The thermodynamic properties of triblock copolymer of polystyrene-poly (ethylene oxide)-polystyrene (PS-b-PEO-b-PS) were investigated by means of inverse gas chromatography (IGC) using 15 different kinds of solvents as the probes. Some thermodynamic parameters, such as specific retention volume, molar heats of sorption, weight fraction activity coefficient, Flory-Huggins interaction parameter, partial molar heats of mixing and solubility parameter were obtained to judge the interactions between PS-b-PEO-b-PS polymers and solvents and the solubility of the polymers in these solvents. It was found that increasing PEO content in PS-b-PEO-b-PS resulted in the increase in the solubility of PS-b-PEO-b-PS in alkanes and acetates solvents, but the solubility in alcohols had no change, and more PEO content in polymer caused a small decrease in the solubility parameter of PS-b-PEO-b-PS polymer. (c) 2007 Wiley Periodicals, Inc.