Morphology and mechanical properties of pullulan/poly(vinyl alcohol) blends crosslinked with glyoxal

We prepared pullulan/poly(vinyl alcohol) (PVA) blend films by casting the p olymer solution in dimethyl sulfoxide. Their morphology and mechanical prop erties were investigated. Scanning electron micrographs revealed that the p ullulan was immiscible with PVA over the entire composition range. The tens ile strength and modulus of the blend films were lower than those predicted by the upper bound composite equation. To improve the mechanical propertie s, we investigated the reaction of the 40/60 blend with glyoxal. The infrar ed spectral change and the increase in the glass-transition temperature (co rresponding to the PVA component) accompanying the reaction indicated that crosslinking with glyoxal had proceeded. The crosslinked films were homogen eous and had higher tensile strengths and moduli than the simple blend. (C) 2001 John Wiley & Sons, Inc.