TEMPERATURE-DEPENDENCE OF THE FLORY INTERACTION PARAMETER IN A SINGLE-PHASE MIXTURE OF POLY(HYDROXY ETHER OF BISPHENOL-A) AND POLY(ETHER SULFONE)

The Flory interaction parameter χ12 in a single-phase mixture of poly(ether sulfone) and poly(hydroxy ether of bisphenol-A) was measured at various temperatures by the light scattering method based on random phase approximation. The χ12 value at two-phase region above LCST (lower critical solution temperature) was estimated by curve fitting of the Flory-Huggins theory to the binodal curve observed. Combining the results, temperature dependence of χ12 was obtained in a wide range. The interactional energy contribution in χ12, χH, was estimated by the infrared spectroscopy method based onthe acid-base interaction theory by Drago. The difference between χ12 and χH, which is assumed to be the free volume term in χ12, was found to be a concave function of temperature; i.e., χ(T) is an increasing function at high temperature region, as has beenpredicted theoretically, but it is a decreasing function at low temperature region. This may lead to a thermodynamic interpretation of the appearance of both LCST and UCST (upper critical solution temperature) in mixtures of dissimilar polymers with high molecular weights, as reported in recent literature. © 1990, The Society of Polymer Science, Japan. All rights reserved.