Modeling of crystal dissolution of poly(vinyl alcohol) gels produced by freezing/thawing processes

A model was developed to describe the overall dissolution kinetics of semic rystalline PVA gels prepared by freezing and thawing techniques. The dissol ution process was described as a three-step mechanism: detachment-, diffusi on-, and disentanglement-controlled dissolution. The unfolding of crystalli ne regions due to detachment and diffusion was calculated. The lamellar thi ckness of a PVA crystal was found to significantly change the rate of unfol ding and thus, the overall dissolution kinetics. The model predicted the ef fect of the lamellar thickness, time of swelling, and sample thickness on t he crystal chain unfolding and potential dissolution of freeze/thawed PVA h ydrogels. (C) 2000 Elsevier Science Ltd. All rights reserved.