Creation of Chiral Thixotropic Gels through a Crown–Ammonium Interaction and their Application to a Memory‐Erasing Recycle System

Abstract

A unique class of oligothiophene-based organogelator bearing two crown ethers at both ends was synthesized. This compound could gelatinize several organic solvents, forming one-dimensional fibrous aggregates. From the observation of circular dichroism, it was confirmed that the helical handedness of the fibrous assembly is controllable by the chirality of 1,2-bisammonium guests, thus suggesting that one guest molecule bridges two gelator molecules through the crown-ammonium interaction. Interestingly, we have found that such chirality is created by thermal gelation, whereas it disappears by thixotropic gelation. The new finding implies that the present organogel system is applicable as a reversible switching memory device, featuring memory creation by a heat mode and memory erasing by a mechanical mode.

Supramolecular Chirality in Self-Assembled Systems

“…162 The helical one-dimensional assemblies were induced by the chirality of 1,2-bisammonium guests through host−guest interactions. It was interesting to note that the chirality of an oligothiophene-based organogel can be created by thermal gelation, whereas it was silent in thixotropic gelation.…”

Helical supramolecular polymers with rationally designed binding sites for chiral guest recognition

“…As the chiral auxiliary is from a "chiral pool" of amino alcohols 34 , a library of chiral supramolecular polymers can be readily formed. Before this work, there were only a few helical supramolecular polymer systems that can non-covalently accommodate various kinds of chiral auxiliaries from chiral pools 12,14,[19][20][21] . Our systematic studies revealed the clear relationship between the stereochemistry of the chiral auxiliaries, helical handedness of the polymers, and copolymerizability of the polymers.…”

“…Later, the scope of polymers was expanded to those with noncovalently formed backbones, the so-called "non-covalent polymers" or "supramolecular polymers", which opened up the new possibilities for polymer sciences [9][10][11][12][13][14][15][16][17] . Similar to covalent polymers, one-handed helicity of supramolecular polymers can be induced by the covalent 18 and non-covalent 14,[19][20][21] interactions of chiral small molecular units (Fig. 1a, iii).…”

Сhiral and Racemic Fields Concept for Understanding of the Homochirality Origin, Asymmetric Catalysis, Chiral Superstructure Formation from Achiral Molecules, and B-Z DNA Conformational Transition

“…This selectivity of silica gel could be attributed individually to silylium ions [214]. However, the experimental variety of the ability to memorize structural information, which is characteristic of different gels, allows us to attribute this property to physical gels [215][216][217][218][219][220][221][222][223].…”