Solution thermodynamics of some organic solutes in supported liquid film of polyethylene glycol6000 - a gas-liquid chromatographic study

The changes of standard thermodynamic functions (Delta H degrees and Delta S degrees) for 21 organic compounds dissolved in supported polyethylene gly col-6000 from gas phase have been determined using gas-liquid chromatograph ic technique. The experimental thermodynamic data have been discussed in th e light of interaction between molecules of the solvent and solute. Selecti ve intermolecular forces are believed to be the main cause of PEG selective ly dissolving and separating solutes. Selectivity of the PEG is not only ob served to polar substances but also to apolar ones such as benzene and cycl ohexane. We believe that the macromolecule can adjust its conformation when it receives a solute molecule, so as to more strongly interact with the sm all molecule. When such strong negative electric groups as carbonyl oxygen atom, nitro group approach ethylene of PEG or strongly positive charged hyd rogen atom(s) approach(s) an oxygen atom of PEG, strong intermolecular forc es occur and solution heats are large. On the other hand, strongly intermol ecular force may be caused by a kind of synergistic interaction between the solvent and solute molecules. In such a case, a solute molecule is attract ed by two or more sites on the polymer chain. (C) 2000 Elsevier Science B.V . All rights reserved.