A NEW MAIN-CHAIN THERMOTROPIC LIQUID-CRYSTALLINE POLYMER-BASED ON A SUBSTITUTED CYANOSTILBENE - SYNTHESIS, THERMOOPTIC OBSERVATIONS AND LINEAR ELECTROOPTIC EFFECT MEASUREMENTS

A main-chain liquid-crystalline polymer based on an unsymmetrically di substituted cyanostilbene has been synthesized and characterized. The polymer exhibited a highly birefringent nematic texture, followed at h igher temperatures by a uniaxial nematic structure the scattering char acteristics of which were two to three orders of magnitude smaller tha n those normally observed in liquid-crystalline materials. Thin solid films prepared by rapid cooling of the polymer in the monotropic state retained the molecular organization and scattering behaviour of this phase. A preliminary evaluation of the second-order nonlinear optical properties associated with these film structures was carried out by me ans of a crossed polarizer technique.