SYNTHESIS OF NOVEL LIQUID-CRYSTALLINE THIOPHENE DERIVATIVES AND EVALUATION OF THEIR PHOTORESPONSIVE BEHAVIOR

Novel liquid-crystalline (LC) thiophene derivatives were synthesized, and their LC behavior and photoresponsive behavior were explored. Amon g the thiophene derivatives synthesized, 4-(4-alkylphenylazo)phenyl 2- thienylacrylates (TAn, n = 4, 5, 6, and 7) were found to show nematic (N) phase. TAn exhibited the N phase only when the azobenzene moiety i n the molecule was in the trans form while no LC phase when the azoben zene was in the cis form. Photoirradiation of TA6 in a cell to bring a bout the trans-cis isomerization of the azobenzene moiety resulted in disappearance of the N phase. The N phase was restored when the irradi ated sample was kept in the dark. Time-resolved measurements by means of a laser pulse (355 nm; 10 ns fwhm) revealed that in transmission-mo de analysis the N-isotropic phase transition was completed in 8 ms, wh ile in reflection-mode analysis it occurred in 100 mu s.