Thermotropic properties of cholesteric liquid crystal from hydroxypropyl cellulose mixed esters

Abstract

Natural polymers such as cellulose are known to form cholesteric liquid crystal (CLC) phases after chemical modification of their side chains. We report on the synthesis of hydroxypropyl cellulose (HPC) ester derivatives and the dependence of their Bragg reflection wavelength on temperature. The reflection wavelengths shifted to longer wavelengths upon heating due to an increase in the CLC helical pitch. When the HPCs were chemically modified by both propionyl and another functional groups such as the cholesteryl moiety, we successfully demonstrated the continuous tuning of the reflection peak throughout the full visible-wavelength range from 400nm to 800nm by sweeping the temperature between 30°C and 80°C.