SURFACE CHARACTERIZATION OF COLLOIDAL POLYPYRROLE PARTICLES SYNTHESIZED WITH REACTIVE STERIC STABILIZERS USING X-RAY PHOTOELECTRON-SPECTROSCOPY

X-ray photoelectron spectroscopy has been used to characterize the sur faces of polypyrrole colloids synthesized using reactive steric stabil izers based on statistical copolymers of 2-(dimethylamino)ethyl methac rylate. Three different copolymer stabilizers, containing 2-vinylpyrro le, 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 o f colloid stability. With the bithiophene-based copolymer stabilizer, the sulfur atoms in the bithiophene groups acted as unique elemental m arkers, and thus aided the detection and quantification of the stabili zer component. The atomic ratio of nitrogen to sulfur as determined by X.p.s. for this polypyrrole colloid was significantly higher than tha t observed for the corresponding copolymer stabilizer. This excess sur face nitrogen was attributed to the polypyrrole component and is consi stent with the relatively high solid-state conductivity (ca. 10(-1) to 10(0) 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 cl ose inspection and comparison of the C-ls and N-ls core-line spectra o f the two polypyrrole colloids, their corresponding copolymer stabiliz ers and a polypyrrole 'bulk powder' control sample respectively. Crown copyright (C) 1996 Published by Elsevier Science Ltd.