| Abstract
| - The homogeneous controlled/“living” free radicalpolymerization of methyl methacrylate(MMA) by atom transfer radical polymerization (ATRP) using aCuIX/4,4‘-di(5-nonyl)-2,2‘-bipyridinecatalytic system (X = Cl, Br) with various initiators R−X wasinvestigated. The rates of polymerizationinitiated by most of the systems exhibited first-order kinetics withrespect to the monomer. A linearincrease of number average molecular weight (Mn)versus monomer conversion was observed for most ofthese initiation systems. The benzhydrylchloride/CuICl system yielded the lowest rate ofpolymerization,which could be increased by slow addition of the initiator. Thereduced rate of polymerization was dueto an increase in the concentration of CuIICl, whichresults from the coupling of benzhydryl radicalsduring initiation. The slow addition of benzhydryl chlorideprevented the formation of a large amountof benzhydryl radicals in the initiation step, thereby reducingradical−radical termination and CuIIformation, and led to an increase in the rate of polymerization.p-Toluenesulfonyl chloride/CuIBrgavebetter control of molecular weight and lower polydispersities thanp-TsCl/CuICl, possibly due to thefasterdeactivation step in ATRP. Ethyl2-bromoisobutyrate/CuIBr gave the fastest rate ofpolymerization amongall the initiation systems but showed some deviation inMn at high conversions. The initiationefficienciesof diethyl 2-bromomalonate and diethyl 2-bromo-2-methylmalonate in theATRP of MMA were examined.The latter can initiate polymerization efficiently, while theformer gave no polymerization. This can beexplained by the difference in the electronic nature of the two malonylradicals generated during initiation.Such experimental observations, coupled with data from theliterature, lead to some general “rules” bywhich successful initiation of ATRP can be achieved.
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