ONE-COMPONENT ROOM-TEMPERATURE VULCANIZING-TYPE SILICONE RUBBER-BASEDSODIUM-SELECTIVE MEMBRANE ELECTRODES

Two different types of one-component room temperature vulcanizing (RTV ) silicone rubber (Dow Coming 3140 and 730 RTV) are examined as altern atives to PVC for formulating ion-selective membranes. Ion-selective m embranes are made by incorporating five different sodium ionophores al ong with either a plasticizer or an ionic additive (without plasticize r). In most cases, these silicone rubber based membranes exhibit bette r potentiometric ion response and selectivities when formulated with p lasticizer rather than with ionic additive. Incorporating high levels of plasticizer does not appreciably affect the adhesion of 3140 RTV-ba sed membranes, but it significantly deteriorates the adhesion of 730 R TV-based membranes. Membranes based upon 730 RTV have lower impedances than those based upon 3140 RTV, and in fact compare favorably to simi larly formulated PVC-based membranes in this regard; as a result, they are better suited for plasticizer-free membrane systems. The use of m embranes based upon either of the RTV materials rather than their PVC- based counterparts greatly enhances the lifetime of solid-state sensor s. (C) 1997 Elsevier Science B.V.