THERMODYNAMICS OF HYDROGEN-BONDED POLYMER GEL-SOLVENT SYSTEMS

A statistical thermodynamic theory, which accounts for hydrogen-bondin g interactions between polymeric gels and solvents, is developed The t heory is shown to provide quantitative predictions of swelling behavio r of poly(ethylene oxide) gels in chloroform and water and qualitative predictions of thermoreversible volume transitions of poly(N-isopropy l acrylamide) (PNIPA) gel in water. At the LCST of PNIPA gel, the theo ry predicts a sharp increase in the number of hydrogen-bonds formed be tween polymer molecules of the gel and a sharp decrease in the hydroge n-bonds formed between polymer molecules and water molecules. The pred ictions of this theory can have significant implications in designing smart gels based on hydrogen-bonding interactions. Such gels have appl ications in separations and in biomedical technology.