Polypyrrole-coated poly(vinyl chloride) powder particles: surface chemical and morphological characterisation by means of X-ray photoelectron spectroscopy and scanning electron microscopy

Abstract

Polypyrrole (PPy)-coated poly(vinyl chloride) (PVC) powder particles were prepared by the in situ chemical polymerisation of pyrrole in aqueous solutions in the presence of PVC powder particles. The PVC particles in suspension served as a hydrophobic substrate for the in situ polymerisation of pyrrole using iron chloride as the oxidising agent and sodium p-toluene sulfonate. In these conditions, tosylate-doped PPy (PPyTS) was obtained and chlorides were inserted as minor codoping species. In some cases, the pyrrole was polymerised after incubating the PVC particles with poly(N-vinyl pyrrolidone). Scanning electron microscope (SEM) micrographs showed that the PVC particles retained their initial, quasispherical shape after coating by PPy. At low magnification, the coated PVC particles appeared smooth, but at high magnification, they exhibited a decoration by elementary nanoparticles of about 200-nm size due to PPy bulk powder grains. Elemental analysis indicated a mass loading of PPy in the range 1–58% w/w. Specific surface analysis by X-ray photoelectron spectroscopy (XPS) resulted in the spectra of the PPy-coated PVC particles resembling those of bulk powder PPyTS even for low PPy mass loading. The surface fraction of PPy repeat units was found to vary in the 55–91% range. This result is consistent with the SEM observation of the PPy nanoparticles at the surface of PVC powder grains. However, despite the important loading of PPy, the XPS estimation of the overlayer thickness is in favour of a patchy coating rather than continuous coatings of PPy.