Self-assembled nanotubes in organic solvents

Self-assembled nanotubes are formed spontaneously in alkane solvents by a simple diamide compound: the 3,5-Bis-(5-hexylcarbamoyl-pentyloxy)-benzoic acid decyl ester (BHPB-10). The tubular shape was proved by freeze fracture TEM and by SANS techniques. The tubes have a mean radius of 121 A and a length of the order of a micron. BHPB-14, a homologue of this compound, bearing a longer ester chain (C14 instead of C10), self-assemble into flat ribbons under the same conditions. FIR and UV spectroscopy showed that H-bonds between amide groups and pi-pi interaction between aromatic groups are involved in both kinds of aggregates and in the solid state as well. The nanotubes feature specific interactions between the ester carbonyls. Hence we show that ester, by its length and by the interactions between carbonyls determines the formation of nanotubes.