Pyrolysis-gas chromatography/ mass spectrometry applied to the identification of different states of polyaniline

L LIZARRAGA,; T VERDEJO,; F. V. MOLINA; GONZALEZ VILA, FJ

Budapest

Congreso; 17th International Symposium on Analytical & Applied Pyrolysis, 21 al 26 de mayo, 2006; 2006

Polyaniline (PANI) is one of the most intensively studied conducting polymers.  Pyrolysis – gas chromatography/ mass spectrometry (Py-CG/MS) has been applied to study and compare the composition of two PANI forms: fully reduced leucoemeraldine and intermediately oxidized emeraldine.   The different PANI forms were electrochemically synthesized using cyclic voltammetry from 0.5 M aniline + 1.5 M sulphuric acid + 1.5 M perchloric acid solutions on platinum electrodes. The polymers obtained were dedoped by stirring for 24 hours in ammoniacal solutions, rinsed and dried. When a 1 M NH3 solution was used, the polymer obtained was emeraldine, whereas when a 1 M NH3 + 0.1 M hidroxylamine solution was used, the polymer obtained was leucoemeraldine.   The pyrolysis was performed at 700 ºC and the fragments obtained were separated by HRGC and identified by using a mass spectrometry detector. The signals obtained were assigned to the monomer, dimers and trimmers as well as to rearrangement products.   Leucoemeraldine and emeraldine pyrograms presented differences in the relative intensity of their fragment signals. Emeraldine pyrograms presented a higher relative intensity of the signals associated to oxidized fragments (i.e. quinone imine) than leucoemeraldine pyrograms. On the other hand, polymer samples synthesized under different anodic potentials did not show appreciable differences. The results obtained indicate that Py-GC/MS may be used for identification among different oxidation states in aryl amine polymers.