Spectroelectrochemistry and preresonance Raman spectroscopy of polyaniline-dodecylbenzenesulfonic acid colloidal dispersions.

Dodecylbenzenesulfonic acid (DBSA) dissolved in 2-propanol (70% solution), a surfactant and dopant, is used in the synthesis of polyaniline (PANI) colloids. The micelle-aided synthesis yields green dispersions that do not undergo macroscopic precipitation for more than a year. UV-vis studies reveal that polymerization is completed in 3 h irrespective of the feed ratio of DBSA/aniline. The polymerization yield depends on the amount of DBSA in the feed. UV-vis spectroscopy as a function of applied potential was carried out for the first time for thin layers of the dispersion. Bands corresponding to both emeraldine salt and emeraldine base were observed during cathodic potential sweeps whereas in an anodic sweep bands due to only emeraldine base were observed. Electronic absorption spectroscopy and preresonance Raman spectroscopy as a function of pH indicate emeraldine salt (metal) to emeraldine base (insulator) transformation at higher pH (pH 9-10). The high aggregation tendency of PANI particles during solvent drying yields particles with irregular shapes.