SORPTION AND SWELLING OF BLOCK-COPOLYMERS IN THE PRESENCE OF SUPERCRITICAL-FLUID CARBON-DIOXIDE

The sorption and swelling of polystyrene, poly(methyl methacrylate), p oly(vinyl pyridine) and polyisoprene, and of styrene-methyl methacryla te, styrene-vinyl pyridine and styrene-isoprene block copolymers, in t he presence of carbon dioxide, is examined at 35 degrees C and at pres sures to 1500 psia. Sorption data were obtained using a quartz spring technique and swelling data were obtained by direct measurement of the dimensions of a separate sample using a cathetometer. Sorption in the glassy polymers increases linearly at low pressures before leveling o ff at higher pressures, while sorption in the rubber polyisoprene is l inear over the entire range of pressures investigated. Sorption in the block copolymers shows a continuous transition from the behavior of o ne homopolymer to the behavior of the other. The Sanchez-Lacombe equat ion of state is used to model the homopolymer data using the concept o f order parameters to extend the model to the glassy polymers. A simpl e linear model based on the homopolymer sorption is adequate to descri be the copolymer results. (C) 1997 Elsevier Science B.V.