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Allahyarov E, Löwen H, Taylor PL. Simulation Study of Ion Diffusion in Charged Nanopores with Anchored Terminal Groups. Electrochim Acta 2017. [DOI: 10.1016/j.electacta.2017.04.158] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Allahyarov E, Taylor PL, Löwen H. Enhanced ionic diffusion in ionomer-filled nanopores. J Chem Phys 2015; 143:243126. [DOI: 10.1063/1.4935114] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Affiliation(s)
- Elshad Allahyarov
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine Universität Düsseldorf, Universitätstrasse 1, 40225 Düsseldorf, Germany
- Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7202, USA
- Theoretical Department, Joint Institute for High Temperatures, Russian Academy of Sciences (IVTAN), 13/19 Izhorskaya Street, Moscow 125412, Russia
- International Research Centre, Baku State University, Baku, Azerbaijan
| | - Philip L. Taylor
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079, USA
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine Universität Düsseldorf, Universitätstrasse 1, 40225 Düsseldorf, Germany
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Lee MT, Vishnyakov A, Neimark AV. Modeling Proton Dissociation and Transfer Using Dissipative Particle Dynamics Simulation. J Chem Theory Comput 2015; 11:4395-403. [DOI: 10.1021/acs.jctc.5b00467] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ming-Tsung Lee
- Department of Chemical and
Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058, United States
| | - Aleksey Vishnyakov
- Department of Chemical and
Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058, United States
| | - Alexander V. Neimark
- Department of Chemical and
Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058, United States
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Pérez-Maciá MA, Curcó D, Bringué R, Iborra M, Alemán C. Atomistic simulations of the structure of highly crosslinked sulfonated poly(styrene-co-divinylbenzene) ion exchange resins. SOFT MATTER 2015; 11:2251-2267. [PMID: 25651925 DOI: 10.1039/c4sm02417f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The microscopic structures of highly crosslinked sulfonated poly(styrene-co-divinylbenzene) resins have been modeled by generating atomistic microstructures using stochastic-like algorithms, which are subsequently relaxed using molecular dynamics. Two different generation algorithms have been tested. The relaxation of the microstructures generated by the first algorithm, which is based on a homogeneous construction of the resin, leads to a significant overestimation of the experimental density as well as to an unsatisfactory description of the porosity. In contrast, the generation approach that combines algorithms for the heterogeneous growing and branching of the chains enables the formation of crosslinks with different topologies. In particular, the intrinsic heterogeneity observed in these resins is efficiently reproduced when the topological loops, which are defined by two or more crosslinks closing a cycle, are present in their microscopic description. Thus, the apparent density, porosity and pore volume estimated using microstructures with these topological loops, called super-crosslinks, are in very good agreement with the experimental results. Although the backbone dihedral angle distribution of the generated and relaxed models is not influenced by the topology, the number and type of crosslinks affect the medium- and long-range atomic disposition of the backbone atoms and the distribution of sulfonic groups. An analysis of the distribution of the local density indicates that super-crosslinks are responsible for the heterogeneous homogenization observed during the MD relaxation. Finally the π-π stacking interactions have been analyzed. Results indicate that those in which the two rings adopt a T-shaped disposition are considerably more abundant as compared to those with the co-facially oriented rings, independently of the resin topology.
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Affiliation(s)
- María A Pérez-Maciá
- Departament d'Enginyeria Química, Facultat de Química, Universitat de Barcelona, Martí i Franqués 1, Barcelona E-08028, Spain.
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Vishnyakov A, Neimark AV. Self-assembly in Nafion membranes upon hydration: water mobility and adsorption isotherms. J Phys Chem B 2014; 118:11353-64. [PMID: 25157931 DOI: 10.1021/jp504975u] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
By means of dissipative particle dynamics (DPD) and Monte Carlo (MC) simulations, we explored geometrical, transport, and sorption properties of hydrated Nafion-type polyelectrolyte membranes. Composed of a perfluorinated backbone with sulfonate side chains, Nafion self-assembles upon hydration and segregates into interpenetrating hydrophilic and hydrophobic subphases. This segregated morphology determines the transport properties of Nafion membranes that are widely used as compartment separators in fuel cells and other electrochemical devices, as well as permselective diffusion barriers in protective fabrics. We introduced a coarse-grained model of Nafion, which accounts explicitly for polymer rigidity and electrostatic interactions between anionic side chains and hydrated metal cations. In a series of DPD simulations with increasing content of water, a classical percolation transition from a system of isolated water clusters to a 3D network of hydrophilic channels was observed. The hydrophilic subphase connectivity and water diffusion were studied by constructing digitized replicas of self-assembled morphologies and performing random walk simulations. A non-monotonic dependence of the tracer diffusivity on the water content was found. This unexpected behavior was explained by the formation of large and mostly isolated water domains detected at high water content and high equivalent polymer weight. Using MC simulations, we calculated the chemical potential of water in the hydrated polymer and constructed the water sorption isotherms, which extended to the oversaturated conditions. We determined that the maximum diffusivity and the onset of formation of large water domains corresponded to the saturation conditions at 100% humidity. The oversaturated membrane morphologies generated in the canonical ensemble DPD simulations correspond to the metastable and unstable states of Nafion membrane that are not realized in the experiments.
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Affiliation(s)
- Aleksey Vishnyakov
- Department of Chemical Engineering, Rutgers, the State University of New Jersey , 98 Brett Road, Piscataway, New Jersey 08854, United States
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Zhang XY, Ding YH. Thickness-dependent structural and transport behaviors in the platinum–Nafion interface: a molecular dynamics investigation. RSC Adv 2014. [DOI: 10.1039/c4ra05523c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Gómez-Marín AM, Hernández-Ortíz JP. Ion effects at electrode/solid polymer electrolyte membrane interfaces. Phys Chem Chem Phys 2014; 16:1945-56. [PMID: 24336802 DOI: 10.1039/c3cp54173h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The differential capacity and the potential distribution at electrode/solid polymer electrolyte membrane/solution interfaces are calculated through an analytical approach. The model considers coions' and counterions' permeation through the membrane from the solvent phase and the ions' partitioning equilibrium at the SPEM/solution interface. The latter effects are included by incorporating the Donnan equilibrium, the steric hindrance, the solvation energy change when ions move from water to membrane pores and ion electrostatic interactions. It is shown that capacitance maxima in capacitance-potential curves may appear because of the acid-base dissociation process inside the membrane and the change in the ions' total interaction energy with the applied potential. For low dielectric constants inside membrane pores, εp, sharp peaks can be obtained. These peaks broaden, decrease in magnitude and shift to positive potentials once εp is increased. Finally, model predictions are discussed in light of recent experimental data obtained on Nafion® covered Pt(111) electrodes, providing a theoretical framework for the qualitative electroanalysis of these systems.
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Affiliation(s)
- Ana Ma Gómez-Marín
- Departamento de Química y Petróleos, Universidad Nacional de Colombia, sede Medellín, Carrera 80 # 65-223, Bloque M3-050, Medellín, Colombia.
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Abstract
Functional polymers have a wide variety of applications ranging from energy storage to drug delivery. For energy storage applications, desirable material properties include low cost, high charge storage and/or mobility, and low rates of degradation. Isotropic thin films have been used for many of these types of applications, but research suggests that different structures such as polymer brushes can improve charge transport by an order of magnitude. Supported polymer brush structures produced by "grafting-from" polymerization methods offer a framework for a controlled study of these materials on the molecular scale. Using these materials, researchers can study the basis of hindered diffusion because they contain a relatively homogeneous polyelectrolyte membrane. In addition, researchers can use fluorescent molecular probes with different charges to examine steric and Coulombic contributions to transport near and within polymer brushes. In this Account, we discuss recent progress in using fluorescence correlation spectroscopy, single-molecule polarization-resolved spectroscopy, and a novel three-dimensional orientational technique to understand the transport of charged dye probes interacting with the strong polyanionic brush, poly(styrene sulfonate). Our preliminary experiments demonstrate that a cationic dye, Rhodamine 6G, probes the brush as a counterion, and diffusion is therefore dominated by Coulombic forces, which results in a 10,000-fold decrease in the diffusion coefficient in comparison with free diffusion. We also support our experimental results with molecular dynamics simulations. Further experiments show that, up to 50% of the time, Rhodamine 6G translates within the brush without significant rotational diffusion, which indicates a strong deviation from Fickian transport mechanisms (in which translational and rotational diffusion are related directly through parameters such as chemical potential, size, solution viscosity, and thermal properties). To understand this oriented transport, we discuss the development of an experimental technique that allows us to quantify the three-dimensional orientation on the time scale of intrabrush transport. This method allowed us to identify a unique orientational transport direction for Rhodamine 6G within the poly(styrene sulfonate) brush and to report preliminary evidence for orientational dye "hopping".
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Affiliation(s)
- Carmen Reznik
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
| | - Christy F. Landes
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
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Curnick OJ, Pollet BG, Mendes PM. Nafion®-stabilised Pt/C electrocatalysts with efficient catalyst layer ionomer distribution for proton exchange membrane fuel cells. RSC Adv 2012. [DOI: 10.1039/c2ra21071a] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Allahyarov E, Taylor PL, Löwen H. Simulation study of poled low-water ionomers with different architectures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:455102. [PMID: 21975381 DOI: 10.1088/0953-8984/23/45/455102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The role of the ionomer architecture in the formation of ordered structures in poled membranes is investigated by molecular dynamics computer simulations. It is shown that the length of the sidechain L(s) controls both the areal density of cylindrical aggregates N(c) and the diameter of these cylinders in the poled membrane. The backbone segment length L(b) tunes the average diameter D(s) of cylindrical clusters and the average number of sulfonates N(s) in each cluster. A simple empirical formula is noted for the dependence of the number density of induced rod-like aggregates on the sidechain length L(s) within the parameter range considered in this study.
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Affiliation(s)
- Elshad Allahyarov
- Department of Physics, Case Western Reserve University, Cleveland, OH 44106, USA
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Allahyarov E, Taylor PL, Löwen H. A simulation study of field-induced proton-conduction pathways in dry ionomers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:234105. [PMID: 21613717 DOI: 10.1088/0953-8984/23/23/234105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The morphological changes that can be induced in a dry ionomer by application of a strong electric field have been studied by means of computer simulation. The internal energy of the membrane at first slowly decreases with increasing field, but then rapidly increases after a certain threshold field is reached. This effect is interpreted as the reorganization of interacting head group dipoles in response to the external perturbation. The resulting morphology contains continuous channels of hydrophilic material capable of facilitating proton conduction. Upon removal of the poling field, the system does not return to its original morphology, but retains the anisotropic structure of the poled material. The poled structure appears to be thermodynamically stable, as confirmed by calculations of the Helmholtz energy of the original and poled samples.
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Affiliation(s)
- Elshad Allahyarov
- Department of Physics, Case Western Reserve University, Cleveland, OH 44106, USA
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Allahyarov E, Taylor PL. Simulation study of the equilibrium morphology in ionomers with different architectures. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/polb.22191] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Noto VD, Piga M, Giffin GA, Quartarone E, Righetti P, Mustarelli P, Magistris A. Structure–property interplay of proton conducting membranes based on PBI5N, SiO2–Im and H3PO4 for high temperature fuel cells. Phys Chem Chem Phys 2011; 13:12146-54. [DOI: 10.1039/c1cp20902g] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Bertran O, Curcó D, Torras J, Ferreira CA, Alemán C. Field-Induced Transport in Sulfonated Poly(styrene-co-divinylbenzene) Membranes. Macromolecules 2010. [DOI: 10.1021/ma102500w] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Oscar Bertran
- Departament de Física Aplicada, EEI, Universitat Politècnica de Catalunya, Pça. Rei 15, 08700 Igualada, Spain
| | - David Curcó
- Department d’Enginyeria Química, Facultat de Química, Universitat de Barcelona, Martí Franques 1, Barcelona E-08028, Spain
| | - Juan Torras
- Departament d’Enginyeria Química, EEI, Universitat Politècnica de Catalunya, Pça. Rei 15, 08700 Igualada, Spain
| | - Carlos A. Ferreira
- Universidade Federal do Rio Grande do Sul, PPGEM, Av. Bento Gonçalves, 9500, setor 4, prédio 74, Cep. 91501-970, Porto Alegre, RS, Brazil
| | - Carlos Alemán
- Departament d’Enginyeria Química, E. T. S. d’Enginyers Industrials, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain
- Center for Research in Nano-Engineering, Universitat Politècnica de Catalunya, Campus Sud, Edifici C’, C/Pasqual i Vila s/n, Barcelona E-08028, Spain
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