Polyaniline synthesis: influence of powder morphology on conductivity of solution cast blends with polystyrene

Synthesis of polyaniline (PANI) was performed under different conditions followed by dedoping, redoping with dodecyl benzene sulfonic acid (DBSA) and then blending with PS. The morphologies of the as-polymerized, doped and blended PANI were studied. The main polymerization stages seem to include: PANI oligomers assembling into nuclei, nuclei growing into primary particles (10 nm), primary particles assembling into aggregates (≈0.5 μm) and aggregates assembling into agglomerates (≈10 μm). The morphology of the as-polymerized PANI was found to be strongly related to the rate of oxidant addition, synthesis duration and synthesis temperature. This morphology dominates the effects of DBSA doping and dispersing the resulting PANI–DBSA in the matrix polymer. A fine PANI–DBSA powder with weakly bound aggregates is likely to disperse well in a solvent and hence promote the formation of the desired fine-network morphology and yield a low percolation threshold and high conductivity. Synthesis at a high oxidant addition rate, an excess of oxidant, a relatively high polymerization temperature and a short synthesis duration should diminish the tendency to form dense complex structures. These dense structures prevent efficient DBSA doping, deaggregation and the desired fine-network dispersion of PANI–DBSA in the blends.