Synthesis and characterization of optically active helical polymers based on 2,5-di(4′-formylphenyl)styrene

2, 5-Di (4′-formylphenyl) styrene was synthesized via Suzuki cross-coupling reaction of 2, 5-dibromostyrene and p-formylphenylboronic acid. In the presence of catalytic amount of glacial acetic acid, a pair of chiral nonracemic vinyl monomers, (+)-2,5-di {4′-[(N-(S)-α- methylbenzylimine)methylene]phenyl} styrene (M 1)and(-)-2,5-di {4′-[(N-(R)-α-methylbenzylimine) methylene] phenyl} styrene (M 2),was synthesized through the condensation reaction between 2, 5-di (4′-formylphenyl) styrene and optically pure α-methylbenzylamine. Optically active polymers were prepared via free radical polymerization of M 1 and M 2 initiated by AIBN or BPO depending on polymerization temperature. The results from specific optical rotation, UV-Vis absorption spectra and circular dichroism spectra indicated that the polymer obtained might adopt a helical conformation with a predominance of one helical screw sense. The polymerization condition had pronounced effects on the chiroptical properties of the polymers. Polymer with larger helical chirality was obtained when the polymerization was carried out in more polar aromatic media at higher temperature. Due to the steric hindrance of the bulky p-terphenyl groups, the main chain helical chirality formed during polymerization was thermally stable and displayed memory effect.