FT-IR-ATR SPECTROSCOPIC STUDY OF THE SPONTANEOUS POLYMERIZATION OF PYRROLE IN IRON-EXCHANGED MONTMORILLONITE

The oxidative polymerization of pyrrole in montmorillonite clay is followed in real time using in situ FT-IR-ATR spectroscopy. A conducting polymer-clay composite is formed as the ferric sites present at the accessible surfaces of the clay particles chemically oxidize the aromatic heterocycle. The infrared spectra indicate that the conducting polymer formed resembles electrochemically prepared polypyrrole and that, due to mass transport control of the reaction, no evidence of overoxidation of the pyrrole ring is found. No IR-evident changes are found for the aluminosilicate structure of the clay mineral. From analysis of the change in pyrrole concentration it can be determined that the overall process consists of three steps: pre-concentration, polymerization and pyrrole diffusion. By comparing diffusion limited data for experiments performed with and without the clay layer a relative measure of the diffusion coefficient for pyrrole in the composite is obtained.