Controlling the lateral aggregation of perfluoroalkylated hexa-peri-hexabenzocoronenes

The investigation of two hexa-peri-hexabenzocoronene (HBC) derivatives carrying linear or branched perfluoroalkylated side chains is reported. Polycondensed aromatic hydrocarbons (PAH) such as HBC derivatives are well known to self-organize to form highly ordered monomolecular stacks, which in turn show a concentration- and solvent-dependent lateral aggregation. However, possible applications of self-assembled HBC derivatives require linear, laterally non-aggregated columnar structures. According to powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC), HBC derivatives with linear perfluoroalkylated side chains show liquid crystalline (LC) properties whereas those with branched perfluoroalkylated side chains have an amorphous structure. The stacking behaviour and the lateral aggregation are found to be greatly influenced by changes in the medium, as shown by fluorescence spectroscopy and cryo-scanning electron microscopy (cryo-SEM).