1
|
Shaya J, Ribierre JC, Correia G, Dappe YJ, Mathevet F, Mager L, Heinrich B, Méry S. Control of the Organization of 4,4'-bis(carbazole)-1,1'-biphenyl (CBP) Molecular Materials through Siloxane Functionalization. Molecules 2023; 28:molecules28052038. [PMID: 36903284 PMCID: PMC10003964 DOI: 10.3390/molecules28052038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 02/10/2023] [Accepted: 02/16/2023] [Indexed: 02/24/2023] Open
Abstract
We show that through the introduction of short dimethylsiloxane chains, it was possible to suppress the crystalline state of CBP in favor of various types of organization, transitioning from a soft crystal to a fluid liquid crystal mesophase, then to a liquid state. Characterized by X-ray scattering, all organizations reveal a similar layered configuration in which layers of edge-on lying CBP cores alternate with siloxane. The difference between all CBP organizations essentially lay on the regularity of the molecular packing that modulates the interactions of neighboring conjugated cores. As a result, the materials show quite different thin film absorption and emission properties, which could be correlated to the features of the chemical architectures and the molecular organizations.
Collapse
Affiliation(s)
- Janah Shaya
- Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS, Strasbourg University, UMR 7504, 23 rue du Loess, 67034 Strasbourg, France
- Department of Chemistry, College of Arts and Sciences, Khalifa University, Abu Dhabi P.O. Box 127788, United Arab Emirates
- College of Medicine and Health Sciences, Khalifa University, Abu Dhabi P.O. Box 127788, United Arab Emirates
| | - Jean-Charles Ribierre
- Service de Physique de l’État Condensé, CEA CNRS UMR 3680, Université Paris Saclay, 91191 Gif-sur-Yvette, France
| | - Gabriel Correia
- Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS, Strasbourg University, UMR 7504, 23 rue du Loess, 67034 Strasbourg, France
| | - Yannick J. Dappe
- Service de Physique de l’État Condensé, CEA CNRS UMR 3680, Université Paris Saclay, 91191 Gif-sur-Yvette, France
| | - Fabrice Mathevet
- Institut Parisien de Chimie Moléculaire (IPCM), CNRS, Sorbonne University, 4 Place Jussieu, 75005 Paris, France
- Center for Organic Photonics and Electronics Research (OPERA), Department of Applied Chemistry, Kyushu Universty, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Loïc Mager
- Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS, Strasbourg University, UMR 7504, 23 rue du Loess, 67034 Strasbourg, France
| | - Benoît Heinrich
- Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS, Strasbourg University, UMR 7504, 23 rue du Loess, 67034 Strasbourg, France
- Correspondence: (B.H.); (S.M.)
| | - Stéphane Méry
- Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS, Strasbourg University, UMR 7504, 23 rue du Loess, 67034 Strasbourg, France
- Correspondence: (B.H.); (S.M.)
| |
Collapse
|
2
|
All Structures Great and Small: Nanoscale Modulations in Nematic Liquid Crystals. NANOMATERIALS 2021; 12:nano12010093. [PMID: 35010040 PMCID: PMC8746648 DOI: 10.3390/nano12010093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 12/25/2021] [Accepted: 12/27/2021] [Indexed: 02/06/2023]
Abstract
The nature of the nanoscale structural organization in modulated nematic phases formed by molecules having a nonlinear molecular architecture is a central issue in contemporary liquid crystal research. Nevertheless, the elucidation of the molecular organization is incomplete and poorly understood. One attempt to explain nanoscale phenomena merely “shrinks down” established macroscopic continuum elasticity modeling. That explanation initially (and mistakenly) identified the low temperature nematic phase (NX), first observed in symmetric mesogenic dimers of the CB-n-CB series with an odd number of methylene spacers (n), as a twist–bend nematic (NTB). We show that the NX is unrelated to any of the elastic deformations (bend, splay, twist) stipulated by the continuum elasticity theory of nematics. Results from molecular theory and computer simulations are used to illuminate the local symmetry and physical origins of the nanoscale modulations in the NX phase, a spontaneously chiral and locally polar nematic. We emphasize and contrast the differences between the NX and theoretically conceivable nematics exhibiting spontaneous modulations of the elastic modes by presenting a coherent formulation of one-dimensionally modulated nematics based on the Frank–Oseen elasticity theory. The conditions for the appearance of nematic phases presenting true elastic modulations of the twist–bend, splay–bend, etc., combinations are discussed and shown to clearly exclude identifications with the nanoscale-modulated nematics observed experimentally, e.g., the NX phase. The latter modulation derives from packing constraints associated with nonlinear molecules—a chiral, locally-polar structural organization indicative of a new type of nematic phase.
Collapse
|
3
|
Chiappini M, Dijkstra M. A generalized density-modulated twist-splay-bend phase of banana-shaped particles. Nat Commun 2021; 12:2157. [PMID: 33846326 PMCID: PMC8041804 DOI: 10.1038/s41467-021-22413-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 02/24/2021] [Indexed: 11/09/2022] Open
Abstract
In 1976, Meyer predicted that bend distortions of the nematic director field are complemented by deformations of either twist or splay, yielding twist-bend and splay-bend nematic phases, respectively. Four decades later, the existence of the splay-bend nematic phase remains dubious, and the origin of these spontaneous distortions uncertain. Here, we conjecture that bend deformations of the nematic director can be complemented by simultaneous distortions of both twist and splay, yielding a twist-splay-bend nematic phase. Using theory and simulations, we show that the coupling between polar order and bend deformations drives the formation of modulated phases in systems of curved rods. We find that twist-bend phases transition to splay-bend phases via intermediate twist-splay-bend phases, and that splay distortions are always accompanied by periodic density modulations due to the coupling of the particle curvature with the non-uniform curvature of the splayed director field, implying that the twist-splay-bend and splay-bend phases of banana-shaped particles are actually smectic phases. The so-called twist-bend and splay-bend nematic liquid crystal phases are important concepts for studying bent-core mesogens. Chiappini et al. use a theory/simulation approach to suggest that the transition proceed via a twist-splay-bend phase which may be obscured by density modulations.
Collapse
Affiliation(s)
- Massimiliano Chiappini
- Soft Condensed Matter, Debye Institute for Nanomaterials Science, Department of Physics, Utrecht University, Utrecht, The Netherlands.
| | - Marjolein Dijkstra
- Soft Condensed Matter, Debye Institute for Nanomaterials Science, Department of Physics, Utrecht University, Utrecht, The Netherlands.
| |
Collapse
|
4
|
Pocock EE, Mandle RJ, Goodby JW. Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases. Molecules 2021; 26:532. [PMID: 33498518 PMCID: PMC7864162 DOI: 10.3390/molecules26030532] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 11/16/2022] Open
Abstract
Liquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (NTB) phases. While the features that give rise to NTB phase formation are now somewhat understood, a comparable structure-property relationship governing the formation of layered (smectic) phases from the NTB phase is absent. In this present work, we find that by selecting mesogenic units with differing polarities and aspect ratios and selecting an appropriately bent central spacer we obtain a material that exhibits both NTB and intercalated smectic phases. The higher temperature smectic phase is assigned as SmCA based on its optical textures and X-ray scattering patterns. A detailed study of the lower temperature smectic ''X'' phase by optical microscopy and SAXS/WAXS demonstrates this phase to be smectic, with an in-plane orthorhombic or monoclinic packing and long (>100 nm) out of plane correlation lengths. This phase, which has been observed in a handful of materials to date, is a soft-crystal phase with an anticlinic layer organisation. We suggest that mismatching the polarities, conjugation and aspect ratios of mesogenic units is a useful method for generating smectic forming dimesogens.
Collapse
Affiliation(s)
- Emily E. Pocock
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;
| | - Richard J. Mandle
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
| | - John W. Goodby
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;
| |
Collapse
|
5
|
Merkel K, Welch C, Ahmed Z, Piecek W, Mehl GH. Dielectric response of electric-field distortions of the twist-bend nematic phase for LC dimers. J Chem Phys 2019; 151:114908. [PMID: 31542029 DOI: 10.1063/1.5114824] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Wide band dielectric spectroscopy of bent-shaped achiral liquid-crystal dimers 1″-n″-bis(4-cyanobiphenyl-4'-yl) n-alkanes (CBnCB n = 7, 9, 11) has been investigated in a frequency range 0.1 Hz-100 MHz using planar-aligned cells of sample thicknesses ranging from 2 to 10 (μm) over a temperature range that covers both nematic and twist bend nematic phases. Two peaks in the dielectric spectrum in the higher frequency range are assigned to the molecular relaxation processes. The peak at the highest frequency, ∼40 to 80 MHz, is assigned to an internal precessional rotation of a single unit of the dimer around the director. The mode in the next lower frequency range of 2-10 MHz is assigned to the spinning rotation of the dimer around its long axis. This involves fluctuations of the dipole moment of the bent-shaped conformation that is directed along its arrow direction of the bow shape formed by the dimer. The peak in the frequency range 100 kHz-1 MHz can be assigned to the collective fluctuations of the local director with reference to the helical axis of the NTB structure. The dependence of its frequency on temperature is reminiscent of the soft mode observed at the SmA* to SmC* phase transition. This result clearly corresponds to the electro-clinic effect-the response of the director to the applied electric field in an electro-optic experiment. The lowest frequency mode, observed in the frequency range of 0.1 Hz-100 Hz, is identified with the Goldstone mode. This mode is concerned with the long range azimuthal angle fluctuations of the local director. This leads to an alternating compression and expansion of the periodic structure of the NTB phase.
Collapse
Affiliation(s)
- K Merkel
- Faculty of Computer Science and Material Science, Institute of Technology and Mechatronics, University of Silesia in Katowice, Katowice, Poland
| | - C Welch
- Department of Chemistry, University of Hull, Hull HU6 7RX, United Kingdom
| | - Z Ahmed
- Department of Chemistry, University of Hull, Hull HU6 7RX, United Kingdom
| | - W Piecek
- Faculty of Advanced Technologies and Chemistry, Military University of Technology, Warszawa, Poland
| | - G H Mehl
- Department of Chemistry, University of Hull, Hull HU6 7RX, United Kingdom
| |
Collapse
|
6
|
Walker R, Pociecha D, Strachan GJ, Storey JMD, Gorecka E, Imrie CT. Molecular curvature, specific intermolecular interactions and the twist-bend nematic phase: the synthesis and characterisation of the 1-(4-cyanobiphenyl-4'-yl)-6-(4-alkylanilinebenzylidene-4'-oxy)hexanes (CB6O.m). SOFT MATTER 2019; 15:3188-3197. [PMID: 30892369 DOI: 10.1039/c9sm00026g] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The syntheses and characterisation of the first ten homologues of the 1-(4-cyanobiphenyl-4'-yl)-6-(4-alkylanilinebenzylidene-4'-oxy)hexanes (CB6O.m) are reported. All ten members of the series exhibit an enantiotropic nematic, N, phase, and a monotropic twist-bend nematic, NTB, phase. Only CB6O.10 shows a smectic phase. The assignment of both nematic phases was confirmed using X-ray diffraction. For short chain lengths (m = 1-6) the local packing in both nematic phases is an intercalated arrangement, for intermediate chain lengths a frustrated local structure is seen and for the longest chain length, a bilayer arrangement is observed. This change in the local structure on increasing m has no apparent effect on the stability of either nematic phase, and TNTBN and TNI show a regular dependence on m. Specifically, TNTBN and TNI decrease on increasing m and superimposed upon this is a weak odd-even effect in which the odd members show the higher values. TNI decreases more rapidly than TNTBN on increasing m such that the ratio TNTBN/TNI increases. The lower temperature liquid crystal phase shown by 1-(4-cyanobiphenyl-4'-yloxy)-5-(4-butylanilinebenzylidene-4'-oxy)pentane (CBO5O.4) is reassigned as a twist-bend nematic phase. The transitional properties of the CB6O.m, CB6O.Om and CBO5O.m series are compared.
Collapse
Affiliation(s)
- Rebecca Walker
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, AB24 3UE Scotland, UK.
| | | | | | | | | | | |
Collapse
|
7
|
Zep A, Pruszkowska K, Dobrzycki Ł, Sektas K, Szałański P, Marek PH, Cyrański MK, Sicinski RR. Cholesterol-based photo-switchable mesogenic dimers. Strongly bent molecules versus an intercalated structure. CrystEngComm 2019. [DOI: 10.1039/c9ce00013e] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A homologous series of cholesterol-based liquid crystalline dimers were synthesized and characterized by polarizing optical microscopy, DSC, and powder and single-crystal XRD.
Collapse
Affiliation(s)
- Anna Zep
- Laboratory of Stereocontrolled Organic Synthesis
- Faculty of Chemistry
- University of Warsaw
- 02-089 Warsaw
- Poland
| | - Kamila Pruszkowska
- The Czochralski Laboratory of Advanced Crystal Engineering
- Faculty of Chemistry
- University of Warsaw
- 02-089 Warsaw
- Poland
| | - Łukasz Dobrzycki
- The Czochralski Laboratory of Advanced Crystal Engineering
- Faculty of Chemistry
- University of Warsaw
- 02-089 Warsaw
- Poland
| | - Katarzyna Sektas
- Laboratory of Stereocontrolled Organic Synthesis
- Faculty of Chemistry
- University of Warsaw
- 02-089 Warsaw
- Poland
| | - Piotr Szałański
- Faculty of Chemistry
- Rzeszow University of Technology
- Rzeszow
- Poland
| | - Paulina H. Marek
- The Czochralski Laboratory of Advanced Crystal Engineering
- Faculty of Chemistry
- University of Warsaw
- 02-089 Warsaw
- Poland
| | - Michał K. Cyrański
- The Czochralski Laboratory of Advanced Crystal Engineering
- Faculty of Chemistry
- University of Warsaw
- 02-089 Warsaw
- Poland
| | - Rafal R. Sicinski
- Laboratory of Stereocontrolled Organic Synthesis
- Faculty of Chemistry
- University of Warsaw
- 02-089 Warsaw
- Poland
| |
Collapse
|
8
|
Mandle RJ, Goodby JW. A novel nematic-like mesophase induced in dimers, trimers and tetramers doped with a high helical twisting power additive. SOFT MATTER 2018; 14:8846-8852. [PMID: 30357232 DOI: 10.1039/c8sm01389f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
From the observation of a previously undiscovered nematic-like mesophase (NX) by Archbold et al., we report on several new binary liquid-crystalline mixtures between the high helical twisting power dopant RM1041 and a selection of dimers with varying average bend angles and conformational landscapes. We also report on mixtures between RM1041 and oligomeric LC materials. We find that dimers and oligomers exhibit not only chiral nematic and twist-bend modulated phases, but also the same NX phase reported by Archbold, indicating that this state of matter (the structure of which is yet to be definitively characterised) is exhibited by a wide range of materials. Mixtures of the dimer CB9CB with a selection of different chiral dopants suggest that it is the helical twisting power of the chiral additive that is responsible incidence of the NX phase.
Collapse
|
9
|
Mandle RJ, Goodby JW. Optically active bimesogens incorporating branched central spacers. RSC Adv 2018; 8:18542-18548. [PMID: 35541138 PMCID: PMC9080582 DOI: 10.1039/c8ra02075b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 05/14/2018] [Indexed: 11/24/2022] Open
Abstract
In the current fascination with liquid crystalline dimers, bimesogens and oligomers the role of the central spacer in these systems has perhaps been somewhat neglected. In compound 1, a phenyl 4-cyanobenzoate bimesogen, the central spacer incorporates a methyl group at the 2-position and is therefore chiral. The helical twisting power of 1, measured in both 5CB and E7, was found to be 0.36 and 0.35 μm-1 wt%-1 respectively. Compound 1 exhibited a monotropic chiral nematic phase, however no twist-bend modulated phase was observed. We prepared a number of analogues of 1 incorporating different mesogenic units and observe that those with a small aspect ratio are non mesogenic, whereas those with larger aspect ratios variously exhibit chiral nematic, TB, SmC and SmB phases.
Collapse
Affiliation(s)
- Richard J Mandle
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - John W Goodby
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| |
Collapse
|
10
|
Abstract
Chiral symmetry breaking in soft matter is a hot topic of current research. Recently, such a phenomenon was found in a fluidic phase showing orientational order of molecules—the nematic phase; although built of achiral molecules, the phase can exhibit structural chirality—average molecular direction follows a short-pitch helix. Here, we report a series of achiral asymmetric dimers with an odd number of atoms in the spacer, which form twisted structures in nematic as well as in lamellar phases. The tight pitch heliconical nematic (NTB) phase and heliconical tilted smectic C (SmCTB) phase are formed. The formation of a variety of helical structures is accompanied by a gradual freezing of molecular rotation. In the lowest temperature smectic phase, HexI, the twist is expressed through the formation of hierarchical structure: nanoscale helices and mesoscopic helical filaments. The short-pitch helical structure in the smectic phases is confirmed by resonant X-ray measurements. Systems that form chiral structures from achiral molecules are not common. Here, the authors synthesise a compound consisting of asymmetric and achiral bent-shaped mesogens, which exhibit a variety of liquid crystal phases including one in which chiral structures form from achiral constituent molecules.
Collapse
|
11
|
Mandle RJ, Goodby JW. Does Topology Dictate the Incidence of the Twist-Bend Phase? Insights Gained from Novel Unsymmetrical Bimesogens. Chemistry 2016; 22:18456-18464. [PMID: 27706844 PMCID: PMC5217080 DOI: 10.1002/chem.201604030] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Indexed: 11/21/2022]
Abstract
We prepared a significant number of unsymmetrical liquid-crystalline dimers that exhibit the twist-bend nematic phase; a state of matter that exhibits spontaneous breaking of mirror symmetry and, for some materials, a microsecond electrooptic response. A number of novel unsymmetrical bimesogens were synthesized and in comparing their thermal behaviour to previous literature examples, we have uncovered an unexpected relationship between the thermal stability of the nematic and NTB phases. This relationship demonstrates that molecular shape dictates the incidence of this fascinating phase of matter and leads us to speculate as to the existence of "twist-bend nematic phases" on length scales beyond those of the molecule.
Collapse
|