Effect of the Phase Transition of Smectic Liquid-Crystalline Solvent on the Thermal lsamerizatian of Thioindigo Derivatives

Abstract

Matsugasaki, Sakyo-ku, Kyoto-shi 606 Japan The rates and the activation parameters for the thermal cis-to-trans isomerization of three different groups of thioindigo dyes, 5, 5'-dialkylthioindigo dyes [1], 7, 7'-bis(alkoxycarbonyl)thioindigo dyes [2], and 7, 7'-bis[(2-alkoxyethyl)oxycarbonyl] thioindigo dyes [3] embedded in a smectic mesophase of butyl stearate were determined. The transition of the liquidcrystalline to the isotropic phase affected the reactivity for isomerization of 1 and 2, depending upon the alkyl length. Whereas the mesophase had no influence on the isomerization of 3, irrespective of the alkyl length.