Spectroscopic investigation of oxidation of p-toluene sulfonic acid doped polypyrrole

Abstract

Oxidative degradation of electrochemically synthesized p-toluene sulfonic acid doped polypyrrole, PTS-PPY was studied by the application of evolved gas analysis using IR spectroscopy and direct insertion probe pyrolysis mass spectrometry techniques. It has been observed that PPY films prepared in aqueous media contained high concentration of oxygenated species even if the synthesis potential was kept low. The extent of overoxidation associated to ketone formation increased by increasing the applied potential and thermal ageing. The decrease in conductivity is attributed to the replacement of dopant, as a result of nucleophlic attack on the polycationic chain, by hydroxide and/or O 2. Pyrolysis analyses also indicated that chemically prepared samples were oxygenated in air more readily and yielded mainly CO groups. Presence of hydroxide groups for these samples may be associated with the adsorption of H 2O in air or H 2O present during synthesis as an impurity. The direct insertion probe pyrolysis mass spectrometry technique was shown to be a very powerful technique for not only determining the thermal decomposition products but a investigating the interaction of dopant and oxygenated species with the polymer matrix.