Surface characterization of poly(3,4-ethylenedioxythiophene)-coated latexes by X-ray photoelectron spectroscopy

Micrometer-sized polystyrene (PS) particles coated with poly(3,4-ethylenedioxythiophene) (PEDOT), an air-stable organic conducting polymer, have been described previously (Langmuir 1999, 15, 3469). X-ray photoelectron spectroscopy (XPS) was used to examine the surface of these coated particles. For the first time, both the conducting polymer overlayer and the steric stabilizer, poly(N-vinylpyrrolidone) (PNVP), could be identified by unique elemental markers − sulfur for the PEDOT and nitrogen for the PNVP, respectively. The line shape of the C 1s core-line spectra of a latex coated with a thin PEDOT overlayer (<15 nm) closely resembled that of the uncoated PS latex. However, as the PEDOT overlayer thickness was increased, the line shape came to resemble that of bulk PEDOT. The surface specificity of XPS indicated that the particle surface becomes PEDOT-rich as the conducting polymer loading is increased. Examination of the S 2p core-line spectra revealed that the PEDOT overlayers had relatively low doping...