Electrostatic interaction between ionic polymer grafted surfaces studied by atomic force microscopy

To study the electrostatic interaction between two ionic polymer grafted surfaces in aqueous media, an atomic force microscopic tip surface was modified by graft polymerization of a cationic monomer, dimethylaminoethyl methacrylate (DMAEMA), after being coated with a thin layer of cyanoacrylate polymer. A poly(ethylene terephthalate) (PET) film which was the countersurface of the modified tip for the measurement of atomic force microscopy was also modified by surface graft polymerization of DMAEMA and an anionic monomer, acrylic acid (AAc). An appreciable adhesive force was observed in water between the DMAEMA-grafted tip and the AAc grafted PET surface, while a repulsive interaction was noticed between the DMAEMA-grafted tip and the DMAEMA-grafted PET film. Addition of KCl to the medium for the atomic force measurement exhibited a remarkable reduction in the adhesive interaction. These interactions were attributed to the Coulombic force between the grafted ionic polymer chains. (C) 1997 Academic Press.