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PRINCIPAL PUBLICATION AND AUTHORS

A columnar liquid quasicrystal with a honeycomb structure that consists of triangular, square and trapezoidal cells, X.B. Zeng (a), B. Glettner (b), U. Baumeister (b), B. Chen (b), G. Ungar (a,c), F. Liu (c), C. Tschierske (b), Nat. Chem. 15, 625-632 (2023); https:/doi.org/10.1038/s41557-023-01166-5 (a) Department of Materials Science and Engineering, Sheffield University, Sheffield (UK) (b) Institute of Chemistry, Martin Luther University Halle-Wittenberg, Halle/Saale (Germany) (c) Shaanxi International Research Centre for Soft Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi an Jiaotong University, Xi an (China)

REFERENCES

[1] D. Shechtman, Phys. Rev. Lett. 53, 1951-1953 (1984). [2] X.B. Zeng et al., Nature 428, 157-160 (2004). [3] X.B. Zeng et al., Science 331, 1302-1306 (2011).

Fig. 45: T-shaped polyphilic molecules and their self-assembly. a) Compound 1 is a T-shaped polyphile, with a terphenyl backbone (coloured in grey), two alkyl end chains (red) and a polar side group (blue). b) Triangular, square and trapezoidal shaped columns form a local optimal dodecagon. c) Packing of dodecagons in (b), leading to a quasiperiodic tiling, overlaid on top of the reconstructed electron density map of CLQC.

reciprocal lattice vectors perpendicular to the substrate surface. The diffraction pattern is therefore equivalent to that from a single CLQC crystal rotating around its vertical (0110) axis. The dodecagonal reciprocal lattice, overlaid on the GIXRD pattern, clearly shows the 12-fold rotational symmetry and the coincidence of experimental spots and the theoretical lattice nodes.

The compound studied is a T-shaped molecule, consisting of a rigid, rod-like aromatic (p-terphenyl) core, two alkyl end-chains and a polar ionic group attached to an oligo-ethylene oxide lateral chain (Figure 45a). Due to the tendency of the three incompatible but connected parts to nanophase separate, such T-shaped polyphiles are extremely versatile in forming different 1D, 2D and 3D liquid crystal (LC) structures. These include the honeycomb type, consisting of columns with a range of polygonal cross-sections [3]. The rigid molecular cores form the flat side walls of the prismatic columns, their end-groups aggregating at column edges and the lateral chains occupying the interior.

The CLQC structure has been determined to consist of triangular, square and trapezoidal columns. A dodecagon, consisting of four triangles, five squares and eight trapezoids, is the basic tile that has been used to generate the unique dodecagonal quasiperiodic tiling of the plane. Molecular arrangement in the dodecagon is schematically shown in Figure 45b, and a reconstructed map of a patch of the quasiperiodic structure is shown in Figure 45c, with schematic molecular arrangement overlaid on top. It was also shown that the driving force for quasiperiodicity in this new CLQC could be attributed primarily to the optimisation of packing, i.e., lowering of the system energy rather than increasing the randomness/entropy as in the case of previously found soft quasicrystals. This work opens an approach to creating other strict instead of random quasiperiodic structures in soft matter.