The effect of molar volume on the swelling of poly(dimethylsiloxane) in fluorocarbon fluids

The vapour sorption of three fluorocarbon fluids (tetrafluoroethane, chlorotetrafluoroethane, and heptafluoropropane) has been measured in crosslinked and uncrosslinked poly(dimethylsiloxane) as a function of the temperature in the interval 35-105°C. For a given solvent, the swelling activity parameter, S, for the solvent/crosslinked polymer system decreases as both the degree of swelling and the temperature increase. The range of experimental conditions examined allowed consideration of S for different solvents, but constant molar volume V₁. Plots of S as a function of degree of swelling can be reduced to families of curves at constant V₁ for the three solvents studied here. The dependence of S on solvent quality and temperature is then encompassed in its variation with V₁.