Determination of exchange enthalpy and entropy parameters of the equation-of-state theory for poly(dimethyl siloxane) and some aromatic solvents by inverse gas chromatography

Abstract

The specific retention volumes, Vgo of toluene, ethyl benzene, n-propyl benzene and isopropyl benzene on poly(dimethyl siloxane)(PDMS) were measured at temperatures between 333 and 403 K by inverse gas chromatography. The parameters of hard-core interaction, χt∞, effective exchange energy, X12, exchange enthalpy, X12, and exchange entropy, Q12 in the equation-of-state theory were determined. The parameters χt∞ of the isopropyl benzene-PDMS pair decreased from 0.65 to 0.60 while those of others decreased from around 0.77 to 0.69 with increasing temperature. The values of the parameters X12 also decreased as molecular weight of the substituted aliphatic group on the benzene ring of the solvent increased, ie 15 J cm−3 in toluene and 5 J cm−3 in isopropyl benzene. Both X12 and Q12 show negligible dependence on temperature. © 2000 Society of Chemical Industry