3D Crystals of Supramolecular Nanotubes Containing up to 94% of Liquid Water

3D crystalline order with 1 nm resolution is observed in aqueous solutions of supramolecular nanotubes at concentrations as low as 6 wt%. The nanotubes are self-assembled from ionic star-like mesogens with three oligobenzamide branches. 50 such molecules arrange radially into supramolecular rings which, in turn, stack on top of each other to form long hollow tubes with 15 nm outer diameter. X-ray based electron density maps and cryo-TEM show that parallel nanotubes arrange on a perfect hexagonal lattice, with interaxial separation up to 25 nm and surface-to-surface water gap up to 10 nm, depending on concentration. Unexpectedly, fiber diffraction on sheared solutions feature numerous hkl Bragg reflections on several layer lines. These indicate longitudinal interlock between the tubes and 3D crystalline order with molecular-scale detail transferred over long distance water. Increasing concentration brings slowing tube dynamics as probed by X-ray photon correlation spectroscopy. The tubes are non-centrosymmetric. The observed high 3D order can be understood in terms of long-range attractive forces between like-charged tubes and the extremely high intra-tube correlation length.