Interpenetrating polymer network (IPN) hydrogels based on poly(propylene glycol) (PPG) and poly(acrylic acid) (PAAc) were prepared by UV irradiation and equilibrium water uptake (EW) and diffusion coefficients were measured by dynamic vapor sorption system (DVS). The EW of IPN hydrogels increased with increasing the PAAc content in IPN hydrogels. With an increase in the hydrophilic content of the IPN hydrogels, the values of diffusion coefficients were found to increase due to greater penetration of water into the hydrogels. Diffusion coefficients of IPN hydrogels increased with increasing temperature and decreased with increasing content of PPG. (C) 2002 Elsevier Science B.V. All rights reserved.