Characterization of the composite film prepared from chemically synthesized poly(o-phenylenediamine) and poly(vinyl alcohol) and the application to a humidity sensor

Spectroscopic and mechanical properties of the composite film prepared from chemically synthesized poly (o-phenylenediamine) (PoPD) and poly (vinyl alcohol)(PVA) have been clarified and the application of this film to a humidity sensor been described. The PoPD produced using ammonium peroxydisulfate as an oxidizing agent had fibrilar morphology, and the PoPD/PVA composite film exhibited much improved mechanical properties compared to those of original PoPD. The electrical conductivity of the composite film was linearly related with the atmospheric humidity, extending from 7.2 x 10(-4) to 1.2 x 10(-1) Scm(-1) in response to the change in humidity from 25% to 98%. The measurements performed in both moistening and desiccating processes accompanied no any hysteresis. These facts are favorable for the application to a humidity sensor. The change in conductivity of the composite film was suggested to relate to the shift of the equilibrium between the conducting salt and the insulating base forms of PoPD that depends on the atmospheric humidity.