Effect of casting solvent on characteristics of hexanoyl chitosan/polylactide blend films

Blend films of hexanoyl chitosan (H-chitosan) and polylactide (PLA) were cast from corresponding blend solutions in chloroform, dichloromethane, or tetrahydrofuran. Thermal degradation behavior of the as-prepared blend films was intermediate to those of the pure components and no significant effect from the type of the casting solvent was observed. All of the blend films exhibited one composition-dependent glass transition temperature, but the results only suggested partial miscibility of the components in the amorphous phase at "low" contents of H-chitosan. As revealed by solvent etching technique, the as-prepared blend films prepared from the blend solutions in chloroform and dichloromethane showed extensive phase separation of the two components, with the minor phase forming into discrete domains throughout the matrix. Both thermal and X-ray analyses showed that the apparent degree of crystallinity of the PLA component in the blends decreased monotonically with increasing Hchitosan content and the choice of the casting solvent did not have an effect on the structure of PLA crystals. (c) 2007 Wiley Periodicals, Inc.