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971.
Svante Holmberg Peter Holmlund Carl‐Eric Wiln Tanja Kallio Gran Sundholm Franciska Sundholm 《Journal of polymer science. Part A, Polymer chemistry》2002,40(4):591-600
The atom transfer radical polymerization (ATRP) of styrene onto poly(vinylidene fluoride)‐graft‐poly(vinylbenzyl chloride) (PVDF‐g‐PVBC) membranes was investigated. Novel membranes were designed for fuel‐cell applications. The benzyl chloride groups in the PVDF‐g‐PVBC membranes functioned as initiators, and a Cu‐based catalytic system with the general formula Cu(n)Xn/ligand [where X is Cl or Br and the ligand is 2,2′‐bipyridyl (bpy)] was employed for the ATRP. In addition, 10 vol % dimethylformamide was added for increased solubility of the catalyst complex in styrene. The system was homogeneous, except for the membrane, when the initiator/copper halide/ligand/monomer molar ratio was 1/1/3/500. As anticipated, the fastest polymerization rate of styrene was observed with the copper bromide/bpy‐based catalyst system. The reaction rate was strongly temperature‐dependent within the studied temperature interval of 100–130 °C. The degree of grafting increased linearly with time, thereby indicating first‐order kinetics, regardless of the polymerization temperature. Furthermore, 120 °C was the maximum polymerization temperature that could be used in practice because the membrane structure was destroyed at higher temperatures. The degree of styrene grafting reached 400% after 3 h at 120 °C. Such a high degree of grafting could not be reached with conventional uncontrolled radiation‐induced grafting methods because of termination reactions. On the basis of an Arrhenius plot, the activation energy for the homogeneous ATRP of styrene was 217 kJ/mol. The prepared membranes became proton‐conducting after sulfonation of the polystyrene grafts. The highest conductivity measured for the prepared membranes was 70 mS/cm, which is comparable to the values normally measured for commercial Nafion membranes. The scanning electron microscopy/energy‐dispersive X‐ray results showed that the membranes had to be grafted through the matrix with both PVBC and polystyrene to become proton‐conducting after sulfonation. In addition, PVDF‐g‐[PVBC‐g‐(styrene‐block‐tert‐butyl acrylate)] membranes were also synthesized by ATRP. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 591–600, 2002; DOI 10.1002/pola.10146 相似文献
972.
U. Tunca T. Erdogan G. Hizal 《Journal of polymer science. Part A, Polymer chemistry》2002,40(12):2025-2032
An asymmetric difunctional initiator 2‐phenyl‐2‐[(2,2,6,6 tetramethylpiperidino)oxy] ethyl 2‐bromo propanoate ( 1 ) was used for the synthesis of ABC‐type methyl methacrylate (MMA)‐tert‐butylacrylate (tBA)‐styrene (St) triblock copolymers via a combination of atom transfer radical polymerization (ATRP) and stable free‐radical polymerization (SFRP). The ATRP‐ATRP‐SFRP or SFRP‐ATRP‐ATRP route led to ABC‐type triblock copolymers with controlled molecular weight and moderate polydispersity (Mw/Mn < 1.35). The block copolymers were characterized by gel permeation chromatography and 1H NMR. The retaining chain‐end functionality and the applying halide exchange afforded high blocking efficiency as well as maintained control over entire routes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2025–2032, 2002 相似文献
973.
Tomohiro Hirano Ryoko Takeyoshi Makiko Seno Tsuneyuki Sato 《Journal of polymer science. Part A, Polymer chemistry》2002,40(14):2415-2426
Radical polymerizations of di‐n‐butyl itaconate were investigated. Unexpected resonances (C resonances) were observed in 13C NMR spectra of C?O of poly(di‐n‐butyl itaconate)s [poly(DBI)s] obtained at temperatures higher than 60 °C, although two kinds of carbonyl groups showed splittings due to triad tacticities in the spectra of polymers obtained at lower temperatures. The poly(DBI)s formed by the different kinds of initiators or formed in the presence of chain‐transfer agents showed hardly any changes in the intensities of the C resonances; this indicated that the C resonances were not due to the structures formed through initiating and terminating reactions. The poly(DBI)s obtained at different yields showed only a slight increase in the intensities of the C resonances with the yield, which suggested that the C resonances were not attributable to the intermolecular chain‐transfer reaction to the monomer and/or polymer. However, the intensities of the C resonances significantly increased with a decreasing feed monomer concentration; this suggested that intramolecular chain‐transfer reactions took place at high temperatures. Furthermore, a Cu complex‐catalyzed atom transfer radical polymerization mechanism was revealed to be effective for suppressing the intramolecular chain‐transfer reaction at 60 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2415–2426, 2002 相似文献
974.
CaRgn+ (Rg=He, Ne, Ar) complexes with n=1–4, are investigated by performing using the B3LYP/6-311+G (3df) density functional theory calculations. The CaHen+ (n=1–4) complexes are found to be stable. In the case of CaNen+ and CaArn+, stable structures and stationary point were found only for n=1 and 2. For n=3 in the C3V and the D3h point group as well as for n=4 in the Td (tetrahedral) point group a saddle point (imaginary frequency) is observed and global minimum could be obtained along the potential energy surface. 相似文献
975.
新型引发体系引发MMA"活性"自由基聚合 总被引:1,自引:0,他引:1
传统的原子转移自由基聚合(ATRP)引发体系是由卤化物(引发剂)、低价过渡金属和合适的配体组成的络合物(催化剂)[1,2],即RX/Mnt/LX,三部分组成的.但由于卤化物的毒性和低价过渡金属易被空气中的氧气氧化,因此Matyjaszewski等[3,4]和Teyssié等[5]提出了新的引发体系反向ATRP.反向ATRP用传统引发剂(如AIBN)代替卤化物,用高价过渡金属络合物代替原来的催化体系,即AIBN/Mn+1t/LX,就避免了上述两个缺点.反向ATRP的引发反应机理表述如下: 目前已见诸报道的关于反向ATRP的文献甚少[3~5],所使用的引发剂均为AIBN.Wang和Matyja… 相似文献
976.
聚合物固载Co-Pd 催化剂的结构与活性 总被引:3,自引:0,他引:3
采用溶剂化金属原子浸渍(SMAI)法制备了几种不同金属含量的Co Pd催化剂,用X射线衍射、X射线光电子能谱和磁测定对催化剂进行表征,并与普通浸渍法(CI)制得的相同金属含量的催化剂进行比较.结果表明SMAI法制备的催化剂金属粒度小于CI法制备的催化剂,且前者零价金属含量高于后者.SMAI法制备的催化剂Co在表面上富集,而CI法制备的催化剂Co在表面和体相的金属含量基本相同.在二丙酮醇加氢及电催化反应中, SMAI法催化剂比相同组成的CI法催化剂具有更高的催化活性. 相似文献
977.
HU Shanying LI Mingheng LI Yourun SHEN Jingzhu & LIU Zheng Center for Industrial Ecology Department of Chemical Engineering Tsinghua University Beijing China 《中国科学B辑(英文版)》2004,47(3):206-213
Being the core of whole process, a chemical process is a key step for reducing waste generation. Therefore, to organize a reasonable reaction path is very important for reducing waste emission. Because of the large amount of the feasible reaction path and other factors in a chemical reaction system, the opti-mizing for reaction path is difficult. Since the reaction path synthesis problem has presented, lots of re-searchers focused on it. At the beginning, only chem-ists took the research work,… 相似文献
978.
979.
以卤化亚铜(CuX)/1,10-邻二氮菲(phen)配合物为催化剂、2-溴代异丁酸 乙酯(EBiB)为引发剂、十二烷基磺酸钠(SLS)为乳化剂,进行了甲基丙烯酸甲 酯(MMA)的原子转移自由基乳液聚合(ATRP)反应。结果表明,与较高温度(70 - 90 ℃)下的聚合反应相比,室温(25 ℃)时聚合反应有更好的可控性,通过 外加钝化剂的复合催化引发体系CuBr/CuBr_2/phen/EBiB或利用CuCl/phen/EBiB催 化引发体系的“卤素交换反应”,可进一步改善聚合反应的可控性。紫外发光谱测 定结果表明,CuBr/phen配合物在MMA相中的分配倾向随着温度的降低而增大,使得 室温下MMA的乳液ATRP保持了较好的可控性和较快的反应速度。 相似文献
980.