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Fatikhova AV, Sergeev AV, Rudyak VY, Kozhunova EY, Chertovich AV. Charge Transfer Kinetics of Redox-Active Microgels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:1840-1847. [PMID: 38197726 DOI: 10.1021/acs.langmuir.3c03187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Polymer microgel particles decorated with redox-active functional groups are a new and promising object for electrochemical applications. However, the process of charge exchange between an electrode and a microgel particle carrying numerous redox-active centers differs fundamentally from charge exchange involving only molecular species. A single act of contact between the microgel and the electrode surface may not be enough to fully discharge the microgel, and partial charge states are to be expected. Understanding the specifics of this process is crucial for the correct analysis of the data obtained from electrochemical experiments with redox-active microgel solutions. In this study, we employed coarse-grained molecular dynamics to investigate in detail the act of charge transfer from a microgel particle to a flat electrode. The simulations take into account both the mobility of functional groups carrying the charge, which depend on the microgel architecture and the charge exchange between the groups, which can accelerate the propagation of charge within the microgel volume. A set of different microgel systems were simulated in order to reveal the impact of their characteristics: fraction of redox-active groups, microgel molecular mass, cross-linker content, cross-linking topology, and solvent quality. We have found trends in microgel composition leading to the most efficient charge transfer kinetics. The obtained results would be useful for understanding experimental results and for optimizing the design of redox-active microgel particles aimed at faster discharge rates.
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Affiliation(s)
- Amina V Fatikhova
- Lomonosov Moscow State University, Faculty of Physics, Moscow 119991, Russia
| | - Artem V Sergeev
- Lomonosov Moscow State University, Faculty of Physics, Moscow 119991, Russia
- Federal Research Center for Chemical Physics, Moscow 119991, Russia
| | - Vladimir Yu Rudyak
- Lomonosov Moscow State University, Faculty of Physics, Moscow 119991, Russia
| | - Elena Yu Kozhunova
- Lomonosov Moscow State University, Faculty of Physics, Moscow 119991, Russia
| | - Alexander V Chertovich
- Lomonosov Moscow State University, Faculty of Physics, Moscow 119991, Russia
- Federal Research Center for Chemical Physics, Moscow 119991, Russia
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Sergeev AV, Rudyak VY, Kozhunova EY, Chertovich AV, Khokhlov AR. Theoretical Study of Microgel Functional Groups' Mobility. J Phys Chem B 2023; 127:11083-11090. [PMID: 38095423 DOI: 10.1021/acs.jpcb.3c06599] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
Polymer microgels, micrometer-sized cross-linked polymer particles, are considered to be a promising type of advanced materials for a wide range of applications. To enhance the microgels' applicability, it is essential to incorporate various functional groups into a microparticle polymer network. Yet, the availability of functional groups for the interaction with surroundings depends strongly on the properties of the polymer network and has a great impact on further effective usage. In this theoretical study, we address this question and, with the help of coarse-grained molecular dynamics computer simulations, assess the segmental mobility and accessibility of functional groups bound to polymer network depending on microgel architecture and solvent quality. Additionally, we evaluate the minimum number of functional groups needed to facilitate the hopping mechanism between the functional groups (i.e., charge transfer). As an example of practical implementation of the obtained results, we estimate the optimal network topology for redox-active microgels to provide the maximum charge capacity for the dispersion electrolyte in redox-flow batteries.
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Affiliation(s)
- A V Sergeev
- Semenov Federal Research Center for Chemical Physics, Moscow 119991, Russia
- Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
| | - V Yu Rudyak
- Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
| | - E Yu Kozhunova
- Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
| | - A V Chertovich
- Semenov Federal Research Center for Chemical Physics, Moscow 119991, Russia
- Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
| | - A R Khokhlov
- Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
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Strauch C, Schneider S. Ionisation and swelling behaviour of weak polyampholyte core-shell networks - a Monte Carlo study. SOFT MATTER 2023; 19:938-950. [PMID: 36632835 DOI: 10.1039/d2sm01301k] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The network charge of polyampholyte microgels can be tuned by varying the pH of the surrounding solution, and a charge reversal from a positively charged microgel at low pH to a negatively charged microgel at high pH can be achieved. In a titration experiment, it is difficult to tell apart the ionisation of the acidic and basic monomers in the network and to determine the distribution of charges in the network, whereas using Metropolis Monte Carlo simulations, both the degree of ionisation and the distribution of ionised monomers can be determined separately for both species. Building on our earlier work on alternating polyampholyte microgels, we now investigated the pH-dependent ionisation and the swelling behaviour of polyampholyte core-shell microgels under good solvent conditions. For this purpose, we performed Metropolis Monte Carlo simulations for a bead-spring model using the constant-pH method. As in our previous study on alternating microgels, the width of the U-shaped curve of the microgels volume as a function of pH depends on the relative dissociation constants of acid and base, and the microgel volume can be approximated by a linear function of the total network charge. Due to the spatial separation of acid and base in core-shell systems, the ionisation is less enhanced compared to a microgel with an alternating distribution of the two species. Nevertheless, we still see an influence of the presence of one species on the ionisation behaviour of the other species under good solvent conditions. Furthermore, the isoelectric point is shifted towards higher pH, which is caused by a higher charge density in the core compared to that in the shell. Added salt changes the Donnan equilibrium, which determines the counterion distribution within and outside of the microgel. At the same time, it contributes to the electrostatic screening of the network charges, leading to a narrowing of the U-shaped volume transition curve.
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Affiliation(s)
- Christian Strauch
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52056 Aachen, Germany.
| | - Stefanie Schneider
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52056 Aachen, Germany.
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Gumerov RA, Rudyak VY, Gavrilov AA, Chertovich AV, Potemkin II. Effect of network topology and crosslinker reactivity on microgel structure and ordering at liquid-liquid interface. SOFT MATTER 2022; 18:3738-3747. [PMID: 35506715 DOI: 10.1039/d2sm00269h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Polymer microgels synthesized in silico were studied at a liquid-liquid interface via mesoscopic computer simulations and compared to microgels with ideal (diamond-like) structure. The effect of crosslinkers reactivity ratio on the single particle morphology at the interface and monolayer behavior was examined. It was demonstrated that single particles deform into an explicit core-corona morphology when adsorbed at the interface. An increase in the crosslinker reactivity ratio decreased both the deformation ratio and the ratio between the core and corona sizes. Meanwhile, the compression of microgel monolayers revealed the existence of five distinct interparticle contact regimes, which have been observed experimentally in the literature. The crosslinker reactivity ratio appeared to define the compression range in these regimes and the sharpness of the transition between them. In particular, the higher the crosslinker reactivity ratio, the smaller the corona, and in turn, the narrower the range of the intermediate regime comprising both core-core and corona-corona contacts. The obtained results demonstrate that the more realistic model of microgels synthesized via precipitation polymerization allows for a more accurate prediction of the properties of the microgels at a liquid-liquid interface in comparison to the conventional diamond-like lattice model.
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Affiliation(s)
- Rustam A Gumerov
- Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991, Russian Federation.
| | - Vladimir Yu Rudyak
- Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991, Russian Federation.
| | - Alexey A Gavrilov
- Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991, Russian Federation.
| | - Alexander V Chertovich
- Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991, Russian Federation.
- Semenov Federal Research Center for Chemical Physics, 119991 Moscow, Russian Federation
| | - Igor I Potemkin
- Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991, Russian Federation.
- National Research South Ural State University, Chelyabinsk 454080, Russian Federation
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Buglakov AI, Larin DE, Vasilevskaya VV. Orientation- and cosolvent-induced self-assembly of amphiphilic homopolymers in selective solvents. POLYMER 2021. [DOI: 10.1016/j.polymer.2021.124160] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Scotti A, Pelaez-Fernandez M, Gasser U, Fernandez-Nieves A. Osmotic pressure of suspensions comprised of charged microgels. Phys Rev E 2021; 103:012609. [PMID: 33601513 DOI: 10.1103/physreve.103.012609] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 12/08/2020] [Indexed: 06/12/2023]
Abstract
We determine the osmotic pressure of microgel suspensions using membrane osmometry and dialysis, for microgels with different softnesses. Our measurements reveal that the osmotic pressure of solutions of both ionic and neutral microgels is determined by the free ions that leave the microgel periphery to maximize their entropy and not by the translational degrees of freedom of the microgels themselves. Furthermore, up to a given concentration it is energetically favorable for the microgels to maintain a constant volume without appreciable deswelling. The concentration where deswelling starts weakly depends on the crosslinker concentration, which affects the microgel dimension; we explain this by considering the dependence of the osmotic pressure and the microgel bulk modulus on the particle size.
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Affiliation(s)
- A Scotti
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - M Pelaez-Fernandez
- Department of Condensed Matter Physics, University of Barcelona, 08028 Barcelona, Spain
| | - U Gasser
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - A Fernandez-Nieves
- Department of Condensed Matter Physics, University of Barcelona, 08028 Barcelona, Spain
- ICREA-Institucio Catalana de Recerca i Estudis Avancats, 08010 Barcelona, Spain
- School of Physics, Georgia Institute of Technology, Atlanta, 30332 Georgia, USA
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