An inverse gas chromatographic study of the PMMA/conducting polypyrrole interface

The poly(methyl methacrylate)/chloride-doped polypyrrole (PMMA/PPyCl) interface in PMMA-coated PPyCl powders has been characterized by inverse gas chromatography (IGC). The study is based on the determination of the surface energy of the various materials tested. It is shown that gamma(S)(d), the dispersive contribution to the surface energy of PPyCl, decreases following adsorption of PMMA onto PPyCl, a high surface energy material. The overall acid-base character of the coated powders shifts from a predominant acidity to a predominant basicity following PMMA adsorption. However, the nature of the casting solvent strongly influences the morphology of the PMMA coatings, as judged from their surface thermodynamic properties. Indeed, for approximately the same relative surface proportion of PMMA, both dispersive and acid-base properties of the coated PPyCl differ, depending on whether PMMA is cast from a good or a poor solvent. The results obtained suggest that from poor solvents, PMMA adsorbs onto PPyCl and leads to homogeneous coatings (provided that the amount of adsorbed PMMA is large enough to reach at least a monolayer), whereas from good solvents, the adsorption of PMMA results in inhomogeneous coatings.