New Evidence Supporting the Interfacial Model of Electrically Conductive Polymer Composites: I. Conductivity Behaviour of Polyaniline-Poly(ethylene-co-vinyl acetate) Composites

Abstract

The change in the conducting properties of polyaniline-poly(ethylene-co-vinyl acetate (EVA)) composite films was investigated as a function of time. For the first time it was shown that the apparent concentration (ϕc), of polyaniline at which a conductivity jump occurs is not constant during ageing. Moreover, the conductivity behaviour of polyaniline-EVA composites is variable and dynamic during storage. The electrical conductivity of the films of low polyaniline content (up to 2.5 wt. %) increased by several orders of magnitude over a period of eight months. It was supposed that the polyaniline phase undergoes flocculation and that subsequently, a continuous conductive network is formed. The conductivity jump was attributed to dynamic interfacial interactions between the constituents of the polyaniline-EVA composites. A decrease in the average conductivity deviations for the samples of low polyaniline content (<2.5 wt.%) was observed, indicating that improvement of conductive pathways took place within the bulk of the insulating EVA matrix. Hence, the present study supported the dynamic interfacial model (particularly the dispersion/flocculation phase transition) of conductive polymer composites, proposed by Wessling.