Low-frequency impedance measurements on two and three-component membranes (poly(vinyl chloride) (PVC), plasticizer, and valinomycin) show routinely surface-rate (so-called “kinetic”) semicircles and can show Warburg character In conventional impedance plane plots. Surface-rate semicircles seem to be the result of exudation of plasticizer (and probably valinomycin) to form site-free resistive surface films. These semicircles are characterized by plasticizer type and concentration, carrier loading, time of soaking in aqueous solutions, and drying time in air. The surface resistance decreases with increased plasticizer at constant carrier concentration and decreases with increasing bathing KCI concentrations at constant plasticizer and carrier loadings, presumably by extraction of K+ as Kval+and Cl+(in water droplets) within the surface films. Warburg diffusional character appears only at low carrier concentrations and in carrier-free membranes. Lowered bulk resistance and altered Warburg impedances by addition of NaTPB or Allquat chloride were confirmed.
ASJC Scopus subject areas
- Analytical Chemistry