Self-Assembly of Alkyl-Substituted Polyphenylene Dendrimers on Graphite

The lateral organization of alkyl-substituted polyphenylene dendrimers on the basal plane of graphite has been investigated using atomic force microscopy. The dendrimers consist of a core of twisted, interlocked benzene rings and an external shell of dodecyl chains. Three kinds of dendrimers were used which in solution show a tetrahedral or a disklike shape. On graphite the dendrimers spontaneously form a stable, almost pinhole free monolayer. Complex two-dimensional arrangements and supramolecular ordering were observed in these monolayers prepared by spin-coating. One prominent structure observed with all three dendrimers was regions consisting of parallel rows of 6 nm spacing. In addition, pairs of dendrimers formed two-dimensional crystals on graphite. A simple model to interpret structure formation is discussed. The structure depends sensitively on the structure of the dendrimer, on the solvent, and on the concentration.