Swelling and mechanical properties of glycol chitosan/poly(vinyl alcohol) IPN-type superporous hydrogels

Glycol chitosan/poly(vinyl alcohol) interpenetrating polymer network type superporous hydrogels were prepared using a gas foaming/freeze-drying method. The effect of the molecular weight of the strengthener, poly(vinyl alcohol) (PVA), on the swelling and mechanical behavior of the superporous hydrogels was investigated. The introduction of a small amount of high molecular Weight PVA significantly enhanced the mechanical strength but slightly reduced the swelling capacity. The freezing/thawing (F/T) drying process had a significant effect on the physical properties of the glycol chitosan/PVA superporous hydrogels, because hydrogen bonds were formed between the PVA molecules as a result of the number of F/T cycles. The swelling ratio decreased but the mechanical strength increased with increasing freezing time. However, this effect was not as strong as the number of F/T cycles. The differential scanning calorimetry was used to examine how the thermal behavior associated with the hydrogen bond-induced crystalline structure was affected by the F/T process. (c) 2006 Wiley Periodicals, Inc.