COAGULATION OF POLYMER-CU2+ COMPLEXES IN POLYMER-FILMS AND ITS APPLICATION FOR PRODUCING SEMICONDUCTING CUI SURFACE-LAYERS

In poly(vinyl alcohol) and polyacrylamide films containing the corresponding polymer–Cu2+ complexes, the reason why the films may gain surface electrical semiconductivity as high as 10−3 Ω−1 when treated with acetone solution of iodine was investigated. Optical and scanning electron microscope observations indicated that the coagulated polymer–Cu2+ complexes favor the appearance of the high conductivity and that the state of coagulation depends on the anions of the copper salts used as well as two parameters, F1 ≡ [Cu2+]/[MU] and F2 ≡ [OH−]/[Cu2+], where [MU] is the molar concentration of monomeric units of the polymer and [OH−] is that of hydroxide ions added. The effectiveness of the anions in causing coagulation decreases in the order of SO42− > Cl− > NO3− ≈ Br−. The whitish substance that appears on the film surface after the iodine treatment gives x‐ray Debye–Scherrer rings characteristic of γ‐CuI. The γ‐CuI surface layer adheres to the film rather firmly, at least in polyacrylamide, and is responsible for the conductivity. By controlling the state of coagulation of the complexes and hence the formation of the γ‐CuI surface layer, we have produced films with anisotropic surface electrical semiconductivity, i.e., σ∥ ≈ 10−4 Ω−1 and σ∥/σ⊥ = 1 ˜ 103. Optical and ESR spectra are also obtained to understand the mechanism of γ‐CuI formation and to clarify the optical properties of the films. Copyright © 1979 John Wiley & Sons, Inc.