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811.
The living cationic polymerization of vinyl ethers (VEs) having a (polar) functional pendant has been achieved by the hydrogen iodide/iodine (HI/I2) initiating system to give polymers with a very narrow molecular weight distribution (MWD) (Mw/Mn ≤ 1.2). The functional pendants include benzyl, saturated or unsaturated ester, (poly) oxyethylene, and substituted phenoxyl groups. Although these polar groups often disturb cationic vinyl polymerization by inducing chain transfer and termination, the HI/I2 initiator cleanly polymerized the “functionalized” VEs without side reactions, mostly in nonpolar media at low temperatures below −15 °C. The HI/I2-initiated living polymerization also provided facile methods to synthesize new functional polymers, including water-soluble polymers, macromolecular amphiphiles, and macromers, all having a narrow MWD. The simplest example is the living polymerization of VEs carrying an oxyethylene chain [-(CH2CH2O)n-R] as pendant, which directly yields water-soluble polymers. The debenzylation of poly(benzyl VE) prepared with HI/I2 led to poly(vinyl alcohol). Polymers of the saturated ester-containing monomers (2-acetoxyethyl and 2-benzoyloxyethyl VEs) were readily hydrolyzed into poly (2-hydroxyethyl VE), soluble in water and swellable in methanol. This lead was extended to the synthesis of a new amphiphile, poly(cetyl VE-b-2-hydroxyethyl VE), from a block copolymer of cetyl and 2-acetoxyethyl VEs prepared by their sequential living polymerization initiated with HI/I2. An adduct between HI and 2-vinyloxyethyl methacrylate [CH3-CH(I)-OCH2CH2OCOC(CH3) =CH2] was found to initiate living polymerizations of VEs in the presence of iodine; the products were methacrylate-type macromers carrying a poly(VE) side chain with a narrow chain-length distribution. 相似文献
812.
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814.
This paper discusses recent developments in living cationic polymerization of vinyl monomers, specifically focusing on (a) new initiating systems, (b) kinetics and mechanism, and (c) controlled polymer synthesis. The new initiating systems were based on nucleophilic stabilization of the growing carbocations, either by counteranions (as in phosphate/ZnI2 and Me3SiI/ZnI2 systems) or by added Lewis bases (as 2,6-dimethylpyridine for EtAlCl2). The kinetic study included the determination of the lifetime of living cationic polymers. The controlled polymer synthesis by living cationic processes led to not only end- and pendant-functionalized polymers of narrow molecular weight distributions but also star-shaped polymers and sequence-regulated vinyl ether oligomers with functional groups. 相似文献
815.
Jun-ichi Kadokawa Yasuhiro Iwasaki Hideyuki Tagaya 《Macromolecular rapid communications》2002,23(13):757-760
Ring-opening polymerization of ethylene carbonate in the presence of ionic liquids, 1-butyl-3-methylimidazolium chloroaluminate melt and 1-butyl-3-methylimidazolium chlorostannate melt, has been investigated. Polymerization takes place accompanied with decarboxylation even at temperatures below 100°C under the reaction conditions selected to give poly(ethylene ether-carbonate)s. 相似文献
816.
Shokyoku Kanaoka Yohtaro Fujita Toshinobu Higashimura 《Macromolecular rapid communications》2000,21(5):218-222
Star‐shaped polymers of isobutyl vinyl ether (IBVE) with many arms (“crew cut” type) have been synthesized by living cationic polymerization using the HCl‐IBVE adduct/ZnCl2 initiating system. A short living polymer (DPn ⪇ 30) of IBVE is allowed to react with a large amount of divinyl ether ([divinyl ether]0/[P*] = 10–15) to give soluble star polymers whose number of arms ranged from 40 to 120. The diameter of such “crew cut” star polymers reached ca. 20 nm. 相似文献