Formation of double helical microfibrils from small molecules

Using a facile vapor-solid route, double helical, organic, small molecular microfibril, i.e. 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) was synthesized, which was based on the spontaneous twisting of supramolecular microtubes. The average diameter of the resulting helical structures was about 200 nm and the overall length was of several micrometers. The helical microfibrils, which were obtained by coiling the multilayer microtubes from the inner to the outer molecular layers, tend to release their internal rotation stress to exhibit the most stable morphology as indicated by a series of characterizations. The change in van der Waals force, together with the surface free energy among the adjacent microtubes molecular layers, were the driving forces to induce the formation of a helical structure. The obtained results present an extremely facile strategy for the fabrication of small molecular, double helical microfibrils with morphological transformation.