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  1. Article ; Online: Effects of Filler Anisometry on the Mechanical Response of a Magnetoactive Elastomer Cell

    Timur A. Nadzharyan / Elena Yu. Kramarenko

    Polymers, Vol 16, Iss 1, p

    A Single-Inclusion Modeling Approach

    2023  Volume 118

    Abstract: A finite-element model of the mechanical response of a magnetoactive elastomer (MAE) volume element is presented. Unit cells containing a single ferromagnetic inclusion with geometric and magnetic anisotropy are considered. The equilibrium state of the ... ...

    Abstract A finite-element model of the mechanical response of a magnetoactive elastomer (MAE) volume element is presented. Unit cells containing a single ferromagnetic inclusion with geometric and magnetic anisotropy are considered. The equilibrium state of the cell is calculated using the finite-element method and cell energy minimization. The response of the cell to three different excitation modes is studied: inclusion rotation, inclusion translation, and uniaxial cell stress. The influence of the magnetic properties of the filler particles on the equilibrium state of the MAE cell is considered. The dependence of the mechanical response of the cell on the filler concentration and inclusion anisometry is calculated and analyzed. Optimal filler shapes for maximizing the magnetic response of the MAE are discussed.
    Keywords magnetoactive elastomers ; magnetorheological elastomers ; theoretical modeling ; ferromagnetic filler ; stiffening effect ; magnetorheological effect ; Organic chemistry ; QD241-441
    Subject code 621
    Language English
    Publishing date 2023-12-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Programming and Reprogramming the Viscoelasticity and Magnetic Response of Magnetoactive Thermoplastic Elastomers

    Sergei A. Kostrov / Josiah H. Marshall / Mitchell Maw / Sergei S. Sheiko / Elena Yu. Kramarenko

    Polymers, Vol 15, Iss 23, p

    2023  Volume 4607

    Abstract: We present a novel type of magnetorheological material that allows one to restructure the magnetic particles inside the finished composite, tuning in situ the viscoelasticity and magnetic response of the material in a wide range using temperature and an ... ...

    Abstract We present a novel type of magnetorheological material that allows one to restructure the magnetic particles inside the finished composite, tuning in situ the viscoelasticity and magnetic response of the material in a wide range using temperature and an applied magnetic field. The polymer medium is an A-g-B bottlebrush graft copolymer with side chains of two types: polydimethylsiloxane and polystyrene. At room temperature, the brush-like architecture provides the tissue mimetic softness and strain stiffening of the elastomeric matrix, which is formed through the aggregation of polystyrene side chains into aggregates that play the role of physical cross-links. The aggregates partially dissociate and the matrix softens at elevated temperatures, allowing for the effective rearrangement of magnetic particles by applying a magnetic field in the desired direction. Magnetoactive thermoplastic elastomers (MATEs) based on A-g-B bottlebrush graft copolymers with different amounts of aggregating side chains filled with different amounts of carbonyl iron microparticles were prepared. The in situ restructuring of magnetic particles in MATEs was shown to significantly alter their viscoelasticity and magnetic response. In particular, the induced anisotropy led to an order-of-magnitude enhancement of the magnetorheological properties of the composites.
    Keywords magnetoactive elastomer ; magnetorheological effect ; molecular bottlebrushes ; Organic chemistry ; QD241-441
    Subject code 530
    Language English
    Publishing date 2023-12-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Dielectric Spectroscopy of Hybrid Magnetoactive Elastomers

    Vitaliy G. Shevchenko / Gennady V. Stepanov / Elena Yu. Kramarenko

    Polymers, Vol 13, Iss 2002, p

    2021  Volume 2002

    Abstract: Dielectric properties of two series of magnetoactive elastomers (MAEs) based on a soft silicone matrix containing 35 vol% of magnetic particles were studied experimentally in a wide temperature range. In the first series, a hybrid filler representing a ... ...

    Abstract Dielectric properties of two series of magnetoactive elastomers (MAEs) based on a soft silicone matrix containing 35 vol% of magnetic particles were studied experimentally in a wide temperature range. In the first series, a hybrid filler representing a mixture of magnetically hard NdFeB particles of irregular shape and an average size of 50 μm and magnetically soft carbonyl iron (CI) of 4.5 μm in diameter was used for MAE fabrication. MAEs of the second series contained only NdFeB particles. The presence of magnetically hard NdFeB filler made it possible to passively control MAE dielectric response by magnetizing the samples. It was shown that although the hopping mechanism of MAEs conductivity did not change upon magnetization, a significant component of DC conductivity appeared in the magnetized MAEs presumably due to denser clustering of interacting particles resulting in decreasing interparticle distances. The transition from a non-conducting to a conducting state was more pronounced for hybrid MAEs containing both NdFeB and Fe particles with a tenfold size mismatch. Hybrid MAEs also demonstrated a considerable increase in the real part of the complex relative permittivity upon magnetization and its asymmetric behavior in external magnetic fields of various directions. The effects of magnetic filler composition and magnetization field on the dielectric properties of MAEs are important for practical applications of MAEs as elements with a tunable dielectric response.
    Keywords magnetoactive elastomers ; magnetic elastomers ; magnetically hard particles ; magnetodielectric effect ; dielectric constant ; Organic chemistry ; QD241-441
    Subject code 541
    Language English
    Publishing date 2021-06-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Adsorption of Silicon-Containing Dendrimers

    Andrey O. Kurbatov / Nikolay K. Balabaev / Mikhail A. Mazo / Elena Yu. Kramarenko

    Polymers, Vol 13, Iss 4, p

    Effects of Chemical Composition, Structure, and Generation Number

    2021  Volume 552

    Abstract: We studied the conformational behavior of silicon-containing dendrimers during their adsorption onto a flat impenetrable surface by molecular dynamics (MD) simulations. Four homologous series of dendrimers from the 4th up to the 7th generations were ... ...

    Abstract We studied the conformational behavior of silicon-containing dendrimers during their adsorption onto a flat impenetrable surface by molecular dynamics (MD) simulations. Four homologous series of dendrimers from the 4th up to the 7th generations were modeled, namely, two types of carbosilane dendrimers differing by the functionality of the core Si atom and two types of siloxane dendrimers with different lengths of the spacers. Comparative analysis of the fractions of adsorbed atoms belonging to various structural layers within dendrimers as well as density profiles allowed us to elucidate not only some general trends but also the effects determined by dendrimer specificity. In particular, it was found that in contrast to the carbosilane dendrimers interacting with the adsorbing surface mainly by their peripheral layers, the siloxane dendrimers with the longer –O–Si(CH 3 ) 2 –O spacers expose atoms from their interior to the surface spreading out on it. These findings are important for the design of functional materials on the basis of silicon-containing dendrimers.
    Keywords dendrimer ; polybutylcarbosilane dendrimer ; siloxane dendrimer ; adsorption ; molecular dynamics ; Organic chemistry ; QD241-441
    Subject code 500
    Language English
    Publishing date 2021-02-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Magnetodielectric Response of Soft Magnetoactive Elastomers

    Sergei A. Kostrov / Mikhail Shamonin / Gennady V. Stepanov / Elena Yu. Kramarenko

    International Journal of Molecular Sciences, Vol 20, Iss 9, p

    Effects of Filler Concentration and Measurement Frequency

    2019  Volume 2230

    Abstract: The magnetodielectric response of magnetoactive elastomers (MAEs) in its dependence on filler concentration, magnetic field, and test frequency is studied experimentally. MAEs are synthesized on the basis of a silicone matrix filled with spherical ... ...

    Abstract The magnetodielectric response of magnetoactive elastomers (MAEs) in its dependence on filler concentration, magnetic field, and test frequency is studied experimentally. MAEs are synthesized on the basis of a silicone matrix filled with spherical carbonyl iron particles characterized by a mean diameter of 4.5 µm. The concentration of the magnetic filler within composite materials is equal to 70, 75, and 80 mass%. The effective lossless permittivity ε′ as well as the dielectric loss tanδ grow significantly when the magnetic field increases. The permittivity increases and the dielectric loss decreases with increasing filler concentration. In the measurement frequency range between 1 kHz and 200 kHz, the frequency hardly affects the values of ε′ and tanδ in the absence of a magnetic field. However, both parameters decrease considerably with the growing frequency in a constant magnetic field. The more strongly the magnetic field is applied, the larger the change in permittivity and loss tangent at the same test frequency is observed. An equivalent circuit formulation qualitatively describes the main tendencies of the magnetodielectric response.
    Keywords magnetoactive elastomers ; magnetodielectric effect ; permittivity ; dielectric loss ; magnetic filler ; Biology (General) ; QH301-705.5 ; Chemistry ; QD1-999
    Subject code 621
    Language English
    Publishing date 2019-05-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: A Comparative Study of Intramolecular Mobility of Single Siloxane and Carbosilane Dendrimers via Molecular Dynamics Simulations

    Andrey O. Kurbatov / Nikolay K. Balabaev / Mikhail A. Mazo / Elena Yu. Kramarenko

    Polymers, Vol 10, Iss 8, p

    2018  Volume 838

    Abstract: A comparative analysis of intramolecular dynamics of four types of isolated dendrimers from the fourth to the seventh generations belonging to the siloxane and carbosilane families, differing in spacer length, core functionality, and the type of chemical ...

    Abstract A comparative analysis of intramolecular dynamics of four types of isolated dendrimers from the fourth to the seventh generations belonging to the siloxane and carbosilane families, differing in spacer length, core functionality, and the type of chemical bonds, has been performed via atomic molecular dynamics simulations. The average radial and angular positions of all Si branching atoms of various topological layers within the dendrimer interior, as well as their variations, have been calculated, and the distributions of the relaxation times of their radial and angular motions have been found. It has been shown that the dendrons of all the dendrimers elongate from the center and decrease in a solid angle with an increasing generation number. The characteristic relaxation times of both angular and radial motions of Si atoms are of the order of a few nanoseconds, and they increase with an increasing generation number and decrease with temperature, with the angular relaxation times being larger than the radial ones. The relaxation times in the carbosilanes are larger than those in the siloxanes. The rotational angle dynamics of the carbosilane dendrimers show that the chain bending is mainly realized via trans-gauche transitions in the Si branching bonds.
    Keywords dendrimers ; siloxane dendrimers ; carbosilane dendrimers ; molecular dynamics simulations ; intramolecular dynamics ; Organic chemistry ; QD241-441
    Subject code 541
    Language English
    Publishing date 2018-07-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article: Microphase Separation in Complex Coacervate Due to Incompatibility between Polyanion and Polycation

    Rumyantsev, Artem M / Elena Yu. Kramarenko / Oleg V. Borisov

    Macromolecules. 2018 Aug. 20, v. 51, no. 17

    2018  

    Abstract: The instability of a homogeneous complex coacervate phase induced by incompatibility of oppositely charged polyelectrolytes is studied by means of the random phase approximation (RPA) and the scaling approach. It is found that in a poor solvent for both ... ...

    Abstract The instability of a homogeneous complex coacervate phase induced by incompatibility of oppositely charged polyelectrolytes is studied by means of the random phase approximation (RPA) and the scaling approach. It is found that in a poor solvent for both polyions their short-range mutual repulsions may result in the formation of a microphase separated structure at low salt concentrations cs. At high cs, a decomposition of the homogeneous coacervate into two macroscopic globular phases enriched either with polyanions or with polycations takes place. Both the RPA and scaling estimations predict the period of the microphase separated structure on the order of a few nanometers in the vicinity of the spinodal. The binodal of macroscopic phase separation of the coacervate and the spinodal with respect to the microphase separation are calculated, and the phase diagram of the coacervate is constructed in terms of salt concentration and incompatibility of polyions. The possibility of experimental observation of a microsegregated coacervate is discussed.
    Keywords anions ; cations ; physical phases ; salt concentration ; separation ; solvents
    Language English
    Dates of publication 2018-0820
    Size p. 6587-6601.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 1491942-4
    ISSN 1520-5835 ; 0024-9297
    ISSN (online) 1520-5835
    ISSN 0024-9297
    DOI 10.1021/acs.macromol.8b00721
    Database NAL-Catalogue (AGRICOLA)

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  8. Article ; Online: Hybrid Polycarbosilane-Siloxane Dendrimers

    Sergey A. Milenin / Elizaveta V. Selezneva / Pavel A. Tikhonov / Viktor G. Vasil’ev / Alexander I. Buzin / Nikolay K. Balabaev / Andrey O. Kurbatov / Maxim V. Petoukhov / Eleonora V. Shtykova / Lev A. Feigin / Elena A. Tatarinova / Elena Yu. Kramarenko / Sergey N. Chvalun / Aziz M. Muzafarov

    Polymers, Vol 13, Iss 4, p

    Synthesis and Properties

    2021  Volume 606

    Abstract: A series of carbosilane dendrimers of the 4th, 6th, and 7th generations with a terminal trimethylsilylsiloxane layer was synthesized. Theoretical models of these dendrimers were developed, and equilibrium dendrimer conformations obtained via molecular ... ...

    Abstract A series of carbosilane dendrimers of the 4th, 6th, and 7th generations with a terminal trimethylsilylsiloxane layer was synthesized. Theoretical models of these dendrimers were developed, and equilibrium dendrimer conformations obtained via molecular dynamics simulations were in a good agreement with experimental small-angle X-ray scattering (SAXS) data demonstrating molecule monodispersity and an almost spherical shape. It was confirmed that the glass transition temperature is independent of the dendrimer generation, but is greatly affected by the chemical nature of the dendrimer terminal groups. A sharp increase in the zero-shear viscosity of dendrimer melts was found between the 5th and the 7th dendrimer generations, which was qualitatively identical to that previously reported for polycarbosilane dendrimers with butyl terminal groups. The viscoelastic properties of high-generation dendrimers seem to follow some general trends with an increase in the generation number, which are determined by the regular branching structure of dendrimers.
    Keywords dendrimers ; synthesis of dendrimers ; synthesis of hybrid carbosilane-siloxane structures ; thermal properties ; Organic chemistry ; QD241-441
    Subject code 500
    Language English
    Publishing date 2021-02-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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