CHARACTERIZATION AND SELECTIVITY OF ELECTRODES COATED WITH GAMMA-RADIATION-IMMOBILIZED HYDROGEL MATRICES

Properties of electrodes coated with γ-radiation-immobilized hydrogel matrices are described. Electrode films cast from monomer-containing solutions of the water-soluble polymer, poly(N-vinylpyrrolidone) (PNVP), are rendered insoluble through γ-irradiation but form highly swollen hydrogels when immersed in aqueous media. Rotating-disk voltammetry (RDV) is used to probe the effects of dose and presence of the polymer's monomer, N-vinylpyrrolidone (NVP), on Immobilization efficiency. Inclusion of NVP in the PNVP solution results in more mechanically stable films and lowers the radiation dose required for irnmobillzation. PNVP/NVP films are further characterized with respect to response toward various organic and Inorganic species. The effects of solution pH and electrolyte on electrode response are investigated, since these factors can profoundly affect gel morphology. The effects of varying NVP content on electrode response also are examined. Evidence of size-exclusion behavior of PNVP/NVP electrodes is demonstrated. Coimmobilization of acrylic acid (AA) monomer within the PNVP/NVP matrix is described. These composite films incorporate cationic species to an extent dictated by solution pH. Because the degree of swelling of PNVP/NVP/AA films is pH-dependent, the potential for pH control of film permeability exists. Preliminary evidence supporting the feasibility of this approach Is offered. © 1990, American Chemical Society. All rights reserved.