Upper critical solution temperature of perfluoro-n-alkane and n-alkane mixtures

Abstract

This paper reports measurements on the upper critical solution temperature (U.C.S.T.) for mixtures of perfluoro-n-heptane with a series of n-alkanes (C₅ to C₁₅). The results are compared with the simple solubility parameter theory and the two modifications proposed by Reed. The more complicated treatments are reasonably successful in predicting the U.C.S.T. The agreement with the simple theory is poor. The results are discussed using the segment extension of the lattice theory. A three-type segment approach has been used for perfluoro-n-heptane and n-alkane mixtures and of perfluoro-n-butane and n-alkane mixtures. This treatment is successful in accounting for the observed. U.C.S.T. in terms of constant “end alkane group”+“average perfluoro-n-alkane group” and “middle alkane group”+“average perfluoro-n-alkane group” interchange energies. A more general treatment, which considers four types of segments is briefly discussed. The limitations and possibilities of this approach are considered.