DIMESOGENIC LIQUID-CRYSTALLINE OLIGOSILOXANES

In this paper, the syntheses, phase properties and ferroelectric prope rties of new Liquid crystalline oligosiloxane dimesogens are described . Smectic phases are dominant in this class of materials. Spontaneous polarizations are in the range of 10 to approximately 100 nC cm(-2). T he materials show interesting properties for display applications. Alt hough offering higher mechanical stability than low molar mass materia ls, their switching is significantly faster (switching times in the ra nge of some 10(-5)s) than is the case for similar side group polymers (typically some 10(-3)s). Therefore these new oligosiloxane derivative s may be ideal for building flexible displays. In addition, mixtures o f oligosiloxane dimesogens were compared with copolymers and with silo xane-free low molar mass materials bearing the same mesogenic groups. The results support the idea of a 'virtual polymer backbone', which is formed by a microphase separation phenomenon. Dimesogenic siloxane mi xtures and copolymers behave quite similarly, while the siloxane-free mixtures show a different phase behaviour.