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Oropesa WGC, Nascimento ES, Vieira AP. Mean-field model for a mixture of biaxial nematogens and dipolar nanoparticles. Phys Rev E 2024; 109:054701. [PMID: 38907419 DOI: 10.1103/physreve.109.054701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 03/27/2024] [Indexed: 06/24/2024]
Abstract
We analyze a mean-field model for mixtures involving biaxial nematogens and dipolar nanoparticles, taking into account not only orientational and isotropic pair interactions between nematogens but also orientational nematogen-nanoparticle interactions. We determine bulk equilibrium phase diagrams for a wide range of interaction strengths, identifying in each case the effect of the nanoparticles on the stability of nematic phases and on the appearance of multicritical points. Special attention is given to the limit of a low concentration of nanoparticles, in which their effect on the temperatures of both the first-order uniaxial-isotropic and the continuous biaxial-uniaxial transitions is investigated in detail.
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Affiliation(s)
- William G C Oropesa
- Universidade de São Paulo, Instituto de Fisica, Rua do Matao, 1371, 05508-090 São Paulo, SP, Brazil
- ICTP South American Institute for Fundamental Research, Instituto de Física Teórica, UNESP-Universidade Estadual Paulista, Rua Doutor Bento Teobaldo Ferraz 271, 01140-070 São Paulo, SP, Brazil
| | - Eduardo S Nascimento
- Departamento de Física, PUC-Rio, Rua Marquês de São Vicente 225, 22453-900 Rio de Janeiro, Rio de Janeiro, Brazil
| | - André P Vieira
- Universidade de São Paulo, Instituto de Fisica, Rua do Matao, 1371, 05508-090 São Paulo, SP, Brazil
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2
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de Oliveira E, Mirantsev L, Lyra M, de Oliveira I. Orientational ordering of active nematics confined to a 2D nanoscopic ring-shaped cavity. J Mol Liq 2023. [DOI: 10.1016/j.molliq.2023.121513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
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3
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de Araújo CB, de Oliveira EJL, Lyra ML, Mirantsev LV, de Oliveira IN. Formation of topological defects in nematic shells with a dumbbell-like shape. SOFT MATTER 2022; 18:4189-4196. [PMID: 35605981 DOI: 10.1039/d2sm00378c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The present study investigates dumbbell-shaped nematic liquid crystal shells. Using molecular dynamics (MD) simulations, we consider the effects of an external electric field on nematic ordering by computing the average molecular alignment's time evolution and equilibrium configuration. We show that the number and location of topological defects are strongly affected by the external field, with the orientational ordering's equilibrium configuration depending on field direction about the shell's long axis. For a transverse external field, it is verified that the defect rearrangement presents a non-linear dynamics, with a field independent characteristic time scale delimiting the short and long time regimes. Effects associated with varying the shell's Gaussian curvature are also analyzed.
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Affiliation(s)
- C B de Araújo
- Instituto de Física, Universidade Federal de Alagoas, Maceió, AL, Brazil.
| | - E J L de Oliveira
- Instituto de Física, Universidade Federal de Alagoas, Maceió, AL, Brazil.
| | - M L Lyra
- Instituto de Física, Universidade Federal de Alagoas, Maceió, AL, Brazil.
| | - L V Mirantsev
- Institute for Problems of Mechanical Engineering, Russian Academy of Sciences, St. Petersburg, Russia
| | - I N de Oliveira
- Instituto de Física, Universidade Federal de Alagoas, Maceió, AL, Brazil.
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4
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Mirantsev LV. Behavior of chiral active nematics confined to nanoscopic circular region. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:112. [PMID: 34476624 DOI: 10.1140/epje/s10189-021-00120-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 08/26/2021] [Indexed: 06/13/2023]
Abstract
We performed molecular dynamic simulations of a model active nematic confined to a two-dimensional nanoscopic circular region under both tangential and radial anchoring boundary conditions. This active material is assumed to be composed of elongated chiral particles which interact with each other by means of isotropic Lennard-Jones and anisotropic Maier-Saupe-like potentials. These particles have the lateral appendage emitting a jet of some substance generated by a certain internal chemical reaction. As a result, such elongated particles are exposed to both the reactive self-propelled force and the torque that provide an additional translational movement of particles and a self-rotation with respect to their geometric centers. It has been found that the chiral active nematics under consideration form time-dependent vortex-like structures with two +1/2 topological defects which are similar to experimentally observed structures in active materials.
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Affiliation(s)
- L V Mirantsev
- Institute for Problems of Mechanical Engineering, Russian Academy of Sciences, Bolshoi 61, V. O., St., Saint Petersburg, Russia, 199178.
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Mirantsev LV, Sonnet AM, Virga EG. Lifting ordered surfaces: Ellipsoidal nematic shells. Phys Rev E 2018; 98:012701. [PMID: 30110838 DOI: 10.1103/physreve.98.012701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Indexed: 11/07/2022]
Abstract
When a material surface is functionalized so as to acquire some type of order, functionalization of which soft condensed matter systems have recently provided many interesting examples, the modeler faces an alternative. Either the order is described on the curved, physical surface where it belongs, or it is described on a flat surface that is unrolled as preimage of the physical surface under a suitable height function. This paper applies a general method that pursues the latter avenue by lifting whatever order tensor is deemed appropriate from a flat to a curved surface. We specialize this method to nematic shells, for which it also provides a simple but perhaps convincing interpretation of the outcomes of some molecular dynamics experiments on ellipsoidal shells.
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Affiliation(s)
- Leonid V Mirantsev
- Institute of the Problems of Mechanical Engineering, Academy of Sciences of Russia, St. Petersburg 199178, Russia
| | - André M Sonnet
- Department of Mathematics and Statistics, University of Strathclyde, Livingstone Tower, 26 Richmond Street, Glasgow G1 1XH, Scotland, United Kingdom
| | - Epifanio G Virga
- Dipartimento di Matematica, Università di Pavia, Via Ferrata 5, 27100 Pavia, Italy
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Garbovskiy Y, Glushchenko A. Ferroelectric Nanoparticles in Liquid Crystals: Recent Progress and Current Challenges. NANOMATERIALS 2017; 7:nano7110361. [PMID: 29104276 PMCID: PMC5707578 DOI: 10.3390/nano7110361] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Revised: 10/24/2017] [Accepted: 10/24/2017] [Indexed: 12/21/2022]
Abstract
The dispersion of ferroelectric nanomaterials in liquid crystals has recently emerged as a promising way for the design of advanced and tunable electro-optical materials. The goal of this paper is a broad overview of the current technology, basic physical properties, and applications of ferroelectric nanoparticle/liquid crystal colloids. By compiling a great variety of experimental data and discussing it in the framework of existing theoretical models, both scientific and technological challenges of this rapidly developing field of liquid crystal nanoscience are identified. They can be broadly categorized into the following groups: (i) the control of the size, shape, and the ferroelectricity of nanoparticles; (ii) the production of a stable and aggregate-free dispersion of relatively small (~10 nm) ferroelectric nanoparticles in liquid crystals; (iii) the selection of liquid crystal materials the most suitable for the dispersion of nanoparticles; (iv) the choice of appropriate experimental procedures and control measurements to characterize liquid crystals doped with ferroelectric nanoparticles; and (v) the development and/or modification of theoretical and computational models to account for the complexity of the system under study. Possible ways to overcome the identified challenges along with future research directions are also discussed.
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Affiliation(s)
- Yuriy Garbovskiy
- UCCS Biofrontiers Center and Department of Physics, University of Colorado Colorado Springs, Colorado Springs, CO 80918, USA.
| | - Anatoliy Glushchenko
- Department of Physics, University of Colorado Colorado Springs, Colorado Springs, CO 80918, USA.
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Choi J, Chung H, Yun JH, Cho M. Molecular Dynamics Study on the Photothermal Actuation of a Glassy Photoresponsive Polymer Reinforced with Gold Nanoparticles with Size Effect. ACS APPLIED MATERIALS & INTERFACES 2016; 8:24008-24024. [PMID: 27552297 DOI: 10.1021/acsami.6b04818] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We investigated the optical and thermal actuation behavior of densely cross-linked photoresponsive polymer (PRP) and polymer nanocomposites containing gold nanoparticles (PRP/Au) using all-atom molecular dynamics (MD) simulations. The modeled molecular structures contain a large number of photoreactive mesogens with linear orientation. Flexible side chains are interconnected through covalent bonds under periodic boundary conditions. A switchable dihedral potential was applied on a diazene moiety to describe the photochemical trans-to-cis isomerization. To quantify the photoinduced molecular reorientation and its effect on the macroscopic actuation of the neat PRP and PRP/Au materials, we characterized the photostrain and other material properties including elastic stiffness and thermal stability according to the photoisomerization ratio of the reactive groups. We particularly examined the effect of nanoparticle size on the photothermal actuation by varying the diameter of the nanofiller (10-20 Å) under the same volume fraction of 1.62%. The results indicated that the insertion of the gold nanoparticles enlarges the photostrain of the material while enhancing its mechanical stiffness and thermal stability. When the diameter of the nanoparticle reaches a size similar to or smaller than the length of the mesogen, the interfacial energy between the nanofiller and the surrounding polymer matrix does not significantly affect the alignment of the mesogens, but rather the adsorption energy at the interface generates a stable interphase layer. Hence, these improvements were more effective as the size of the gold nanoparticle decreased. The present findings suggest a wider analysis of the nanofiller-reinforced PRP composites and could be a guide for the mechanical design of the PRP actuator system.
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Affiliation(s)
- Joonmyung Choi
- Division of Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University , San 56-1, Shillim-Dong, Kwanak-Ku, Seoul151-744, Korea
| | - Hayoung Chung
- Division of Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University , San 56-1, Shillim-Dong, Kwanak-Ku, Seoul151-744, Korea
| | - Jung-Hoon Yun
- Division of Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University , San 56-1, Shillim-Dong, Kwanak-Ku, Seoul151-744, Korea
| | - Maenghyo Cho
- Division of Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University , San 56-1, Shillim-Dong, Kwanak-Ku, Seoul151-744, Korea
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de Oliveira EJL, de Oliveira IN, Lyra ML, Mirantsev LV. Tunable topological valence in nematic shells on spherocylindrical colloidal particles. Phys Rev E 2016; 93:012703. [PMID: 26871131 DOI: 10.1103/physreve.93.012703] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Indexed: 06/05/2023]
Abstract
We perform molecular dynamics simulations of the orientational ordering on nematic shells delimited by spherocylindrical nanoscopic colloidal particles. We show that under conditions of degenerate planar anchoring, the equilibrium director field structure in these shells exhibits pairs of +1/2 topological defects at the poles of spherical cups in the absence of an external electric field. In addition, a certain number of pairs of ±1/2 defects occurs on the spherical cups far from the poles, thus resulting in a total of eight valence spots. A strong field applied along the main spherocylindrical axis removes the ±1/2 defect pairs while it coalesces the polar ones into a single +1 topological defect. A strong transverse field destroys all defects on the spherical cups but generates four +1/2 defects in the cylindrical part. Therefore, an external field can be used to control the number of valence centers in spherocylindrical nematic shells, thus unveiling their capability of acting as multivalent building blocks for nanophotonic devices.
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Affiliation(s)
- E J L de Oliveira
- Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió-Alagoas, Brazil
| | - I N de Oliveira
- Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió-Alagoas, Brazil
| | - M L Lyra
- Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió-Alagoas, Brazil
| | - L V Mirantsev
- Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió-Alagoas, Brazil
- Institute for Problems of Mechanical Engineering, Russian Academy of Sciences, St. Petersburg, Russia
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Podoliak N, Buchnev O, Herrington M, Mavrona E, Kaczmarek M, Kanaras AG, Stratakis E, Blach JF, Henninot JF, Warenghem M. Elastic constants, viscosity and response time in nematic liquid crystals doped with ferroelectric nanoparticles. RSC Adv 2014. [DOI: 10.1039/c4ra06248e] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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10
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Sigdel KP, Iannacchione GS. Calorimetric study of phase transitions in ocylcyanobiphenyl-barium titanate nanoparticle dispersions. J Chem Phys 2014; 139:204906. [PMID: 24289378 DOI: 10.1063/1.4830430] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
High-resolution ac-calorimetry is reported on the weakly first-order isotropic to nematic (I-N) and the continuous nematic to smectic-A (N-SmA) phase transitions in the liquid crystal octylcyanobiphenyl (8CB) doped with a ferroelectric nanoparticle barium titanate, BaTiO3 (BT). Measurements were performed as a function of BT concentration and over a wide temperature range well above and below the two transitions. From the thermal scans of all samples (having BT mass fraction φ(m) = 0.001 to 0.014 and pure 8CB), both the I-N and the N-SmA transitions evolve in character. Specifically, there appears an unusual change of the I-N specific heat peak shape on heating as φ(m) increases. Both the transitions shift to lower temperature at a different rate for φ(m)<φ(m)(c)=0.002 as compared to that for φ(m)>φ(m)(c). The effective transition enthalpies are essentially constant and similar to that seen in the bulk. Using a simple geometric model, the mean distance between the BT particles at the cross-over φ(m)(c) is found to be x(c)~3 μm, which is consistent with an estimated surface extrapolation length b for the nematic director. This suggests that the low φ(m) regime is dominated by an impurity/disorder effect while for φ(m)>φ(m)(c) the mean distance is small enough for the LC to mediate coupling between the BT ferroelectric nanoparticles.
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Affiliation(s)
- Krishna P Sigdel
- Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
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Salerno KM, Ismail AE, Lane JMD, Grest GS. Coating thickness and coverage effects on the forces between silica nanoparticles in water. J Chem Phys 2014; 140:194904. [DOI: 10.1063/1.4874638] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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Pal K, Maiti UN, Majumder TP, Debnath SC, Ghosh S, Roy SK, Otón JM. Switching of ferroelectric liquid crystal doped with cetyltrimethylammonium bromide-assisted CdS nanostructures. NANOTECHNOLOGY 2013; 24:125702. [PMID: 23459239 DOI: 10.1088/0957-4484/24/12/125702] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Large scale high yield cadmium sulfide (CdS) nanowires with uniform diameter were synthesized using a rapid and simple solvo-chemical and hydrothermal route assisted by the surfactant cetyltrimethylammonium bromide (CTAB). Unique CdS nanowires of different morphologies could be selectively produced by only varying the concentration of CTAB in the reaction system with cadmium acetate, sulfur powder and ethylenediamine. We obtained CdS nanowires with diameters of 64-65 nm and lengths of up to several micrometers. A comparative study of the optical properties of ferroelectric liquid crystal (FLC) Felix-017/100 doped with 1% of CdS nanowires was performed. Response times of the order of from 160 to 180 μs, rotational viscosities of the order of from 5000 to 3000 mN s m(-2) and polarizations of the order of from 10 to 70 nC cm(-2) were measured. We also observed an anti-ferroelectric to ferroelectric transition for CdS doped FLC instead of the ferroelectric to paraelectric transition for pure FLC.
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Affiliation(s)
- Kaushik Pal
- Department of Physics, University of Kalyani, Kalyani-741235, West Bengal, India
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Mirantsev LV, Sonnet AM, Virga EG. Geodesic defect anchoring on nematic shells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:020703. [PMID: 23005713 DOI: 10.1103/physreve.86.020703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Revised: 06/23/2012] [Indexed: 06/01/2023]
Abstract
Nematic shells are colloidal particles coated with nematic liquid crystal molecules, which may freely glide and rotate on the colloid's surface while keeping their long axis on the local tangent plane. Molecular dynamics simulations on a nanoscopic spherical shell indicate that under appropriate adhesion conditions for the molecules on the equator, the equilibrium nematic texture exhibits at each pole a pair of +1/2 defects so close to one another to be treated as one +1 defect. Spirals connect the polar defects, though the continuum limit of the interaction potential would not feature any elastic anisotropy. A molecular averaging justifies an anchoring defect energy that feels the geodesics emanating from the defect. All our observations are explained by such a geodesic anchoring, which vanishes on flat manifolds.
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Affiliation(s)
- Leonid V Mirantsev
- Institute of the Problems of Mechanical Engineering, Academy of Sciences of Russia, St Petersburg 199178, Russia
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Lopatina LM, Selinger JV. Maier-Saupe-type theory of ferroelectric nanoparticles in nematic liquid crystals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:041703. [PMID: 22181153 DOI: 10.1103/physreve.84.041703] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Indexed: 05/31/2023]
Abstract
Several experiments have reported that ferroelectric nanoparticles have drastic effects on nematic liquid crystals-increasing the isotropic-nematic transition temperature by about 5 K, and greatly increasing the sensitivity to applied electric fields. In a recent paper [Lopatina and Selinger, Phys. Rev. Lett. 102, 197802 (2009)], we modeled these effects through a Landau theory, based on coupled orientational order parameters for the liquid crystal and the nanoparticles. This model has one important limitation: Like all Landau theories, it involves an expansion of the free energy in powers of the order parameters, and hence it overestimates the order parameters that occur in the low-temperature phase. For that reason, we now develop a new Maier-Saupe-type model, which explicitly shows the low-temperature saturation of the order parameters. This model reduces to the Landau theory in the limit of high temperature or weak coupling, but shows different behavior in the opposite limit. We compare these calculations with experimental results on ferroelectric nanoparticles in liquid crystals.
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Affiliation(s)
- Lena M Lopatina
- Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
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Ghosh S, Nayek P, Roy SK, Gangopadhyay R, Rahaman Molla M, Majumder TP. Effect of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes on electro-optical and dielectric properties of a ferroelectric liquid crystal. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2011; 34:35. [PMID: 21476135 DOI: 10.1140/epje/i2011-11035-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 02/24/2011] [Indexed: 05/30/2023]
Abstract
A detailed comparative study of the dielectric and electro-optical properties of a ferroelectric liquid crystal (FLC) and FLC after having doped with conducting polymer Poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes is done. The electro-optic study reveals a lower electrical response time, rotational viscosity and spontaneous polarization in the FLC/PEDOT nanocomposite system. By fitting the capacitance with voltage in a Preisach model, four dipolar species in both FLC and composites system have been obtained. The orientation of the four dipolar species in the composites system is such that the effective dipole moment in the transverse direction of the FLC molecule is less than that in FLC compound.
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Affiliation(s)
- S Ghosh
- Department of Spectroscopy, Indian Association for the Cultivation of Science, Kolkata, India
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Stamatoiu O, Mirzaei J, Feng X, Hegmann T. Nanoparticles in liquid crystals and liquid crystalline nanoparticles. Top Curr Chem (Cham) 2011; 318:331-93. [PMID: 21928012 DOI: 10.1007/128_2011_233] [Citation(s) in RCA: 138] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Combinations of liquid crystals and materials with unique features as well as properties at the nanoscale are reviewed. Particular attention is paid to recent developments, i.e., since 2007, in areas ranging from liquid crystal-nanoparticle dispersions to nanomaterials forming liquid crystalline phases after surface modification with mesogenic or promesogenic moieties. Experimental and synthetic approaches are summarized, design strategies compared, and potential as well as existing applications discussed. Finally, a critical outlook into the future of this fascinating field of liquid crystal research is provided.
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Affiliation(s)
- Oana Stamatoiu
- Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada, R3T 2N2
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