含矽氧烷液晶化合物之合成

Abstract

The goal of this reserach is to synthesize some new siloxane-containing nematic liquid crystals and ferroelectic liquid crystals. The effects of different siloxane moieties, spacer length and mesogenic group on the mesomorphic properties of the liquid crystals were studied. Spontaneous polarization of some ferroelectric liquid crystals was also examined. In this study, pentamethydisiloxane and heptamethyltrisiloxane were reacted with olefinic precursors via hydrosilylation reaction using platium divinylteramethyldisiloxane complex as a catalyst to yield six series of new siloxane-containing liquid crystals. In the first series of obtained compounds, most of siloxane-containing liquid crystals present a smectic phase, while the corresponding olefinic precursors display a nematic phase. The obtaind compounds also have a tendency to show a lower phase transition temperature and a higher-ordered mesophase, i. e., smectic phase comparing to their precursors. The second and third series of siloxane-containing compounds exhibit a nematic phase as we expected. Three series of siloxane-containing ferroelectric liquid crystals were also prepared. They all contained a (2S, 3S)-2-chloro-3-methyl-valverate chiral group. The fifth serires of siloxane-containing compounds exhibit smectic A and smectic B phases, while the others reveal the chiral smectic C phase besides the smectic A phase. Several siloxane-containing compounds also show a chiral smectic C phase which covers the room temperature range. The obtained compounds indeed show boarder mesophase temperature ranges and lower Sc* transition temperatures than their precursor. In our study, most of obtained ferroelctric liquid crystals posess rather high spontaneous polarization (Ps) value, which have the potential applications in ferroelectric liquid crytal display.