Abstract : The technique of gas chromatography has been used to investigate the solution properties of many solvents with a propargyl (acetylene-terminated) sulfone (PATS). In this case, unlike previous work on the RADEL polysulfone, no correlation between the strength of the specific interaction parameter and the solubility as determined from beaker tests is found. Furthermore, curing of the PATS at 240 deg C for 24 hours did not change the measured plasticizer/solvent interactions. Piezoelectric sorption techniques were used to study the solution properties of a P1700/ATS/dichloromethane system. Phase equilibrium data are presented for ATS/dichloromethane, P1700/dichloromethane and P1700/ATS/ dichloromethane. The ternary system contained 70% P1700 and 30% ATS by weight on a dry basis. Both the Flory-Huggins and corresponding states solutions were used in the data analysis. In both cases, the binary interaction parameter for P1700- ATS interactions indicated strong interactions, in agreement with experimental observations that these polymers form a compatible system. Gas chromatographic investigations of the Radel polysulfone indicate the presence of a phase transition of undetermined character between 185 and 200 deg C in addition to the glass transition between 220 and 230 deg C.