Most commercially available fluorous polymers are ill suited for the fabrication of ion-selective electrode (ISE) membranes. Therefore, we synthesized semifluorinated polymers for this purpose. Ionophore-free ion-exchanger electrodes made with these polymers show a selectivity range (≈14 orders of magnitude) that is nearly as wide as found previously for liquid fluorous ion-exchanger electrodes. These polymers were also used to construct ISE membranes doped with fluorophilic silver ionophores. While the resulting ISEs were somewhat less selective than their fluorous counterparts, the semifluorinated polymers offer the advantage that they can be doped both with fluorophilic ionophores and traditional lipophilic ionophores, such as the silver ionophore Cu(II)-I (o-xylylenebis[N,N-diisobutyldithiocarbamate]). We also cross-linked these polymers, producing very durable membranes that retained broad selectivity ranges. K+ ISEs made with the cross-linked semifluorinated polymer and the ionophore valinomycin showed selectivities similar to those of PVC membrane ISEs but with a superior thermal stability, the majority of the electrodes still giving a theoretical (Nernstian) response after exposure to a boiling aqueous solution for 10 h.
- Ion-selective electrode