A fluorescent organic nanotube assembled from novel p-phenylene ethynylene-based dicationic amphiphiles

Novel π-extended conjugated amphiphiles composed of a hydrophilic section of two quaternary ammonium groups and p-phenylene ethynylene with adjustable alkyl chain hydrophobic section were prepared by a multistep synthesis. These dicationic amphiphiles showed good water solubility and formed a tubular assembly in water. The evidence for the nanotubular comes from direct optical and TEM observations. A strong π-π stacking interaction between neighboring molecules, as evidenced by the red-shift and self-quenching in fluorescence, is proposed for the self-assembly. At the same time, dehydration of the bromide led to strong counterion condensation in headgroups, which resulted in the small curvature structure of the nanotubes. A bilayer lamellar structural model for the organic nanotube is proposed, and a reasonable structural model based on the experimental XRD pattern, as well as cell constants, is proposed.