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

The synthesis of side-chain liquid crystalline polysiloxanes and polym ethacrylates 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 polari zing microscopy, and X-ray diffraction measurements reveal chiral smec tic mesomorphism for all polymers. All three polysiloxanes present ena ntiotropic smectic A and chiral smectic C phases. The chiral smectic C phase covers a very broad temperature range (about 200-degrees-C). Am ong polymethacrylates prepared in this study, the polymethacrylate whi ch contains three oxyethylene units in its spacer is the only one reve aling smectic A and chiral smectic C phases. The results seem to demon strate that the tendency toward a chiral smectic C phase increases wit h increasing the flexibility of the polymer backbone and the oligooxye thylene spacer can increase dramatically the thermal stability of the chiral smectic C phase.