Static Scanning Tunneling Microscopy Images Reveal the Mechanism of Supramolecular Polymerization of an Oligopyridine on Graphite

Supramolecular polymerization of a donor–acceptor bisterpyridine (BTP) equipped with an electron‐rich carbazole unit is observed by scanning tunneling microscopy (STM) at the highly oriented pyrolytic graphite (HOPG)|solution interface. It is shown that two‐dimensional crystals of supramolecular (co)polymers are formed by chain growth polymerization, which in turn can be described by copolymerization statistics. From concentration‐dependent measurements, derived copolymerization parameters and DFT calculations, a mechanism for self‐assembly is developed that suggests a kinetically driven polymerization process in combination with thermodynamically controlled crystallization. To be or not to be: The pressing question of the fundamental mechanism of two‐dimensional self‐assembly processes, namely that of thermodynamic or kinetic control, is demonstrated using the example of a donor–acceptor oligopyridine on graphite. A statistical analysis of STM images and DFT calculations suggest that there is a significant contribution of kinetics similar to copolymerization in bulk.