Diffusion of organic solvents in thermoplastic elastomers: infinite dilution experiments

Diffusion parameters, activity coefficients, and Flory-Huggins interaction parameters of n-hexane, cyclohexane, and benzene in several styrene-diene block copolymers (styrene-butadiene-styrene (SBS), styrene-ethylene/butylene-styrene (SEBS), and styrene-isoprene-styrene (SIS)) were obtained using the inverse gas chromatography (IGC) method with a packed column in the infinite dilution region and the range of 40-70 degrees C. Diffusion coefficients based on the change in chromatographic peak width with carrier gas flow rate were calculated using the Van Deemter equation. The strong linear relationship indicated that using the Van Deemter equation was appropriate. The temperature increase caused the infinite dilution diffusion coefficient to increase, while the infinite dilution activity coefficient decreased; this proved the different behavior of the kinetics and thermodynamic parameters as a function of temperature. All solutes' infinite dilution diffusion coefficients decreased going from SBS to SEBS with the following order: SBS > SIS > SEBS. Activation energies were calculated from the Arrhenius equation, which provides the temperature dependence of diffusion coefficients. Graphical abstract Chromatograms for SBS-Cyclohexane system at different carrier gas flow rate (Tc = 60 degrees C).