Dual stimuli responsive neutral/cationic polymers/clay nanocomposite hydrogels

In this work, a thermodynamic-based equilibrium-swelling model was proposed to predict the swelling process of neutral/cationic polymers-clay nanocomposite hydrogels sensitive to dual stimuli temperature and pH. Indeed, the new swelling model can estimate the effect of the rigid clay nanoparticles component on swelling behavior of blend nanocomposite hydrogels. The mixing term in model was developed based on lattice theory by considering the effects of solvent-polymers, solvent-clay, and polymer-clay interaction parameters. The influence of the ionic groups of the clay layers and cationic polymer on the swelling was also taken into account in the proposed model. The model was verified by preparation of polyvinyl alcohol/chitosan/montmorillonite intelligent nanocomposite hydrogel by tripolyphosphate crosslinking method followed by freezing–thawing process. It was found that it could give good prediction for the equilibrium swelling of polymer-clay nanocomposite hydrogels in the case of phantom network, especially where the swelling temperature and clay loading level are high and the pH of swelling medium is low. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48797.