Swelling behavior of poly(N-vinyl-2-pyrrolidone) and poly(N-vinyl-2-pyrrolidone)/K2S2O8 hydrogels in urea solutions

Hydrogels with varying cross-linking densities and average molecular weight s between two consecutive cross-links were prepared from the binary poly(N- vinyl-2-pyrrolidone)/water and ternary poly(Nw-vinyl-2-pyrrolidone)/water/K 2S2O8 systems by irradiation with gamma rays at ambient temperature. Both h ydrogel systems were employed for diffusion and swelling experiments in var ious urea solutions at room temperature. Diffusion of urea solutions into h ydrogels has been found to be of the non-Fickian type, except for the sampl es of PVP/K2S2O8 hydrogels irradiated at higher doses in dilute urea soluti ons. The percent swelling, equilibrium swelling, initial rate of swelling, swelling rate constant, equilibrium water/urea content, and diffusion const ant values were evaluated for PVP and PVP/K2S2O8 hydrogel systems at two di fferent urea concentrations. With regard to swelling data, it was determine d that the dilute urea solution tan penetrate much more effectively into th e PVP/K2S2O8 hydrogel system. (C) 2000 John Wiley & Sons, Inc.