Synthesis and anionic polymerization of optically active N-phenylmaleimides bearing bulky oxazoline substituents

Anionic polymerizations of chiral N-phenylmaleimide derivatives bearing an oxazoline pendant (OPMI) were carried out with n-BuLi initiator to obtain optically active polymers. The polymer yields and specific optical rotations (image) were found to be significantly influenced by the reaction solvent, temperature, and the molar ratio of initiator to monomer. Particularly, the specific optical rotations exhibited a linear dependence on the molecular weights for the formed polymers, and the inversion from levo- to dextro-specific rotation was also observed with an increase in the molecular weights. On the basis of the results from circular dichroism (CD) and 13C NMR spectral analyses, the optical activity of poly(OPMI)s was attributed not only to the chirality of oxazolinyl groups in monomeric units but also to the partial helical structure due to an excess of threo-diisotactic configuration in the main chain.