Enhancement of corrosion protection effect in polyaniline via the formation of polyaniline-clay nanocomposite materials

A series of nanocomposite materials that consisted of emeraldine base of po lyaniline and layered montmorillonite (MMT) clay were prepared by effective ly dispersing the inorganic nanolayers of MMT clay in organic polyaniline m atrix via in-situ polymerization. Organic aniline monomers were first inter calated into the interlayer regions of organophilic clay hosts and followed by an one-step oxidative polymerization. The as-synthesized polyaniline-cl ay lamellar nanocomposite materials were characterized by infrared spectros copy, wide-angle powder X-ray diffraction, and transmission electron micros copy. Polyaniline-clay nanocomposites (PCN) in the form of coatings with lo w clay loading (e.g., 0.75 wt %) on cold-rolled steel (CRS) were found much superior in corrosion protection over those of conventional polyaniline ba sed on a series of electrochemical measurements of corrosion potential, pol arization resistance, and corrosion current in 5 wt % aqueous NaCl electrol yte. The molecular weights of polyaniline extracted from PCN materials and bulk polyaniline were determined by gel permeation chromatography (GPC). Ef fects of the material composition on the gas barrier property, thermal stab ility, and mechanical strength of polyaniline along with PCN materials, in the form of both fine powder and free-standing film, were also studied by g as permeability measurements, differential scanning calorimetry, thermograv imetric analysis, and dynamic mechanical analysis.