Aggregation of polyaniline in dilute and semidilute solutions

Summary form only given. Aggregation of polyaniline chains in dilute solutions was observed in N-methyl-2-pyrrolidone (NMP) by light scattering, gel permeation chromatography, and viscosity measurements. The origin of the aggregation is a cooperation with hydrogen bonding between the imine and amine groups and the rigidity of the backbone. Effect of external salt on aggregation equilibirium was also investigated, and a simple model based on the aggregation equilibrium and electrostatic repulsion in the polyelectrolyte is proposed to explain the role of the salt on polyaniline chaffis in dilute solutions. The aggregation of polyaniline in semidilute solutions results in reversible gelation. The existing percolation in the gel provides an opportunity of obtaining low percolation threshold when using sulfonated polymeric dopants even with the degree of sulfunation being low as 6%. We have followed the volume change with pH, temperature and solvent quality in addition to interesting electric field effects on the expansion-shrinkage behavior.