Adsorbed surfactant at the solid/liquid interface: Use of adsorbed surfactant aggregates in the synthesis of electrically conducting polymers

The underlying theme to this work is surfactant adsorption at the solid/liquid interface. More specifically, surfactant adsorption has been studied in relation to the critical micelle concentration (cmc) and to the applicability of adsorbed surfactant as a template for the synthesis of electrically conducting polymers. Measurement of the cmc of sodium dodecyl sulfate (SDS) in the presence of alumina and titania particles has been determined using ultracentrifuge membranes. Such membranes are able to allow individual SDS monomer to permeate while excluding aggregated SDS. Adsorbed SDS and sodium dodecylbenzene sulfonate (SDBS) have been used to fabricate thin films of polyaniline (PAni) and polypyrrole (PPy) respectively on the surface of alumina particles. Powder conductivities were found to reach ∼10−1 S/cm exhibiting an eight order of magnitude increase over bare alumina (∼10−9 S/cm). PAni and PPy films on alumina were characterized by loss ignition, wetting, and X-ray photoelectron spectroscopy (XPS) experiments. In addition, atomic force microscopy (AFM) was used to investigate the morphology of PAni and PPy films synthesized, in the presence of surfactant, on flat surfaces. Control over film morphology can be achieved by either the nature of the surfactant or the surface chemistry of the substrate. Shape transitions between spheres → cylinders → flat films were observed in direct relation to what has been previously observed in the bulk.