SYNTHESIS OF LIQUID-CRYSTALLINE POLYSILOXANES AND POLYMETHACRYLATES WITH BROAD TEMPERATURE RANGES OF THE CHIRAL SMECTIC-C PHASE

Abstract

The synthesis of side-chain liquid crystalline polysiloxanes and polymethacrylates containing oligooxyethylene spacers and 4-(S)-2-methyl-1-butyl [[(4-hydroxybiphenyl-4'-yl)carbony;]oxy]benzoate mesogenic side groups is presented. Differential scanning calorimetry, optical polarizing microscopy, and X-ray diffraction measurements reveal chiral smectic mesomorphism for all polymers. All three polysiloxanes present enantiotropic smectic A and chiral smectic C phases. The chiral smectic C phase covers a very broad temperature range (about 200-degrees-C). Among polymethacrylates prepared in this study, the polymethacrylate which contains three oxyethylene units in its spacer is the only one revealing smectic A and chiral smectic C phases. The results seem to demonstrate that the tendency toward a chiral smectic C phase increases with increasing the flexibility of the polymer backbone and the oligooxyethylene spacer can increase dramatically the thermal stability of the chiral smectic C phase.