Synthesis and characterization of optically active helical vinyl polymers via free radical polymerization

A facile synthetic route to prepare the dual-functional molecule, 2,5-bis(4′-carboxyphenyl)styrene, was developed. The esterification of this compound with chiral alcohols, that is, (S)-(+)-sec-butanol/(R)-(-)-sec- butanol, (S)-(+)-sec-octanol/(R)-(-)-sec-octanol, and D-(+)-menthol/L-(-)- menthol, respectively, yielded three enantiomeric pairs of novel vinyl monomers, which underwent radical polymerization to obtain helical polymers with an excess screw sense. These polymers exhibited optical rotations as large as fourfold those of the corresponding monomers. Their helical conformations were quite stable as revealed by the almost unchanged chiroptical properties measured at different temperatures. The polymers with linear alkyl tails in the side-groups formed irreversibly columnar nematic phases in melt although the corresponding monomers were not liquid crystalline. Whereas, the polymers with cyclic tails generated no mesophase.