Structure and Swelling Properties of Crosslinked Blend Films of Hydroxypropyl Cellulose and Chitosan.

Abstract

We prepared the blend solution of hydroxypropyl cellulose (HPC) and chitosan (CS), which has the chemical structure similar to HPC, in a co-solvent (aqueous acetic acid solution) and tried to crosslink HPC and CS with a crosslinker (Glutaraldehyde) in the presence of acid catalyst (Hydrochloric acid: HCI). The texture of the cast blend films observed with a polarized microscope depended on the cast conditions; the blend films casted in the presence of HCl exhibited the smooth surface and were insoluble in water and in an aqueous acetic acid solution. The piled network structures were observed with a scanning electron microscope. Circular dichroic (CD) spectroscopy revealed that the homogeneity of macroscopic molecular order is improved and the cholesteric pitch increases with adding HCl.The additivity rule could not be applied to blend composition dependence of both half-value width and wavelength at CD peak. These results suggested that HPC is partially miscible with CS in macroscopic order, and HPC/CS blend would possibly result in a semi-interpenetrating polymer network. The swell ratio depended on the blend compositions and acidity of swelling agent. The blend films of higher HPC component swelled greatly in 100% acetic acid. This will be due to the higher crosslinking density of CS component than that of HPC component.