Electrochemical formation of chiral polyaniline colloids codoped with (+)- or (-)-10-camphorsulfonic acid and polystyrene sulfonate

Chiral polyaniline colloids have been generated via the electrohydrodynamic polymerization of aniline in aqueous (+)- or (-)-10-camphorsulfonic acid (HCSA) using polystyrene sulfonate (PSS) as a steric stabilizer and codopant. Potentiostatic polymerization at +0.9 V (vs Ag/AgCl) was employed. The colloidal PAn.HCSA/PSS dispersions produced after various electropolymerization periods (30-90 min) became optically active upon aging over 24 h, revealing mirror-imaged circular dichroism (CD) spectra for PAn.(+)-HCSA/PSS and PAn.(-)-HCSA/PSS samples. This indicated an enantioselective rearrangement of the polyaniline chains induced by the chiral HCSA dopants after the initial electropolymerization and acid doping. Dialyzed colloidal dispersions were stable for extended periods (6 months) and revealed particles with a mean size of 180 +/- 10 nm, although particles were observed at up to 1000 nm. Similar particles were observed by TEM studies. Chemical dedoping with ammonia of films cast from these dispersions yielded the optically active emeraldine base form of the polymer, while reduction with hydrazine gave the corresponding leucoemeraldine base.