A clear effect of Lewis acids, such as scandium trifluoromethanesulfonate [Sc(OTf)_3], on Stereocontrol during the radical polymerization of a designed monomer, benzyl α-(methoxymethyl)acrylate was found. This Lewis acid also influenced the stereochemistry in the radical polymerization of methyl methacrylate giving a less syndiotactic and more isotactic polymer, although many Lewis acids were not effective. A catalytic amount of Lewis acids, such as Y(OTf)_3 and Yb(OTf)_3, also significantly enhanced isotactic-specificity during the radical polymerization of acrylamide and its derivatives, N-isopropylacrylamide (NIPAM) and N, N-dimethylacrylamide. Obvious solvent and temperature effects on tacticity were observed in these polymerizations, and poly(NIPAM) with >80% triad isotactic content has been obtained in the presence of Lewis acids.
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