Preparation of Electronically Conducting Ultra-Thin Polymer Films

Admicellar polymerization uses adsorbed surfactant aggregates to concentrate monomeric species at the solution-solid interface and to localize the polymer-forming reaction over a surface. The process has been adapted for the deposition of polypyrrole thin films on mica substrates. Amphiphiles adsorb from aqueous solution onto mica substrates and form self-assembled arrays. These arrays have been characterized by atomic force microscopy (AFM). Polypyrrole films prepared by polymerization in the self-assembled arrays (PSAA) were characterized and compared with samples made by polymerization in the absence of self-assembled arrays (surface nucleation, PSN). Images and measurements by AFM indicate that PSAA films over mica surfaces tend to be much smoother than PSN layers at the same condition. The ultra-thin PSAA (130 nm) can be fabricated simply, controlled by changing the ratio between water, surfactant, and pyrrole concentration under ambient conditions. Although thinner, PSAA films have more stable and higher conductivity than the PSN films. The relationship between film morphology and electronic properties has been discussed.