SURFACE-COMPOSITION OF SURFACTANT-STABILIZED POLYPYRROLE COLLOIDS

We have examined a colloidal dispersion of surfactant-stabilised polyp yrrole particles by surface-enhanced Raman spectroscopy (SERS), time-o f-flight secondary ion mass spectroscopy (TOF-SIMS) and X-ray photoele ctron spectroscopy (XPS). These surface-specific techniques have enabl ed us to probe the surface composition of the conducting polymer parti cles. All three techniques indicate that the polypyrrole component is present at (or near) the particle surface: this observation is consist ent with the relatively high pressed-pellet conductivities exhibited b y these colloids. Our TOF-SIMS results suggest that the surfactant sta biliser is the dominant component in the first monolayer. Similarly, o ur wide-scan XPS spectra indicate that the sulfur/nitrogen surface ato mic ratio of the polypyrrole colloid is significantly higher than that of polypyrrole bulk powder; curve fitting of the corresponding core-l ine sulfur spectra confirm that a significant proportion of this exces s sulfur is due to the sulfonate-based surfactant. Thus, both our TOF- SIMS and XPS studies confirm that the surface of the polypyrrole parti cles is distinctly 'surfactant-rich', which is consistent with the obs erved long-term colloidal stability of these dispersions.