Selective Synthesis of Single- and Multi-Walled Supramolecular Nanotubes by Using Solvophobic/Solvophilic Controls: Stepwise Radial Growth via "Coil-on-Tube" Intermediates

Novel hexa-peri-hexabenzocoronene (HBC) derivatives, (HBC)-H-F and (HBC)-H-F*, which carry perfluoroalkyl segments on one side of the HBC core and long alkyl tails on the other, were synthesized. Their perfluoroalkyl segments are highly solvated in C6F6 (solvophilic effect) and do not assemble, whereas in CH2Cl2, they are excluded (solvophobic effect) and assemble together consequently. For example, the use of C6F6 and CH2Cl2 as assembling media for FHBC leads to the selective formation of single- and multi-walled nanotubes, respectively. When a higher monomer concentration is applied in CH2Cl2, multi-walled nanotubes with a larger number of walls result. FHBC in CH2Cl2 self-assembles rather slowly, thereby allowing for the observation of coil-on-tube structures, which are possible intermediates for the stepwise radial growth of the nanotubular wall. Casting of the multi-walled nanotubes onto a quartz plate yields a superhydrophobic thin film with a water contact angle of 161 perpendicular to 2 degrees.