Abstract

Two mesogenic thioindigo derivatives containing oligomeric di- and trisiloxane end-groups were synthesized in optically pure form. These materials form enantiotropic SmA* liquid crystal phases over temperature ranges of 120–143 °C and 110–146 °C, respectively, and exhibit electroclinic switching. The electroclinic coefficient for the trisiloxane derivative at T − T_C = 8 K is 0.4° V⁻¹ µm⁻¹. The formation of a SmA* phase by these thioindigo derivatives is due primarily to the tendency of siloxane and paraffinic moieties to micro-segregate into distinct sublayers within a lamellar structure. To the best of our knowledge, these are the first two examples of thioindigo-containing liquid crystals to be reported in the literature.