EFFECT OF ACID-BASE INTERACTIONS ON THE ADSORPTION OF PMMA ON CHLORIDE-DOPED POLYPYRROLE FROM NEUTRAL, ACIDIC AND BASIC SOLVENTS - AN XPS STUDY

This paper reports an XPS study of the adsorption of PMMA on chloride- doped polypyrrole (PPyCl) from neutral, acidic and basic solvents. It is shown that acid-phase interactions govern the absorption of PMMA (b asic) on PPyCl (predominantly acidic). Lewis acids dissolve PMMA and p revent this polymer from adsorption on PPyCl, whereas Lewis bases comp ete for the acidic sites on PPyCl surface, thus hampering the adsorpti on of PMMA. High amounts of PMMA can only adsorb from neutral solvents since these do not compete with the substrate for strong molecular in teractions with PMMA. The effect of the solvent power as measured by t he viscosity or the solubility parameter is also an important paramete r but we found that it has limitations in interpreting the adsorption measurement data. The thickness of the PMMA overlayers was found in th e range of 2-9 angstrom as estimated using the sampling depths and the attenuation signals of Cl(2p) and Cl(LMM) photoelectrons and Auger el ectrons, respectively.