Asymmetric Polymerization of N-1-Naphthylmaleimide with Chiral Anionic Initiator: Preparation of Highly Optically Active Poly(N-1-naphthylmaleimide)

Abstract

Asymmetric anionic homopolymerizations of N-1-naphthylmaleimide (1-NMI) were carried out with chiral anionic initiator consisting of diethylzinc (Et2Zn) and (4S)-2,2‘-(1-ethylpropylidene)bis(4-benzyl-4,5-dihydrooxazole) (Bnbox) to obtain optically active polymers. Poly(1-NMI) obtained with diethylzinc (Et2Zn)−Bnbox complex in THF exhibited high specific optical rotation of +296.6°. 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°. 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.