“Annular Ring” microtubes formed by SDS@2β-CD complexes in aqueous solution

Abstract

Traditional aqueous self-assembly of tubular structures (as well as other aggregates) usually relies on the hydrophobic effect, a relatively weak and nondirectional interaction. The resultant aggregates are inherently soft, fluid, and less-ordered. Alternatively, we report a novel kind of nonamphiphilic self-assembly of microtubes in aqueous solutions of cyclodextrin/ionic surfactant (CD/IS) complexes. This self-assembly is driven exclusively by H-bonds, relatively strong, directional interactions. The CD/IS microtubes feature an unbundling nature, ultralong persistence lengths, highly monodispersed diameters, and remarkable rigidity. Every single CD/IS microtube is constituted by a set of coaxial, equally spaced, hollow cylinders, resembling the annular rings of trees (thus termed as “annular ring” microtubes). Furthermore, bearing in mind the fundamental difference between the amphiphilic counterpart in driving forces, this H-bond-driven hydrophilic self-assembly is envisioned to complement its counterpart and expand the field of molecular self-assembly.