Impedance measurements of the high-frequency bulk semicircle provide bulk resistance and geometric capacitance values of two and three-component membranes: plasticizer, poly(vinyl chloride) (PVC), and valinomycin in combinations. Intrinsic conductivity is traced to previously postulated counterions from slightly dissociated fixed sites in PVC. Bulk resistances of valinomycin-free membranes were determined for three commercial PVC types, at short soaking times. Bulk resistances increase with soaking times, but with different time dependences for KCI, NaCl, or pure H20. Dielectric constants of membranes are always greater than for dry component values. Part of this increase may depend on water content, but there is an increase from motion of plasticized PVC chains, presumably C—CI bonds. Responses are dominated by fixed sites and impurity counterions, modified by charge trapping in water regions (in the absence of carrier). Increased charge carrier concentration results from the presence of carriers that solubilize ions in the organic regions.
ASJC Scopus subject areas
- Analytical Chemistry