Percolation of electrical conductivity in solution-cast blends containing polyaniline

The potential offered by intrinsically conductive polymers is limited by th eir poor mechanical properties. Blending with common thermoplastics can imp rove processability and mechanical properties and still preserve the electr ical conductivity. In such blends, the morphology determines the mechanical and electrical properties. In this research, blends of polyaniline (PANI)- dodecyl benzene sulfonic acid (DBSA) with either polystyrene (PS) in xylene or polyvinylchloride (PVC) in bromobenzene were solution cast. The morphol ogies of the blends were characterized by optical microscopy (OM), electron microscopy, and small-angle X-ray scattering (SAXS). Electrical conductivi ty was measured for various compositions. The formation of a continuous net work was strongly associated with percolation and conductivity. The morphol ogies of the two blends are significantly different. This difference arises from the different solvents used and their ability to swell the PANI aggre gates and to promote their disintegration into small particles. Molecular c alculations. show that, indeed, bromobenzene, used in the PVC system, is ab le to penetrate the PANI-DBSA aggregates, while xylene, used in the PS syst em, cannot. Nevertheless, the small PANI-DBSA particles in the PVC matrix f orm a conductive network only at a relatively high content, while the coars e aggregates in the PS matrix form conductive paths at a relatively low con tent. These results are discussed in terms of the formation and stability o f the PANI-DBSA dispersion.