ISOTOPE AND PRESSURE-DEPENDENCE OF LIQUID-LIQUID EQUILIBRIA IN POLYMER-SOLUTIONS .7. SOLUTE AND SOLVENT H D ISOTOPE EFFECTS IN POLYSTYRENE-PROPIONITRILE SOLUTIONS/

Cloud and spinodal loci have been obtained as functions of pressure (P ), temperature (T), polymer segment number (r), segment fraction (psi) , and H/D substitution on solute (z(D)) or solvent (y(D)) for polystyr ene-h/propionitrile-h (PSh/PNh) solutions, polystyrene-h/propionitrile -2,2d(2) solutions (PSh/PNd), and polystyrene-d/propionitrile-h soluti ons (PSd/PNh). A light scattering technique was employed. An increase in pressure or an increase in the H/D ratio in the solvent (or decreas e in the polymer H/D ratio) increases the region of miscibility. The s olutions show upper and lower branches which may join at hypercritical points depending on the pressure, molecular weight, or solvent H/D ra tio. A least-squares technique to fit experimental data to the continu ous mean-field thermodynamic description of polymer-solvent demixing d eveloped by Luszczyk, Rebelo, and Van Hook (Macromolecules 1995, 28, 7 45) is described and then illustrated by application to the PS/PN data .