Structured electrically conductive polyaniline/polymer blends

This paper describes electrically conductive polymer blends consisting of polyaniline (PANI) dispersed in a polymer matrix. Melt blending of previously mixed, coagulated and dried aqueous dispersions of PANI and the polymer matrix lead to high conductivities at extremely low PANI concentrations (approximately 0.5 wt% PANI). In these blends the surface properties (surfactants used) of the PANI and the polymer particles play a major role in the structuring process, in addition to the very small size of the PANI particles. In another approach, i.e. conventional melt blending of PANI powder with a given polymer powder, the success of generating an efficient conductive network depends on the PANI/polymer interaction level. A high interaction level (for example, similar solubility parameters) leads under dynamic hot blending conditions to the formation of conductive networks, but still at relatively high PANI concentration (>10 wt% PANI). To further reduce the PANI conductivity threshold concentration, ternary PANI/polymer/polymer blends can be designed, in which PANI is selectively attracted to the minor polymer component, thus generating double-percolation structures. The threshold PANI concentration in the ternary blends may be reduced by a factor of approximately 2 compared to the binary blends. Further reduction can be expected in special ternary blends designed so that the PANI particles will mostly locate at the interfaces, rather than within the dispersed minor polymer particles. The blending method of aqueous dispersions is limited to matrix polymers which can be synthesized by emulsion polymerization. Thus, the conventional melt blending procedure and also the formation of ternary blend systems are particularly beneficial for condensation-type polymers, whereas melt blending of PANI/polymer powders prepared by the aqueous dispersions method is beneficial for the addition-type polymers.