Imaging of single polyethylenimine polymers adsorbed on negatively charged latex spheres by chemical force microscopy

In this study scanning force microscopy was applied to image single polyethylenimine (PEI) polymers adsorbed onto negatively charged latex spheres. The tip of an atomic force microscope was chemically modified to induce a strong chemical interaction to the PEI molecules. Operating the atomic force microscope in the constant height mode, chemical imaging by measuring the normal force as well as the friction force was achieved and high image contrast could be obtained. The results demonstrate that polymer adsorption can be visualized directly.