethylene-butadiene-styrene grafted maleic anhydride and its nanocomposites filled with 1-5wt% silicon carbide nanoparticles (SiCp) were prepared by melt processing followed by injection molding. Tensile tests show that both Young’s modulus and tensile strength increase with increasing SiCp loading. Essential work of fracture (EWF) method was used to evaluate the fracture toughness of resulting nanocomposites. EWF test demonstrates that the fracture toughness of TPO blend generally decreases with increasing SiCp content. Shield yielding and fibrillation are the main fracture mechanisms for TPO blend and composites. SiCp are found to improve the heat deflection temperature of the TPO blend.
Synthesis and water/oil repellency properties of cationic perfluoralkyl acrylate copolymer latices
Authors: Tang Xin , Shen Yi-Ding 
Published: August 2014

AbstractA series of cationic perfluoralkyl acrylate copolymer latices were prepared by two-stage emulsifier-free emulsion polymerization method. Perfluoroalkylethyl acrylate (FEA) and [2-(methacryloxy)ethyl] trimethyl ammonium chloride (DMC) were used as fluoromonomer and cationic monomer, respectively. The structure and composition of copolymer were characterized by Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC). Thermal stability of copolymer latex film was investigated by thermogravimetic analysis (TGA). The relationships of polymerization conditions between the conversion and coagulation ratio were discussed in detail and the optimal polymerization condition was identified. The water and oil repellency performance of perfluoralkyl acrylate copolymer latices applied to textiles is significantly investigated. Increasing the FEA amount in the emulsion will lead to increase in the contact angle and water and oil repellency on cotton fabrics. When the FEA dosage was 3.9%, the static contact angles of water and liquid paraffin on the surface of cotton fabrics treated were 142.5° and 126.5°, respectively.
Functional nano fillers in epoxy-dicyandiamide adhesives for prolonged shelf life and efficient cure
Authors: Gaukler Jan Christoph , Müller Ulrich , Krüger Jan Kristian , Possart Wulff 
Published: August 2014

AbstractShelf life at room temperature and curing behaviour at elevated temperature are studied for hot-curing accelerated epoxies (EP, diglycidylether of bisphenol A plus dicyandiamide (Dicy)) by FTIR-spectroscopy and modulated DSC. The accelerator is added either directly or with nano-zeolite filler to the EP. Due to the immobilisation of the accelerator in the pores of the nano-zeolite, the shelf life of this EP is 5 times longer than for the EP containing free accelerator. While the free accelerator acts during the whole heating step to curing temperature, the nano-zeolite does not release the accelerator before ca. 100 °C. As monitored by light microscopy, the released accelerator not only supports the curing but also stimulates the dissolution of the solid Dicy. As the result, network formation at 170 °C finishes within less than 25 minutes for the nano-filled EP.
Synthesis and characterization of some polyimide-epoxy composites
Authors: Akhter Toheed , Siddiqi Humaira Masood , Akhter Zareen , Butt M. Saeed 
Published: August 2014

AbstractComposites from some novel polyimide and commercial epoxy were prepared aiming to improve the thermal behavior of epoxy resins. Two diamines namely 4-4'-diamino-4''-hydroxytriphenyl methane (DHTM) and 4-4'- diaminotriphenyl methane (DTM) were synthesized by reacting aniline and aldehydes according to a reported method. The synthesized diamines were blended with commercially available epoxy 1, 4-butanedioldiglycidylether (BDDE) to synthesize model epoxy amine networks which were compared with polyimideepoxy composites. The polyimides were synthesized by reaction of these diamines with aromatic anhydride namely 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA). These synthesized polyimides were dispersed in epoxy diamine networks to prepare composites. All the monomers and composites were characterized by making use of various analytical techniques including FTIR, NMR, TGA, DSC and XRD. Presence of hydroxyl group in the diamine helped in better dispersion of polyimide leading to high Tg and high char yield at 600 °C.
The pervaporation performance and mass transfer process of PDMS membranes for acetic acid/water mixture
Authors: Hong Housheng , Chen Longxiang , Zhang Qingwen , You Tao 
Published: August 2014

AbstractPolydimethylsiloxane (PDMS) membranes with different silica content were prepared without support. The characterization and performance of the membranes were investigated by scanning electron microscope (SEM), thermogravimetry analysis (TGA), contact angle meter and swelling experiment. The pervaporation process was investigated with acetic acid/water mixture. And the process of mass transfer was analysed depending on the solution-diffusion model. The addition of silica could greatly improve the pervaporation flux and enhance the thermal stability of membrane. With an increase in feed temperature, selectivity decreased and permeation flux increased for the unfilled PDMS membrane. However, the separation factor of silica loading of 10 wt. % membranes, exhibited a maximum at 50 °C, and it was higher than unfilled membrane when feed temperature was above 40 °C. With the enhancement of acetic acid concentration, flux and separation factor increased. And the unfilled membrane and the silica filled membrane were prior permeation membranes for water when the downstream pressure of unfilled membrane and silica filled membrane was over 1000 Pa and 1500 Pa respectively.
Polymerization of ethylene using a nickel α-diimine complex covalently supported SiO2-MgCl2 bisupport
Authors: Jiang Hongliu , Lu Jinshan , Xiao Jianhua 
Published: August 2014

AbstractBisupported catalyst for ethylene polymerization was prepared by mixing alcohol solution of MgCl2 with pretreated SiO2 in heptane, the prepared bisupport was modified by treatment with alkyl aluminum compounds, and further treatment with bis(4-(4-amine-3,5-diisopropylbenzyl)-2,6-diisopropylphenylimino) acenaphthene NiBr2 (abbreviaed as NiLBr2) solution. The most significant feature of the supported catalyst is that it polymerizes ethylene with high activities in the presence of inexpensive general alkylaluminum compounds. According to the results of high temperature GPC, the number-average molecular weights of the polymers ranged from 2.15×105 to 9.27×105 and the polydispersities ranged from 3.12 to 4.23. By modulating the polymerization temperatures, the products of different and good morphologies were obtained. The resultant PE was confirmed by 13C NMR to contain significant amounts of not only methyl but also ethyl, propyl, butyl,amyl, and long branches (longer than six carbons).
Bioactive support for cell cultivation and potential grafting. Part 1: Surface modification of 2-hydroxyethyl methacrylate hydrogels for avidin immobilization
Authors: Hobzova Radka , Pradny Martin , Zhunusbekova Nazym M. , Sirc Jakub , Guryca Vilem , Michalek Jiri 
Published: August 2014

AbstractSynthetic hydrogels are often used in biomedical applications as many of them are compatible with living tissue and moreover they can meet most criteria for artificial tissue properties. For applications in tissue engineering modification of polymer surface using some bioactive compounds (e.g. saccharides, proteins) for promoting the process of cell adhesion and proliferation is widely used. In this work, a series of modified hydrogels was prepared by three different methods: by copolymerization of 2-hydroxyethyl methacrylate with methacrylic acid, by hydrolysis and oxidation of poly(2-hydroxyethyl methacrylate) to obtain carboxyl-rich supports. The influence of the reaction conditions of the hydrogel surface treatment on the total carboxylic group content and the swelling degree was studied. The modified hydrogels were characterized by attenuated total reflectance FT-IR spectroscopy and refractive index measurements. Obtained carboxylic groups on the hydrogel surface have allowed the immobilization of avidin in two ways: 1) electrostatically through dissociated carboxylic groups and 2) covalently bonded through activated carboxylic groups by Nhydroxysuccinimide. The capacity of hydrogels for avidin immobilization was determined by Bradford spectrophotometric method. The results so far obtained from the preliminary biological tests showed that immobilized avidin on the hydrogel surface provides better adhesion and proliferation of keratinocytes compared to supports without avidin.
Preparation and characterization of high molecular weight poly(trimethylene terephthalate) by solid-state polymerization
Authors: Hoon Kim Seok , Ho Kim Joon 
Published: August 2014

AbstractSolid-state polymerization has been widely used to prepare high molecular weight poly(ethylene terephthalate). Solid-state polymerization is generally carried out by heating solid, melt-phase-polymerized polymer below its melting temperature but above its glass transition temperature. Solid-state polymerization of poly(trimethylene terephthalate)(PTT) is not an independent process but rather an additional process with respect to melt polymerization that is used when PTT of a higher molecular weight is required. Two kinds of commercial PTT chips were polymerized in the solid state to prepare high molecular weight PTT, which were characterized by end group contents, molecular weight, thermal analysis and X-ray diffraction. In the solid-state polymerization of PTT, the overall reaction rate was governed by the reaction temperature, reaction time and pellet size. The content of carboxyl end groups was decreased during the solid-state polymerization with increasing reaction time and temperature. The melting temperature and crystallinity of solid-state-polymerized PTT were higher at longer times and higher temperatures of polymerization. The activation energy for the solid-state polymerization of PTT was in the range of 24~25 kcal/mol for each chip. Through the solid-state polymerization of commercial PTT chips, we could get high molecular weight polymers up to an intrinsic viscosity value of 1.63 dl/g, which is equivalent to about a 117,000 weight-average molecular weight.
Oligomeric alkylpyridinium surfactants prepared via ATRP
Authors: Su Xin , Chu Zonglin , Shuai Ya , Guo Zanru , Feng Yujun 
Published: August 2014

AbstractA series of oligomeric alkylpyridinium surfactants were prepared directly in aqueous media by atom transfer radical polymerization (ATRP) of a surfmer, 4- vinyl-N-dodecylpyridinium bromide, and their surface activities were examined in comparison with the surfmer. The resulting oligomers have narrow molecular weight distributions, with polydispersity indices in the range of 1.17-1.23. By using 2-morpholinoethyl 2-bromo-2-methylpropanoate as ATRP initiator, the molecular weight of oligomeric surfactants was characterized by 1H NMR and the results were close to those obtained from GPC analysis. It was found that critical micelle concentration (CMC) of the oligomeric alkylpyridinium surfactants shifted to lower concentrations with increasing degree of polymerization (DPn), and their γ-cmc values were smaller by about 4 to 8 mN/m than that of the corresponding surfmer. Among the series of surfactants, the oligomer with highest DPn showed the greatest efficiency in lowering the surface tension in aqueous solution.
Thin-layer synthesized acrylamide copolymers modified with montmorillonite. Flocculation efficiency evaluation
Authors: Ubowska Agnieszka , Spychaj Tadeusz , Paździoch Waldemar 
Published: August 2014

AbstractHydrophilic copolymers based on acrylamide and diallyldimethylammonium chloride including those modified with montmorillonite have been synthesized, characterized by capillary viscometry and FTIR, and their flocculation efficiency has been tested. As an inorganic modifier sodium montmorillonite has been used. In situ copolymerization reactions were carried out as thin-layer processes in aqueous solutions. The results from numerous tests based on model water suspensions (talc and coal fine) confirm high flocculation efficiency of the investigated copolymers. The new type of acrylamide copolymers allow to ascertain that their synthesis in the presence of layered silicates can improve flocculation performance in comparison with unmodified copolymers. These copolymers may potentially compete with acrylamide copolymers in terms of price and flocculation effectiveness.