| Abstract: | This paper focuses on the relationship between diffusive transport and membrane composition (crosslinker content and relaxed polymer volume fraction) in membranes whose permeability can be actively controlled by chemical or electrical stimuli. First, pH induced changes in permeability to uncharged fluorescent solutes were measured. Then, by correlating bath pH with membrane hydration, the transport properties of membranes of different crosslinker content and/or relaxed polymer volume fraction were compared at constant hydration. The membrane permeability was found to decrease as the amount of crosslinker added to the membrane formulation at the time of polymerization increased, while the permeability increased as the solvent content during polymerization increased. A free volume theory which was fit to the data shows good agreement, and predicts a monotonically decreasing porosity factor with increased crosslinker content. |
