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Instruments / Technical Area	Publication Details	Published
I16-Materials and Magnetism I22-Small angle scattering & Diffraction	A case of antiferrochirality in a liquid crystal phase of counter-rotating staircases Ya-Xin Li , Hong-Fei Gao , Rui-Bin Zhang , Kutlwano Gabana , Qing Chang , Gillian A. Gehring , Xiao-Hong Cheng , Xiang-Bing Zeng , Goran Ungar Nature Communications 13 DOI: 10.1038/s41467-022-28024-1 Open Access Show Abstract ▼ Abstract: Helical structures continue to inspire, prompted by examples such as DNA double-helix and alpha-helix in proteins. Most synthetic polymers also crystallize as helices, which relieves steric clashes by twisting, while keeping the molecules straight for their ordered packing. In columnar liquid crystals, which often display useful optoelectronic properties, overall helical chirality can be induced by inclusion of chiral chemical groups or dopants; these bias molecular twist to either left or right, analogous to a magnetic field aligning the spins in a paramagnet. In this work, however, we show that liquid-crystalline columns with long-range helical order can form by spontaneous self-assembly of straight- or bent-rod molecules without inclusion of any chiral moiety. A complex lattice with Fddd symmetry and 8 columns per unit cell (4 right-, 4 left-handed) characterizes this “antiferrochiral” structure. In selected compounds it allows close packing of their fluorescent groups reducing their bandgap and giving them promising light-emitting properties.	Jan 2022
I16-Materials and Magnetism I22-Small angle scattering & Diffraction	Tailoring liquid crystal honeycombs by head-group choice in bird-like bent-core mesogens Ya-Xin Li , Huifang Cheng , Xiangbing Zeng , Yuan Tao , Xiaohong Cheng , Goran Ungar Journal Of Materials Chemistry C 106 DOI: 10.1039/D0TC01879A Open Access Show Abstract ▼ Abstract: We introduce a new class of mesogens that are bird-like in shape and form honeycomb-type supramolecular liquid crystals. They have a bent pi-conjugated aromatic core as wings, a linear or branched chain as the tail and a selection of functional headgroups. Honeycombs of non-centrosymmetric trigonal type (p3m1) are obtained, along with two different complex honeycomb superlattices (p31m and p2gg) and a randomized hexagonal mesophase (p6mm). The key determinant of the self-assembled structure is the nature of interaction of the headgroup with the glycerols at the ends of the wings. The structure depends on whether the sub-columns lying along the edges of the prismatic cells contain pure or mixed headgroups and wing-end hydrogen-bonding groups. Its assembly is further controlled by reducing the tail-chain volume, inducing out-of-plane buckling of the honeycomb. These two modes of symmetry breaking lead to structural polarity both in- and out-of-plane, opening the way to applications in devices relying on properties such as ferroelectricity and second harmonic generation.	May 2020
I16-Materials and Magnetism I22-Small angle scattering & Diffraction	New type of columnar liquid crystal superlattice in double‐taper ionic minidendrons Ya-Xin Li , Fang-Fang Fan , Jie Wang , Liliana Cseh , Min Xue , Xiang-Bing Zeng , Goran Ungar Chemistry – A European Journal DOI: 10.1002/chem.201902639 Show Abstract ▼ Abstract: Wedge‐shaped molecules, such as dendrons, are among the most important building blocks for directed supramolecular self‐assembly. Here we present a new approach aimed at widening the range and complexity of potential mesophases by introducing double‐tapered mesogens. Two series of compounds are presented, both alkali metal salts (Li, Na, Cs) of 3,4,5‐tris‐alkoxybenzoic acid with a second tapered tris‐alkoxyaryl group attached at the end of an alkoxy chain. The double‐tapered compounds all display an unusual hexagonal columnar phase consisting of one ionic and three non‐ionic columns per unit cell. The cation size has an unexpectedly drastic effect on unit cell size. Unlike most columnars, the current phases show unusually high dimensional stability on heating, and high stiffness in spite of being 80‐85% aliphatic, attributed to their molecular topology. The described approach may lead to co‐assemblies of multifunctional materials, e.g. parallel p‐ and n‐semiconducting nanowires or parallel ionic and electronic conductors.	Jul 2019
I22-Small angle scattering & Diffraction	Gyroid structured aqua-sheets with sub-nanometer thickness enabling 3D fast proton relay conduction Tsubasa Kobayashi , Ya-Xin Li , Ayaka Ono , Xiang-Bing Zeng , Takahiro Ichikawa Chemical Science 10, 6245 - 6253 DOI: 10.1039/C9SC00131J Open Access Show Abstract ▼ Abstract: A polymerizable amphiphile having two zwitterionic head-groups has been designed. This compound co-organizes with an acid, bis(trifluoromethanesulfonyl)imide (HTf2N), into a gyroid bicontinuous cubic liquid-crystalline phase. In situ polymerization of this phase has been successfully achieved by UV irradiation in the presence of a photoinitiator, yielding a self-standing gyroid-nanostructured polymer film. When the polymer film is placed under different relative humidity conditions or in water, it absorbs water owing to the strong hydration ability of the zwitterionic parts. It has been found that the polymer film preserves the gyroid nanostructure after the water absorption. Based on reconstructed electron density maps, it is assumed that the absorbed water molecules form a 3D continuous network along the gyroid minimal surface, which satisfies several key conditions for inducing fast proton conduction. As expected, such hydrated films show high ionic conductivities in the order of 10−1 S cm−1 when the water content of the film reaches 15.6 wt% at RH = 90%. The high conductivity is attributed to the induction of the Grotthuss mechanism, that is, proton conduction via the hydrogen-bonding network of the incorporated water molecules.	Jun 2019
I22-Small angle scattering & Diffraction	Trigonal columnar self-assembly of bent phasmid mesogens Huifang Cheng , Ya-Xin Li , Xiang-Bing Zeng , Hongfei Gao , Xiaohong Cheng , Goran Ungar Chemical Communications 11 DOI: 10.1039/C7CC06714C Open Access Show Abstract ▼ Abstract: Three compounds with a bent rod-like aromatic core and with three alkoxy chains at each end were synthesised by click reaction. The compounds form a columnar liquid crystal phase with non-centrosymmetric trigonal p31m symmetry, the columns having a 3-arm star-like cross-section.	Dec 2017

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