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Catalyst System. (catalyst + system)
Selected AbstractsReverse atom transfer radical polymerization of MMA via immobilized catalysts in imidazolium ionic liquidsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Najun Li Abstract Reverse atom transfer radical polymerization (RATRP) of methyl methacrylate (MMA) employing immobilized catalyst was approached at 50 and 60°C in [C8mim]PF6, and compared with the polymerization of MMA DMF as solvent. Other ionic liquids, [C6mim]BF4, [C8mim]BF4, and [C12mim]BF4, were used as solvents to perform the RATRP of MMA. By comparison, we found that the [C8mim]PF6 was the best solvent in this immobilized catalyst system and the polymerization was best controlled. In addition, the immobilized catalyst spherules can easily separate from the reaction mixture, which avoids the prevalent problem of the catalyst residual in RATRP and also gives us a possibility to recycle the catalyst system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3915,3919, 2007 [source] Preparation of high cis -1,4 polyisoprene with narrow molecular weight distribution via coordinative chain transfer polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010Changliang Fan Abstract High cis -1,4 polyisoprene with narrow molecular weight distribution has been prepared via coordinative chain transfer polymerization (CCTP) using a homogeneous rare earth catalyst composed of neodymium versatate (Nd(vers)3), dimethyldichlorosilane (Me2SiCl2), and diisobutylaluminum hydride (Al(i -Bu)2H) which has strong chain transfer affinity is used as both cocatalyst and chain transfer agent (CTA). Differentiating from the typical chain shuttling polymerization where dual-catalysts/CSA system has been used, one catalyst/CTA system is used in this work, and the growing chain swapping between the identical active sites leads to the formation of high cis -1,4 polyisoprene with narrowly distributed molecular weight. Sequential polymerization proves that irreversible chain termination reactions are negligible. Much smaller molecular weight of polymer obtained than that of stoichiometrically calculated illuminates that, differentiating from the typical living polymerization, several polymer chains can be produced by one neodymium atom. The effectiveness of Al(i -Bu)2H as a CTA is further testified by much broad molecular weight distribution of polymer when triisobutylaluminum (Al(i -Bu)3), a much weaker chain transfer agent, is used as cocatalyst instead of Al(i -Bu)2H. Finally, CCTP polymerization mechanism is validated by continuously decreased Mw/Mn value of polymer when increasing concentration of Al(i -Bu)2H extra added in the Nd(ver)3/Me2SiCl2/Al(i -Bu)3 catalyst system. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Preparation and characterization of SBA-15 supported iron(II)-bisimine pyridine catalyst for ethylene polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2004Chao Guo Abstract 2,6-Diacetylpyridinebis (2,6-diisopropylani) iron dichloride, a late-transition metal catalyst for olefin polymerization, was supported on SBA-15 successfully and the property of the supported catalyst was carefully studied. Ethylene polymerization was systematically investigated in the presence of MAO under various conditions employing this type of catalyst system. In general, after support, a decrease in the catalytic activity was observed and higher molecular weight and fibrous morphology of polyethylene were obtained. The "extrusion polymerization" phenomenon was observed in ethylene polymerization by using the supported catalyst system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4830,4837, 2004 [source] Facile synthetic route to polymerizable hindered amine light stabilizers for transition-metal-catalyzed olefin copolymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2004M. Auer Abstract This work describes a facile method by which a polymerizable hindered amine light stabilizer, 4-(10-undecylidene)-2,2,6,6-tetramethylpiperidine, was prepared in a single-step procedure by means of a Wittig reaction. The monomer was successfully copolymerized with ethylene with a rac -[dimethylsilylenebis(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride/methylalumoxane catalyst system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1350,1355, 2004 [source] | ||||||||||