Modulation in sorption dynamics of a pH-sensitive interpenetrating polymer network (IPN)

The water sorption dynamics of a binary interpenetrating polymer network (IPN) composed of polyvinyl alcohol (PVA) and poly(acrylamide-co-acrylic acid) was studied gravimetrically. The IPN was characterized by IR spectral analysis and various network parameters such as molecular weight between crosslinks (M-c), crosslink density (q) and number of elastically effective chains (V-e) were also evaluated. The effects of various parameters such as composition of the IPN, pH, and temperature of the swelling medium and addition of inorganic salts were investigated on the kinetics of the swelling process. The dynamic swelling parameters such as the swelling exponent, diffusion constants and penetration velocity were evaluated and the possible mechanisms of water sorption were evolved on the basis of the swelling exponent (n), diffusion constant (D), and penetration velocity (v). The enthalpy of mixing of the IPN and the solvent (water) was also calculated using the Gibbs-Helmholtz equation.