The Heats of Dilution of Atactic Polystyrene Solutions

Abstract

Abstract The heats of dilution of atactic polystyrene (\barP=244)-various solvent systems have been measured by using a micro-twin-calorimeter at 25°C. Toluene, anisole, ethyl methyl ketone, dioxane and ethyl acetate were used as the solvents. For the analysis of the experimental data obtained by each dilution process, the simple Van Laar formula has been used, and the apparent enthalpy parameter between the polymer and the solvent has been derived. Since these interaction parameters seemed to depend on the concentration, we tried to analyze the experimental data with a modified Van Laar formula which contained interaction parameters depending on the concentration. The interaction parameters obtained by these analyses are considerably dependent on the concentration in good solvents, while those in poor solvents depend hardly at all on the concentration. This dependence of the interaction parameters on the concentration has been explained by using the dilute solution theory of polymer solutions proposed by Flory and Krigbaum (J. Chem. phys., 18, 1086 (1951)). The interaction parameters in the dilute region have been compared with those obtained by other methods, and the agreement between our values and those obtained by other methods has been found to be fairly good.