Self-Assembled Dual Helical Nanofibers of Amphiphilic Perylene Diimides with Oligopeptide Substitution

We designed an asymmetric amphiphilic perylene diimide (PDI) with the oligopeptide substituting one of the imides. The self-assembly mechanism of this PDI in different solvents was investigated. Right-handed dual helical nanofibers/nanowires with a uniform lateral dimension of similar to 8 nm are constructively self-assembled. The long-term ordered degree within the nanofibers stems from the delicate balance between pi-pi stacking of the PDI rings and beta-sheet-like hydrogen bond formed by the oligopeptide. The synergistic interplay between the hydrogen bond and pi-pi stacking rather than competition endows the nanofibers with the controllable longitudinal dimensions by different factors such as the concentration and solvents. The transition from the nano-fibers to the small aggregates is also achieved by the addition of trifluoroacetic acid because of breakup of the hydrogen bonds, which is reversed by further addition of trimethylamine. The acid-base stimulation can be extended to different solvents as long as the existence of the unique hydrogen bonds.