Preparation and characterization of poly(o-methoxyaniline)/Na+–MMT clay nanocomposite via emulsion polymerization: Electrochemical studies of corrosion protection

A series of poly(o-methoxyaniline) (PMA)/Na+–montmorillonite (MMT) clay nanocomposite (Na+–PCN) materials have been successfully prepared by in situ emulsion polymerization in the presence of inorganic nanolayers of hydrophilic Na+–MMT clay with DBSA and APS as surfactant and initiator, respectively. The as-synthesized Na+–PCN materials were characterized by Fourier-transformation infrared (FTIR) spectroscopy, wide-angle powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Na+–PCN materials in the form of coatings with low loading of Na+–MMT clay (e.g., 5 wt.%, CLMA5) on cold rolled steel (CRS) were found much superior in corrosion protection over those of neat PMA based on a series of electrochemical measurements of corrosion potential, polarization resistance, corrosion current and impedance spectroscopy in 5 wt.% aqueous NaCl electrolyte. The molecular weight of PMA extracted from Na+–PCN materials and net PMA were determined by gel permeation chromatography (GPC) with NMP as eluant. Effects of material composition on the optical properties, electrical conductivity, thermal stability and surface morphology of neat PMA and/or a series of Na+–PCN materials, in the form of solution, powder-pressed pellet and fine powder, were also studied by ultraviolet–visible spectra, four-point probe technique, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), respectively.