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

Synthesis of polyaniline (PANI) was performed under different conditions fo llowed by dedoping, redoping with dodecyl benzene sulfonic acid (DBSA) and then blending with PS. The morphologies of the as-polymerized, doped and bl ended PANI were studied. The main polymerization stages seem to include: PA NI oligomers assembling into nuclei, nuclei growing into primary particles (10 nm), primary particles assembling into aggregates (approximate to 0.5 m u m) and aggregates assembling into agglomerates (approximate to 10 mu m). The morphology of the as-polymerized PANI was found to be strongly related to the rate of oxidant addition, synthesis duration and synthesis temperatu re. This morphology dominates the effects of DBSA doping and dispersing the resulting PANI-DBSA in the matrix polymer. A fine PANI-DBSA powder with we akly bound aggregates is likely to disperse well in a solvent and hence pro mote the formation of the desired fine-network morphology and yield a low p ercolation threshold and high conductivity. Synthesis at a high oxidant add ition rate, an excess of oxidant, a relatively high polymerization temperat ure and a short synthesis duration should diminish the tendency to form den se complex structures. These dense structures prevent efficient DBSA doping , deaggregation and the desired fine-network dispersion of PANI-DBSA in the blends. (C) 1999 Elsevier Science S.A. All rights reserved.