Measurement of the infinite dilution diffusion coefficients of small molecule solvents in silicone rubber by inverse gas chromatography

The infinite dilution diffusion coefficients of n-hexane, n-heptane and n-decane in crosslinked silicone rubber with different crosslinking agent concentrations were measured in the temperature range of 348.15 K–368.15 K by inverse gas chromatography. The crosslinked silicone rubber was obtained by dissolving PDMS prepolymer, crosslinking agent and catalyst in n-heptane solvent and characterized by FTIR spectra. The Van Deemter equation was used to determine diffusion coefficients from the variation in chromatographic peak width with carrier gas flow rate. The good linear relation indicated the Van Deemter equation used in this work was reliable. The influences of small molecule solvent, crosslinking agent concentration and temperature on the infinite dilution diffusion coefficient were investigated. The results showed that the infinite dilution diffusion coefficient decreased with an increasing number of CH2 group in the alkane series. The increase in crosslinking agent concentration resulted in decrease of the infinite dilution diffusion coefficient. The infinite dilution diffusion coefficient increased with the rising of temperature. The interdependence on the infinite dilution diffusion coefficient and temperature accorded with Arrhenius equation well. Diffusion constant and activation energy obtained from the Arrhenius equation provided straight lines with the specific critical volume and crosslinking agent concentration.