Preparation and surface analysis of pigment@polypyrrole composites

Two novel pigment@polypyrrole composites were prepared by the in situ polymerization of pyrrole in aqueous media in the presence of two anticorrosion pigments, namely Shieldex (calcium-exchanged silica) and K-White (based on aluminium triphosphate). The pigments were used as inorganic templates for the surface-confined oxidative polymerization of pyrrole. The pigment@polypyrrole composites were characterised by scanning electron microscopy, elemental analysis and X-ray photoelectron spectroscopy (XPS). SEM highlighted the presence of polypyrrole (PPy) microspheres at the surface of the pigment particles. This observation is confirmed by both elemental analysis and XPS. Indeed, PPy mass loading could be as high ∼34 wt% for the Shieldex@PPy composite prepared with 0.5 ml of pyrrole in the presence of 1.5 g of pigment. Moreover, the N 1s peaks from PPy are readily detected in the XPS spectra of the pigment@PPy composites. Comparison of the bulk and surface N/Si and N/(Al + P) atomic ratios determined for Shieldex@PPy and K-White@PPy composites, respectively, suggest conductive polymer-rich surfaces for the modified pigments. However, there is a clear difference in the mechanisms of PPy loading on the two pigment surfaces.