1
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Dorenbos G. How fork-length asymmetry affects solvent connectivity and diffusion in grafted polymeric model membranes. J Chem Phys 2024; 160:064901. [PMID: 38341779 DOI: 10.1063/5.0193120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 01/15/2024] [Indexed: 02/13/2024] Open
Abstract
The hydrophilic pore morphology and solvent diffusion within model (amphiphilic) polymer membranes are simulated by dissipative particle dynamics (DPD). The polymers are composed of a backbone of 18 covalently bonded A beads to which at regular intervals side chains are attached. The side chains are composed of linear Ap chains (i.e., -A1-A2…Ap) from which two branches, [AsC] and [ArC], split off (s ≤ r). C beads serve as functionalized hydrophilic pendent sites. The branch lengths (s + 1 and r + 1) are varied. Five repeat unit designs (with general formula A3[Ap[AsC][ArC]]) are considered: A2[A3C][A3C] (symmetric branching), A2[A2C][A4C], A2[AC][A5C], A2[C][A6C] (highly asymmetric branching), and A4[AC][A3C]. The distribution of water (W) and W diffusion through nanophase segregated hydrophilic pores is studied. For similar primary length p, an increase in side chain symmetry favors hydrophilic pore connectivity and long-range water transport. C beads located on the longer [ArC] branches reveal the highest C bead mobility and are more strongly associated with water than the C beads on the shorter [AsC] branches. The connectivity of hydrophilic (W and W + C) phases through mapped replica of selected snapshots obtained from Monte Carlo tracer diffusion simulations is in line with trends found from the W bead diffusivities during DPD simulations. The diffusive pathways for protons (H+) in proton exchange membranes and for hydronium (OH-) in anion exchange membranes are the same as for solvents. Therefore, control of the side chain architecture is an interesting design parameter for optimizing membrane conductivities.
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Affiliation(s)
- G Dorenbos
- Private research, Sano 1107-2, Belle Crea 502, 410-1118 Susono, Japan
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2
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Kim YS. Hydrocarbon Ionomeric Binders for Fuel Cells and Electrolyzers. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2303914. [PMID: 37814366 DOI: 10.1002/advs.202303914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 08/08/2023] [Indexed: 10/11/2023]
Abstract
Ionomeric binders in catalyst layers, abbreviated as ionomers, play an essential role in the performance of polymer-electrolyte membrane fuel cells and electrolyzers. Due to environmental issues associated with perfluoroalkyl substances, alternative hydrocarbon ionomers have drawn substantial attention over the past few years. This review surveys literature to discuss ionomer requirements for the electrodes of fuel cells and electrolyzers, highlighting design principles of hydrocarbon ionomers to guide the development of advanced hydrocarbon ionomers.
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Affiliation(s)
- Yu Seung Kim
- MPA-11: Materials Synthesis and Integrated Devices, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
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3
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Dorenbos G. Simulated and Experimental Trends Regarding Water Uptake in Polymeric Electrolyte Membranes. J Phys Chem B 2023; 127:9630-9641. [PMID: 37882051 DOI: 10.1021/acs.jpcb.3c05309] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2023]
Abstract
Polymeric membranes in an anion or a proton exchange membrane fuel cell need sufficient hydration in order to provide a high hydroxide ion or proton conductivity. The water uptake for six model ionomer membranes, all of the same ion exchange capacity, is modeled by dissipative particle dynamics. The architectures cover three types of families that are of potential interest in fuel cell membrane research. All architectures consist of connected hydrophobic backbone A beads, to which side chains are grafted. For the type I family, the hydrophilic (functional) C beads are pendent on (amphiphilic) [AxC] side chains. The type II architecture contains both hydrophobic [A4] and short hydrophilic [C] side chains. For type III, the C beads are embedded along various locations within the [AxCAy] side chains (x + y = constant). For similar equilibrium time, the membrane water volume fraction increases with side chain length x for type I, and for type III, it increases with the distance x that C beads are separated from the backbone. Among the architectures (types I and III) for which the number of covalent C-A bonds are the same, the water uptake increases with the average number of A-A and A-C bonds (dpd springs) between A beads and the nearest C bead. A picture emerges in which for similar ion exchange capacity model membranes water uptake increases as a function of ⟨Nbondphob-phyl⟩.
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Affiliation(s)
- G Dorenbos
- Private Researcher, Belle Crea 502, 1107-2 Susono 410-1118, Japan
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4
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Eskandari H, Paul DK, Young AP, Karan K. Humidity-Dependent Hydration and Proton Conductivity of PFSA Ionomer Thin Films at Fuel-Cell-Relevant Temperatures: Effect of Ionomer Equivalent Weight and Side-Chain Characteristics. ACS APPLIED MATERIALS & INTERFACES 2022; 14:50762-50772. [PMID: 36342365 DOI: 10.1021/acsami.2c12667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Studies on the hydration properties, proton conductivity, and water content of perfluorinated ionomer thin films at temperatures relevant to fuel cell operation temperatures (around 80 °C) and the effect of ionomer chemistry are scarce. In this work, we report the water content and proton conductivity properties of thin-film ionomers (30 nm) at 80 °C over a wide range of relative humidity (0-90%) for seven different ionomers differing in the side-chain structure, including the number of protogenic groups, with the equivalent weight ranging from 620 to 1100 g/mol of sulfonic acid. The results show that the acid content or equivalent weight of the ionomer is the strongest determinant of both the swelling and the proton conductivity of ionomer films at a given relative humidity. The molar water content (λ) of ionomer films normalized to the molar protogenic group is observed to be equivalent-weight-dependent, implying that the affinity for water is acid-content-dependent. At high relative humidity conditions (>70%) pertinent to fuel cell operations, the proton conductivity of low-equivalent-weight ionomers was higher than that of higher-equivalent-weight ionomers. However, upon correlating the proton conductivity with molar water content (λ), the differences reduce dramatically, highlighting that water content is the controlling factor for proton conduction. Significantly higher values of both water content and proton conductivity are observed at 80 °C compared to those at 30 °C, implying that room temperature data are not reliable for estimating ionomer properties in the fuel cell catalyst layer.
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Affiliation(s)
- Hamideh Eskandari
- Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Drive, Calgary, AlbertaT2N 1N4, Canada
| | - Devproshad K Paul
- Ballard Power Systems Inc., 9000 Glenlyon Parkway, Burnaby, British ColumbiaV5J 5J8, Canada
| | - Alan P Young
- Ballard Power Systems Inc., 9000 Glenlyon Parkway, Burnaby, British ColumbiaV5J 5J8, Canada
| | - Kunal Karan
- Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Drive, Calgary, AlbertaT2N 1N4, Canada
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5
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Abstract
Ion-containing polymers have continued to be an important research focus for several decades due to their use as an electrolyte in energy storage and conversion devices. Elucidation of connections between the mesoscopic structure and multiscale dynamics of the ions and solvent remains incompletely understood. Coarse-grained modeling provides an efficient approach for exploring the structural and dynamical properties of these soft materials. The unique physicochemical properties of such polymers are of broad interest. In this review, we summarize the current development and understanding of the structure-property relationship of ion-containing polymers and provide insights into the design of such materials determined from coarse-grained modeling and simulations accompanying significant advances in experimental strategies. We specifically concentrate on three types of ion-containing polymers: proton exchange membranes (PEMs), anion exchange membranes (AEMs), and polymerized ionic liquids (polyILs). We posit that insight into the similarities and differences in these materials will lead to guidance in the rational design of high-performance novel materials with improved properties for various power source technologies.
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Affiliation(s)
- Zhenghao Zhu
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Xubo Luo
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Stephen J Paddison
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
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6
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Zelovich T, Tuckerman ME. Controlling Hydronium Diffusivity in Model Proton Exchange Membranes. J Phys Chem Lett 2022; 13:2245-2253. [PMID: 35238561 DOI: 10.1021/acs.jpclett.1c04071] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Fuel-cell-based proton exchange membranes (PEMs) show great potential as cost-effective and clean energy conversion devices. In our recent work, we found that for the low-hydrated model PEMs with a inhomogeneous water distribution and a sulfonate anionic functional end group (SO3-), the H3O+ reacts with SO3- according to SO3- + H3O+ ↔ SO3H + H2O, indicating that the anions in PEMs become active participants in the hydronium diffusion. In this work, we use fully atomistic ab initio molecular dynamics simulations to elucidate the optimal conditions that would promote the participation of SO3- in the hydronium diffusion mechanism by increasing the H3O+/SO3- reactivity, thus increasing the hydronium diffusivity along the cell. The results presented in this work allow us to suggest a set of design rules for creating novel, highly conductive PEMs operating at high temperatures under a nonuniform water distribution using a linker/anion with a relatively high pKa such as (CH2)2SO3. We expect that the discovery of these key design principles will play an important role in the synthesis of high-performing materials for emerging PEM-based fuel cell technologies.
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Affiliation(s)
- Tamar Zelovich
- Department of Chemistry, New York University, New York, New York 10003, United States
| | - Mark E Tuckerman
- Department of Chemistry, New York University, New York, New York 10003, United States
- Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, United States
- NYU-ECNU Center for Computational Chemistry, New York University Shanghai, 3663 North Zhongshan Rd, Shanghai 200062, China
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7
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Wang J, Chen J, Xu Z, Yang X, Ramakrishna S, Liu Y. Mesoscale hydrated morphology of perfluorosulfonic acid membranes. J Appl Polym Sci 2022. [DOI: 10.1002/app.52275] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jihao Wang
- Beijing Key Laboratory of Advanced Functional Polymer Composites, College of Materials Science and Engineering Beijing University of Chemical Technology Beijing China
| | - Jia Chen
- Beijing Key Laboratory of Advanced Functional Polymer Composites, College of Materials Science and Engineering Beijing University of Chemical Technology Beijing China
| | - Zhiyang Xu
- Beijing Key Laboratory of Advanced Functional Polymer Composites, College of Materials Science and Engineering Beijing University of Chemical Technology Beijing China
| | - Xiaozhen Yang
- State Key Laboratory of Polymer Physics and Chemistry Institute of Chemistry, Chinese Academy of Science Beijing China
| | - Seeram Ramakrishna
- Nanoscience and Nanotechnology Initiative National University of Singapore Singapore Singapore
| | - Yong Liu
- Beijing Key Laboratory of Advanced Functional Polymer Composites, College of Materials Science and Engineering Beijing University of Chemical Technology Beijing China
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8
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Guo W, Liu Q, Zhang L, Du J, Zhu X, Fung KY, Yu Y, Ng KM. Computer-Aided Design of a Perfluorinated Sulfonic Acid Proton Exchange Membrane Using Stochastic Optimization and Molecular Dynamic Method. Ind Eng Chem Res 2021. [DOI: 10.1021/acs.iecr.1c03661] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wenjing Guo
- Institute of Process Systems Engineering, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
| | - Qilei Liu
- Institute of Process Systems Engineering, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
| | - Lei Zhang
- Institute of Process Systems Engineering, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
| | - Jian Du
- Institute of Process Systems Engineering, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
| | - Xiuling Zhu
- State Key Lab of Fine Chemicals, Department of Polymer Science & Materials, Dalian University of Technology, Dalian 116024, China
| | - Ka Yip Fung
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, 999077 Hong Kong
| | - Yong Yu
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, 999077 Hong Kong
| | - Ka Ming Ng
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, 999077 Hong Kong
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9
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Wang J, Xu Z, Chen J, Yang X, Ramakrishna S, Liu Y. Mesoscale Simulation on the Hydrated Morphologies of SPEEK Membrane. MACROMOL THEOR SIMUL 2021. [DOI: 10.1002/mats.202100006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jihao Wang
- Beijing Key Laboratory of Advanced Functional Polymer Composites College of Materials Science and Engineering Beijing University of Chemical Technology Beijing 100029 China
| | - Zhiyang Xu
- Beijing Key Laboratory of Advanced Functional Polymer Composites College of Materials Science and Engineering Beijing University of Chemical Technology Beijing 100029 China
| | - Jia Chen
- Beijing Key Laboratory of Advanced Functional Polymer Composites College of Materials Science and Engineering Beijing University of Chemical Technology Beijing 100029 China
| | - Xiaozhen Yang
- State Key Laboratory of Polymer Physics and Chemistry Institute of Chemistry Chinese Academy of Science Beijing 100190 China
| | - Seeram Ramakrishna
- Nanoscience and Nanotechnology Initiative National University of Singapore Singapore 11576 Singapore
| | - Yong Liu
- Beijing Key Laboratory of Advanced Functional Polymer Composites College of Materials Science and Engineering Beijing University of Chemical Technology Beijing 100029 China
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10
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11
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Li T, Shen J, Chen G, Guo S, Xie G. Performance Comparison of Proton Exchange Membrane Fuel Cells with Nafion and Aquivion Perfluorosulfonic Acids with Different Equivalent Weights as the Electrode Binders. ACS OMEGA 2020; 5:17628-17636. [PMID: 32715248 PMCID: PMC7377320 DOI: 10.1021/acsomega.0c02110] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 06/23/2020] [Indexed: 06/07/2023]
Abstract
A perfluorosulfonic acid (PFSA) ionomer, used as the proton conductor in the catalyst layer, influences significantly the performance of proton exchange membrane fuel cell catalyst-coated membrane (CCM). In this paper, SSC-CCM is prepared by the SSC-PFSA (Aquivion, EW 720) ionomer, and the comparative sample (LSC-CCM) is based on the LSC-PFSA ionomer (Nafion, EW 1100). Compared with LSC-CCM, SSC-CCM shows higher porosity, larger electrochemical surface area (ECSA), and smaller high-frequency resistance. Polarization curves of SSC-CCM tested by the short stack show better performance than those of LSC-CCM, especially under the lower relative humidity operations. Moreover, the SSC-CCM outputs higher voltage and is more stable in the dynamic process with temperature continuously increasing under lower relative humidity operation. Such excellent performance of SSC-CCM is confirmed from the higher proton conductivity of SSC-PFSA under low relative humidity. These results indicate that the SSC-PFSA ionomer could be employed for the CCM catalyst layer under the operation conditions of low relative humidity and dynamic running for automotive applications.
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Affiliation(s)
- Ting Li
- The
State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
- Energy
Conversion R&D Center, Central Academy
of Dongfang Electric Corporation, Chengdu 611731, China
| | - Jiabin Shen
- The
State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Guangying Chen
- Energy
Conversion R&D Center, Central Academy
of Dongfang Electric Corporation, Chengdu 611731, China
| | - Shaoyun Guo
- The
State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Guangyou Xie
- Energy
Conversion R&D Center, Central Academy
of Dongfang Electric Corporation, Chengdu 611731, China
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12
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Dissipative Particle Dynamics Modeling of Polyelectrolyte Membrane-Water Interfaces. Polymers (Basel) 2020; 12:polym12040907. [PMID: 32295222 PMCID: PMC7240515 DOI: 10.3390/polym12040907] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/10/2020] [Accepted: 04/11/2020] [Indexed: 12/03/2022] Open
Abstract
Previous experiments of water vapor penetration into polyelectrolyte membrane (PEM) thin films have indicated the influence of the water concentration gradient and polymer chemistry on the interface evolution, which will eventually affect the efficiency of the fuel cell operation. Moreover, PEMs of different side chains have shown differences in water cluster structure and diffusion. The evolution of the interface between water and polyelectrolyte membranes (PEMs), which are used in fuel cells and flow batteries, of three different side-chain lengths has been studied using dissipative particle dynamics (DPD) simulations. Higher and faster water uptake is usually beneficial in the operation of fuel cells and flow batteries. The simulated water uptake increased with the increasing side chain length. In addition, the water uptake was rapid initially and slowed down afterwards, which is in agreement with the experimental observations. The water cluster formation rate was also found to increase with the increasing side-chain length, whereas the water cluster shapes were unaffected. Water diffusion in the membranes, which affects proton mobility in the PEMs, increased with the side-chain length at all distances from the interface. In conclusion, side-chain length was found to have a strong influence on the interface water structure and water penetration rates, which can be harnessed for the better design of PEMs. Since the PEM can undergo cycles of dehydration and rehydration, faster water uptake increases the efficiency of these devices. We show that the longer side chains with backbone structure similar to Nafion should be more suitable for fuel cell/flow battery usage.
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13
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Kuo AT, Miyazaki Y, Jang C, Miyajima T, Urata S, Nielsen SO, Okazaki S, Shinoda W. Large-scale molecular dynamics simulation of perfluorosulfonic acid membranes: Remapping coarse-grained to all-atomistic simulations. POLYMER 2019. [DOI: 10.1016/j.polymer.2019.121766] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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14
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Clark JA, Santiso EE, Frischknecht AL. Morphology and proton diffusion in a coarse-grained model of sulfonated poly(phenylenes). J Chem Phys 2019; 151:104901. [DOI: 10.1063/1.5116684] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Affiliation(s)
- Jennifer A. Clark
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Erik E. Santiso
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Amalie L. Frischknecht
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
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15
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Su GM, Cordova IA, Yandrasits MA, Lindell M, Feng J, Wang C, Kusoglu A. Chemical and Morphological Origins of Improved Ion Conductivity in Perfluoro Ionene Chain Extended Ionomers. J Am Chem Soc 2019; 141:13547-13561. [DOI: 10.1021/jacs.9b05322] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Gregory M. Su
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Isvar A. Cordova
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | | | | | - Jun Feng
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Cheng Wang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Ahmet Kusoglu
- Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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16
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Kononenko NA, Loza NV, Andreeva MA, Shkirskaya SA, Dammak L. Influence of Electric Field during the Chemical Synthesis of Polyaniline on the Surface of Heterogeneous Sulfonated Cation-Exchange Membranes on the Their Structure and Properties. MEMBRANES AND MEMBRANE TECHNOLOGIES 2019. [DOI: 10.1134/s2517751619040036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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17
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Coarse-grained study of the effect of hydrophobic side chain length on cluster size distributions and water diffusion in (amphiphilic-hydrophobic) multi-block co-polymer membranes. POLYMER 2019. [DOI: 10.1016/j.polymer.2019.04.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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18
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Brownell M, Nair AK. Deformation mechanisms of polytetrafluoroethylene at the nano- and microscales. Phys Chem Chem Phys 2019; 21:490-503. [DOI: 10.1039/c8cp05111a] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Polytetrafluoroethylene (PTFE) coefficient of friction is dependent on a particles density and surface roughness.
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Affiliation(s)
- Matthew Brownell
- Multiscale Materials Modeling Lab
- Department of Mechanical Engineering
- University of Arkansas
- Fayetteville
- USA
| | - Arun K. Nair
- Multiscale Materials Modeling Lab
- Department of Mechanical Engineering
- University of Arkansas
- Fayetteville
- USA
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19
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Shrivastava UN, Fritzsche H, Karan K. Interfacial and Bulk Water in Ultrathin Films of Nafion, 3M PFSA, and 3M PFIA Ionomers on a Polycrystalline Platinum Surface. Macromolecules 2018. [DOI: 10.1021/acs.macromol.8b01240] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Udit N. Shrivastava
- Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada
| | - Helmut Fritzsche
- Material Sciences Branch, Canadian Nuclear Laboratories, 286 Plant Road, Chalk River, ON K0J 10J, Canada
| | - Kunal Karan
- Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada
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20
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Mesoscale modeling of sulfonated polyimides copolymer membranes: Effect of sequence distributions. J Memb Sci 2018. [DOI: 10.1016/j.memsci.2018.07.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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21
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Vishnyakov A, Mao R, Lee MT, Neimark AV. Coarse-grained model of nanoscale segregation, water diffusion, and proton transport in Nafion membranes. J Chem Phys 2018; 148:024108. [PMID: 29331134 DOI: 10.1063/1.4997401] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a coarse-grained model of the acid form of Nafion membrane that explicitly includes proton transport. This model is based on a soft-core bead representation of the polymer implemented into the dissipative particle dynamics (DPD) simulation framework. The proton is introduced as a separate charged bead that forms dissociable Morse bonds with water beads. Morse bond formation and breakup artificially mimics the Grotthuss hopping mechanism of proton transport. The proposed DPD model is parameterized to account for the specifics of the conformations and flexibility of the Nafion backbone and sidechains; it treats electrostatic interactions in the smeared charge approximation. The simulation results qualitatively, and in many respects quantitatively, predict the specifics of nanoscale segregation in the hydrated Nafion membrane into hydrophobic and hydrophilic subphases, water diffusion, and proton mobility. As the hydration level increases, the hydrophilic subphase exhibits a percolation transition from a collection of isolated water clusters to a 3D network of pores filled with water embedded in the hydrophobic matrix. The segregated morphology is characterized in terms of the pore size distribution with the average size growing with hydration from ∼1 to ∼4 nm. Comparison of the predicted water diffusivity with the experimental data taken from different sources shows good agreement at high and moderate hydration and substantial deviation at low hydration, around and below the percolation threshold. This discrepancy is attributed to the dynamic percolation effects of formation and rupture of merging bridges between the water clusters, which become progressively important at low hydration, when the coarse-grained model is unable to mimic the fine structure of water network that includes singe molecule bridges. Selected simulations of water diffusion are performed for the alkali metal substituted membrane which demonstrate the effects of the counter-ions on membrane self-assembly and transport. The hydration dependence of the proton diffusivity reproduces semi-qualitatively the trend of the diverse experimental data, showing a sharp decrease around the percolation threshold. Overall, the proposed model opens up an opportunity to study self-assembly and water and proton transport in polyelectrolytes using computationally efficient DPD simulations, and, with further refinement, it may become a practical tool for theory informed design and optimization of perm-selective and ion-conducting membranes with improved properties.
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Affiliation(s)
- Aleksey Vishnyakov
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058, USA
| | - Runfang Mao
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058, USA
| | - Ming-Tsung Lee
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058, USA
| | - Alexander V Neimark
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058, USA
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22
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Vanya P, Sharman J, Elliott JA. Mesoscale simulations of confined Nafion thin films. J Chem Phys 2017; 147:214904. [PMID: 29221394 DOI: 10.1063/1.4996695] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- P. Vanya
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - J. Sharman
- Johnson Matthey Technology Centre, Blounts Court Road, Sonning Common, Reading RG4 9NH, United Kingdom
| | - J. A. Elliott
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
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23
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Doping proton transport channels in poly-electrolyte membranes with high acidic site density polymers. Eur Polym J 2017. [DOI: 10.1016/j.eurpolymj.2017.09.040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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24
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Kuo AT, Okazaki S, Shinoda W. Transferable coarse-grained model for perfluorosulfonic acid polymer membranes. J Chem Phys 2017; 147:094904. [DOI: 10.1063/1.4986287] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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25
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Abstract
In this comprehensive review, recent progress and developments on perfluorinated sulfonic-acid (PFSA) membranes have been summarized on many key topics. Although quite well investigated for decades, PFSA ionomers' complex behavior, along with their key role in many emerging technologies, have presented significant scientific challenges but also helped create a unique cross-disciplinary research field to overcome such challenges. Research and progress on PFSAs, especially when considered with their applications, are at the forefront of bridging electrochemistry and polymer (physics), which have also opened up development of state-of-the-art in situ characterization techniques as well as multiphysics computation models. Topics reviewed stem from correlating the various physical (e.g., mechanical) and transport properties with morphology and structure across time and length scales. In addition, topics of recent interest such as structure/transport correlations and modeling, composite PFSA membranes, degradation phenomena, and PFSA thin films are presented. Throughout, the impact of PFSA chemistry and side-chain is also discussed to present a broader perspective.
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Affiliation(s)
- Ahmet Kusoglu
- Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, MS70-108B, Berkeley, California 94720, United States
| | - Adam Z Weber
- Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, MS70-108B, Berkeley, California 94720, United States
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26
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Yu C, Ma L, Li K, Li S, Liu Y, Liu L, Zhou Y, Yan D. Computer Simulation Studies on the pH-Responsive Self-Assembly of Amphiphilic Carboxy-Terminated Polyester Dendrimers in Aqueous Solution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:388-399. [PMID: 28001081 DOI: 10.1021/acs.langmuir.6b03480] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This paper investigates the pH-responsive self-assembly of an amphiphilic carboxyl-terminated polyester dendrimer, H20-COOH, in aqueous solution using the dissipative particle dynamics method. The electrostatic interactions were described by introducing the explicit interaction between the smeared charges on ionized polymer beads and the counterions. The results show that the self-assemblies could change from unimolecular micelles, microphase-separated small micelles, wormlike micelles, sheetlike micelles, and small vesicles to large vesicles with the decrease in the degree of ionization (α) of carboxylic acid groups. In addition, the detailed self-assembly mechanisms and the molecular packing models have also been disclosed for each self-assembly stages. Interestingly, the wormlike micelles are found to change from linear to branched when α decreases from 0.182 to 0.109. The current work might serve as a comprehensive understanding on the effect of carboxylic acid groups on the self-assembly behaviors of dendritic polymers.
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Affiliation(s)
- Chunyang Yu
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, China
| | - Li Ma
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, China
| | - Ke Li
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, China
| | - Shanlong Li
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, China
| | - Yannan Liu
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, China
| | - Lifen Liu
- Center for Membrane and Water Science and Technology, Ocean College, Zhejiang University of Technology , Hangzhou 310014, China
| | - Yongfeng Zhou
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, China
| | - Deyue Yan
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, China
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27
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Akbari S, Mosavian MTH, Moosavi F, Ahmadpour A. Molecular dynamics simulation of Keggin HPA doped Nafion® 117 as a polymer electrolyte membrane. RSC Adv 2017. [DOI: 10.1039/c7ra05929a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Nafion®/heteropoly acid (HPA) composite membranes and the impact of the anionic charge of HPA on water and hydronium dynamics were investigated using molecular dynamics simulation.
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Affiliation(s)
- S. Akbari
- Chemical Engineering Department
- Faculty of Engineering
- Ferdowsi University of Mashhad
- Iran
| | - M. T. Hamed Mosavian
- Chemical Engineering Department
- Faculty of Engineering
- Ferdowsi University of Mashhad
- Iran
| | - F. Moosavi
- Department of Chemistry
- Faculty of Science
- Ferdowsi University of Mashhad
- Iran
| | - A. Ahmadpour
- Chemical Engineering Department
- Faculty of Engineering
- Ferdowsi University of Mashhad
- Iran
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28
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Dorenbos G. Dependence of Solvent Diffusion on Hydrophobic Block Length within Amphiphilic-Hydrophobic Block Copolymer Membranes. J Phys Chem B 2016; 120:13102-13111. [PMID: 27976579 DOI: 10.1021/acs.jpcb.6b10913] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pore networks and water diffusion within model (amphiphilic-hydrophobic) diblock copolymer membranes in the presence of 16 vol % water is studied by dissipative particle dynamics in combination with Monte Carlo tracer diffusion calculations. The amphiphilic block (parent architecture (A[A3C])10) is composed of a backbone that contains 10 consecutively connected hydrophobic A beads; to each A bead, a side chain is grafted composed of three connected A beads and a pendant hydrophilic C bead. Hydrophobic blocks are constructed from x covalently bonded A beads, with x = 20, 30, or 50. Water diffusion through the pores is modeled by Monte Carlo tracer diffusion within more than 500 mapped morphologies. Long range water diffusion within the amphiphilic-hydrophobic ((A[A3C])10-Ax) diblock architectures increases with hydrophobic block length. Diffusion increases with Q = ⟨Nbond⟩|C||1 - C|-1, where C is the hydrophilic C bead fraction and ⟨Nbond⟩ the average number of bonds that A beads are separated from the nearest C bead. These trends are also anticipated for amphiphilic parent architectures (ACA3)10, (A2[C]A2)10, and (A2[AC]A)10. This is explained by the squeezing of water from the hydrophobic phase into the amphiphilic phase. Two characteristic distances are observed: The shorter distance corresponds to the interpore (or intercluster) separation within the "parent architecture-water" phase and obeys the earlier obtained linear relation between intercluster distance and ⟨Nbond⟩amphi of the amphiphilic parent architecture. The longer distance is governed by the phase separation between the amphiphilic-water phase and hydrophobic blocks.
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Affiliation(s)
- G Dorenbos
- T410-1118, 1107-2, sanno, Belle Crea 502, Susono, Japan
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29
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Lu J, Jacobson LC, Perez Sirkin YA, Molinero V. High-Resolution Coarse-Grained Model of Hydrated Anion-Exchange Membranes that Accounts for Hydrophobic and Ionic Interactions through Short-Ranged Potentials. J Chem Theory Comput 2016; 13:245-264. [PMID: 28068769 DOI: 10.1021/acs.jctc.6b00874] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Jibao Lu
- Department
of Chemistry, The University of Utah, Salt Lake City, Utah 84112-0850, United States
| | - Liam C. Jacobson
- Department
of Chemistry, The University of Utah, Salt Lake City, Utah 84112-0850, United States
| | - Yamila A. Perez Sirkin
- Departamento
de Química Inorgánica, Analítica y Química
Física, and INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EHA, Argentina
| | - Valeria Molinero
- Department
of Chemistry, The University of Utah, Salt Lake City, Utah 84112-0850, United States
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30
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Dorenbos G. Water Diffusion Dependence on Amphiphilic Block Design in (Amphiphilic-Hydrophobic) Diblock Copolymer Membranes. J Phys Chem B 2016; 120:5634-45. [PMID: 27266679 DOI: 10.1021/acs.jpcb.6b03171] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polyelectrolyte membranes (PEMs) are applied in polyelectrolyte fuel cells (PEFC). The proton conductive pathways within PEMs are provided by nanometer-sized water containing pores. Large-scale application of PEFC requires the production of low-cost membranes with high proton conductivity and therefore good connected pore networks. Pore network formation within four alternative model diblock (hydrophobic_amphiphilic) copolymers in the presence of water is studied by dissipative particle dynamics. Each hydrophobic block contains 50 consecutively connected hydrophobic (A) fragments, and amphiphilic blocks contain 40 hydrophobic A beads and 10 hydrophilic C beads. For one amphiphilic block the C beads are distributed uniformly along the backbone. For the other architectures C beads are located at the end of the side chains attached at regular intervals along the backbone. Water diffusion through the pores is modeled by Monte Carlo tracer diffusion through mapped morphologies. Diffusion is highest for the grafted architectures and increases with increase of length of the side chains. A consistent picture emerges in which diffusion strongly increases with the value of ⟨Nbond⟩ within the amphiphilic block, where ⟨Nbond⟩ is the average number of bonds between hydrophobic A beads and the nearest C bead.
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Affiliation(s)
- Gert Dorenbos
- T410-1118, sano 1107-2, Belle Crea 502, Susono, Japan
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31
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32
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Lee MT, Vishnyakov A, Neimark AV. Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane. J Chem Phys 2016; 144:014902. [DOI: 10.1063/1.4938271] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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, USA
| | - Aleksey Vishnyakov
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058, USA
| | - Alexander V. Neimark
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058, USA
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33
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Dorenbos G. Modelling linear and branched amphiphilic star polymer electrolyte membranes and verification of the bond counting method. RSC Adv 2016. [DOI: 10.1039/c5ra24172c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Water diffusion through hydrated amphiphilic star polymer membranes depends strongly on hydrophilic position within the linear and Y-shaped arms.
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34
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Berrod Q, Lyonnard S, Guillermo A, Ollivier J, Frick B, Manseri A, Améduri B, Gébel G. Nanostructure and Transport Properties of Proton Conducting Self-Assembled Perfluorinated Surfactants: A Bottom-Up Approach toward PFSA Fuel Cell Membranes. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00770] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Quentin Berrod
- CNRS/CEA-INAC-SPrAM, F-38000 Grenoble, France
- Université
Grenoble-Alpes, F-38000 Grenoble, France
| | - Sandrine Lyonnard
- CNRS/CEA-INAC-SPrAM, F-38000 Grenoble, France
- Université
Grenoble-Alpes, F-38000 Grenoble, France
| | - Armel Guillermo
- CNRS/CEA-INAC-SPrAM, F-38000 Grenoble, France
- Université
Grenoble-Alpes, F-38000 Grenoble, France
| | | | | | - Abdelatif Manseri
- UMR CNRS 5253, Institut Charles Gerhardt Ingenierie & Architectures Macromoleculaires, Ecole Nationale Superieure de Chimie Montpellier, 8 Rue Ecole Normale, F-34296 Montpellier, France
| | - Bruno Améduri
- UMR CNRS 5253, Institut Charles Gerhardt Ingenierie & Architectures Macromoleculaires, Ecole Nationale Superieure de Chimie Montpellier, 8 Rue Ecole Normale, F-34296 Montpellier, France
| | - Gérard Gébel
- Université
Grenoble-Alpes, F-38000 Grenoble, France
- CEA, LITEN, DTNM, F-38054 Grenoble, France
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35
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Mao R, Lee MT, Vishnyakov A, Neimark AV. Modeling Aggregation of Ionic Surfactants Using a Smeared Charge Approximation in Dissipative Particle Dynamics Simulations. J Phys Chem B 2015; 119:11673-83. [PMID: 26241704 DOI: 10.1021/acs.jpcb.5b05630] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using dissipative particle dynamics (DPD) simulations, we explore the specifics of micellization in the solutions of anionic and cationic surfactants and their mixtures. Anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant cetyltrimethylammonium bromide (CTAB) are chosen as characteristic examples. Coarse-grained models of the surfactants are constructed and parameterized using a combination of atomistic molecular simulation and infinite dilution activity coefficient calibration. Electrostatic interactions of charged beads are treated using a smeared charge approximation: the surfactant heads and dissociated counterions are modeled as beads with charges distributed around the bead center in an implicit dielectric medium. The proposed models semiquantitatively describe self-assembly in solutions of SDS and CTAB at various surfactant concentrations and molarities of added electrolyte. In particular, the model predicts a decline in the free surfactant concentration with the increase of the total surfactant loading, as well as characteristic aggregation transitions in single-component surfactant solutions caused by the addition of salt. The calculated values of the critical micelle concentration reasonably agree with experimental observations. Modeling of catanionic SDS-CTAB mixtures show consecutive transitions to worm-like micelles and then to vesicles caused by the addition of CTAB to micellar solution of SDS.
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Affiliation(s)
- Runfang Mao
- Department of Chemical Engineering, Rutgers, the State University of New Jersey , 98 Brett Road, Piscataway, New Jersey 08854, United States
| | - Ming-Tsung Lee
- Department of Chemical Engineering, Rutgers, the State University of New Jersey , 98 Brett Road, Piscataway, New Jersey 08854, United States
| | - Aleksey Vishnyakov
- Department of Chemical Engineering, Rutgers, the State University of New Jersey , 98 Brett Road, Piscataway, New Jersey 08854, United States
| | - Alexander V Neimark
- Department of Chemical Engineering, Rutgers, the State University of New Jersey , 98 Brett Road, Piscataway, New Jersey 08854, United States
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36
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Dorenbos G. Morphology and diffusion within model membranes: Application of bond counting method to architectures with bimodal side chain length distributions. Eur Polym J 2015. [DOI: 10.1016/j.eurpolymj.2015.05.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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37
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Dorenbos G. Searching for low percolation thresholds within amphiphilic polymer membranes: The effect of side chain branching. J Chem Phys 2015; 142:224902. [DOI: 10.1063/1.4922156] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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38
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Clark JK, Habenicht BF, Paddison SJ. Ab initio molecular dynamics simulations of aqueous triflic acid confined in carbon nanotubes. Phys Chem Chem Phys 2015; 16:16465-79. [PMID: 24983213 DOI: 10.1039/c4cp01066c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ab initio molecular dynamics simulations were performed to investigate the effects of nanoscale confinement on the structural and dynamical properties of aqueous triflic acid (CF3SO3H). Single-walled carbon nanotubes (CNTs) with diameters ranging from ∼11 to 14 Å were used as confinement vessels, and the inner surface of the CNT were either left bare or fluorinated to probe the influence of the confined environment on structural and dynamical properties of the water and triflic acidic. The systems were simulated at hydration levels of n = 1-3 H2O/CF3SO3H. Proton dissociation expectedly increased with increasing hydration. Along with the level of hydration, hydrogen bond connectivity between the triflic acid molecules, both directly and via a single water molecule, played a role on proton dissociation. Direct hydrogen bonding between the CF3SO3H molecules, most commonly found in the larger bare CNT, also promoted interactions between water molecules allowing for greater separation of the dissociated protons from the CF3SO3(-) as the hydration level was increased. However, this also resulted in a decrease in the overall proportion of dissociated protons. The confinement dimensions altered both the hydrogen bond network and the distribution of water molecules where the H2O in the fluorinated CNTs tended to form small clusters with less proton dissociation at n = 1 and 2 but the highest at n = 3. In the absence of nearby hydrogen bond accepting sites from H2O or triflic acid SO3H groups, the water molecules formed weak hydrogen bonds with the fluorine atoms. In the bare CNT systems, these involved the CF3 groups of triflic acid and were more frequently observed when direct hydrogen bonding between CF3SO3H hindered potential hydrogen bonding sites. In the fluorinated tubes, interactions with the covalently bound fluorine atoms of the CNT wall dominated which appear to stabilize the hydrogen bond network. Increasing the hydration level increased the frequency of the OH···F (CNT) hydrogen bonding which was highly pronounced in the smaller fluorinated CNT indicating an influence on the confinement dimensions on these interactions.
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Affiliation(s)
- Jeffrey K Clark
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA.
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39
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Dorenbos G. Water diffusion within hydrated model grafted polymeric membranes with bimodal side chain length distributions. SOFT MATTER 2015; 11:2794-2805. [PMID: 25703230 DOI: 10.1039/c5sm00016e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The effect of bimodal side chain length distributions on pore morphology and solvent diffusion within hydrated amphiphilic polymeric membranes is predicted. Seven polymeric architectures are constructed from hydrophobic backbones from which at regular intervals side chains branch off that are alternatingly short (composed of p hydrophobic A fragments or beads) and long (q A fragments, q > p). The side chains are end-linked with a hydrophilic C fragment. Pore morphologies at a water volume fraction of 0.16 are calculated by dissipative particle dynamics (DPD). Water diffusion through the water containing pores is calculated by tracer diffusion calculations through 140 selected snapshots and from the water bead motions. Diffusion constants decrease with difference in side chain lengths, q - p. Overall, the distance between pores also decreases with q - p. The results are explained by counting for every architecture the average number of bonds 〈N(bond)〉 between an A and the nearest C fragment. These results are in line with a database that contains more than 60 architectures. Diffusion constants tend to increase linearly with 〈N(bond)〉|C|(-1)|A|, where |C| and |A| are the C and A bead fractions within the architecture. 〈N(bond)〉 is therefore expected to be an interesting design parameter for obtaining low percolation thresholds for solvent and/or proton diffusion.
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Affiliation(s)
- G Dorenbos
- 410-1118, 1107-2 sano, Belle Crea 502, Susono-shi, Shizuoka-ken, Japan.
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40
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Dorenbos G. Pore design within amphiphilic polymer membranes: linear versus Y-shaped side chain architectures. RSC Adv 2014. [DOI: 10.1039/c4ra00919c] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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41
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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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42
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Balog S, Jetsrisuparb K, Gasser U, Scherer GG, Gubler L. Structure of the aqueous phase and its impact on the conductivity of graft copolymer ionomers at saturation. POLYMER 2014. [DOI: 10.1016/j.polymer.2014.05.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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43
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Wang C, Paddison SJ. Mesoscale modeling of hydrated morphologies of sulfonated polysulfone ionomers. SOFT MATTER 2014; 10:819-830. [PMID: 24651930 DOI: 10.1039/c3sm52330f] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The hydrated morphologies of sulfonated poly(phenylene) sulfone (sPSO2) ionomers as a function of equivalent weight (EW), molecular weight (MW), and water content were investigated by using mesoscale dissipative particle dynamics (DPD) simulations. The morphological changes were characterized by analyzing the water distribution and plotting the radial distribution functions for the water particles. The results were compared to typical PFSA ionomers (i.e., Nafion and Aquivion) to evaluate the effects of backbone and side chain chemistry. Our results show that water is more likely to be equally distributed within the hydrophilic domains of the sPSO2 ionomers particularly at low water content, which is in contrast to strong phase separation observed in PFSA ionomers at the same level of hydration. As the degree of sulfonation is increased (i.e., decreasing the EW), well-connected water clusters develop in the sPSO2 ionomers even at low water content which are less affected by changes in the MW than observed for PFSA ionomers. The size of the water clusters is estimated to be from 1.2 to 1.5 nm (compared to ∼ 3.5 nm in Nafion) at a water content of 7H2O/SO3H, which is consistent with results determined from previous experiments. This suggests that the high proton conductivity observed in the sPSO2 ionomers is due to the well-connected hydrophilic pathways.
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Affiliation(s)
- Chen Wang
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA.
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44
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Li J, Pan M, Tang H. Understanding short-side-chain perfluorinated sulfonic acid and its application for high temperature polymer electrolyte membrane fuel cells. RSC Adv 2014. [DOI: 10.1039/c3ra43735c] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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45
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Mecheri B, Felice V, D'Epifanio A, Tavares AC, Licoccia S. Composite Polymer Electrolytes for Fuel Cell Applications: Filler-Induced Effect on Water Sorption and Transport Properties. Chemphyschem 2013; 14:3814-21. [DOI: 10.1002/cphc.201300637] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 09/09/2013] [Indexed: 11/09/2022]
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46
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Xiao P, Li J, Tang H, Wang Z, Pan M. Physically stable and high performance Aquivion/ePTFE composite membrane for high temperature fuel cell application. J Memb Sci 2013. [DOI: 10.1016/j.memsci.2013.04.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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47
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Guo H, Qiu X, Zhou J. Self-assembled core-shell and Janus microphase separated structures of polymer blends in aqueous solution. J Chem Phys 2013; 139:084907. [DOI: 10.1063/1.4817003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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48
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49
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Giffin GA, Haugen GM, Hamrock SJ, Di Noto V. Interplay between structure and relaxations in perfluorosulfonic acid proton conducting membranes. J Am Chem Soc 2013; 135:822-34. [PMID: 23249300 DOI: 10.1021/ja3099799] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This study focuses on changes in the structure of ionomer membranes, provided by the 3M Fuel Cells Component Group, as a function of the equivalent weight (EW) and the relationship between the structure and the properties of the membrane. Wide-angle X-ray diffraction results showed evidence of both non-crystalline and crystalline ordered hydrophobic regions in all the EW membranes except the 700 EW membrane. The spectral changes evident in the vibrational spectra of the 3M membranes can be associated with two major phenomena: (1) dissociation of the proton from the sulfonic acid groups even in the presence of small amounts of water; and (2) changes in the conformation or the degree of crystallinity of the poly(tetrafluoroethylene) hydrophobic domains both as a function of EW and membrane water content. All the membranes, regardless of EW, are thermally stable up to 360 °C. The wet membranes have conductivities between 7 and 20 mS/cm at 125 °C. In this condition, the conductivity values follow VTF behavior, which suggests that the proton migration occurs via proton exchange processes between delocalization bodies (DBs) that are facilitated by the dynamics of the host polymer. The conductivity along the interface between the hydrophobic and hydrophilic domains makes a larger contribution in the smaller EW membranes likely due to the existence of a greater number of interfaces in the membrane. The larger crystalline domains present in the higher EW membranes provide percolation pathways for charge migration between DBs, which reduces the probability of charge transfer along the interface. Therefore, at higher EWs although there is charge migration along the interface within the hydrophobic-hydrophilic domains, the exchange of protons between different DBs is likely the rate-limiting step of the overall conduction process.
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Affiliation(s)
- Guinevere A Giffin
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, I-35131 Padova, Italy
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Nikolić D, Moffat KA, Farrugia VM, Kobryn AE, Gusarov S, Wosnick JH, Kovalenko A. Multi-scale modeling and synthesis of polyester ionomers. Phys Chem Chem Phys 2013; 15:6128-38. [DOI: 10.1039/c3cp44285c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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