Temperature-Dependent Tilt Angle in the SmecticCPhase of a Liquid Crystal

Abstract

Measurement of the tilt angle of the smectic $C$ phase of terephthal-bis-($4-n-\mathrm{b}\mathrm{u}\mathrm{t}\mathrm{y}\mathrm{l}\mathrm{a}\mathrm{n}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{n}\mathrm{e}$) has been made using conoscopic observation and circularly polarized light. The new phenomenon of a smectic $C$ phase with a temperature-dependent tilt angle is reported. Terephthal-bis-($4-n-\mathrm{b}\mathrm{u}\mathrm{t}\mathrm{y}\mathrm{l}\mathrm{a}\mathrm{n}\mathrm{a}\mathrm{l}\mathrm{i}\mathrm{n}\mathrm{e}$) has nematic, smectic $A$, smectic $C$, and smectic $B$ liquid-crystalline phases. The tilt angle of smectic $C$ changes from 0° at the smectic-$A-\mathrm{s}\mathrm{m}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{c}-C$ transition to approximately 26° at the $\mathrm{s}\mathrm{m}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{c}-C-\mathrm{s}\mathrm{m}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{c}-B$ transition temperature.