PLASTICIZED POLYVINYL-CHLORIDE) PROPERTIES AND CHARACTERISTICS OF VALINOMYCIN ELECTRODES - DC CURRENT VOLTAGE CURVES

Steady-state current-voltage curves for plasticized poly(vinyl chloride) membranes with and without the neutral carrier valinomycin have been measured. Morf''s equations, based on coupled Nernst-Planck equations, give an expression for the I-Vappl characteristic that includes the membrane resistance. The function is reminiscent of a voltammetric wave in a high-resistance medium. Three regions are observed: low-voltage ohmic, medium-voltage limiting (plateau), and high-voltage Donnan breakdown, again ohmic but with a greater resistivity. Low-voltage resistances are in agreement with independently determined impedance values. Limiting currents are determined by back diffusion of free carrier and diffusion coefficients were measured Failure of the "closed circuit" model at very high voltages was found to be caused by field-induced Donnan failure that depends on hydrophobicity of the bathing anions.