Synthesis and Optical Properties of Completely Etherified Hydroxypropyl Cellulose Derivatives

Previously, we have reported on the preparation of hydroxypropyl cellulose (HPC) ether derivatives by the Williamson ether synthesis as SN2 reaction. In this article, we carried out the optimization of synthesis conditions to obtain the completely etherified HPC derivatives tethering hexyl ethers in the side chains (HPC-HeEt). By adopting N-methyl-2-pyrrolidinone (NMP) as a reaction solvent, as-synthesized HPC-HeEt showed high substitution degree of hexyl ethers, probably arising from high solubility of NaOH in NMP. Moreover, this optimized reaction condition enabled to apply the synthesis of completely etherified HPC derivatives with different length of alkyl chains. These HPC ether derivatives showed thermotropic cholesteric liquid crystal (CLC) phase with visible Bragg reflection. As a result, their reflection properties would be stable against humidity due to the robust bonding of ether group rather than ester.