POLYANILINE - CLAY NANOCOMPOSITES AS CORROSION PROTECTION

Polyaniline is unique in the family of conjugated polymers ^[1] and the most intensively investigated electronically conductive polymer because of its potential commercial applications in e.g. rechargeable batteries, electrochromic display devices, electrochemical sensors, electrochemical capacitors and in the last few years in active corrosion protection ^{[2, 3, 4, 5, 6, 7]}. Recently, conducting polymer layered inorganic solid nanocomposites have been the subject of considerable research interest because, being derived from a unique combination of inorganic and organic components they have possible technological application as well as scientific issues concerning them^{[8, 9, 10]} . One of the most prevalent class of these nanocomposites is composed of materials containing polyaniline (PANI) and montmorillonite (MMT) (clay minerals), because MMT minerals have attractive advantages such as large surface area, ion exchange and expandability properties.
A PANI-MMT nanocomposite can be synthesized either by chemical oxidation of aniline inside the layers or via an electrochemical way. Recently, several reports have been published on the chemical method of synthesis of PANI-MMT nanocomposites ^{[4, 6, 11, 12, 13, 14, 15]}. Electrochemical polymerization of monomers on an electrode surface offers many advantages over chemical methods. The resulting product is a solid, does not necessarily need to be extracted from the initial monomer/oxidant/solvent mixture and is easily amenable to numerous techniques for characterization such as UV-Visible, infrared and Raman spectroscopies and in situ conductimetry^[16]. Inoue et al.^[17] have reported the electropolymerization of PANI-MMT using a clay modified electrode and aniline was intercalated by dipping the electrode in aniline followed by drying in air. However, this method does not yield a homogeneous composite because the intercalation is not homogeneous and excess of aniline is not removed. Feng et al. ^[18] have also electropolymerized PANI in MMT potentiostatically at ESCE = 0.8 V in a pre-treated mixture of aniline-MMT and HCl where the final concentration of HCl is 1 M under magnetic stirring. However, the PANI-MMT composite is obtained in the dispersion and not on the surface of the electrode. Getting PANI-MMT on the electrode by electropolymerization for further characterized and application studies is very interesting work and needs a lot of work on it.

Planning Research
In the present work, we will synthesize PANI-MMT nanocomposites electrochemically in the acidic solution. The expansion of d-spacing between layers of MMT due to the intercalation of anilinium ion and polyaniline into clay MMT layers will be investigated by X-ray diffraction. The PANI-MT nanocomposites will be characterized by in situ UV-Vis spectroscopy, cyclic voltammetry, FT-IR spectroscopy and in situ conductivity measurements. The result deposited PANI-MMT will be studied on anti-corrosion of metals.