Membrane-solvent-solute interaction in a model permeation system.

In this study, methyl- and propylparaben flux from various alcohol donors through polydimethylsiloxane membranes was investigated. Flux from saturated alcohol vehicles was markedly increased relative to water and glycol systems. The uptake of neat alcohol, a measure of solvent membrane interaction, gave a good rank order correlation to the flux data for a particular paraben. The major influence of the alcohols was an increase in membrane solubility of paraben, with a smaller effect on the diffusion coefficient. High paraben donor solubility indirectly reduced the solvent-membrane interaction leading to attenuated flux. Paraben membrane solubility was influenced by the amount of alcohol sorbed from saturated systems and the affinity of the paraben for the alcohol. This conforms to the concept of imbibed alcohol molecules being organized into clusters. The alteration in barrier properties of the membrane was found to require the presence of sorbed alcohol and was reversible upon removal of the solvent.