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

The specific retention volumes, V-g(o) of toluene, ethyl benzene, n-propyl benzene and isopropyl benzene on poly(dimethyl siloxane)(PDMS) were measure d at temperatures between 333 and 403K by inverse gas chromatography. The p arameters of hard-core interaction, chi(t)(infinity), effective exchange en ergy, (X) over bar(12), exchange enthalpy, X-12, and exchange entropy, Q(12 ), in the equation-of-state theory were determined. The parameters chi(t)(i nfinity) of the isopropyl benzene-PDMS pair decreased from 0.65 to 0.60 whi le those of others decreased from around 0.77 to 0.69 with increasing tempe rature. The values of the parameters X-12 also decreased as molecular weigh t of the substituted aliphatic group on the benzene ring of the solvent inc reased, ie 15J cm(-3) in toluene and 5Jcm(-3) in isopropyl benzene. Both X- 12 and Q(12) show negligible dependence on temperature. (C) 2000 Society of Chemical industry.