Asymmetric polymerization of N-1-naphthylmaleimide with chiral anionic initiator:: Preparation of highly optically active Poly(N-1-naphthylmaleimide)

Asymmetric anionic homopolymerizations of N-1-naphthylmaleimide (1-NMI) were carried out with chiral anionic initiator consisting of diethylzinc (Et(2)Zn) and (4S)-2,2'-(1-ethylpropylidene)bis-(4-benzyl-4,5-dihydrooxazole) (Bnbox) to obtain optically active polymers. Poly(1-NMI) obtained with diethylzinc (Et(2)Zn)-Bnbox complex in THF exhibited high specific optical rotation of +296.6 degrees. The high molecular weight part of the poly(1-NMI) resolved by gel permeation chromatography (GPC) showed the highest specific optical rotation of +762.3 degrees. Optical activity of poly(1-NMI) with high specific optical rotation was attributed to not only configurational chirality due to asymmetric carbons in the polymer main chain but also a conformational one based on higher-order structures, i.e., partial helical conformation, judging from the dependence of specific optical rotation on temperatures and molecular weights.