DIFFUSION OF ORGANIC-SOLVENTS IN ISOBUTYLENE-BASED POLYMERS

Diffusion behavior of several organic solvents in polyisobutylene (PIE ) and in poly(p-methylstyrene-co-isobutylene) (PMS-BR) with different monomer ratios has been studied. The experiments have been conducted o ver a temperature range of 50 to 100 degrees C using a conventional gr avimetric sorption technique. The PMS-BR copolymers contained 2, 7, an d 15 weight percent p-methylstyrene, respectively. Although employing temperatures were far above the glass transition temperatures of polym ers, the diffusion coefficients are correlated well with the Vrentas-D uda free-volume theory. For all the solvents, the PIE shows the highes t diffusivity while the copolymer with the 15% p-methylstyrene gives t he lowest value. This behavior can be explained by the amount of fract ional free-volume present in a system.