PRETRANSITION ELECTROOPTIC PROPERTIES OF SOLUTIONS OF LIQUID-CRYSTAL POLYSILOXANES IN THE PHASE-SEPARATION REGION

This paper discusses the electrooptic Ken: effect in dilute solutions close to their stratification temperature and in melts in the neighbor hood of the temperature of the isotropic-liquid-nematic-phase transiti on of two comb-shaped liquid-crystal polysiloxanes with different chem ical structures of the mesogenic side groups. It is shown that pretran sition effects associated with self-organization processes of the mole cules of the polymers in the critical temperature region are observed both in solutions and in melts of the polymers. The largest variations were observed close to the stratification temperature of polysiloxane solutions, where not only did the absolute magnitude of the Ken const ant increase (by a factor of about 10(3)), but the sign of the effect also changed. The electrooptic properties studied here in polysiloxane s are compared with the features of the chemical structure of the poly mers and low-molecular-weight analogs of their mesogenic groups. (C) 1 998 The Optical Society of America.