Silicone Rubber Blended with Polyurethane as the Matrix for Ion-Selective Membrane Electrodes

Silicone rubber-based sodium-selective membranes are developed for solid-state ion sensors. It was shown that the potetiometric performance of SR-based membranes are greatly dependent on the type of neutral carriers employed; among the three ionophores, N,N,N',N'-tetracyclohexyl-1,2-phenylenedioxydiacetamide (ETH 2120), bis[(12-crown-4)methyl]dodecylmethylmalonate (D12C4DMM) and monensin methyl ester (MME), examined, only ETH 2120 was compatible with the SR-based matrix. Addition of about 20 wt% plasticizer to the SR-based matrix provided the resulting membranes with potentiometric properties essentially equivalent to those of the corresponding PVC-based membranes. Owing to the strong adhesive strength of SR-based membranes, the CWEs coated \vith those membranes exhibited long lifetime with conventional electrode-like performance. Blending of PU into the SR matrix increased the lifetime of CWEs from two weeks to one month.