Cholesteric Liquid Crystals from Cellulose Derivatives with Alkyl Ether Groups

In this study, we synthesized hydroxypropyl cellulose (HPC) derivatives possessing alkyl ether side chains through Williamson ether synthesis. Such HPC ether derivatives exhibited thermotropic cholesteric liquid crystals (CLCs) with Bragg reflection. The temperature dependence of reflection wavelength could be controlled by changing the side chain lengths and etherification degrees in the HPC derivatives. Moreover, the thermal stability of both HPC ester and ether was evaluated before and after heating at 60 degrees C for 20 days. The reflection peak of HPC ester shifted to the longer wavelength upon the heating treatment due to the hydrolysis of ester linkage. On the other hand, we found that the reflection peak of HPC ether can be robustly preserved even after the prolonged heating treatment, arising from the thermal stability of ether linkage. The rational approach addressed here provides promising clues to fabricate the stable photonic CLC devices with refection features by exploiting anti-hydrolysis of the cellulose ether derivatives.