Characterization and determination of swelling and diffusion characteristics of poly(N-vinyl-2-pyrrolidone) hydrogels in water

Hydrogels in the form of rods with varying crosslink densities and three-di mensional network structures were prepared from Poly(N-vinyl-2-pyrrolidone) (PVP)/water and PVP/water/persulfate systems by irradiation with gamma ray s at ambient temperature. Average molecular weights between crosslinks, per cent swelling, swelling equilibrium values, diffusion/swelling characterist ics (i.e., the structure of network constant, the type of diffusion, the in itial swelling rate, swelling rate constant), and equilibrium water content were evaluated for both hydrogel systems. Water diffusion to the hydrogel is a non-Fickian type diffusion and diffusion coefficients vary from 6.56 x 10(-7) to 2.51 x 10(-7) cm(2)min(-1) for PVP and 6.09 x 10(-7) to 2.14 x 1 0(-7) cm(2)min(-1) for PVP/persulfate hydrogel systems. (C) 2000 John Wiley & Sons, Inc.