Properties of Single Dendrimer Molecules Studied by Atomic Force Microscopy

Well-separated, individual polyphenylene dendrimer molecules have been prepared by spin coating on a mica surface, and subsequently imaged by noncontact atomic force microscopy (NCAFM). The observed height is in good agreement with the size of a single dendrimer molecule, as calculated by molecular dynamics simulation. By using pulsed force mode (PFM) AFM, stiffness and adhesion properties of individual polyphenylene dendrimers have been studied. They could be related to the molecular structure and the chemical nature of the outer surface of the dendrimers and the thin film of water adsorbed on mica when imaged under ambient conditions. Finally, by changing the concentration of the spin-coating solution, two different kinds of aggregates have been characterized.