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Wei X, Junot G, Golestanian R, Zhou X, Wang Y, Tierno P, Meng F. Molecular dynamics simulations of microscopic structural transition and macroscopic mechanical properties of magnetic gels. J Chem Phys 2024; 161:074902. [PMID: 39145560 DOI: 10.1063/5.0210769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Accepted: 07/25/2024] [Indexed: 08/16/2024] Open
Abstract
Magnetic gels with embedded micro-/nano-sized magnetic particles in cross-linked polymer networks can be actuated by external magnetic fields, with changes in their internal microscopic structures and macroscopic mechanical properties. We investigate the responses of such magnetic gels to an external magnetic field, by means of coarse-grained molecular dynamics simulations. We find that the dynamics of magnetic particles are determined by the interplay of magnetic dipole-dipole interactions, polymer elasticity, and thermal fluctuations. The corresponding microscopic structures formed by the magnetic particles, such as elongated chains, can be controlled by the external magnetic field. Furthermore, the magnetic gels can exhibit reinforced macroscopic mechanical properties, where the elastic modulus increases algebraically with the magnetic moments of the particles in the form of ∝(m-mc)2 when magnetic chains are formed. This simulation work can not only serve as a tool for studying the microscopic and the macroscopic responses of the magnetic gels, but also facilitate future fabrications and practical controls of magnetic composites with desired physical properties.
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Affiliation(s)
- Xuefeng Wei
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325000, China
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China
| | - Gaspard Junot
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Ramin Golestanian
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), D-37077 Göttingen, Germany
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Xin Zhou
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325000, China
- School of Physical Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China
| | - Yanting Wang
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325000, China
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China
| | - Pietro Tierno
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain
- Universitat de Barcelona Institute of Complex Systems, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Fanlong Meng
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325000, China
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China
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Weeber R, Kreissl P, Holm C. Magnetic field controlled behavior of magnetic gels studied using particle-based simulations. PHYSICAL SCIENCES REVIEWS 2021. [DOI: 10.1515/psr-2019-0106] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Abstract
This contribution provides an overview of the study of soft magnetic materials using particle-based simulation models. We focus in particular on systems where thermal fluctuations are important. As a basis for further discussion, we first describe two-dimensional models which demonstrate two deformation mechanisms of magnetic gels in a homogeneous field. One is based on the change of magnetic interactions between magnetic particles as a response to an external field; the other is the result of magnetically blocked particles acting as cross-linkers. Based on the qualitative behavior directly observable in the two-dimensional models, we extend our description to three-dimensions. We begin with particle-cross-linked gels, as for those, our three-dimensional model also includes explicitly resolved polymer chains. Here, the polymer chains are represented by entropic springs, and the deformation of the gel is the result of the interaction between magnetic particles. We use this model to examine the influence of the magnetic spatial configuration of magnetic particles (uniaxial or isotropic) on the gel’s magnetomechanical behavior. A further part of the article will be dedicated to scale-bridging approaches such as systematic coarse-graining and models located at the boundary between particle-based and continuum modeling. We will conclude our article with a discussion of recent results for modeling time-dependent phenomena in magnetic-polymer composites. The discussion will be focused on a simulation model suitable for obtaining AC-susceptibility spectra for dilute ferrofluids including hydrodynamic interactions. This model will be the basis for studying the signature of particle–polymer coupling in magnetic hybrid materials. In the long run, we aim to compare material properties probed locally via the AC-susceptibility spectra to elastic moduli obtained for the system at a global level.
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Affiliation(s)
- Rudolf Weeber
- Institute for Computational Physics, University of Stuttgart , Stuttgart , Germany
| | - Patrick Kreissl
- Institute for Computational Physics, University of Stuttgart , Stuttgart , Germany
| | - Christian Holm
- Institute for Computational Physics, University of Stuttgart , Stuttgart , Germany
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Massana-Cid H, Martinez-Pedrero F, Cebers A, Tierno P. Orientational dynamics of fluctuating dipolar particles assembled in a mesoscopic colloidal ribbon. Phys Rev E 2017; 96:012607. [PMID: 29347116 DOI: 10.1103/physreve.96.012607] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Indexed: 06/07/2023]
Abstract
We combine experiments and theory to investigate the dynamics and orientational fluctuations of ferromagnetic microellipsoids that form a ribbonlike structure due to attractive dipolar forces. When assembled in the ribbon, the ellipsoids display orientational thermal fluctuations with an amplitude that can be controlled via application of an in-plane magnetic field. We use video microscopy to investigate the orientational dynamics in real time and space. Theoretical arguments are used to derive an analytical expression that describes how the distribution of the different angular configurations depends on the strength of the applied field. The experimental data are in good agreement with the developed model for all the range of field parameters explored. Understanding the role of fluctuations in chains composed of dipolar particles is important not only from a fundamental point of view, but it may also help understanding the stability of such structures against thermal noise, which is relevant in microfluidics and laboratory-on-a-chip applications.
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Affiliation(s)
- Helena Massana-Cid
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Fernando Martinez-Pedrero
- Departamento de Química Física I, Universidad Complutense de Madrid, Ciudad Universitaria, 28040, Madrid, Spain
| | - Andrejs Cebers
- Faculty of Physics and Mathematics, University of Latvia, Zellu 23, LV-1002
| | - Pietro Tierno
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain
- Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, IN2 UB, Universitat de Barcelona, 08028 Barcelona, Spain
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Huang S, Pessot G, Cremer P, Weeber R, Holm C, Nowak J, Odenbach S, Menzel AM, Auernhammer GK. Buckling of paramagnetic chains in soft gels. SOFT MATTER 2016; 12:228-37. [PMID: 26463270 DOI: 10.1039/c5sm01814e] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We study the magneto-elastic coupling behavior of paramagnetic chains in soft polymer gels exposed to external magnetic fields. To this end, a laser scanning confocal microscope is used to observe the morphology of the paramagnetic chains together with the deformation field of the surrounding gel network. The paramagnetic chains in soft polymer gels show rich morphological shape changes under oblique magnetic fields, in particular a pronounced buckling deformation. The details of the resulting morphological shapes depend on the length of the chain, the strength of the external magnetic field, and the modulus of the gel. Based on the observation that the magnetic chains are strongly coupled to the surrounding polymer network, a simplified model is developed to describe their buckling behavior. A coarse-grained molecular dynamics simulation model featuring an increased matrix stiffness on the surfaces of the particles leads to morphologies in agreement with the experimentally observed buckling effects.
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Affiliation(s)
- Shilin Huang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Giorgio Pessot
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Peet Cremer
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Rudolf Weeber
- Institute for Computational Physics, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Christian Holm
- Institute for Computational Physics, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Johannes Nowak
- Chair of Magnetofluiddynamics, Measuring and Automation Technology, Institute of Fluid Mechanics, Technische Universität Dresden, 01069 Dresden, Germany
| | - Stefan Odenbach
- Chair of Magnetofluiddynamics, Measuring and Automation Technology, Institute of Fluid Mechanics, Technische Universität Dresden, 01069 Dresden, Germany
| | - Andreas M Menzel
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Günter K Auernhammer
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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Cremer P, Löwen H, Menzel AM. Superelastic stress–strain behavior in ferrogels with different types of magneto-elastic coupling. Phys Chem Chem Phys 2016; 18:26670-26690. [DOI: 10.1039/c6cp05079d] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Anisotropic ferrogels and magnetorheological elastomers allow for reversible tunability of their markedly nonlinear stress–strain properties.
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Affiliation(s)
- Peet Cremer
- Institut für Theoretische Physik II, Weiche Materie
- Heinrich-Heine-Universität Düsseldorf
- 40225 Düsseldorf
- Germany
| | - Hartmut Löwen
- Institut für Theoretische Physik II, Weiche Materie
- Heinrich-Heine-Universität Düsseldorf
- 40225 Düsseldorf
- Germany
| | - Andreas M. Menzel
- Institut für Theoretische Physik II, Weiche Materie
- Heinrich-Heine-Universität Düsseldorf
- 40225 Düsseldorf
- Germany
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Sánchez-Ferrer A, Rogez D, Martinoty P. Influence of the degree of polymerisation and of the architecture on the elastic properties of new polyurea elastomers. RSC Adv 2015. [DOI: 10.1039/c4ra09879j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The elastic properties of new polyurea elastomers have been studied by varying the segmental molecular weight and the chemical nature of the polymer end groups showing up to two plateaus.
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Affiliation(s)
- Antoni Sánchez-Ferrer
- Institute of Supramolecular Science and Engineering
- University Louis Pasteur
- Strasbourg
- France
| | - Daniel Rogez
- Institute Charles Sadron
- UPR 22 CNRS
- Strasbourg Cedex
- France
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Rogez D, Brömmel F, Finkelmann H, Martinoty P. Influence of Swelling on the Shear Mechanical Properties of Monodomain Side-Chain Liquid-Crystal Elastomers: Gaussian Versus Non-Gaussian Elasticity. MACROMOL CHEM PHYS 2011. [DOI: 10.1002/macp.201100426] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Rogez D, Martinoty P. Mechanical properties of monodomain nematic side-chain liquid-crystalline elastomers with homeotropic and in-plane orientation of the director. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2011; 34:69. [PMID: 21755436 DOI: 10.1140/epje/i2011-11069-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 04/02/2011] [Accepted: 06/22/2011] [Indexed: 05/31/2023]
Abstract
We present the first study of the shear mechanical properties of monodomain nematic side-chain liquid-crystal elastomers (SCLCEs) prepared by cross-linking with UV irradiation a nematic side-chain liquid-crystal polymer oriented with an electric or a magnetic field. Their elastic behavior was studied in the dry, swollen and stretched states, in order to check the various theoretical descriptions of these systems. The shear measurements taken on the dry samples show that the shear anisotropy is much smaller than that of the usual twice cross-linked samples oriented by a mechanical stretching of the network formed after the first cross-linking step, demonstrating that the elasticity of the networks strongly depends on the preparation procedure used. The shear experiments performed on the swollen state of these two different types of elastomers reveal that the elasticity of the network is Gaussian for the elastomers oriented with the electric or the magnetic field, and non-Gaussian for the elastomers oriented with the usual stretching procedure. The analysis of the stress-strain curves of both types of elastomers with the neoclassical model based on Gaussian rubber elasticity confirms the Gaussian and non-Gaussian nature of their elasticity. The shear experiments performed as a function of the elongation of the homeotropically oriented elastomer when the shear is applied in a direction parallel to the elongation, do not show the decrease of the associated shear modulus, which is theoretically expected when the strain approaches the threshold value marking the beginning of the elastic plateau. However, the observation of this effect could be prevented by possible small misalignments of the director, as suggested by a calculation presented in one of the theories describing this effect.
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Affiliation(s)
- D Rogez
- UPR 22, CNRS/UDS, Institut Charles Sadron, 23 rue du Loess, 67034 Strasbourg, France
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Kretzschmar I, Song JH(K. Surface-anisotropic spherical colloids in geometric and field confinement. Curr Opin Colloid Interface Sci 2011. [DOI: 10.1016/j.cocis.2011.01.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Roth M, D’Acunzi M, Vollmer D, Auernhammer GK. Viscoelastic rheology of colloid-liquid crystal composites. J Chem Phys 2010; 132:124702. [DOI: 10.1063/1.3358331] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Pozo O, Collin D, Finkelmann H, Rogez D, Martinoty P. Gel-like elasticity in glass-forming side-chain liquid-crystal polymers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:031801. [PMID: 19905137 DOI: 10.1103/physreve.80.031801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Indexed: 05/28/2023]
Abstract
We study the complex shear modulus G of two side-chain liquid-crystal polymers (SCLCPs), a methoxy-phenylbenzoate substituted polyacrylate (thereafter called PAOCH3 ), and a cyanobiphenyl substituted polyacrylate supplied by Merck (thereafter called LCP105) using a piezoelectric rheometer. Two methods of filling the cell are used: (a) a capillary method, which can be used only at high temperature because of the low value of the viscosity, and (b) the classical one, thereafter called compression method, which consists in placing the sample between the two slides of the cell and to bring them closer. By filling the cell at high temperature either with the compression or the capillary method, we show that the response of both compounds is liquidlike ( G' approximately f2 and G'' approximately f , where f is the frequency) for temperatures higher than a certain temperature T0 and gel-like (G' approximately const, G'' approximately f) below T0. This change in behavior from the conventional flow response to a gel-like response, when approaching the glass transition, is observed for nonsliding conditions and for very weak-imposed shear strains. It can be explained by a percolation-type mechanism of preglassy elastic clusters, which correspond to long-range and long-lived density fluctuations that are frozen at the time scale of the experiment. The sample response is therefore the sum of two contributions: one is due to the flow response of the polymer melt and the other to the elastic response of the network formed by the preglassy elastic clusters. By filling the cell below T0 with the compression method, both compounds exhibit a gel-type behavior by gently bringing closer the slides of the cell and an anomalous low-frequency behavior characterized by G'=const and G''=const by increasing the pressure used to bring closer the slides of the cell. A compression-assisted aggregation of the preglassy elastic clusters can explain both the increase in the low-frequency elastic plateau when the sample thickness is decreased and the anomalous low-frequency behavior. Further evidence for the existence of these elastic clusters is provided by the following results: (a) the nonlinear response of the samples as a function of the strain amplitude, which can be explained by the Payne effect, and (b) the aggregation effects, which can be mimicked by a polydimethylsiloxane melt filled with silica particles, the silica particles playing the role of the preglassy elastic clusters. All these observations show that PAOCH3 is not a macroscopically solidlike material with an unconventional type of elasticity, as claimed by Mendil [Phys. Rev. Lett. 96, 077801 (2006)]. The gel-type behavior observed here on two SCLCPs ( PAOCH3 and LCP105) and previously on some conventional flexible polymers (atactic polystyrene, poly-n-butylacrylate) seems to be a generic effect of the glass transition. The presence of the preglassy elastic clusters questions the widely accepted hypothesis of ergodicity in the supercooled state.
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Affiliation(s)
- O Pozo
- Institut Charles Sadron, UPR 22, 67034 Strasbourg Cedex 2, France
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Monz S, Tschöpe A, Birringer R. Magnetic properties of isotropic and anisotropic CoFe2O4-based ferrogels and their application as torsional and rotational actuators. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:021404. [PMID: 18850833 DOI: 10.1103/physreve.78.021404] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Indexed: 05/26/2023]
Abstract
CoFe2O4-based ferrogels were prepared with both isotropic and anisotropic orientation of the magnetic anisotropy axis of the magnetic particles. In contrast to the superparamagnetic properties of the ferrofluid, the ferrogels exhibit hysteresis, indicating that (i) a significant fraction of magnetic particles has volumes beyond the critical value that allows Néelian relaxation, and (ii) a mechanical interaction between the particles and the polymer network exists, which prevents the particles from Brownian relaxation. The contribution of such particles was investigated by field cooling field warming and zero field cooling field warming measurements as well as temperature-dependent magnetization measurements. By application of an external field during gel polymerization, a magnetic texture was induced as confirmed by the angular dependence of mRmS and HC . The net-magnetic torque, exerted on the magnetic particles in an anisotropic ferrogel in combination with the soft elastic properties of the gel matrix enables the application as torsional soft actuator as demonstrated.
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Affiliation(s)
- S Monz
- FR 7.3 Technische Physik, Geb. D2 2, Universität des Saarlandes, 66041 Saarbrücken, Germany.
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Maus A, Saalwächter K. Crystallization Kinetics of Poly(dimethylsiloxane) Molecular-Weight Blends—Correlation with Local Chain Order in the Melt? MACROMOL CHEM PHYS 2007. [DOI: 10.1002/macp.200700051] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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