Viscoelastic properties of cholesteric liquid crystals from hydroxypropyl cellulose derivatives

Abstract

In this study, we investigated the rheological behavior of a cholesteric liquid crystalline polymer prepared by esterification of hydroxyl propyl cellulose (HPC) with propionyl chloride. The HPC ester tethering propionyl side chains (HPC-Pr) showed thermotropic cholesteric liquid crystal (CLC) phase with visible Bragg reflection in the temperature range between 100 ºC and 135 ºC. Although visible Bragg reflection of HPC-Pr disappeared even after cooling from the temperature above isotropic phase transition temperature, we observed birefringence under crossed Nicols. Therefore, at this state, the molecular structure of HPC-Pr might be partially isotropic. The partially isotropic HPC-Pr had a relatively high viscosity as confirmed by rheological measurements. On the other hand, the viscosity decreased by shearing.