No abstract

The radical polymerization of various (meth)acrylamides in the presence of Lewis acids such as Yb(OTf)3 and Y(OTf)3 was carried out. The polymerization with Lewis acids led to highly isotactic polymers, while the polymers synthesized without Lewis acids were atactic or syndiotactic. The dependence of the polymer properties on the tacticity was also demonstrated.

The effects of Lewis acids, that is, rare earth metal trifluoromethanesulfonates, on the free-radical polymerization of N-methylmethacrylamide (MMAM), Nisopropylmethacrylamide (IPMAM), N-tert-butylmethacrylamide (tBMAM), N-phenylmethacrylamide (PMAM), and methacrylamide were examined under various conditions. A catalytic amount of Yb(OSO 2 CF 3 ) 3 significantly affected the stereochemistry during the radical polymerization. Polymerization solvents strongly influenced the effect of the Lewis acids. Methanol was the best solvent for increasing the isotactic specificity during the polymerization of MMAM and IPMAM, whereas tetrahydrofuran was more effective for the tBMAM and PMAM polymerizations.

The radical polymerization of an optically active methacrylamide, N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide, was carried out in the absence and presence of Lewis acids such as yittribium trifluoromethanesulfonate [Yb(OTf)3] and scandium trifluoromethanesulfonate [Sc(OTf)3]. Catalytic amounts of the Lewis acids significantly affected the stereoregularity of the obtained polymers. The polymerization with Yb(OTf)3 in tetrahydrofuran afforded isotactic polymers (up to mm = 87%), whereas the conventional radical method without the Lewis acid produced polymers rich in syndiotacticity (up to rr = 88%). The radical polymerization in the presence of MgBr2 proceeded in a heterotactic‐selective manner (mr = 63%). Thus, the isotactic, syndiotactic, and heterotactic poly(methacrylamide)s were synthesized by the radical processes. The chiral recognition abilities of the obtained optically active poly(methacrylamide)s were affected by the stereoregularity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3354–3360, 2003