Chemical imaging of single polyethylenimine polymers by chemical force microscopy

Polymer adsorption effects are of prime importance in technical applications i.e. for flocculation in paper making or the cleaning of waste water. In this paper we report on the direct imaging of single polyethylenimine polymers adsorbed on negatively charged latex spheres. Chemical imaging was achieved by a proper chemical modification of the tip of a conventional scanning force microscope. The imaging was performed by operating the microscope in the friction mode thus giving information about the adhesion properties of the polymers under investigation. Imaging is even possible in an aqueous environment. The results are in good agreement with quasi elastic light scattering measurements and former models of the mechanism of action of polyethylenimine in flocculation processes.