Water-Induced Self-Assembly of Amphiphilic Discotic Molecules for Adaptive Artificial Water Channels.

Inspired by the induced-fit mechanism in nature, we developed the process of water-induced self-assembly (WISA) to make water an active substrate that regulates the self-assembly and function of amphiphilic discotic molecules (ADMs). The ADM is an isotropic liquid that self-assembles only when in contact with water. Characterization results indicate that water fits into the hydrophilic core of the ADMs and induces the formation of a hexagonal columnar phase (Colh), where each column contains a hydrated artificial water channel (AWC). The hydrated AWCs are adaptive rather than static; the dynamic incorporation/removal of water results in the reversible assembly/disassembly of the adaptive AWCs (aAWCs). Furthermore, its dynamic characteristics can enable water to act as an orientation-directional guest molecule that controls the growth direction of the aAWCs. Well-aligned aAWC arrays that showed the ability of water transport were obtained via a "directional WISA" method. In WISA, water thus governs the supramolecular chemistry and function of synthetic molecules as it does with natural materials. By making water an active component in adaptive chemistry and enabling host molecules to dynamically interact with water, this adaptive aquatic material may motivate the development of synthetic molecules further toward biomaterials.

Cylindrical micelles of a POSS amphiphilic dendrimer as nano-reactors for polymerization.

A low generation amphiphilic dendrimer, POSS-AD, which has a POSS core and eight amphiphilic arms, was synthesized and used as a nano-reactor to produce well-defined polymer nano-cylinders. Confirmed by small-angle X-ray scattering (SAXS), Raman and NMR spectrometry, monodispersed cylindrical micelles that contain a hydrophilic cavity with a diameter of 2.09 nm and a length of 4.26 nm were produced via co-assembling POSS-AD with hydrophilic liquids, such as H2O and HEMA in hydrophobic solvents. Taking the HEMA/POSS-AD cylindrical micelles as nano-reactors, polymerization of HEMA within the micelles results in polymer nano-cylinders (POSS-ADNPs) with a diameter of 2.24 nm and a length of 5.02 nm. The study confirmed that despite the inability to maintain specific shape in solution, low generation dendrimers form well-defined nano-containers or nano-reactors, which relies on co-assembling with hydrophilic guest molecules. These nano-reactors are robust enough to maintain their shape during the polymerization of the guest molecules. Polymer nano-cylinders with dimensions less than 10 nm can thus be produced from the HEMA/POSS-AD micelles. Since the chemical structure of low-generation dendrimers and the contents of the co-assembled nano-reactors can be easily adjusted, the concept holds the potential for the further developments of low-generation amphiphilic dendrimers.