Spontaneous Induction and Amplification of Macroscopic Homochirality in Isotropic Liquid and Liquid Crystals

Lead Research Organisation: University of Sheffield
Department Name: Materials Science and Engineering

Abstract

Recently it was discovered that macroscopic chirality, i.e. left- or right-handedness, can be achieved in some cubic liquid crystal phases and even in isotropic liquid from molecules that are not chiral. Despite the huge scientific and industrial implications of the discovery, we are still at an early stage of understanding the origin of these remarkable phenomena. The aim of this project is to identify the molecular and structural basis for spontaneous long-range chirality propagation even in a liquid, and to achieve them by molecular design. We will also investigate how these systems act as chirality amplifiers using small amounts of chiral dopants, and how new complex nanoscale structures can be obtained by breaking the symmetry of non-chiral structures through the introduction of chiral centres. Furthermore, we aim to demonstrate how the recent discoveries can be utilized for applications e.g. in enantioselective membranes and in chiro-optics for potential use e.g. in high-contrast displays and optical communication.

Planned Impact

The subject is highly topical and these studies are expected to have a major impact on the scientific areas of organic self-assembly, supramolecular chemistry, liquid crystals, molecular liquids, and soft matter in general. Among other innovations, the project aims to truly start a new research field of highly chiral liquids, the door of which has only been crack opened by the recent first reports of their existence in dithiophene-based mesogens. Solving the structure of new bicontinuous phases, and finding the correct structure of the triple network phase all have implications not only for small molecule self-assembly, but also to that of block and star copolymers, lyotropic LCs, as well as porous ceramics which are often templated on liquid crystal precursors. Here we point out that a number of mesophases that we first discovered and characterized in thermotropic LC systems (i.e. the Frank-Kasper A15 phase, the F-K sigma-phase and the liquid quasicrystal) have subsequently also been identified in block copolymers (F. Bates et al., Science 2010, 330, p. 349 and PNAS 2016, 113, p. 5167, and M.K. Mahanthappa et al. PNAS 2017, 114, p. 4072). The field of Frank-Kasper phases in soft matter that we opened in 2003 is now one of the most topical in ordered fluids. Furthermore, our first report of a soft and the first nanoscale quasicrystal in 2004 has been included in Nature's list of Milestones in Crystallography, the only entry in 21st century (https://www.nature.com/milestones/milecrystal/library/chemistry/index.html).

The issues involved are fundamental and wide-reaching. E.g. the Iso* phase and a liquid-liquid transition in a one-component system are unprecedented phenomena in the physical world, which demand further studies that will undoubtedly give impetus to new theoretical activities and revival of some earlier theories such as that of 'ferrochirality". The rapid long-range propagation of homochirality that we find in cubic LC and the Iso* liquid are also relevant to the understanding of how homochirality spread across the prebiotic Earth, a hotly debated subject in the study of origin of life.

The development of new enantioselective membranes based on symmetry-broken mesostructures is original and highly promising, and could benefit society as it may provide a novel route to, e.g. natural products isolation and drug purification. A common pharmaceutical example of chirality is the drug ibuprofen, in which the molecule's left hand form is 100-times more powerful than the right enantiomer. CP light-emitting devices emerging on the principle developed here would be highly desirable in a variety of applications such as displays and telecommunications. Direct CP light emission would replace the polarizer/quarter-wave plate combination in current displays and thus double their energy efficiency. The chiral structure of bicontinuous phases can also provide blueprints for photonic crystal, of interest in photonics, lasing, quantum optics and spintronics.

The proposed project will impact industries that have relevant key product areas, e.g. bulk materials for organic electronics, OLED materials and pharmaceutical products, materials for photonics, lasing, quantum optics and spintronics, either directly from the materials, or indirectly from transfer and exploitation of knowledge and IPs, resulting from the project.

Our competitive advantage of having solved the structure of the largest number of mesophases of any single research group, and of the fact that we first discovered the role of twist in bicontinuous phases, give us high confidence in the success of this project. Furthermore, our close collaborative links with some of the most prestigious international research groups give us a firm base to compete successfully in future bids for European and other international funding.

Publications

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Scholte A (2020) A self-assembled liquid crystal honeycomb of highly stretched (3-1-1)-hexagons. in Chemical communications (Cambridge, England)

 
Title Front cover for Adv. Funct. Mater. 
Description The formation of two different bicontinuous cubic phases, consists of 2- and 3- interpenetrating chiral networks. 
Type Of Art Artwork 
Year Produced 2020 
Impact Raise the awareness of the readers to the paper and attract attention from general public. 
URL https://onlinelibrary.wiley.com/doi/10.1002/adfm.202070298
 
Title Front cover for J. Mater. Chem. 
Description The artwork shows how polycatenar compounds, through complex self-assembly, form complex chiral cubic phase of hierarchical structures from molecular bundles, to helical segments, to infinitely perioidic networks with 3-way junctions, to three interpenetrating but never crossing networks in space. 
Type Of Art Artwork 
Year Produced 2020 
Impact Raise awareness of potential readers of the journal and help explain a complex concept visually. 
URL https://pubs.rsc.org/en/content/articlelanding/2020/tc/d0tc90083d
 
Description The major progress we have carried out so far is a detailed re-examination of the current model of the triple network bicontinuous phase, and proposed a completely new molecular model which is compatible with the current models of other bicontinuous phases, with small twisting of molecular direction in helical columnar segment with planar junctions. The work has been published in J. Mater. C. and Adv. Funct. Mater.
Exploitation Route The model has predicted that the true space group of the chiral cubic phase should be I23 instead, and this can and will be verified by further work in this and other research groups.
Sectors Chemicals,Education,Electronics