Thioindigo-containing organosiloxane liquid crystals with electroclinic properties

Two mesogenic thioindigo derivatives containing oligomeric di- and trisilox ane end-groups were synthesized in optically pure form. These materials for m enantiotropic SmA* liquid crystal phases over temperature ranges of 120-1 43 degreesC and 110-146 degreesC, respectively, and exhibit electroclinic s witching. The electroclinic coefficient for the trisiloxane derivative at T - T-C = 8 K is 0.4 degrees V-1 mum(-1). The formation of a SmA* phase by t hese thioindigo derivatives is due primarily to the tendency of siloxane an d paraffinic moieties to micro-segregate into distinct sublayers within a l amellar structure. To the best of our knowledge, these are the first two ex amples of thioindigo-containing liquid crystals to be reported in the liter ature.