Chemical preparation and characterization of conductive polypyrrole composite thin films

Abstract

Chemically synthesized polypyrrole (PPY) composites with polymethyl methacrylate (PMMA), using sodium persulfate (Na2S2O8) or bromine (Br2) as the oxidant, have been prepared and studied by thermogravimetry (TG) and x-ray photoelectron spectroscopy (XPS). Results show PMMA/PPY oxidized by persulfate yields the best films. In the case of the PMMA/PPY/bromine composite. XPS results suggest interaction between the bromine dopant and the PMMA substrate. The dopant anion in the persulfate oxidized films is identified to be mainly HSO4-$/ instead of SO4-$/. The bulk concentration of the dopant is about 30% by weight, which is higher than that found at the surface. In addition, the degree of doping as assessed by charged nitrogen by XPS is found to be between 10 and 15%. The air side is rich in the matrix polymer while the oxidized side is rich in PPY. Such films combine good electrical properties with excellent mechanical strength of the matrix polymer. Extensive penetration of the conducting PPY/bromine system into the PMMA substrate was observed, in marked contrast to previously prepared PMMA/polyaniline laminate films.