Liquid‐liquid junction membranes prepared from a modified Polyvinylchloride (PVC) polymer with 0.6 weight percent (w/o) OH introduced, (PVC‐OH) and 0.25 w/o added during casting have substantially enhanced adhesion on glass or Si compared to PVC‐based membranes. Ion‐selective electrodes for based on a dioctyladipate/nonactin ion exchanger show enhanced adhesion, as do Ca2+ membranes using a neutral ion carrier/o‐nitrophenyloctylether mixture. Enhanced surface adhesion is demonstrated to result in improved lifetime for K+‐sensitive membranes coated on n‐Si electrodes and on ion‐sensitive field effect transistors (ISFET's). Electron micrographs show large differences in surface quality for PVC vs. membranes after aqueous storage.