CHARACTERIZATION OF CONDUCTING POLYMERS BY INVERSE GAS-CHROMATOGRAPHY .2. EFFECT OF DOPANT ON THE DISPERSIVE AND SPECIFIC PROPERTIES OF POLYPYRROLE

A series of polypyrroles, synthesized using iron(III) oxidizing agent, was characterized by inverse gas chromatography (IGC). The dispersive component to the surface tension of these materials falls in the range 40-60 mJ/ml for Cl-- and NO3--doped polypyrroles, whereas that of Fe(CN)64- is extremely high (106 mJ/m2) when compared to a conventional polymer. These values rank conducting polypyrroles between conventional insulating polymers and high surface energy materials such as metals, metal oxides and graphite. In addition, all polymers exhibit strong specific adsorption of acidic and basic molecular probes, confirming the Lewis amphoteric behaviour of conducting polypyrroles. The hard and soft acids and bases (HSAB) concept is also emphasized in an original manner based on acidic and basic Lewis probes and in connection with the nature of the dopant. This IGC study shows that the dopant plays an important role in the surface thermodynamics of conducting polypyroles, as evidenced by the magnitude of the dispersive and acid-base properties.