Spectroscopic Study of Polyaniline Emeraldine Base: Modelling Approach

Medhat Ibrahima* and Eckhard Koglinb
a Spectroscopy Department, National Research Center Dokki, Cairo, EgyptE-mail: ibrahim@physik.rwth-aachen.de
b Institute of Physical Chemistry (ICG-IV), Research Center Juelich, 52425 Juelich, Germany

The polymerization of aniline by Cu(II) montmorillonite was studied using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Experimental spectra were compared with that calculated by AM1, PM3, PM5, MINDO, Hatree Fock, HF/6-31g(d), as well as Density Functional Theory, BLYP/DZVP and B3LYP/6-31g(d,p). Furthermore, the final heat of formation is studied as a function of temperature. Results indicate that, for aniline B3LYP/6-31G(d,p) calculated frequencies are in a good agreement with experimental data, while HF/6-31G(d) is the optimal in case of polyaniline. The vibrational calculations of a four-ring unit (emeraldine base: EB) are believed to be a good representation of the polyaniline at Cu(II)-montmorillonite. The final heat of formation is a function of polymerization and changed from aniline monomer to 5 ring repeat unit of polyaniline structure.

Key words: aniline, polyaniline, vibrational spectroscopy, Ab initio calculation, heat of formation