Thermodynamic Modelling of Hydrogel Systems

Abstract

In the present work, the PC-SAFT model was used and extended for modelling poly(N-isopropylacrylamide) PNIPAAm and its behaviour as loose polymer chains in solution and as cross-linked hydrogel. For the application of PC-SAFT to hydrogel modelling, the elastic forces which characterise swellable polymer networks were taken into account by a specific additional contribution to the Helmholtz energy. The binary system of water/PNIPAAm as polymer solution and hydrogel as well as the influence of various additives on the gel was extensively studied. These additives comprised organic solvents (methanol, ethanol, acetone), poly(ethylene glycol) as well as inorganic electrolytes (alkali halogenides and sodium nitrate). A method for predicting their influence on the re-entrant behaviour of PNIPAAm hydrogels was developed and the model capability of the extended PC-SAFT was shown for modelling of temperature, component and composition sensitivity.