Correlation of data on preferential sorption using the modified flory‐huggins equation

An equation derived from the Flory‐Huggins relation with the concentration‐dependent interaction parameters g ij and the ternary parameter g T was used in the correlation of reported data on the preferential sorption in macromolecular coils. A linear plot was suggested, assuming that the dependence of g T on the composition of the mixed solvent resembles that of g 12 , i.e. g T ( u 1 ) = a g g 12 ( u 1 ). Linear correlation could be carried out in 19 ternary systems out of 22, and the correlation constants were used to calculate the difference of interaction parameters g 13 − ( V 1 / V 2 ) g 23 and the proportionality constant a g . For most systems, a g is positive and smaller than unity; for systems containing chloroform it approaches zero. The difference between the interaction parameters g ij and the interaction parameters χ ij is discussed. A comparison between the difference g 13 −( V 1 / V 2 ) g 23 obtained by a linear correlation of data on preferential sorption with the values calculated using data on the respective binary systems was possible only for the system benzene/cyclohexane/polystyrene; the fit was very good. It is shown how the individual parameters of the Flory‐Huggins equation affect the occurrence, position and type of inversion in preferential sorption.