Properties Research on Chiral Liquid Crystalline Polysiloxanes Containing Chiral and Electron Withdrawing Group

Abstract

A series of new chiral side-chain liquid crystalline polysiloxanes(P0-P7) bearing cyano groups were synthesized with a cholesteric LC monomer and a nematic monomer with cyano units(electron withdrawing). The chemical structures and LC properties of the polymers were measured by spectrum and thermal analysis techniques. The obtained polymers were soluble in many solvents and the specific rotations showed negative values and increased with the increasing content of chiral reagent. P1 showed grained texture of smectic A, P2~P7 showed lined texture of chiral smectic C(SC*). XRD curves of P1~P7 samples showed sharp and strong peaks at low angle, but no sharp peak was seen for P0 sample. The temperatures at which 5% weight loss occurred(Td) were greater than 300oC for all the polymers, which reveals all the polymers were stable. And the Tg values of polymers were all low. The Tg and Ti values are all increased with the increasing chiral contents. All the polymers displayed wide range of liquid crystal phase on heating and cooling cycle.