Conductive polyaniline/surfactant ion complex Langmuir-Blodgett films

Organic-solvent-soluble amphiphilic polyanilne was prepared by ion complex formation of protonated polyaniline (PANI) and anionic surfactant dodecylbenzenesulfonic acid (DBSA). The amphiphilic PANI/DBSA ion complex shows stable monolayer behavior at the air-water interface and formation of LB films on solid substrates. The cyclic voltammograms for the monolayer PANI/DBSA LB films show two distinct redox process waves, that is, the quasi-reversible redox wave at around 0.05 V vs SCE as a lucoemeralidine/emeraldine couple and the symmetric surface wave behavior of PANI at 0.75 V vs SCE as an emeraldine/pernigraniline couple. The surface morphology of the monolayer PANI/DBSA LB film on a Si wafer shows that monolayer surface roughness is smooth at a molecular level with fiberlike bundle structures where the elongated main chains of polyanilines were assembled by pi-pi interaction of the polyanilines. Conductivity of PANI/DBSA LB films depends on the number of layers at less than four layers, and it becomes similar to the bulk conductivity, 0.5 S/cm, at more than four layers.