Thermodynamic properties of the hyperbranched poly (ester amide) (Hybrane(R) 1200) were investigated by inverse gas chromatography (IGC) using 19 different solvents as the probes at infinite dilution. Retention data of probes were used for an extensive characterization of the polymer, which includes the determination of the Flory-Huggins interaction parameter, the weight fraction activity coefficient, the total, partial, and additive solubility parameters. The analysis of the results indicated that the additive value of the solubility parameter is lower than the value obtained from a standard procedure. Furthermore, the solubility parameter decreases with increase of temperature. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2166-2172, 2008