Emphasis is placed on ophthalmic applications.
Materials that change structurally upon exposure to external or physiologic triggers can be used to deliver drug in a programmed or responsive fashion. We are investigating several concepts for responsive membranes. We have shown that dispersed domains formed in side chain liquid crystalline polymers can be aligned electrically thus giving varying permeabilities, and that the permeability response to electric field is consistent with our theoretical predictions. We are also working on a concept that combines the responsive swelling of hydrogels with the unique transport properties of heterogeneous media to develop responsive composite membranes. As hydrogel regions dispersed in hydrophobic elastomeric polymers swell and shrink in response to external stimuli, they also become connected or disconnected, thus opening or closing permeation channels.