Determination of exchange enthalpy and entropy parameters of poly(dimethyl siloxane) with some n-alkanes by inverse gas chromatography

The total interaction parameter at infinitely high polymer concentration. χ_t^∞, and the effective exchange energy parameter, X̄₁₂, of poly(dimethyl siloxane) with n-pentane, n-hexane, n-heptane and n-nonane were determined around room temperature using the inverse gas chromatography technique. The values of χ_t^∞ are in agreement with corresponding literature values. The exchange enthalpy X₁₂ and entropy, Q₁₂, parameters were determined at the same temperature. The X₁₂ parameters increase with the carbon number of the n-alkanes, while their temperature dependence is almost negligible. The Q₁₂ parameters are approximately independent of temperature and carbon number of the n-alkanes.