Self-assembly of alkyl-substituted polyphenylene dendrimers on graphite

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