Optically active poly(meth)acrylamides were synthesized by the stereospecific radical polymerization of (S)-N-(2-hydroxy-1-phenylethyl)methacrylamide ((S)-HPEMA) and (S)-N-(2-hydroxy-1-phenylethyl)acrylamide ((S)-HPEA) in the absence and presence of Lewis acid ytterbium trifluoromethanesulfonate (Yb(OTf)3).The effect of the Lewis acid on the radical polymerization of (S)-HPEMA and (S)-HPEA was investigated.In the presence of a catalytic amount of the Lewis acid

the isotactic specificity of the polymers remarkably increased when the radical polymerization proceeded in methanol and n-butanol. However

the isotactic selectivity disappeared when the radical polymerization proceeded in DMSO.The interaction between the Lewis acid and monomers (S)-HPEMA and (S)-HPEA was investigated by 1H-NMR.It was found that the monomers strongly interacted with the Lewis acid in methanol-d4

which included the coordination of the amide group to the rare earth metal ion and the hydrogen bond between the hydroxyl group of the monomers and the trifluoromethanesulfonate ion of the Lewis acid.The plausible mechanism of stereocontrol in the radical polymerization of (S)-HPEMA and (S)-HPEA was analyzed.The monomers are activated by the interaction with the Lewis acid

and the activated monomer is preferentially polymerized.Therefore

the Lewis acid is incorporated into the propagating chain end.The Lewis acid could interact with two or more structural units

because of its high coordination numbers and more than one triflate ions

and control the stereochemistry of the polymerization to an isotactic-selective manner.The Lewis acid might weakly interact with the polymer chain to be readily transferred to another monomer and activate it.