Solution behavior of polyethylene oxide in water as a function of temperature and pressure

A model of the solution behavior for hydrosoluble polymers [based on a model of Matsuyama and Tanaka, Phys. Rev, Lett. 65, 341 (1990)] is introduced that accounts for hydrogen bonding of solvent molecules onto polymer chains. In the limit of small volume fraction of H-bonded solvent molecules, the resulting free energy has the standard Flory-Huggins form with a good solvent contribution to the effective chi parameter coming from the fraction of solvents H-bonded to the chain. This simple theory is capable of semiquantitatively, explaining the experimental temperature-concentration (T-phi) and temperature-pressure (T-P) phase diagrams of polyethylene oxide in water.