Liquid Crystalline Side Chain Polysiloxanes with 4-Cyano- and 4-Alkoxy-Stilbene Mesogenic Units

Abstract

Side chain homo- and copolysiloxanes with 4-cyano- and 4-alkoxy-4′-stilbene mesogens, spaced apart from the backbone by oligomethylene segments of variable lengths, were synthesized via a hydrosilylation coupling reaction of five stilbene-containing α-olefins with four commercial poly(methylhydrosiloxane)s and poly(methyl-hydro-∞-dimethylsiloxane)s. Broad smectic phases were observed for the polysiloxanes with cyanostilbene mesogens, whereas the homologous with alkoxy-terminated stilbenes displayed only narrow mesophases in the high temperature range. Preliminary room tem-perature X-ray diffraction studies on mechanically oriented samples evidenced the occurrence of side chain crystallization, microphase separation and indicated the interdigitated smectic A nature of the mesophases.