Evaluation of the Soret coefficient for polystyrene in decalin by means ofthermal field-flow fractionation

One of the most appealing features of FFF (Field-Flow Fractionation) techni ques is their capability of easily finding out direct mathematical relation ships between the retention parameter and physico-chemical parameters of th e analytes. In the case of thermal FFF applied to macromolecules in solutio n, these parameters are the Soret coefficient and the molar mass. In this w ork, a rich set of retention data for polystyrene in a mixture of cis and t rans decalin. in a wide range of temperatures and molar masses, is used for finding out an empirical relationship between Soret coefficient. temperatu re, and molar mass using a refined approach of handling thermal FFF data. T his law is then statistically tested and very good agreement between experi mental and predicted values of Soret coefficient is found. The importance o f this law lies in the fact that it makes possible a truly universal calibr ation of the polystyrene-decalin system on any thermal FFF apparatus in the investigated ranges of temperatures and molar masses. The thermodiffusion coefficient of polystyrene in cis + trans decalin is evaluated for various molar masses at the temperature of 333 K and a slight dependence of this pa rameter on molar mass at that temperature is observed.