NEW LOW MOLAR-MASS ORGANOSILOXANES WITH UNUSUAL FERROELECTRIC PROPERTIES

A new low molar mass chiral organosiloxane mesogen and its racemic analogue have been synthesized and their mesomorphic and ferroelectric properties investigated. The chiral derivative, denoted A*B, exhibits one tilted enantiotropic ferroelectric smectic C mesophase over a broad temperature range, with very high tilt angles and moderate spontaneous polarization (36-degrees and 19 nC cm-2 at 20-degrees-C). The achiral siloxane derivative, denoted A(+/-)B, exhibits one broad enantiotropic smectic C phase. Preliminary electro-optic measurements indicate that the spontaneous polarization is weakly dependent on temperature between 10-degrees-C and 50-degrees-C, the latter being the S(C)* to isotropic phase transition. The tilt angle and layer spacing are temperature independent, and current response times of less than 200 mus were measured at 25-degrees-C for fields of 10 V mum-1. These results are discussed in comparison with those for side chain polymer liquid crystal structures and other low molar mass ferroelectric materials.