Radical polymerization of poly(ethylene oxide) macromonomers carrying a methoxy group on the one end and a p-vinylbenzyl or a (p-vinylphenyl)butyl group on the other end was investigated in benzene and water. The overall rate of polymerization was found to be more than 50 times higher in water than that in benzene. Apparent rate constants of propagation and termination were evaluated based on ESR measurements under irradiation, while initiator efficiency was estimated from inhibition period measurements. Very rapid polymerization in water was then reasonably attributed to a combined result of locally concentrated propagating radicals and monomers in their micellar organization, together with high initiator efficiency, enhanced rate of propagation, and reduced rate of termination there.
ABSTRACT:We report organocuprates initiated anionic polymerizations of various a,{J-unsaturated ester monomers in tetrahydrofuran (THF) under various conditions. It was found that catalysts prepared by reaction of Cul with methyllithium (MeLi) very effectively cause the polymerization of meth(acrylate) monomers. At molar ratio of [MeLi] to [Cul] higher than 2 the polymerization of t-butyl methacrylate (TBMA) proceeded quantitatively in THF at 0--45°C to afford high molecular weight poly(t-butyl methacrylate) (PTBMA) with extremely narrow molecular weight distribution (MWD) (Mw/M.=l.0 5-1.17). Initiator efficiency was less than 10% and highest at about [MeLi]/[Cul]=4.0. The post-polymerization proved the livingness of the polymerization of TBMA caused by lithium methylcuprate in THF at O °C. The active species for the polymerization ofTBMA was thought to be higher cuprate, such as Li2Cu(CH3h. For the polymerizations of other methacrylates and t-butyl acrylate lithium methylcuprate initiators effectively afforded the polymers but with very broad MWD.
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