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Cywiak D, Gil-Villegas A, Patti A. Long-time relaxation dynamics in nematic and smectic liquid crystals of soft repulsive colloidal rods. Phys Rev E 2022; 105:014703. [PMID: 35193200 DOI: 10.1103/physreve.105.014703] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Accepted: 01/04/2022] [Indexed: 06/14/2023]
Abstract
Understanding the relaxation dynamics of colloidal suspensions is crucial to identifying the elements that influence the mobility of their constituents, assessing their macroscopic response across the relevant time and length scales, and thus disclosing the fundamentals underpinning their exploitation in formulation engineering. In this work, we specifically assess the impact of long-ranged ordering on the relaxation dynamics of suspensions of soft repulsive rodlike particles, which are able to self-organize into nematic and smectic liquid-crystalline phases. Rods are modeled as soft repulsive spherocylinders with a length-to-diameter ratio L^{★}=5, interacting via the truncated and shifted Kihara potential. By performing dynamic Monte Carlo simulations, we analyze the effect of translational and orientational order on the diffusion of the rods along the relevant directions imposed by the morphology of the background phases. To provide a clear picture of the resulting dynamics, we assess its dependence on temperature, which can dramatically determine the response time of the system relaxation and the self-diffusion coefficients of the rods. The computation of the van Hove correlation functions allows us to identify the existence of rods that diffuse significantly faster than the average and whose concentration can be accurately adjusted by a suitable choice of temperature.
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Affiliation(s)
- Daniela Cywiak
- División de Ciencias e Ingenierías, Universidad de Guanajuato, Campus León, Mexico
| | | | - Alessandro Patti
- Department of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, United Kingdom
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Salamonczyk M, Zhang J, Portale G, Zhu C, Kentzinger E, Gleeson JT, Jakli A, De Michele C, Dhont JKG, Sprunt S, Stiakakis E. Smectic phase in suspensions of gapped DNA duplexes. Nat Commun 2016; 7:13358. [PMID: 27845332 PMCID: PMC5116068 DOI: 10.1038/ncomms13358] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 09/23/2016] [Indexed: 11/09/2022] Open
Abstract
Smectic ordering in aqueous solutions of monodisperse stiff double-stranded DNA fragments is known not to occur, despite the fact that these systems exhibit both chiral nematic and columnar mesophases. Here, we show, unambiguously, that a smectic-A type of phase is formed by increasing the DNA's flexibility through the introduction of an unpaired single-stranded DNA spacer in the middle of each duplex. This is unusual for a lyotropic system, where flexibility typically destabilizes the smectic phase. We also report on simulations suggesting that the gapped duplexes (resembling chain-sticks) attain a folded conformation in the smectic layers, and argue that this layer structure, which we designate as smectic-fA phase, is thermodynamically stabilized by both entropic and energetic contributions to the system's free energy. Our results demonstrate that DNA as a building block offers an exquisitely tunable means to engineer a potentially rich assortment of lyotropic liquid crystals.
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Affiliation(s)
- Miroslaw Salamonczyk
- Department of Physics and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
| | - Jing Zhang
- Institute of Complex Systems ICS-3, JARA-SOFT, Forschungszentrum Jülich, Leo-Brandt-Str, Jülich D-52425, Germany
- Department of Environmental Nano-materials, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Giuseppe Portale
- Zernike Institute for Advanced Materials, Department of Macromolecular Chemistry and New Polymeric Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Chenhui Zhu
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, 94720 California, USA
| | - Emmanuel Kentzinger
- Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich, Jülich D-52425, Germany
| | - James T. Gleeson
- Department of Physics and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
| | - Antal Jakli
- Department of Physics and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
| | - Cristiano De Michele
- Department of Physics, Sapienza Università di Roma, Piazzale A. Moro 5, Roma 00185, Italy
| | - Jan K. G. Dhont
- Institute of Complex Systems ICS-3, JARA-SOFT, Forschungszentrum Jülich, Leo-Brandt-Str, Jülich D-52425, Germany
- Department of Physics, Heinrich-Heine-Universität Düsseldorf, Universitätsstrae 1, D-40225 Düsseldorf, Germany
| | - Samuel Sprunt
- Department of Physics and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
| | - Emmanuel Stiakakis
- Institute of Complex Systems ICS-3, JARA-SOFT, Forschungszentrum Jülich, Leo-Brandt-Str, Jülich D-52425, Germany
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van Westen T, Oyarzún B, Vlugt TJH, Gross J. An analytical equation of state for describing isotropic-nematic phase equilibria of Lennard-Jones chain fluids with variable degree of molecular flexibility. J Chem Phys 2015; 142:244903. [DOI: 10.1063/1.4922921] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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Viveros-Méndez PX, Gil-Villegas A, Aranda-Espinoza S. Monte Carlo computer simulation of sedimentation of charged hard spherocylinders. J Chem Phys 2014; 141:044905. [PMID: 25084954 DOI: 10.1063/1.4890819] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this article we present a NVT Monte Carlo computer simulation study of sedimentation of an electroneutral mixture of oppositely charged hard spherocylinders (CHSC) with aspect ratio L/σ = 5, where L and σ are the length and diameter of the cylinder and hemispherical caps, respectively, for each particle. This system is an extension of the restricted primitive model for spherical particles, where L/σ = 0, and it is assumed that the ions are immersed in an structureless solvent, i.e., a continuum with dielectric constant D. The system consisted of N = 2000 particles and the Wolf method was implemented to handle the coulombic interactions of the inhomogeneous system. Results are presented for different values of the strength ratio between the gravitational and electrostatic interactions, Γ = (mgσ)/(e(2)/Dσ), where m is the mass per particle, e is the electron's charge and g is the gravitational acceleration value. A semi-infinite simulation cell was used with dimensions Lx ≈ Ly and Lz = 5Lx, where Lx, Ly, and Lz are the box dimensions in Cartesian coordinates, and the gravitational force acts along the z-direction. Sedimentation effects were studied by looking at every layer formed by the CHSC along the gravitational field. By increasing Γ, particles tend to get more packed at each layer and to arrange in local domains with an orientational ordering along two perpendicular axis, a feature not observed in the uncharged system with the same hard-body geometry. This type of arrangement, known as tetratic phase, has been observed in two-dimensional systems of hard-rectangles and rounded hard-squares. In this way, the coupling of gravitational and electric interactions in the CHSC system induces the arrangement of particles in layers, with the formation of quasi-two dimensional tetratic phases near the surface.
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Affiliation(s)
- P X Viveros-Méndez
- Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esq. Paseo, La Bufa s/n, 98060 Zacatecas, Zacatecas, México
| | - Alejandro Gil-Villegas
- Departamento de Ingeniería Física, División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León, Guanajuato, México
| | - S Aranda-Espinoza
- Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esq. Paseo, La Bufa s/n, 98060 Zacatecas, Zacatecas, México
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Müller EA, Jackson G. Force-Field Parameters from the SAFT-γ Equation of State for Use in Coarse-Grained Molecular Simulations. Annu Rev Chem Biomol Eng 2014; 5:405-27. [DOI: 10.1146/annurev-chembioeng-061312-103314] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A description of fluid systems with molecular-based algebraic equations of state (EoSs) and by direct molecular simulation is common practice in chemical engineering and the physical sciences, but the two approaches are rarely closely coupled. The key for an integrated representation is through a well-defined force field and Hamiltonian at the molecular level. In developing coarse-grained intermolecular potential functions for the fluid state, one typically starts with a detailed, bottom-up quantum-mechanical or atomic-level description and then integrates out the unwanted degrees of freedom using a variety of techniques; an iterative heuristic simulation procedure is then used to refine the parameters of the model. By contrast, with a top-down technique, one can use an accurate EoS to link the macroscopic properties of the fluid and the force-field parameters. We discuss the latest developments in a top-down representation of fluids, with a particular focus on a group-contribution formulation of the statistical associating fluid theory (SAFT-γ). The accurate SAFT-γ EoS is used to estimate the parameters of the Mie force field, which can then be used with confidence in direct molecular simulations to obtain thermodynamic, structural, interfacial, and dynamical properties that are otherwise inaccessible from the EoS. This is exemplified for several prototypical fluids and mixtures, including carbon dioxide, hydrocarbons, perfluorohydrocarbons, and aqueous surfactants.
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Affiliation(s)
- Erich A. Müller
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - George Jackson
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom
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Querciagrossa L, Ricci M, Berardi R, Zannoni C. Mesogen polarity effects on biaxial nematics. Centrally located dipoles. Phys Chem Chem Phys 2013; 15:19065-72. [DOI: 10.1039/c3cp52970c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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7
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Wu L, Wensink H, Jackson G, Müller E. A generic equation of state for liquid crystalline phases of hard-oblate particles. Mol Phys 2012. [DOI: 10.1080/00268976.2011.649794] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Mu D, Li JQ, Wang S. Mesoscopic simulation of the surface inducing effects on the compatibility of PS-b-PMMA copolymers. J Appl Polym Sci 2011. [DOI: 10.1002/app.35121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Wensink HH, Jackson G. Cholesteric order in systems of helical Yukawa rods. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:194107. [PMID: 21525561 DOI: 10.1088/0953-8984/23/19/194107] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We consider the interaction potential between two chiral rod-like colloids which consist of a thin cylindrical backbone decorated with a helical charge distribution on the cylinder surface. For sufficiently slender helical rods a simple scaling expression is derived which relates the chiral 'twisting' potential to the microscopic properties of the particles, such as the internal helical pitch, charge density and electrostatic screening parameter. To predict the behaviour of the macroscopic cholesteric pitch of the fluid bulk phase we invoke a simple second-virial theory generalized to treat anisotropic states with weakly twisted director fields. It is shown that, while particles with weakly coiled helices always form a cholesteric phase whose helical sense is commensurate with that of the internal helix, more strongly coiled rods lead to the formation of a cholesteric state of opposite sense. The correlation between the helical symmetry at the microscopic and macroscopic scale is found to be very sensitive to the pitch of the Yukawa helix. Mixing helical particles of sufficiently disparate length and internal pitch may give rise to a demixing of the uniform cholesteric phase into two fractions with a different macroscopic pitch. Our findings could be relevant to the interpretation of experimental observations in systems of cellulose and chitin microfibres, DNA and fd virus rods.
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Affiliation(s)
- H H Wensink
- Department of Chemical Engineering, Imperial College London, London, UK.
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10
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Varga S, Jackson G. A study of steric chirality: the chiral nematic phase of a system of chiral two-site HGO molecules. Mol Phys 2011. [DOI: 10.1080/00268976.2011.556577] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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11
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Brumby PE, Haslam AJ, de Miguel E, Jackson G. Subtleties in the calculation of the pressure and pressure tensor of anisotropic particles from volume-perturbation methods and the apparent asymmetry of the compressive and expansive contributions. Mol Phys 2011. [DOI: 10.1080/00268976.2010.530301] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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12
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Jiménez-Serratos G, Avendaño C, Gil-Villegas A, González-Tovar E. Computer simulation of charged hard spherocylinders at low temperatures. Mol Phys 2011. [DOI: 10.1080/00268976.2010.524171] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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13
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Horiuchi K, Yamamura Y, Pełka R, Sumita M, Yasuzuka S, Massalska-Arodz M, Saito K. Entropic Contribution of Flexible Terminals to Mesophase Formation Revealed by Thermodynamic Analysis of 4-Alkyl-4′-isothiocyanatobiphenyl (nTCB). J Phys Chem B 2010. [DOI: 10.1021/jp100301r] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Katsuya Horiuchi
- Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan, and The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow 31-342, Poland
| | - Yasuhisa Yamamura
- Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan, and The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow 31-342, Poland
| | - Robert Pełka
- Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan, and The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow 31-342, Poland
| | - Masato Sumita
- Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan, and The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow 31-342, Poland
| | - Syuma Yasuzuka
- Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan, and The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow 31-342, Poland
| | - Maria Massalska-Arodz
- Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan, and The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow 31-342, Poland
| | - Kazuya Saito
- Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan, and The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow 31-342, Poland
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Affiliation(s)
- JOSEPH M. BRADER
- a The James Franck Institute, University of Chicago , 5640 South Ellis Avenue, Chicago , Il , 60637 , USA
| | - CHRISTIAN VON FERBER
- b Theoretical Polymer Physics, Freiburg University , Herman-Herder-StraIße 3, 79104 , Freiburg , Germany
| | - MATTHIAS SCHMIDT
- c Institut für Theoretische Physik II, Heinrich-Heine-Universität Düsseldorf , Universitätsstraße 1, D-40225 , Düsseldorf , Germany
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15
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Franco-Melgar M, Haslam AJ, Jackson G. Advances in generalised van der Waals approaches for the isotropic–nematic fluid phase equilibria of thermotropic liquid crystals–an algebraic equation of state for attractive anisotropic particles with the Onsager trial function. Mol Phys 2009. [DOI: 10.1080/00268970903352335] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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16
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AlSunaidi A, den Otter WK, Clarke JHR. Microphase separation and liquid-crystalline ordering of rod-coil copolymers. J Chem Phys 2009; 130:124910. [DOI: 10.1063/1.3089701] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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17
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Avendaño C, Gil-Villegas A, González-Tovar E. A Monte Carlo simulation study of binary mixtures of charged hard spherocylinders and charged hard spheres. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.01.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Avendaño C, Gil-Villegas A, González-Tovar E. Computer simulation of charged hard spherocylinders. J Chem Phys 2008; 128:044506. [DOI: 10.1063/1.2823736] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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19
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Ding W, Lin S, Lin J, Zhang L. Effect of Chain Conformational Change on Micelle Structures: Experimental Studies and Molecular Dynamics Simulations. J Phys Chem B 2008; 112:776-83. [DOI: 10.1021/jp076939p] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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20
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Ibarra-Avalos N, Gil-Villegas A, Martinez Richa A. Excluded volume of hard cylinders of variable aspect ratio. MOLECULAR SIMULATION 2007. [DOI: 10.1080/08927020701191349] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Lin S, Numasawa N, Nose T, Lin J. Brownian Molecular Dynamics Simulation on Self-Assembly Behavior of Rod−Coil Diblock Copolymers. Macromolecules 2007. [DOI: 10.1021/ma062064l] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shaoliang Lin
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China; School of Dentistry, Nihon University, Tokyo 101-8310, Japan; and Department of Nanochemistry, Tokyo Polytechnic University, Atsugi, Kanagawa 243-0297, Japan
| | - Naoko Numasawa
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China; School of Dentistry, Nihon University, Tokyo 101-8310, Japan; and Department of Nanochemistry, Tokyo Polytechnic University, Atsugi, Kanagawa 243-0297, Japan
| | - Takuhei Nose
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China; School of Dentistry, Nihon University, Tokyo 101-8310, Japan; and Department of Nanochemistry, Tokyo Polytechnic University, Atsugi, Kanagawa 243-0297, Japan
| | - Jiaping Lin
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China; School of Dentistry, Nihon University, Tokyo 101-8310, Japan; and Department of Nanochemistry, Tokyo Polytechnic University, Atsugi, Kanagawa 243-0297, Japan
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Fukunaga H, Takimoto JI, Doi M. Molecular dynamics simulation study on the phase behavior of the Gay-Berne model with a terminal dipole and a flexible tail. J Chem Phys 2006; 120:7792-800. [PMID: 15267694 DOI: 10.1063/1.1687681] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
To study the effect of the alkyl tail and the terminal dipole on the stability of the liquid crystalline phase of mesogens, we have carried out molecular dynamics simulations for 1CB(4-methyl-4'-cyanobiphenyl) and 5CB(4-n-pentyl-4'-cyanobiphenyl) by using a coarse-grained model. In the coarse-grained model, a 5CB molecule is divided into the rigid part of 1CB moiety, which is represented by an ellipsoid, and the remaining flexible part which is represented by a chain of united atoms. The nonbonded potential between coarse-grained segments is represented by the generalized Gay-Berne (GB) potential and the potential parameters are determined by directly comparing the GB potential with the atomistic potentials averaged over the rotation of the mesogen around its axis. In addition, a dipole moment is placed at one end of the ellipsoid opposite to the flexible tail. The ordered state obtained in the polar 5CB model was assigned as the nematic phase, and the experimental static and dynamical properties were reproduced well by using this coarse-grained model. Both the dipole-dipole interactions and the thermal fluctuation of the flexible tail increase the positional disorder in the director direction, and stabilize the nematic phase. Thus, the nematic phase in the polar 5CB is induced by a cooperative effect of the flexible tail and the terminal dipole. It is noted that a local bilayer structure with head-to-head association is formed in the nematic phase, as experimentally observed by x-ray diffraction measurements.
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Affiliation(s)
- Hiroo Fukunaga
- Ashigara Research Laboratories, Fuji Photo Film Company, Limited, Kanagawa 250-0193, Japan.
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Qian HJ, Chen LJ, Lu ZY, Li ZS, Sun CC. The dependence of nanostructures on the molecule rigidity of A2(B4)2-type miktoarm block copolymer. J Chem Phys 2006; 124:14903. [PMID: 16409059 DOI: 10.1063/1.2145756] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using the dissipative particle dynamics simulation technique, we have studied the influence of the molecule rigidity on the nanostructures of the A2(B4)2-type miktoarm block copolymers. A typical spherical micellar ordered structure is obtained for a coil-coil miktoarm block copolymer in melt. By introducing a bond angle potential in our model to enhance the molecule rigidity systematically, we find, respectively, a hexagonal cylindrical structure and a parallel ellipsoid in lamellae structure which is discovered for the first time.
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Affiliation(s)
- Hu-Jun Qian
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, China
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Dewar A, Camp PJ. Dipolar interactions, molecular flexibility, and flexoelectricity in bent-core liquid crystals. J Chem Phys 2005; 123:174907. [PMID: 16375569 DOI: 10.1063/1.2062007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effects of dipolar interactions and molecular flexibility on the structure and phase behavior of bent-core molecular fluids are studied using Monte Carlo computer simulations. Some calculations of flexoelectric coefficients are also reported. The rigid cores of the model molecules consist of either five or seven soft spheres arranged in a "V" shape with external bend angle gamma. With purely repulsive sphere-sphere interactions and gamma = 0 degrees (linear molecules) the seven-sphere model exhibits isotropic, uniaxial nematic, and untilted and tilted smectic phases. With gamma > or = 20 degrees the untilted smectic phases disappear, while the system with gamma > or = 40 degrees shows a direct tilted smectic-isotropic fluid transition. The addition of electrostatic interactions between transverse dipole moments on the apical spheres is generally seen to reduce the degree of molecular inclination in tilted phases, and destabilizes the nematic and untilted smectic phases of linear molecules. The effects of adding three-segment flexible tails to the ends of five-sphere bent-core molecules are examined using configurational-bias Monte Carlo simulations. Only isotropic and smectic phases are observed. On the one hand, molecular flexibility gives rise to pronounced fluctuations in the smectic-layer structure, bringing the simulated system in better correspondence with real materials; on the other hand, the smectic phase shows almost no tilt. Lastly, the flexoelectric coefficients of various nematic phases--with and without attractive sphere-sphere interactions--are presented. The results are encouraging, but a large computational effort is required to evaluate the appropriate fluctuation relations reliably.
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Affiliation(s)
- Alastair Dewar
- School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, United Kingdom
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26
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Cinacchi G. Making the core of a mesogenic particle bulkier could enhance mesophase stability. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.08.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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27
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AlSunaidi A, Den Otter WK, Clarke JHR. Liquid-crystalline ordering in rod-coil diblock copolymers studied by mesoscale simulations. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2004; 362:1773-1781. [PMID: 15306447 DOI: 10.1098/rsta.2004.1414] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Using mesoscale dissipative particle dynamics (DPD) simulations, which ignore all atomistic details, we show the formation of lamella mesophases by cooling a fully disordered system composed of symmetric (A7B7) rod-coil diblock copolymers. Equilibration is achieved very rapidly using DPD, and isotropic, smectic A and crystalline phases of the rod-like blocks can be observed either by heating or cooling. An interesting pseudo-smectic phase can be characterized when the order-disorder transition temperature is above the clearing temperature. This phase gradually fades into a normal microphase-separated structure as the system is heated through the clearing temperature. Simulations of pure rods, however, show the formation of isotropic, nematic, smectic A and crystalline phases.
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Affiliation(s)
- A AlSunaidi
- Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia.
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García-Sánchez E, Martínez-Richa A, Villegas-Gasca JA, Mendoza-Huizar LH, Gil-Villegas A. Predicting the Phase Diagram of a Liquid Crystal Using the Convex Peg Model and the Semiempirical PM3 Method. J Phys Chem A 2002. [DOI: 10.1021/jp021453o] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Eduardo García-Sánchez
- Facultad de Química, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto., 36050, México, Instituto de Física, Universidad de Guanajuato, Lomas del Bosque 103, León, Gto., 37150, México, and Molecular Engineering Program, Instituto Mexicano del Petróleo, México
| | - Antonio Martínez-Richa
- Facultad de Química, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto., 36050, México, Instituto de Física, Universidad de Guanajuato, Lomas del Bosque 103, León, Gto., 37150, México, and Molecular Engineering Program, Instituto Mexicano del Petróleo, México
| | - José Antonio Villegas-Gasca
- Facultad de Química, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto., 36050, México, Instituto de Física, Universidad de Guanajuato, Lomas del Bosque 103, León, Gto., 37150, México, and Molecular Engineering Program, Instituto Mexicano del Petróleo, México
| | - Luis Humberto Mendoza-Huizar
- Facultad de Química, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto., 36050, México, Instituto de Física, Universidad de Guanajuato, Lomas del Bosque 103, León, Gto., 37150, México, and Molecular Engineering Program, Instituto Mexicano del Petróleo, México
| | - Alejandro Gil-Villegas
- Facultad de Química, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto., 36050, México, Instituto de Física, Universidad de Guanajuato, Lomas del Bosque 103, León, Gto., 37150, México, and Molecular Engineering Program, Instituto Mexicano del Petróleo, México
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DOMÍNGUEZ HECTOR, VELASCO ENRIQUE, ALEJANDRE JOSÉ. Stress anisotropy in liquid crystalline phases. Mol Phys 2002. [DOI: 10.1080/00268970210132513] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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EARL DAVIDJ, ILNYTSKYI JAROSLAV, WILSON MARKR. Computer simulations of soft repulsive spherocylinders. Mol Phys 2001. [DOI: 10.1080/00268970110069551] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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