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Aliabadi R, Nasirimoghadam S, Wensink HH. Evidence of T-type structures of hard square boards in capillary confinement. Phys Rev E 2023; 107:054117. [PMID: 37329060 DOI: 10.1103/physreve.107.054117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 04/05/2023] [Indexed: 06/18/2023]
Abstract
We employ Onsager's second virial density functional theory combined with the Parsons-Lee theory within the restricted orientation (Zwanzig) approximation to examine the phase structure of hard square boards of dimensions (L×D×D) uniaxially confined in narrow slabs. Depending on the wall-to-wall separation (H), we predict a number of distinctly different capillary nematic phases, including a monolayer uniaxial or biaxial planar nematic, homeotropic with a variable number of layers, and a T-type structure. We determine that the favored phase is homotropic, and we observe first-order transitions from the homeotropic structure with n layers to n+1 layers as well as from homeotropic surface anchoring to a monolayer planar or T-type structure involving both planar and homeotropic anchoring at the pore surface. By increasing the packing fraction, we further demonstrate a reentrant homeotropic-planar-homeotropic phase sequence in a particular range (i.e., H/D=1.1 and 0.25≤L/D<0.26). We find that the T-type structure is more stable when the pore is wide enough with respect to the planar phase. The enhanced stability of the mixed-anchoring T-structure is unique for square boards and becomes manifest at pore width exceeding L+D. More specifically, the biaxial T-type structure emerges directly from the homeotropic state without intervention of a planar layer structure as observed for other convex particle shapes.
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Affiliation(s)
| | | | - Henricus Herman Wensink
- Laboratoire de Physique des Solides - UMR 8502, CNRS, Université Paris-Saclay, 91405 Orsay, France
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2
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Morillo N, Martínez-Haya B, Cuetos A. Tailoring the phase diagram of discotic mesogens. SOFT MATTER 2021; 17:8693-8704. [PMID: 34519327 DOI: 10.1039/d1sm00624j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The computational modelling of discotic molecules is a central topic in colloid science that is key for the smart design of a broad range of modern functional materials. This work lays out a versatile interaction model capable of exposing the rich mesogenic behaviour of discotics. A single coarse-grained spheroplatelet core framework is employed to generate a variety of pair interaction anisotropy classes, favouring specific relative orientations of the particles (stacked, side-side, crossed, T-shaped). This paves the way for the systematic tailoring of the discotic liquid phase diagram. Monte Carlo simulations are performed for an ensemble of case studies to illustrate the correlation between the topology of the interaction and the formation of stable nematic, smectic and columnar phases, as well as of less common cubatic, uniaxial and biaxial columnar domains.
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Affiliation(s)
- Neftalí Morillo
- Department of Theoretical Physics, Universidad Complutense de Madrid, Avda. de la Complutense S/N, 28040 Madrid, Spain.
| | - Bruno Martínez-Haya
- Department of Physical, Chemical and Natural Systems, Pablo de Olavide University, 41013 Sevilla, Spain
| | - Alejandro Cuetos
- Department of Physical, Chemical and Natural Systems, Pablo de Olavide University, 41013 Sevilla, Spain
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Labalette V, Praga A, Girard F, Meireles M, Hallez Y, Morris JF. Shear-induced glass-to-crystal transition in anisotropic clay-like suspensions. SOFT MATTER 2021; 17:3174-3190. [PMID: 33621310 DOI: 10.1039/d0sm02081h] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
A new numerical framework based on Stokesian dynamics is used to study a shear-induced glass-to-crystal transition in suspensions of clay-like anisotropically charged platelets. The structures obtained in quiescent conditions are in agreement with previous Monte Carlo results: a liquid phase at very short interaction range (high salt concentration), phase separation and a gel without large scale density fluctuations at intermediate interaction ranges, and glassy states at very large interaction ranges. When initially glassy suspensions are sheared, hydrodynamic torques first rotate platelets so they can reach a transient quasi-nematic disordered state. These orientational correlations permit to unlock translational degrees of freedom and the platelets then form strings aligned with the velocity direction and hexagonally packed in the gradient-vorticity plane. Under steady shear, platelet orientations are correlated but the system is not nematic. After flow cessation and relaxation in quiescent conditions, positional and orientational order are further improved as the platelet suspension experiences a transition to a nematic hexagonal crystal. Energy calculations and the existence of residual stress anisotropy after relaxation show that this final structure is not an equilibrium state but rather a new ordered, arrested state. The transient, nematic, disordered state induced by shear immediately after startup and unlocking translational degrees of freedom is thought to be an initial step that may be generic for other suspensions of strongly anisotropic colloids with important translation-orientation coupling induced by long-range interactions.
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Affiliation(s)
- Vincent Labalette
- Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France.
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Mizani S, Aliabadi R, Salehi H, Varga S. Orientational ordering and layering of hard plates in narrow slitlike pores. Phys Rev E 2019; 100:032704. [PMID: 31639981 DOI: 10.1103/physreve.100.032704] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Indexed: 11/07/2022]
Abstract
We examine the ordering behavior of hard platelike particles in a very narrow, slitlike pore using the Parsons-Lee density functional theory and the restricted orientation approximation. We observe that the plates are orientationally ordered and align perpendicularly (face-on) to the walls at low densities, a first-order layering transition occurs between uniaxial nematic structures having n and n+1 layers at intermediate densities, and even a phase transition between a monolayer with parallel (edge-on) orientational order and n layers with a perpendicular one can be detected at high densities. In addition to this, the edge-on monolayer is usually biaxial nematic, and a uniaxial-biaxial nematic phase transition can be also seen at very high densities.
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Affiliation(s)
- Sakine Mizani
- Department of Physics, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Roohollah Aliabadi
- Department of Physics, Faculty of Science, Fasa University, 74617-81189 Fasa, Iran
| | - Hamdollah Salehi
- Department of Physics, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Szabolcs Varga
- Institute of Physics and Mechatronics, University of Pannonia, P.O. Box 158, Veszprém H-8201, Hungary
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Affiliation(s)
- Michael P. Allen
- Department of Physics, University of Warwick, Coventry, UK
- H. H. Wills Physics Laboratory, Royal Fort, Bristol, UK
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Hagita K, Shudo Y, Shibayama M. Two-dimensional scattering patterns and stress-strain relation of elongated clay nano composite gels: Molecular dynamics simulation analysis. POLYMER 2018. [DOI: 10.1016/j.polymer.2018.08.047] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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7
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Xu D, Gersappe D. Structure formation in nanocomposite hydrogels. SOFT MATTER 2017; 13:1853-1861. [PMID: 28177007 DOI: 10.1039/c6sm02543a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We use molecular dynamics simulations to study structure formation in physically associating nanocomposite hydrogels. Nanofillers were modeled as rigid bodies of disk-like shapes and physical crosslinks were simulated by introducing a short-range attraction between the nanofillers and polymer chain ends. The structure, dynamics and mechanics of these polymer gels were studied as a function of nanofiller volume fraction. We observe the formation of a percolated network in the hydrogels, with an ordered local structure but disordered globally, as we increase the filler fraction. This locally ordered structure was a result of the anisotropy of the disk-like fillers. The dynamics of polymers showed significant caging effects in the gel state. Stress autocorrelation and elongation results were analyzed as a function of nano-filler concentrations. Comparisons with nanofillers of different shapes showed that disk-like nanofillers are more effective in strengthening the hydrogels than spherical nanofillers.
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Affiliation(s)
- Di Xu
- Department of Material Science and Chemical Engineering, Stony Brook University, Stony Brook, NY 11794, USA.
| | - Dilip Gersappe
- Department of Material Science and Chemical Engineering, Stony Brook University, Stony Brook, NY 11794, USA.
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Lin F, Tong X, Wang Y, Bao J, Wang ZM. Graphene oxide liquid crystals: synthesis, phase transition, rheological property, and applications in optoelectronics and display. NANOSCALE RESEARCH LETTERS 2015; 10:435. [PMID: 26546325 PMCID: PMC4636539 DOI: 10.1186/s11671-015-1139-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 10/23/2015] [Indexed: 05/21/2023]
Abstract
Graphene oxide (GO) liquid crystals (LCs) are macroscopically ordered GO flakes dispersed in water or polar organic solvents. Since the first report in 2011, GO LCs have attracted considerable attention for their basic properties and potential device applications. In this review, we summarize recent developments and present a comprehensive understanding of GO LCs via many aspects ranging from the exfoliation of GO flakes from graphite, to phases and phase transitions under various conditions, the orientational responses of GO under external magnetic and electric fields, and finally Kerr effect and display applications. The emphasis is placed on the unique and basic properties of GO and their ordered assembly. We will also discuss challenges and issues that need to be overcome in order to gain a more fundamental understanding and exploit full device potentials of GO LCs.
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Affiliation(s)
- Feng Lin
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China.
| | - Xin Tong
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China.
| | - Yanan Wang
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China.
- Department of Electrical and Computer Engineering, University of Houston, Houston, TX, 77204, USA.
| | - Jiming Bao
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China.
- Department of Electrical and Computer Engineering, University of Houston, Houston, TX, 77204, USA.
| | - Zhiming M Wang
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China.
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China.
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Jabbari-Farouji S, Weis JJ, Davidson P, Levitz P, Trizac E. Interplay of anisotropy in shape and interactions in charged platelet suspensions. J Chem Phys 2015; 141:224510. [PMID: 25494763 DOI: 10.1063/1.4903045] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Motivated by the intriguing phase behavior of charged colloidal platelets, we investigate the structure and dynamics of charged repulsive disks by means of Monte Carlo simulations. The electrostatic interactions are taken into account through an effective two-body potential, obtained within the nonlinear Poisson-Boltzmann formalism, which has the form of anisotropic screened Coulomb potential. Recently, we showed that the original intrinsic anisotropy of the electrostatic potential in competition with excluded volume effects leads to a rich phase behavior that not only includes various liquid-crystalline phases but also predicts the existence of novel structures composed of alternating nematic-antinematic sheets. Here, we examine the structural and dynamical signatures of each of the observed structures for both translational and rotational degrees of freedom. Finally, we discuss the influence of effective charge value and our results in relation to experimental findings on charged platelet suspensions.
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Affiliation(s)
- Sara Jabbari-Farouji
- LPTMS, CNRS and Université Paris-Sud, UMR8626, Bat. 100, 91405 Orsay, France and Laboratoire Interdisciplinaire de Physique, UMR 5588, F-38041 Grenoble, France
| | - Jean-Jacques Weis
- Laboratoire de Physique Théorique, Université Paris-Sud, UMR 8627 Bâtiment 210, 91405 Orsay Cedex, France
| | - Patrick Davidson
- Laboratoire de Physique des Solides, Université Paris-Sud, UMR 8502 Bâtiment 510, 91405 Orsay Cedex, France
| | - Pierre Levitz
- Laboratoire PECSA, UMR 7195, Université Pierre et Marie Curie, Case Courrier 51, 4 place Jussieu, 72522 Paris Cedex 5, France
| | - Emmanuel Trizac
- LPTMS, CNRS and Université Paris-Sud, UMR8626, Bat. 100, 91405 Orsay, France
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Vis M, Wensink H, Lekkerkerker H, Kleshchanok D. Nematic and lamellar liquid-crystalline phases in suspensions of charged silica-coated gibbsite platelets. Mol Phys 2014. [DOI: 10.1080/00268976.2014.985276] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Wensink HH, Trizac E. Generalized Onsager theory for strongly anisometric patchy colloids. J Chem Phys 2014; 140:024901. [PMID: 24437905 DOI: 10.1063/1.4851217] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The implications of soft "patchy" interactions on the orientational disorder-order transition of strongly elongated colloidal rods and flat disks is studied within a simple Onsager-van der Waals density functional theory. The theory provides a generic framework for studying the liquid crystal phase behaviour of highly anisometric cylindrical colloids which carry a distinct geometrical pattern of repulsive or attractive soft interactions localized on the particle surface. In this paper, we apply our theory to the case of charged rods and disks for which the local electrostatic interactions can be described by a screened-Coulomb potential. We consider infinitely thin rod like cylinders with a uniform line charge and infinitely thin discotic cylinders with several distinctly different surface charge patterns. Irrespective of the backbone shape the isotropic-nematic phase diagrams of charged colloids feature a generic destabilization of nematic order at low ionic strength, a dramatic narrowing of the biphasic density region, and a reentrant phenomenon upon reducing the electrostatic screening. The low screening regime is characterized by a complete suppression of nematic order in favor of positionally ordered liquid crystal phases.
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Affiliation(s)
- H H Wensink
- Laboratoire de Physique des Solides - UMR 8502, Université Paris-Sud and CNRS, 91405 Orsay Cedex, France
| | - E Trizac
- Laboratoire de Physique Théorique et Modèles Statistiques - UMR 8626, Université Paris-Sud and CNRS, 91405 Orsay Cedex, France
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Turesson M, Nonat A, Labbez C. Stability of negatively charged platelets in calcium-rich anionic copolymer solutions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:6713-6720. [PMID: 24850266 DOI: 10.1021/la501228w] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Controlling the stability of anisotropic particles is key to the development of advanced materials. Here, we report an investigation, by means of mesoscale molecular dynamics simulations, of the stability and structural change of calcium-rich dispersions containing negatively charged nanoplatelets, neutralized by calcium counterions, in the presence of either comb copolymers composed of anionic backbones with attached neutral side chains or anionic-neutral linear block copolymers. In agreement with experimental observations, small stacks of platelets (tactoids) are formed, which are greatly stabilized in the presence of copolymers. In the absence of polymers, tactoids will grow and aggregate strongly due to large attractive Ca(2+)-Ca(2+) correlation forces. Unlike comb copolymers which only adsorb on the external surfaces, block copolymers are found to intercalate between the platelets. The present results show that the stabilization is the result of a free energy barrier induced by the excluded volume of hydrophilic chains, while the intercalation is due to bridging forces. More generally, the results shed new light on the recent finding of the first hybrid cementitious mesocrystal.
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Affiliation(s)
- Martin Turesson
- ICB, UMR 6303 CNRS, Université de Bourgogne, F-21078 Dijon Cedex, France
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Delhorme M, Jönsson B, Labbez C. Gel, glass and nematic states of plate-like particle suspensions: charge anisotropy and size effects. RSC Adv 2014. [DOI: 10.1039/c4ra05555a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The influence of the charge anisotropy and platelet size on the formation of gel and glass states and nematic phases in suspensions of plate-like particles is investigated using Monte Carlo simulations in the canonical ensemble.
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Affiliation(s)
- Maxime Delhorme
- Laboratoire Interdisciplinaire Carnot de Bourgogne
- UMR 6303 CNRS
- Université de Bourgogne
- F-21078 Dijon, France
- Theoretical Chemistry
| | - Bo Jönsson
- Theoretical Chemistry
- Lund University
- Chemical Center
- S-221 00 Lund, Sweden
| | - Christophe Labbez
- Laboratoire Interdisciplinaire Carnot de Bourgogne
- UMR 6303 CNRS
- Université de Bourgogne
- F-21078 Dijon, France
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