X-ray Photoelectron Spectroscopy Studies on Sterically-Stabilized Polypyrrole Particles

Abstract

The surface composition of a sterically-stabilized polypyrrole colloid has been examined by X-ray photoelectron spectroscopy (XPS). The sulfur atom of the polyelectrolyte stabilizer poly(potassium 3-sulfopropyl methacrylate) [PKSPM] and the nitrogen atom of the polypyrrole were used as unique elemental markers for each component. The S/N atomic ratio at the particle surface determined using XPS was found to be significantly higher than the corresponding ‘macroscopic' S/N atomic ratio calculated from elemental microanalyses. This is the first direct evidence for the presence of a stabilizer-rich layer at the surface of sterically-stabilized conducting polymer particles. Changing to a lower energy X-ray source (Mg Kα) did not lead to an increase in the surface S/N ratio; thus, the stabilizer layer is probably ‘patchy' rather than a continuous coating. XPS also revealed that the surface concentrations of the K+ and Cl- counterions in the colloid were substantially depleted relative to those found in the PKSPM stabilizer and chloride-doped polypyrrole ‘bulk powder'. Moreover, the surface dopant level of the polypyrrole particles calculated on the basis of the remaining chloride ions was unusually low (Cl/N = 0.07). More realistic surface dopant levels were obtained if it was assumed that some of the sulfonate groups of the polyelectrolyte stabilizer acted as dopant anions for the conducting polymer component. It was concluded that the PKSPM stabilizer is adsorbed onto the surface of the polypyrrole particles as a polymeric dopant anion, with the concomitant expulsion of KCl. Finally, there is some evidence that this stabilizer is present as a polymeric dopant in the interior of the particles as well.

Nanomorphology characterization of sterically stabilized polypyrrole-palladium nanocomposite particles

“…8 The sulfonate group is known to be an efficient dopant anion for PPy and has stronger interactions with PPy compared with chloride ions. 8,27,28 It has been confirmed that the PPy-Pd nanocomposite particles were doped with sulfonate groups rather than chloride ions by X-ray photoelectron spectroscopy studies. 8 Therefore, it can be expected that the PLSSA colloidal stabilizer is adsorbed onto the surfaces of the PPy-Pd nanocomposite particles as a polymeric dopant anion ( Figure 1).…”

Biocatalytic synthesis of polypyrrole powder, colloids, and films using horseradish peroxidase

“…8a) shows the same peaks as the sample prepared in absence of PVAL. Nevertheless the addition of PVAL to the reaction media resulted in the adsorption of this oxygen containing polymer on the surface of the colloids, as evidenced by the reduction of the S 2p signal intensity and the increase of the O/C and O/N ratio, similar to chemically synthesized PPy colloids stabilized with polyelectrolytes [38]. In fact, the deconvolution of the C 1s peak from the colloids (Fig.…”

Space science applications for conducting polymer particles: synthetic mimics for cosmic dust and micrometeorites

“…3). Typically, the polymeric stabiliser is merely physically adsorbed onto the surface of the polypyrrole particles via either hydrogen bonding 21 or electrostatics; 22 although chemicallygrafted stabilisers have also been developed, 23,24 this latter approach has not yet been utilised for space science applications. The biocompatible nature of polypyrrole, coupled with its intense intrinsic pigmentation and strong absorption of near-IR radiation, has led to various biomedical applications being explored for such polypyrrole-based nanoparticles.…”