THERMODYNAMICS OF POLYMER BLENDS OF POLY(VINYL METHYL-ETHER) AND POLYSTYRENE

Heats of mixing, excess volumes, and a cloud point curve were experimentally obtained for the poly(vinyl methyl ether)/polystyrene blends. The heats of mixing for the blend obtained by application of Hess law to heats of dissolution of the component polymers and their blends and to heats of mixing of polymer solutions were negative. The excess volumes also showed the negative values. Flory's equation-of-state theory with modified combining rules was applied to this blend system. For this purpose, densities, thermal expansion coefficients, and thermal pressure coefficients for poly(vinyl methyl ether) were also measured, from which the equation-of-state parameters were obtained. The exchange enthalpy parameter obtained so that the calculated values of the excess volume and heat of mixing can fit those experimental data was negative. The calculated dependences of the interaction parameter x on the concentration as well as temperaure were in agreement with those obtained from the neutron scattering measurements by Stein and co-workers. © 1990, American Chemical Society. All rights reserved.