Capillary column inverse gas chromatography experiments at infinite solvent dilution were conducted for 15 polyethylene/solvent systems. Thermodynamic data were collected for various types of penetrant molecules (normal alkanes, 1-alkenes, isomers of hexane, and ring compounds). Theoretical predictions of the solubility data were made with an activity coefficient model (Universal Functional Group Activity-van der Waals-Free-Volume) (UNIFAC-vdw-FV) and an equation-of-state model (Group-Contribution, Lattice-Fluid, Equation of State) (GCLF-EoS). Although good agreement between the experimental data and theoretical predictions was obtained above the melting point of the polymer, at temperatures below the melting point, significant differences were found. This occurred because at those temperatures, the polymer had a semicrystalline structure and the solubility of the solvent was reduced on account of the constraints on some of the chains in the amorphous phase by the polymer crystallites. The theory developed by Michaels and Hausslein to account for such elastic effects on solubility was incorporated into the two predictive models. After these modifications, the new estimations of the solubility showed significantly improved agreement with the experimental results. Moreover, the elasticity effect resulted in elevated estimates of the crystallinity when inverse gas chromatography retention volumes were used. (C) 2007 Wiley Periodicals, Inc.