Surface characterization of colloidal polypyrrole particles synthesized with reactive steric stabilizers using X-ray photoelectron spectroscopy

Abstract

Abstract X-ray photoelectron spectroscopy has been used to characterize the surfaces of polypyrrole colloids synthesized using reactive steric stabilizers based on statistical copolymers of 2-(dimethylamino)ethyl methacrylate. Three different copolymer stabilizers, containing 2-vinylpyrrole, 3-vinylthiophene and 2,2′-bithiophene-5-methyl methacrylate graft sites respectively, were examined. In each case, the grafted copolymer stabilizer was detected at the surface of the polypyrrole particles, which is consistent with the accepted steric stabilization mechanism of colloid stability. With the bithiophene-based copolymer stabilizer, the sulfur atoms in the bithiophene groups acted as unique elemental markers, and thus aided the detection and quantification of the stabilizer component. The atomic ratio of nitrogen to sulfur as determined by X.p.s. for this polypyrrole colloid was significantly higher than that observed for the corresponding copolymer stabilizer. This excess surface nitrogen was attributed to the polypyrrole component and is consistent with the relatively high solid-state conductivity (ca. 10−1 to 100 S cm−1) measured on compressed pellets of this dried colloid. The presence of the other two copolymer stabilizers at the surface of the polypyrrole particles is less obvious but can be verified from close inspection and comparison of the C1s and N1s core-line spectra of the two polypyrrole colloids, their corresponding copolymer stabilizers and a polypyrrole ‘bulk powder’ control sample respectively.