THERMODYNAMICS OF HYDROGEN-BONDED POLYMER GEL-SOLVENT SYSTEMS

A statistical thermodynamic theory, which accounts for hydrogen-bonding interactions between polymeric gels and solvents, is developed The theory is shown to provide quantitative predictions of swelling behavior of poly(ethylene oxide) gels in chloroform and water and qualitative predictions of thermoreversible volume transitions of poly(N-isopropyl acrylamide) (PNIPA) gel in water. At the LCST of PNIPA gel, the theory predicts a sharp increase in the number of hydrogen-bonds formed between polymer molecules of the gel and a sharp decrease in the hydrogen-bonds formed between polymer molecules and water molecules. The predictions of this theory can have significant implications in designing smart gels based on hydrogen-bonding interactions. Such gels have applications in separations and in biomedical technology.