MULTICOMPONENT POLYMER SOLVENTS EQUILIBRIA - AN EVALUATION OF FLORY-HUGGINS THEORY FOR CROSS-LINKED PDMS NETWORKS SWELLED BY BINARY-MIXTURES/

The prediction of equilibrium volume fractions of solvents mixtures in a polymer network is of utmost importance for processes dealing with polymeric materials (e.g. chromatographic and membrane processes). Up to now, few studies have studied the ability of existing theories to p redict experimental multicomponent sorption data in polymers; this wor k intends to achieve that purpose on model liquid mixtures in contact with silicone rubber (polydimethylsiloxane). The equilibrium volume fr actions of three liquid mixtures (chloroform/toluene; ethanol/toluene; ethanol/2-butanol) in crosslinked PDMS samples have been determined e xperimentally at 40 degrees C. Results are compared to predictions by the Flory-Huggins theory applied to ternary mixtures (one polymer and two liquids) with constant interaction parameters and negligible elast ic contribution. Solvent/polymer interaction parameters have been dete rmined by swelling the crosslinked samples in pure liquids, while liqu id/liquid interaction parameters have been estimated from liquid/vapor equilibrium data It is shown that the Flory-Huggins theory offers goo d predictions in the case of good (chloroform, toluene) and fair (2-bu tanol) PDMS solvents, while significant discrepancies are obtained wit h a non solvent (ethanol). Implications in ternary diagrams simulation and possible prediction improvements, based on non constant interacti on parameters, are discussed.