Characterization of blend films of chitin regenerated from porous chitosan with poly(vinyl alcohol)

To regenerate chitin with high degree of N-acetylation and low degree of crystallinity, porous chitosan was N-acetylated with acetic anhydride in 10% aqueous methanol solution. Regenerated chitin (r-Ch) showed a quick dissolution in N,N-dimethylacetamide (DMA) containing 5% LiCl. In this solvent, r-Ch and poly(vinyl alcohol) (PVA) were compatible, and a series of blend films of r-Ch/PVA ranging in composition from 20/80 to 95/5 (w/w) were prepared from these solutions by coagulation in 2-propanol and subsequent drying. The miscibility of component polymers in the blends was investigated by differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectrophotometry. The glass transition temperature of the blends slightly shifted to the higher temperature region with increasing the r-Ch content, suggesting that the component polymers were partially miscible. The melting temperature and the heat of fusion of PVA in the blends decreased with decreasing the PVA content. These results denoted that the crystallinity of PVA decreased with increasing the r-Ch content, suggesting that the miscibility mas higher at the higher r-Ch content region. FT-IR spectra indicated the presence of specific intermolecular interaction between the component polymers:hydrogen bonding between -OH groups.