The swelling of polyacrylamide (PAAm) gels increased with rising glucose concentrations, and so did the osmotic pressure of the soluble polymer and its intrinsic viscosity. A Flory-Huggins-based model for the osmotic pressure of a nonionic hydrophilic polymer in a ternary solution consisting of a main solvent, a polymer, and a nondissociating low-molecular-weight cosolute was developed and examined. The model-calculated values were in reasonably good agreement with experimental results for the water-PAAm-glucose system studied when PAAm-water and glucose-water interaction coefficients from the binary systems were used, and only the PAAm-glucose interaction coefficient was adjusted. Its negative value suggested a favorable interaction of glucose and PAAm, supporting the notion of glucose being a good cosolvent for PAAm. Isothermal titration microcalorimetry results showed no evidence for the binding of glucose to PAAm, but an exothermic interaction was indicated between glucose and PAAm. Microcalorimetrically determined enthalpic contributions to the Flory-Huggins interaction coefficients showed enthalpically favorable binary interactions, particularly the enthalpic component of the PAAm-glucose interaction coefficient (X-H23), which was slightly negative. The enthalpically favorable interaction between glucose and PAAm may explain the increased osmotic pressure of PAAm in glucose solutions. (C) 2003 Wiley Periodicals, Inc.