Methods to determine solubility parameters of polymers at high temperature using inverse gas chromatography

Experimental values of Flory-Huggins parameters, X, between polymers and probes, are frequently used to determine the solubility parameters of the polymers by the method of DiPaola-Baranyi and Guillet. The solubility parameters of probes were usually estimated by using heat of vaporization. When X is measured at a temperature near the critical temperature of the probes and used to determine the solubility parameter of polymers, the departure of enthalpy of the probe vapor from the ideal gas state should be considered. This study discussed the method to make the correction and its effect on the determination solubility parameter of polymers. Without correction in the vapor phase enthalpy, the solubility parameters of the probes and polymer tend to be underestimated and the error increases when the critical temperature is approaching. Analytical expressions for the effect of correction on the solubility parameter of probes and parameters of polymers were derived. By use of probes with a range of solubility parameters on both sides of the solubility parameter of polymers, the correlation between parameters of polymers was shown to be reduced. (C) 2004 Wiley Periodicals, Inc.