Synthesis and characterization of optically active polyimidothioethers

New optically active polyimidothioethers derived from chiral bismaleimides and 1, 5-pentandithiol were synthesized by Michael-type polyaddition. Chiral bismaleimides were obtained by the reaction of 4-maleimidobenzoic acid or its acid chloride with (L)-cystine, (L)-lysine or (R)-2-amino-1-butanol, and they are prochiral monomers too. The polyaddition proceeds with a quite low stereoselectivity in terms of asymmetric induction on the configuration of the newly formed chiral centers. The structures of the new polymers were confirmed by elemental analysis and spectral methods (IR and H-1-NMR). The molecular weights of the polymers were estimated by gel permeation chromatography and a correlation with viscometric data was found. Optical activity was evidenced by polarimetric measurements. Thermal behavior was investigated by thermogravimetric analysis and differential scanning calorimetry. The X-ray diffractograms revealed an amorphous structure of polymers due to a low degree of stereoregularity originated by the presence of randomly distributed constitutional repeating units having different diastereomeric configurations.