A high resolution temperature scanning technique for optical studies of liquid crystal phase transitions

Abstract

A temperature scanning attachment for the polarizing microscope is described that offers a simple but powerful technique with which to detect even subtle paramorphotic phase transitions in liquid crystals with high temperature resolution. This technique was applied to CE8, a well known reference compound exhibiting rich mesomorphism. All smectic transitions in CE8 were clearly detected by distinct singularities in the temperature dependence of the transmitted light intensity. Repeated temperature scans across the second order ferroelectric smectic A*-C* transition with various orientations of polarizer and analyser provide high resolution data of optical birefringence and optical tilt angle. These data confirm a mean-field to tricritical crossover in the power law exponent of the optical tilt.