1
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Rodríguez-Rivas Á, Patti A, Cuetos A. Dynamics in field-induced biaxial nematic liquid crystals of board-like particles. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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2
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Nematic ordering of model racemic mixture of stiff trimer chains. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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3
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Peroukidis SD, Klapp SHL, Vanakaras AG. Field-induced anti-nematic and biaxial ordering in binary mixtures of discotic mesogens and spherical magnetic nanoparticles. SOFT MATTER 2020; 16:10667-10675. [PMID: 33084728 DOI: 10.1039/d0sm01366h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Using computer simulations we explore the equilibrium structure and response to external stimuli of complex magnetic hybrids consisting of magnetic particles in discotic liquid crystalline matrices. We show that the anisotropy of the liquid crystalline matrix (either in the nematic or in the columnar phase) promotes the collective orientational ordering of self-assembled magnetic particles. Upon applying an external homogeneous magnetic field in an otherwise isotropic state, the magnetic particles self-assemble into linear-rodlike-chains. At the same time structural changes occur in the matrix. The matrix transforms from an isotropic to a non-conventional anti-nematic state in which the symmetry axis of the discs is, on average, perpendicular to the magnetic field. In addition, a stable biaxial nematic state is found upon applying an external field to an otherwise uniaxial discotic nematic state. These observed morphologies constitute an appealing alternative to binary mixtures of rigid rod-disc system and indicate that non-trivial biaxial ordering can be obtained in the presence of a uniaxial external stimulus.
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4
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Mirzad Rafael E, Corbett D, Cuetos A, Patti A. Self-assembly of freely-rotating polydisperse cuboids: unveiling the boundaries of the biaxial nematic phase. SOFT MATTER 2020; 16:5565-5570. [PMID: 32539067 DOI: 10.1039/d0sm00484g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Colloidal cuboids have the potential to self-assemble into biaxial liquid crystal phases, which exhibit two independent optical axes. Over the last few decades, several theoretical works have predicted the existence of a wide region of the phase diagram where the biaxial nematic phase would be stable, but imposed rather strong constraints on the particle rotational degrees of freedom. In this work, we use molecular simulation to investigate the impact of size dispersity on the phase behaviour of freely-rotating hard cuboids, here modelled as self-dual-shaped nanoboards. This peculiar anisotropy, exactly in between the oblate and prolate geometry, has been proposed as the most appropriate to promote phase biaxiality. We observe that size dispersity radically changes the phase behaviour of monodisperse systems and leads to the formation of an elusive biaxial nematic phase, being found in a large region of the packing fraction vs. polydispersity phase diagram. Although our results confirm the tendencies reported in past experimental observations on colloidal dispersions of slightly prolate goethite particles, they cannot reproduce the direct isotropic-to-biaxial nematic phase transition observed in these experiments.
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Affiliation(s)
- Effran Mirzad Rafael
- Department of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, M13 9PL, UK.
| | - Daniel Corbett
- Department of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, M13 9PL, UK.
| | - Alejandro Cuetos
- Department of Physical, Chemical and Natural Systems, Pablo de Olavide University, 41013 Sevilla, Spain
| | - Alessandro Patti
- Department of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, M13 9PL, UK.
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5
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Eichler JC, Skutnik RA, Sengupta A, Mazza MG, Schoen M. Emergent biaxiality in nematic microflows illuminated by a laser beam. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1663286] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Jan-Christoph Eichler
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
| | - Robert A. Skutnik
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
| | - Anupam Sengupta
- Physics and Materials Science Research Unit, University of Luxembourg, Luxembourg City, Grand Duchy of Luxembourg
| | - Marco G. Mazza
- Interdisciplinary Centre for Mathematical Modelling and Department of Mathematical Sciences, Loughborough University, Loughborough, UK
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen, Germany
| | - Martin Schoen
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
- Department of Chemical Engineering, Imperial College London, London, UK
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6
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D'Urso C, Celebre G, Cinacchi G. Phase behavior of hard C_{2h}-symmetric particle systems. Phys Rev E 2019; 100:012709. [PMID: 31499787 DOI: 10.1103/physreve.100.012709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Indexed: 06/10/2023]
Abstract
Using Monte Carlo numerical simulation, this work sketches the phase diagram of systems of certain hard C_{2h}-symmetric particles, formed by gluing two aligned and displaced hard spherocylinders with a cylindrical-length-to-diameter ratio realistically, if viewed not only from the lyotropic colloidal liquid-crystal side but also from the thermotropic low-molecular-mass liquid-crystal side, equal to 5, as a function of the displacement. Several distinctive phases are observed, such as a nonperiodic smectic-B-like phase, a nonperiodic smectic-H-like phase, a smectic-C phase, and a short-layer-spacing uniaxial smectic-A phase but no biaxial nematic phase.
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Affiliation(s)
- Christian D'Urso
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, via P. Bucci, I-87036 Arcavacata di Rende (CS), Italy
| | - Giorgio Celebre
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, via P. Bucci, I-87036 Arcavacata di Rende (CS), Italy
| | - Giorgio Cinacchi
- Departamento de Física Teórica de la Materia Condensada, Instituto de Física de la Materia Condensada (IFIMAC), Instituto de Ciencias de Materiales "Nicolás Cabrera," Universidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco, E-28049 Madrid, Spain
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7
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Chrzanowska A. Mean-field model of boomerang nematic liquid crystals with diminished coupling of molecular uniaxial and biaxial susceptibilities. Phys Rev E 2019; 99:062703. [PMID: 31330725 DOI: 10.1103/physreve.99.062703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Indexed: 06/10/2023]
Abstract
The mean-field theory approach has been applied to the boomerang type particles from P. I. C. Teixeira, A. Masters, and B. Mulder [Mol. Cryst. Liq. Cryst. 323, 167 (1998)MCLCE91058-725X10.1080/10587259808048440] but with diminished strength of the interaction coefficient responsible for the coupling between molecular uniaxial and biaxial susceptibilities. For the rodlike particles, when the apex boomerang angle is larger than 107.35^{∘}, the stable uniaxial rodlike phase occurs. For smaller angles, beyond the point where the transition is of the second order (the Landau point) and for diminished parameter of molecular biaxial-uniaxial coupling, a biaxial phase is observed with the transition undergoing directly from the isotropic phase. According to the order parameters the character of this transition is of the first order. Such behavior is in accordance with the Sonnet-Durand-Virga model of the biaxial phases. The change in the type of the phase transition order is also illustrated by the changes in the equations of state and the changes in second and third derivatives of the free energy. The possibilities to tailor interaction coefficients of real molecules to obtain such a phase transition scenario are discussed.
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Affiliation(s)
- Agnieszka Chrzanowska
- Institute of Physics, Kraków University of Technology, ul. Podchorążych 1, 30-084 Kraków, Poland
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8
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Skutnik RA, Lehmann L, Püschel-Schlotthauer S, Jackson G, Schoen M. The formation of biaxial nematic phases in binary mixtures of thermotropic liquid-crystals composed of uniaxial molecules. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1581292] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Robert A. Skutnik
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
| | - Louis Lehmann
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
| | - Sergej Püschel-Schlotthauer
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
| | - George Jackson
- Department of Chemical Engineering, South Kensington Campus, Imperial College London, London, UK
| | - Martin Schoen
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
- Department of Chemical Engineering, South Kensington Campus, Imperial College London, London, UK
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
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9
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Experimental Conditions for the Stabilization of the Lyotropic Biaxial Nematic Mesophase. CRYSTALS 2019. [DOI: 10.3390/cryst9030158] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Nematic phases are some of the most common phases among the lyotropic liquid crystalline structures. They have been widely investigated during last decades. In early studies, two uniaxial nematic phases (discotic, ND, and calamitic, NC) were identified. After the discovery of the third one, named biaxial nematic phase (NB) in 1980, however, some controversies in the stability of biaxial nematic phases began and still continue in the literature. From the theoretical point of view, the existence of a biaxial nematic phase is well established. This review aims to bring information about the historical development of those phases considering the early studies and then summarize the recent studies on how to stabilize different nematic phases from the experimental conditions, especially, choosing the suitable constituents of lyotropic mixtures.
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10
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Yang Y, Chen G, Thanneeru S, He J, Liu K, Nie Z. Synthesis and assembly of colloidal cuboids with tunable shape biaxiality. Nat Commun 2018; 9:4513. [PMID: 30375393 PMCID: PMC6207716 DOI: 10.1038/s41467-018-06975-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Accepted: 10/01/2018] [Indexed: 12/13/2022] Open
Abstract
The design and assembly of monodisperse colloidal particles not only advances the development of functional materials, but also provides colloidal model systems for understanding phase behaviors of molecules. This communication describes the gram-scale synthesis of highly uniform colloidal cuboids with tunable dimension and shape biaxiality and their molecular mesogen-like assembly into various mesophasic structures in pristine purity. The synthesis relies on the nanoemulsion-guided generation of ammonium sulfate crystals that template the subsequent silica coating. The shape of the cuboidal particles can be tuned from square platelike, to biaxial boardlike, and to rodlike by independently controlling the length, width and thickness of the particles. We demonstrated the assembly of the cuboidal colloids into highly pure mesoscopic liquid crystal phases, including smectic A, biaxial smectic A, crystal B, discotic, and columnar phases, as well as established a correlation between mesophasic formation and colloidal biaxiality in experiments.
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Affiliation(s)
- Yang Yang
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, China
| | - Guangdong Chen
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA
| | - Srinivas Thanneeru
- Department of Chemistry, Institute of Materials Sciences, University of Connecticut, Storrs, CT, 06269, USA
| | - Jie He
- Department of Chemistry, Institute of Materials Sciences, University of Connecticut, Storrs, CT, 06269, USA
| | - Kun Liu
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, China.
| | - Zhihong Nie
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.
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11
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Patti A, Cuetos A. Monte Carlo simulation of binary mixtures of hard colloidal cuboids. MOLECULAR SIMULATION 2017. [DOI: 10.1080/08927022.2017.1402307] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- A. Patti
- School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, UK
| | - A. Cuetos
- Department of Physical, Chemical and Natural Systems, Pablo de Olavide University,
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12
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Sokolova E, Vlasov A, Venediktova A. Biaxial nematic stability in the rod-plate mixture with a dopant: The restricted-orientation model on the 3rd virial level. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2017.04.050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Cuetos A, Dennison M, Masters A, Patti A. Phase behaviour of hard board-like particles. SOFT MATTER 2017; 13:4720-4732. [PMID: 28617489 DOI: 10.1039/c7sm00726d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We examine the phase behaviour of colloidal suspensions of hard board-like particles (HBPs) as a function of their shape anisotropy, and observe a fascinating spectrum of nematic, smectic, and columnar liquid-crystalline phases, whose formation is entirely driven by excluded volume effects. We map out the phase diagram of short and long HBPs by gradually modifying their shape from prolate to oblate and investigate the long-range order of the resulting morphologies along the phase directors and perpendicularly to them. The intrinsic biaxial nature of these particles promotes the formation of translationally ordered biaxial phases, but does not show solid evidence that it would, per se, promote the formation of the biaxial nematic phase. Our simulations shed light on the controversial existence of the discotic smectic phase, whose layers are as thick as the minor particle dimension, which is stable in a relatively large portion of our phase diagrams. Additionally, we modify the Onsager theory to describe the isotropic-nematic phase transition of freely rotating biaxial particles as a function of the particle width, and find a relatively strong first-order signature, in excellent agreement with our simulations. In an attempt to shed light on the elusive formation of the biaxial nematic phase, we apply this theory to predict the uniaxial-biaxial nematic phase transition and confirm, again in agreement with simulations, the prevailing stability of the translationally ordered smectic phase over the orientationally ordered biaxial nematic phase.
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Affiliation(s)
- Alejandro Cuetos
- Department of Physical, Chemical and Natural Systems, Pablo de Olavide University, 41013 Sevilla, Spain
| | - Matthew Dennison
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany
| | - Andrew Masters
- School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, M13 9PL, UK.
| | - Alessandro Patti
- School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, M13 9PL, UK.
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14
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Querciagrossa L, Ricci M, Berardi R, Zannoni C. Can multi-biaxial mesogenic mixtures favour biaxial nematics? A computer simulation study. Phys Chem Chem Phys 2017; 19:2383-2391. [DOI: 10.1039/c6cp05117k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A mixture of mesogens with different anisotropies favours the biaxial nematic phase.
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Affiliation(s)
- Lara Querciagrossa
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
| | - Matteo Ricci
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
| | - Roberto Berardi
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
| | - Claudio Zannoni
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
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15
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Wöhrle T, Wurzbach I, Kirres J, Kostidou A, Kapernaum N, Litterscheidt J, Haenle JC, Staffeld P, Baro A, Giesselmann F, Laschat S. Discotic Liquid Crystals. Chem Rev 2015; 116:1139-241. [PMID: 26483267 DOI: 10.1021/acs.chemrev.5b00190] [Citation(s) in RCA: 423] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tobias Wöhrle
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Iris Wurzbach
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Jochen Kirres
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Antonia Kostidou
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Nadia Kapernaum
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Juri Litterscheidt
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Johannes Christian Haenle
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Peter Staffeld
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Angelika Baro
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Frank Giesselmann
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Sabine Laschat
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
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16
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Zhu J, Han Y, Kumar R, He Y, Hong K, Bonnesen PV, Sumpter BG, Smith SC, Smith GS, Ivanov IN, Do C. Controlling molecular ordering in solution-state conjugated polymers. NANOSCALE 2015; 7:15134-15141. [PMID: 26242896 DOI: 10.1039/c5nr02037a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Rationally encoding molecular interactions that can control the assembly structure and functional expression in a solution of conjugated polymers hold great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with the desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution, we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.
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Affiliation(s)
- J Zhu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak ridge, TN 37831, USA
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17
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Mederos L, Velasco E, Martínez-Ratón Y. Hard-body models of bulk liquid crystals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:463101. [PMID: 25335432 DOI: 10.1088/0953-8984/26/46/463101] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Hard models for particle interactions have played a crucial role in the understanding of the structure of condensed matter. In particular, they help to explain the formation of oriented phases in liquids made of anisotropic molecules or colloidal particles and continue to be of great interest in the formulation of theories for liquids in bulk, near interfaces and in biophysical environments. Hard models of anisotropic particles give rise to complex phase diagrams, including uniaxial and biaxial nematic phases, discotic phases and spatially ordered phases such as smectic, columnar or crystal. Also, their mixtures exhibit additional interesting behaviours where demixing competes with orientational order. Here we review the different models of hard particles used in the theory of bulk anisotropic liquids, leaving aside interfacial properties and discuss the associated theoretical approaches and computer simulations, focusing on applications in equilibrium situations. The latter include one-component bulk fluids, mixtures and polydisperse fluids, both in two and three dimensions, and emphasis is put on liquid-crystal phase transitions and complex phase behaviour in general.
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Affiliation(s)
- Luis Mederos
- Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz, 3, E-28049 Madrid, Spain
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18
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Peroukidis SD. Biaxial mesophase behavior of amphiphilic anisometric colloids: a simulation study. SOFT MATTER 2014; 10:4199-4207. [PMID: 24770386 DOI: 10.1039/c4sm00036f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The phase behavior of amphiphilic anisometric particles is explored using Monte Carlo simulations. The particles are composed of two incompatible laterally attached units: a spherocylinder and a spheroplatelet. A liquid crystalline phase polymorphism is obtained including biaxial nematic, (quasi long range biaxial) calamitic smectic-A, biaxial lamellar and columnar phases. The simulation results demonstrate intriguing phase transitions such as nematic-nematic, discotic nematic to (quasi long range biaxial) calamitic smectic-A, biaxial nematic to uniaxial calamitic smectic-A, and isotropic or discotic nematic to biaxial lamellar phases that possess nematic ordering within the layers. These findings are rationalized in terms of molecular geometry and amphiphilicity of different molecular units. The molecular model can be used as a tool for the prediction of the complex phase behavior that is relevant to liquid crystalline colloids.
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19
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Kapanowski A, Abram M. Model of hard spheroplatelets near a hard wall. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:062503. [PMID: 25019801 DOI: 10.1103/physreve.89.062503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Indexed: 06/03/2023]
Abstract
A system of hard spheroplatelets near an impenetrable wall is studied in the low-density Onsager approximation. Spheroplatelets have optimal shape between rods and plates, and the direct transition from the isotropic to biaxial nematic phase is present. A simple local approximation for the one-particle distribution function is used. Analytical results for the surface tension and the entropy contributions are derived. The density and the order-parameter profiles near the wall are calculated. The preferred orientation of the short molecule axes is perpendicular to the wall. Biaxiality close to the wall can appear only if the phase is biaxial in the bulk.
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Affiliation(s)
- A Kapanowski
- Institute of Physics, Jagiellonian University, ulica Reymonta 4, 30-059 Kraków, Poland
| | - M Abram
- Institute of Physics, Jagiellonian University, ulica Reymonta 4, 30-059 Kraków, Poland
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20
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Lekkerkerker HNW, Vroege GJ. Liquid crystal phase transitions in suspensions of mineral colloids: new life from old roots. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20120263. [PMID: 23459965 DOI: 10.1098/rsta.2012.0263] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A review is given of the field of mineral colloidal liquid crystals: liquid crystal phases formed by individual mineral particles within colloidal suspensions. Starting from their discovery in the 1920s, we discuss developments on the levels of both fundamentals and applications. We conclude by highlighting some promising results from recent years, which may point the way towards future developments.
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Affiliation(s)
- H N W Lekkerkerker
- Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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21
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Polineni S, Figueirinhas JL, Cruz C, Wilson DA, Mehl GH. Capacitance and optical studies of elastic and dielectric properties in an organosiloxane tetrapode exhibiting a N(B) phase. J Chem Phys 2013; 138:124904. [PMID: 23556748 DOI: 10.1063/1.4795582] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Biaxial (N(B)) and uniaxial nematic (N(U)) phase behavior was detected and confirmed for an organosiloxane tetrapode material using capacitance and birefringence measurements. Elastic constants, permittivities at two distinct low frequencies, and birefringencies were determined as a function of temperature over both the N(U) and the N(B) phase ranges. The N(U)-N(B) transition is clearly observed in the birefringencies and conoscopy data. A temperature dependent cross-over frequency is also detected in this material for the permittivities, allowing the electrical switching of both planar and homeotropic aligned samples.
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Affiliation(s)
- S Polineni
- IST-Technical University of Lisbon, Dept. de Física, Av. Rovisco Pais, P-1049-001 Lisboa, Portugal
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22
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Gupta SK, Setia S, Sidiq S, Gupta M, Kumar S, Pal SK. New perylene-based non-conventional discotic liquid crystals. RSC Adv 2013. [DOI: 10.1039/c3ra41186a] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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23
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Kishikawa K. Utilization of the Perfluoroarene-Arene Interaction for Stabilization of Liquid Crystal Phases. Isr J Chem 2012. [DOI: 10.1002/ijch.201200028] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Belli S, Dijkstra M, van Roij R. Depletion-induced biaxial nematic states of boardlike particles. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:284128. [PMID: 22739023 DOI: 10.1088/0953-8984/24/28/284128] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
With the aim of investigating the stability conditions of biaxial nematic liquid crystals, we study the effect of adding a non-adsorbing ideal depletant on the phase behavior of colloidal hard boardlike particles. We take into account the presence of the depletant by introducing an effective depletion attraction between a pair of boardlike particles. At fixed depletant fugacity, the stable liquid-crystal phase is determined through a mean-field theory with restricted orientations. Interestingly, we predict that for slightly elongated boardlike particles a critical depletant density exists, where the system undergoes a direct transition from an isotropic liquid to a biaxial nematic phase. As a consequence, by tuning the depletant density, an easy experimental control parameter, one can stabilize states of high biaxial nematic order even when these states are unstable for pure systems of boardlike particles.
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Affiliation(s)
- S Belli
- Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, NL-3584 CE Utrecht, The Netherlands.
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OJHA DURGAPRASAD. ORDERING OF A THERMOTROPIC MESOGEN AT PHASE TRANSITION TEMPERATURE — A STATISTICAL APPROACH BASED ON QUANTUM MECHANICS. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2011. [DOI: 10.1142/s0219633605001805] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The molecular ordering of a thermotropic mesogen, 4-alkenyl bicyclohexylnitrile (ALKBCHN), has been carried out on the basis of quantum mechanics and intermolecular forces. The evaluation of atomic charges and dipole moment at each atomic centre has been done through the Complete Neglect Differential Overlap (CNDO/2) method. The configurational energy has been computed using the Rayleigh-Schrodinger perturbation method. The total interaction energy values obtained through these computations were used to calculate the probability of each configuration in a dielectric medium (i.e. non-interacting and non-mesogenic solvent, benzene) at phase transition temperature (364.7 K) using the Maxwell–Boltzmann formula. It has been observed that in dielectric medium the energies/probabilities are redistributed and there is a considerable rise in the probability of interactions, although the order of preference remains the same. An attempt has been made to develop a new and interesting model of mesogen in a dielectric medium. The present article offers a theoretical support to the experimental observations.
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Affiliation(s)
- DURGA PRASAD OJHA
- Liquid Crystal Research Laboratory, Post-Graduate Department of Physics, Andhra Loyola College, Vijayawada-520 008, A.P., India
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26
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Belli S, Patti A, Dijkstra M, van Roij R. Polydispersity stabilizes biaxial nematic liquid crystals. PHYSICAL REVIEW LETTERS 2011; 107:148303. [PMID: 22107241 DOI: 10.1103/physrevlett.107.148303] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Indexed: 05/31/2023]
Abstract
Inspired by the observations of a remarkably stable biaxial nematic phase [van den Pol et al., Phys. Rev. Lett. 103, 258301 (2009)], we investigate the effect of size polydispersity on the phase behavior of a suspension of boardlike particles. By means of Onsager theory within the restricted orientation (Zwanzig) model we show that polydispersity induces a novel topology in the phase diagram, with two Landau tetracritical points in between which oblate uniaxial nematic order is favored over the expected prolate order. Additionally, this phenomenon causes the opening of a huge stable biaxiality regime in between uniaxial nematic and smectic states.
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Affiliation(s)
- S Belli
- Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands
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27
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Martínez-Ratón Y, Varga S, Velasco E. Biaxial nematic phases in fluids of hard board-like particles. Phys Chem Chem Phys 2011; 13:13247-54. [DOI: 10.1039/c1cp20698b] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Varga S, Martinez-Ratón Y, Velasco E. Competition between capillarity, layering and biaxiality in a confined liquid crystal. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2010; 32:89-101. [PMID: 20521078 DOI: 10.1140/epje/i2010-10601-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Accepted: 05/03/2010] [Indexed: 05/29/2023]
Abstract
The effect of confinement on the phase behaviour and structure of fluids made of biaxial hard particles (cuboids) is examined theoretically by means of Onsager second-order virial theory in the limit where the long particle axes are frozen in a mutually parallel configuration. Confinement is induced by two parallel planar hard walls (slit-pore geometry), with particle long axes perpendicular to the walls (perfect homeotropic anchoring). In bulk, a continuous nematic-to-smectic transition takes place, while shape anisotropy in the (rectangular) particle cross-section induces biaxial ordering. As a consequence, four bulk phases, uniaxial and biaxial nematic and smectic phases, can be stabilised as the cross-sectional aspect ratio is varied. On confining the fluid, the nematic-to-smectic transition is suppressed, and either uniaxial or biaxial phases, separated by a continuous transition, can be present. Smectic ordering develops continuously from the walls for increasing particle concentration (in agreement with the supression of nematic-smectic second-order transition at confinement), but first-order layering transitions, involving structures with n and n + 1 layers, arise in the confined fluid at high concentration. Competition between layering and uniaxial-biaxial ordering leads to three different types of layering transitions, at which the two coexisting structures can be both uniaxial, one uniaxial and another biaxial, or both biaxial. Also, the interplay between molecular biaxiality and wall interactions is very subtle: while the hard wall disfavours the formation of the biaxial phase, biaxiality is against the layering transitions, as we have shown by comparing the confined phase behaviour of cylinders and cuboids. The predictive power of Onsager theory is checked and confirmed by performing some calculations based on fundamental-measure theory.
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Affiliation(s)
- S Varga
- Departamento de Física Téorica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
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29
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van den Pol E, Petukhov AV, Thies-Weesie DME, Byelov DV, Vroege GJ. Experimental realization of biaxial liquid crystal phases in colloidal dispersions of boardlike particles. PHYSICAL REVIEW LETTERS 2009; 103:258301. [PMID: 20366292 DOI: 10.1103/physrevlett.103.258301] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Indexed: 05/29/2023]
Abstract
Biaxial nematic and biaxial smectic phases were found in a colloidal model system of goethite (alpha-FeOOH) particles with a simple boardlike shape and short-range repulsive interaction. The macroscopic domains were oriented by a magnetic field and their structure was revealed by small angle x-ray scattering. In accordance with theoretical predictions, biaxiality appears in a system with particles that have a shape almost exactly in between rodlike and platelike. Our results suggest that biaxial phases can be readily obtained by a proper choice of the particle shape.
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Affiliation(s)
- E van den Pol
- Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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Berardi R, Muccioli L, Orlandi S, Ricci M, Zannoni C. Computer simulations of biaxial nematics. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:463101. [PMID: 21693834 DOI: 10.1088/0953-8984/20/46/463101] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Biaxial nematic (N(b)) liquid crystals are a fascinating condensed matter phase that has baffled, for more than thirty years, scientists engaged in the challenge of demonstrating its actual existence, and which has only recently been experimentally found. During this period computer simulations of model N(b) have played an important role, both in providing the basic physical properties to be expected from these systems, and in giving clues about the molecular features essential for the thermodynamic stability of N(b) phases. However, simulation studies are expected to be even more crucial in the future for unravelling the structural features of biaxial mesogens at the molecular level, and for helping in the design and optimization of devices towards the technological deployment of N(b) materials. This review article gives an overview of the simulation work performed so far, and relying on the recent experimental findings, focuses on the still unanswered questions which will determine the future challenges in the field.
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Affiliation(s)
- Roberto Berardi
- Dipartimento di Chimica Fisica e Inorganica, and INSTM-CRIMSON, Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
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Cruz C, Figueirinhas JL, Filip D, Feio G, Ribeiro AC, Frère Y, Meyer T, Mehl GH. Biaxial nematic order and phase behavior studies in an organosiloxane tetrapode using complementary deuterium NMR experiments. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:051702. [PMID: 19113138 DOI: 10.1103/physreve.78.051702] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Revised: 07/10/2008] [Indexed: 05/27/2023]
Abstract
The biaxial nematic phase was recently observed in different thermotropic liquid crystals, namely bent-core compounds, side-chain polymers, bent-core dimers, and organosiloxane tetrapodes. In this work, a series of experiments with a nematic organosiloxane tetrapode where nuclear magnetic resonance (NMR) spectra are collected while the sample is continuously rotating around an axis perpendicular to the magnetic field, are discussed in conjunction with the analysis of a deuterium NMR experiment on the same system reported earlier. The sample used is a mixture of a deuterated probe with the tetrapode. The mixture exhibits a nematic range between -40 degrees C and 37 degrees C. The results of the two independent, but complementary deuterium NMR experiments confirm the existence of a biaxial nematic phase for temperatures below 0 degrees C with high values of the asymmetry parameter at low temperatures. The presence of slow movements of the tetrapode mesogenic units in the low-temperature regime could also be detected through the analysis of the NMR spectra. Simulations indicate that these movements are mainly slow molecular reorientations of the mesogenic units associated with the presence of collective modes in the nematic phases of this compound. In the case of tetrapodes, recent investigations attribute the origin of biaxiality to the hindering of reorientations of the laterally attached mesogenic units which constitute the tetrapode. This study relates the molecular movements with the nematic biaxial ordering of the system.
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Affiliation(s)
- C Cruz
- CFMC-UL, Av. Prof. Gama Pinto 2, 1649-003 Lisboa, Portugal
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33
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Martínez-Ratón Y, Varga S, Velasco E. Biaxial nematic and smectic phases of parallel particles with different cross sections. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:031705. [PMID: 18851053 DOI: 10.1103/physreve.78.031705] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Indexed: 05/26/2023]
Abstract
We have calculated the phase diagrams of one-component fluids made of five types of biaxial particles differing in their cross sections. The orientation of the principal particle axis is fixed in space, while the second axis is allowed to freely rotate. We have constructed a free-energy density functional based on fundamental-measure theory to study the relative stability of nematic and smectic phases with uniaxial, biaxial, and tetratic symmetries. Minimization of the density functional allows us to study the phase behavior of the biaxial particles as a function of the cross-section geometry. For low values of the aspect ratio of the particle cross section, we obtain smectic phases with tetratic symmetry, although metastable with respect to the crystal, as our Monte Carlo simulation study indicates. For large particle aspect ratios and in analogy with previous work [A. G. Vanakaras, M. A. Bates, and D. J. Photinos, Phys. Chem. Chem. Phys. 5, 3700 (2003)], we have found a four-phase point where four spinodals, corresponding to phase transitions between phases with different symmetries, meet together. The location of this point is quite sensitive to particle cross section, which suggests that optimizing the particle geometry could be a useful criterion in the design of colloidal particles that can exhibit an increased stability of the biaxial nematic phase with respect to other competing phases with spatial order.
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Affiliation(s)
- Yuri Martínez-Ratón
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Departamento de Matemáticas, Escuela Politécnica Superior, Universidad Carlos III de Madrid, Avenida de la Universidad 30, E-28911, Leganés, Madrid, Spain.
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Vanakaras AG, Photinos DJ. Thermotropic biaxial nematic liquid crystals: Spontaneous or field stabilized? J Chem Phys 2008; 128:154512. [DOI: 10.1063/1.2897993] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Mettout B. Theory of two- and three-dimensional bent-core mesophases. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:011706. [PMID: 17358172 DOI: 10.1103/physreve.75.011706] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Revised: 07/18/2006] [Indexed: 05/14/2023]
Abstract
An extension of the vector-wave theory of antiferroelectric bent-core liquid crystals to columnar and soft-crystalline mesophases is presented. We enumerate and describe the phases resulting from the condensation of one, two, and three vector waves in the isotropic liquid of bent-core molecules. Beside the one-dimensional B2 and smectic- CP phases, 24 columnar and soft-crystalline orthorhombic, monoclinic, and triclinic phases can be stabilized when two or three waves have nonparallel wave vectors. Their symmetry groups, molecular arrangements, and phase diagrams are worked out and used to identify the structures of the main observed bent-core phases and their various subphases.
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Affiliation(s)
- B Mettout
- GCL, 33 rue St Leu, 80000 Amiens, France
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36
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Ojha DP. Computational analysis of ordering in higher homologous series of nBAC: The effect of a dielectric medium. CRYSTALLOGR REP+ 2006. [DOI: 10.1134/s1063774506070182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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37
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Teixeira PIC, Osipov MA, Luckhurst GR. Simple model for biaxial smectic-A liquid-crystal phases. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:061708. [PMID: 16906850 DOI: 10.1103/physreve.73.061708] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Indexed: 05/11/2023]
Abstract
We have generalized the McMillan theory of liquid crystalline smectic order in uniaxial particle fluids to biaxial particles. Upon varying the control parameter, a uniaxial nematic phase may: (i) order biaxially first, then smectically; (ii) order smectically first, then biaxially; and (iii) simultaneously order biaxially and smectically. We investigate, in the limit of complete orientational order of the molecular major axes, which of these scenarios are realized for a simple model of particles with the symmetry of rectangular parallelepipeds. We also present a generic variational derivation of the theory based on the identification of the dominant order parameters for the most ordered phase.
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Affiliation(s)
- P I C Teixeira
- Faculdade de Engenharia, Universidade Católica Portuguesa, Estrada de Talaíde, P-2635-631 Rio de Mouro, Portugal
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Ojha DP. Ordering of a monotropic nematic liquid crystal in dielectric medium at phase transition temperature: A computational analysis. RUSS J GEN CHEM+ 2006. [DOI: 10.1134/s1070363206040025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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40
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Sokolowska D, Moscicki JK. Phase equilibria in solutions of platelike particles: systems with steric and dispersive interactions between the platelets. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:031701. [PMID: 15903441 DOI: 10.1103/physreve.71.031701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Indexed: 05/02/2023]
Abstract
Our statistical thermodynamics model of solution of stiff, platelike, biaxial particles interacting solely via repulsion on contact (athermal limit) [Phys. Rev. E 62, 5011 (2000)] is extended to incorporate dispersion interactions between the particles. Dispersion forces between anisotropic particles are accounted for using the Imura-Okano approach. Numerical calculations specialized to solutions of either rods or disks show that besides the isotropic-nematic biphasic coexistence range, inclusion of attractive forces resulted in the appearance of nematic-nematic coexistence in both, disks and rods, solutions. The critical divergence of the difference between the order parameters and concentrations of the two nematics is observed while approaching the critical temperature. The minimum aspect ratio of rods or disks for the formation of the nematic phase is also discussed.
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Affiliation(s)
- Dagmara Sokolowska
- Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland
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