Electrochemical Response of Clay/Polyelectrolyte Composite Barrier Coatings

Abstract

Composite materials made of polymer and clay are effective at blocking mass transport. In this study, the blocking efficacy of layer-by-layer (LbL) coatings of exfoliated montmorillonite (MMT) and polyethylenimine (PEI) was studied using cyclic voltammetry and a redox couple, indigo carmine (IC). The pH of the MMT solution was varied from 4 to 10 to prepare LbL coatings of different surface roughness on metal substrates. It was found that the coated electrode had a lower redox peak current value than without the coating, demonstrating the reduction of the mass transport of IC to the metal surface. The peak values decreased with decreasing the coating’s roughness and increasing the number of layers, indicating that the blocking capability can be controlled by changing the deposition conditions. Smooth LbL coatings deposited with MMT at pH 4 showed the highest blocking efficacy up to 97.5%. The IC adsorbed at the interface between the coating and the metal substrate was found to cause the peak current measured for the coated electrode. It was also confirmed that the same coating on the copper substrate reduced the corrosion of the copper during the electrochemical potential cycling.

Molecular Organization in Exponentially Growing Multilayer Thin Films Assembled with Polyelectrolytes and Clay

“…Clay is one such component that has also been successfully LbL-assembled with polyelectrolytes to form advanced materials. Some of the most recent examples of the potential applications of the polymer-clay multilayers are as barrier thin films [ 2 , 3 ], anti-corrosion coatings [ 4 , 5 ], membranes with tailored nanochannels [ 6 ], phosphorescence thin films [ 7 ], waste treatment membranes [ 8 ], fire-retardant nanocomposites [ 9 ], super-strong chemically inert films [ 10 ], and in biomedical applications [ 11 , 12 ]. Clays are phyllosilicate minerals and are known for their exceptional mechanical and barrier properties.…”