The solution and diffusion properties of cyclohexane, cyclohexanol, and cyclohexanone in poly(ethylene glycol) (PEG) and crosslinked PEG have been studied in the temperature range of 368.15 to 403.15 K using inverse gas chromatography (IGC) technique. The infinite dilute activity coefficient (Omega(infinity)(ip)) and diffusion coefficient (D-ip(infinity)) have been determined for the above solvent/polymer systems. Accordingly, several thermodynamic functions, the diffusion pre-exponential factor, and activation energy have been attained. The results showed a decrease in Omega(infinity)(ip) and an increase in D-ip(infinity) with rising temperature. The order of the relative magnitude of Omega(infinity)(ip) and D-ip(infinity) of the solvents were explained by comparing their interactions with the polymer and their collision diameters, respectively. Moreover, Omega(infinity)(ip) and D-ip(infinity) in crosslinked PEG were smaller than those in PEG at various temperatures. The analysis of Omega(infinity)(ip), the infinite dilute selectivity and capacity showed the possibility of using crosslinked PEG as an appropriate membrane material for the separation of cyclohexane, cyclohexanol, and cyclohexanone mixture. A thermodynamic study also implied that the solvent sorptions in the polymers were all enthalpically driven in the experimental range. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 124-134, 2012