Mesomorphism and photocuring processes of (2-hydroxypropyl) cellulose cinnamate

Abstract

Mesomorphism and photocuring processes of (2- hydroxypropyl)cellulose cinnamate (CYPC) were investigated. The CYPC was synthesized in the course of estrification of (2-hydroxypropyl)cellulose (HPC) by cinnamoyl chloride. The chemical structure of CYPC was confirmed by IR and Raman spectroscopy. The substitution degree of HPC by cinnamoyl ester groups was calculated from 1H-NMR studies. The thermotropic mesomorphism of CYPC was confirmed by DSC, thermo-optical and X-ray investigations. The thermo-optical behaviors of CYPC tablet obtained under pressure and results of the dielectric spectroscopy investigations were interpreted in terms of the strong hydrophobic effect of the cinnamoyl ester groups. The cycloaddition of the cinnamoyl groups is initiated either by UV radiation or temperature, inside of the hydrophobic aggregates of the cinnamoyl ester groups. The chemical modification of the hydrophobic aggregates in the course of thermo- or photoaddition of the cinnamoyl ester groups slightly changes a molecular movement of the poly(saccharide) main chains of CYPC. However, these crossed aggregates can recover macromolecular orientation of CYPC from the isotropic state via the cooling of sample. These suggest that the hydrophobic aggregates after thermal or photochemical modification shows an anisotropic behavior.