PVC as a sensor membrane material: influence of solvent casting variables

Unplasticized polyvinyl chloride (PVC) has proved an especially difficult membrane material to form reproducibly. In its fabrication for sensor use, variable temperature solvent casting has been assessed and related to function as external membranes of a classical dual membrane amperometric oxidase electrode. The thermal history of the casting solution was shown to have an effect on both thickness and the permeability. With increasing temperature of the cast solution (4-37 degrees C) membrane thicknesses increased (5-30 microm). Amperometric responses to catechol and hydrogen peroxide decreased with increasing casting solution temperature whereas responses to ascorbate remained unchanged. These properties are tentatively attributed to the formation of discrete layers through differential changes in the rate of solvent evaporation. Scanning electron microscopy revealed distinct microstructure zones supporting this proposition and attesting to the need to factor in environmental temperature during casting.