Lyotropic Supramolecular Helical Columnar Phases Formed by C₃‐Symmetric and Unsymmetric Rigid Molecules

Abstract

Unlike thermotropic liquid-crystalline C(3)-symmetric molecules with flexible chains, the herein-designed fully rigid three-armed molecules (C(3)-symmetric and unsymmetric) create a fancy architecture for the formation of lyotropic liquid crystals in water. First, hollow columns with triple-stranded helices, analogous to helical rosette nanotubes, are spontaneously constructed by self-organization of the rigid three-armed molecules. Then, the helical nanotubes arrange into hexagonal liquid-crystalline phases, which show macroscopic chirality as a result of supramolecular chiral symmetry breaking. Interestingly, the helical nanotubes constructed by the fully rigid molecules are robust and stable over a wide concentration range in water. They are hardly affected by ionic defects at the molecular periphery, that is, further decoration of functional groups on the molecular arms can presumably be realized without changing the helical conformation. In addition, the formed columnar phases can be aligned macroscopically by simple shear and show anisotropic ionic conductivity, which suggests promising applications for low-dimensional ion-conductive materials.

Robust Ordered Bundles of Porous Helical Nanotubes Assembled from Fully Rigid Ionic Benzene‐1,3,5‐tricarboxamides

“…Figure 4 displays examples of electron‐density profiles of BTA/water mixtures at selected concentrations; the plots reveal a similar hexagonal arrangements of annular cylinders or nanotubes separated by continuous regions of low electron‐density (shown in deep‐blue) corresponding to a solvent sea of water. The annuli of high density and central cylinders of intermediate density correspond to the helical columns assembled by BTA molecules and the central water channels, respectively, indicating the assembly of structures similar to the helical rosette nanotubes reported previously for P‐7 ‐ 3 8. The tubular structure is further demonstrated by TEM as shown in Figure 4 e.…”

“…10 nm) overlap rather well, as shown in Figure 5 b–c, manifesting the robust and universal architecture of the assembled helical nanotubes by the fully rigid ionic BTAs despite discrepancies between the molecular details. The stable assembly in water is attributed to the synergy of various noncovalent interplays between the molecules, which demonstrates not only tolerance to ionic defects as previously reported8 but also to certain geometric perturbations and even to the coalescence of the two types. The moiety‐independent dimensions of supramolecular nanotubes might lead to similar macroscopic properties for different BTAs.…”

“…Therefore, by decorating BTA molecules with ionic terminals, it was anticipated that control over the size and the order of the assemblies could be achieved. Preceding research by our group8 on lyoptropic phases self‐assembled by fully rigid ionic BTA molecules revealed robust hexagonal phases of supramolecular helical nanotubes with tolerance for defects in the peripheral ionic groups for a series of molecules with almost identical structure. The self‐organized nanotubes adopt a helical rosette architecture to minimize the electrostatic repulsion among the terminal charges and also to maximize hydrogen bonding between amide groups as well as the π–π interactions between phenyl rings of adjacent molecules.…”

“…However, in the case of ionic BTA molecules with rigid arms, hydrophobic effects are no longer the main driving force. Instead, the assembly is packed much looser (molecules are separated from each other along the azimuth of the rosette walls, resulting in a high void ratio) and is maintained by electrostatic interactions together with hydrogen bonding and π–π interactions 8. The synergetic optimization of various noncovalent interplays between the ionic BTA molecules could thus provide new opportunities to obtain organic channels with robust size and long‐range ordering on the nanoscale 3a.…”

Hierarchical Self‐Assembly of Supramolecular Helical Fibres from Amphiphilic C3‐Symmetrical Functional Tris(tetrathiafulvalenes)

“…C 3 ‐symmetric discotic platforms such as benzene‐1,3,5‐tricarboxamides (BTA) substituted with different chiral units proved to be particularly efficient as triggers of the self‐assembly of molecular units into helical aggregates; they have been thoroughly investigated in solution by circular dichroism (CD) and in solid state by microscopy techniques 25. Furthermore, even symmetry breaking can occur in BTA derivatives with rigid achiral arms 26. Meijer and co‐workers have shown that the functionalisation of BTA by 3,3′‐diamino‐2,2′‐bipyridine wedges,27 which can be then appropriately substituted by chiral units, induces a propeller conformation to the molecular building blocks, which is further transmitted to the supramolecular aggregates built up upon π–π stacking 28.…”