Dimesogenic liquid crystalline oligosiloxanes

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Abstract
In this paper, the syntheses, phase properties and ferroelectric properties 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 nCcm−2. The materials show interesting properties for display applications. Although offering higher mechanical stability than low molar mass materials, their switching is significantly faster (switching times in the range of some 10−5s) than is the case for similar side group polymers (typically some 10−3s). Therefore these new oligosiloxane derivatives may be ideal for building flexible displays. In addition, mixtures of oligosiloxane dimesogens were compared with copolymers and with siloxane-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 mixtures and copolymers behave quite similarly, while the siloxane-free mixtures show a different phase behaviour.