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Teschke O, Burguim JA, Gomes WE, Soares DM. Fibrillary Arrangement of Elongated, Almost Parallel Aggregates of Hydrophobic and Hydrophilic Domains Forming the Nafion Surface Structure Improved Contrast Atomic Force Microscopy Images. ACS OMEGA 2023; 8:49073-49079. [PMID: 38162764 PMCID: PMC10753714 DOI: 10.1021/acsomega.3c06927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/27/2023] [Accepted: 11/29/2023] [Indexed: 01/03/2024]
Abstract
A significant improvement in spatial resolution is reported in Nafion surface maps when compared to previous atomic force microscopy images of the Nafion surface scanned in air. The technique ability is to generate maps showing approximately few nanometer (∼2-5 nm) patterns to the long fiber length (>2 μm). Atomic force microscopy force vs separation curve profiles registered in water are used to characterize the surface hydrophobic and hydrophilic domains. Initially, Nafion surfaces were imaged in air for comparison and then immersed in water. Nafion surfaces immersed in water display a matrix of hydrophilic and hydrophobic regions with fibrillary structure dimensions of ∼40 nm formed by fiber pairs. Ribbons formed by two pairs with diameters of ∼83 nm are separated by larger channels.
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Affiliation(s)
- Omar Teschke
- Laboratório
de Nanoestruturas e Interfaces, Instituto
de Física, UNICAMP, Campinas, SP 13083-859, Brazil
| | | | - Wyllerson Evaristo Gomes
- Faculdade
de Quimica, Pontificia Universidade Catolica
de Campinas, Campinas, SP 13012-970, Brazil
| | - David Mendez Soares
- Laboratório
de Nanoestruturas e Interfaces, Instituto
de Física, UNICAMP, Campinas, SP 13083-859, Brazil
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2
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Cui R, Li S, Yu C, Zhou Y. The Evolution of Hydrogen Bond Network in Nafion via Molecular Dynamics Simulation. Macromolecules 2023. [DOI: 10.1021/acs.macromol.2c02106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- Rui Cui
- School of Chemistry & Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Shanlong Li
- School of Chemistry & Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Chunyang Yu
- School of Chemistry & Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Yongfeng Zhou
- School of Chemistry & Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
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3
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4
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Roget SA, Piskulich ZA, Thompson WH, Fayer MD. Identical Water Dynamics in Acrylamide Hydrogels, Polymers, and Monomers in Solution: Ultrafast IR Spectroscopy and Molecular Dynamics Simulations. J Am Chem Soc 2021; 143:14855-14868. [PMID: 34491037 DOI: 10.1021/jacs.1c07151] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The dynamics and structure of water in polyacrylamide hydrogels (PAAm-HG), polyacrylamide, and acrylamide solutions are investigated using ultrafast infrared experiments on the OD stretch of dilute HOD/H2O and molecular dynamics simulations. The amide moiety of the monomer/polymers interacts strongly with water through hydrogen bonding (H-bonding). The FT-IR spectra of the three systems indicate that the range of H-bond strengths is relatively unchanged from bulk water. Vibrational population relaxation measurements show that the amide/water H-bonds are somewhat weaker but fall within the range of water/water H-bond strengths. A previous study of water dynamics in PAAm-HG suggested that the slowing observed was due to increasing confinement with concentration. Here, for the same concentrations of the amide moiety, the experimental results demonstrate that the reorientational dynamics (infrared pump-probe experiments) and structural dynamics (two-dimensional infrared spectroscopy) are identical in the three acrylamide systems studied. Molecular dynamics simulations of the water orientational relaxation in aqueous solutions of the acrylamide monomer, trimer, and pentamer are in good agreement with the experimental results and are essentially chain length independent. The simulations show that there is a slower, low-amplitude (<7%) decay component not accessible by the experiments. The simulations examine the dynamics and structure of water H-bonded to acrylamide, in the first solvent shell, and beyond for acrylamide monomers and short chains. The experiments and simulations show that the slowing of water dynamics in PAAm-HG is not caused by confinement in the polymer network but rather by interactions with individual acrylamide moieties.
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Affiliation(s)
- Sean A Roget
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Zeke A Piskulich
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Ward H Thompson
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Michael D Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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5
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Cheng RH, Cai H, Huang YR, Cui X, Chen Z, Chen HY, Ding S. A broad-range variable-temperature solid state NMR spectral and relaxation investigation of the water state in Nafion 117. Phys Chem Chem Phys 2021; 23:10899-10908. [PMID: 33908418 DOI: 10.1039/c9cp05978d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Understanding the water state in Nafion is not only crucial for operating a proton-exchange membrane (PEM)-based fuel cell, but also intimately related to the elucidation of the proton transport mechanism in a PEM. Although many studies have been published on this subject, some controversies and ambiguities remain unresolved. In this work, we design three different types of Nafion samples by substituting protons with lithium or sodium cations. We also pay special attention to the preparation of samples for carrying out broad-range variable temperature solid state NMR experiments so that no membrane dehydration occurs during the long experimental time at low temperatures. With these precautions and improvements, clear and largely straightforward information could be obtained to ensure minimal ambiguity and complexity in the interpretation of the experimental data. Our results show that about 40-60% of water remains unfrozen at -70 °C, depending on the type of the substituting cation. Both the 1H and 2H spectral and relaxation results indicate that water freezing starts from the center of the nanopores inside Nafion and increases gradually as the temperature decreases. The protons remain dissociated with sulfonate groups even at the lowest temperature we reached (-70 °C), whereas both lithium and sodium are associated with sulfonate groups at most temperatures below 0 °C. The experimental data also suggest that besides frozen and unfrozen water, there is broad distribution of water state and dynamics in Nafion as the temperature is lowered from above zero down to -70 °C. The effect of the size of the substituting cation significantly affects the properties of supercooled water by modifying the cation-water interaction and impeding the rotation of sulfonate groups. These novel results not only help us in establishing a better understanding of the water state in Nafion and its performance as a proton exchange mebrane, but also provide insights into water freezing, antifreeze and supercooling in other nanoscopic environments.
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Affiliation(s)
- Ren-Hao Cheng
- Department of Chemistry and Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, 70 Lien-Hai Road, Kaohsiung, 80424, Taiwan.
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6
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Chang K, Luo H, Geise GM. Influence of Salt Concentration on Hydrated Polymer Relative Permittivity and State of Water Properties. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02188] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kevin Chang
- Department of Chemical Engineering, University of Virginia, 102 Engineers’ Way, P.O.
Box 400741, Charlottesville, Virginia 22904, United States
| | - Hongxi Luo
- Department of Chemical Engineering, University of Virginia, 102 Engineers’ Way, P.O.
Box 400741, Charlottesville, Virginia 22904, United States
| | - Geoffrey M. Geise
- Department of Chemical Engineering, University of Virginia, 102 Engineers’ Way, P.O.
Box 400741, Charlottesville, Virginia 22904, United States
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7
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Yamada SA, Hung ST, Thompson WH, Fayer MD. Effects of pore size on water dynamics in mesoporous silica. J Chem Phys 2020; 152:154704. [DOI: 10.1063/1.5145326] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- Steven A. Yamada
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Samantha T. Hung
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Ward H. Thompson
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA
| | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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8
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Eneh CI, Bolen MJ, Suarez-Martinez PC, Bachmann AL, Zimudzi TJ, Hickner MA, Batys P, Sammalkorpi M, Lutkenhaus JL. Fourier transform infrared spectroscopy investigation of water microenvironments in polyelectrolyte multilayers at varying temperatures. SOFT MATTER 2020; 16:2291-2300. [PMID: 32043105 DOI: 10.1039/c9sm02478f] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Polyelectrolyte multilayers (PEMs) are thin films formed by the alternating deposition of oppositely charged polyelectrolytes. Water plays an important role in influencing the physical properties of PEMs, as it can act both as a plasticizer and swelling agent. However, the way in which water molecules distribute around and hydrate ion pairs has not been fully quantified with respect to both temperature and ionic strength. Here, we examine the effects of temperature and ionic strength on the hydration microenvironments of fully immersed poly(diallyldimethylammonium)/polystyrene sulfonate (PDADMA/PSS) PEMs. This is accomplished by tracking the OD stretch peak using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy at 0.25-1.5 M NaCl and 35-70 °C. The OD stretch peak is deconvoluted into three peaks: (1) high frequency water, which represents a tightly bound microenvironment, (2) low frequency water, which represents a loosely bound microenvironment, and (3) bulk water. In general, the majority of water absorbed into the PEM exists in a bound state, with little-to-no bulk water observed. Increasing temperature slightly reduces the amount of absorbed water, while addition of salt increases the amount of absorbed water. Finally, a van't Hoff analysis is applied to estimate the enthalpy (11-22 kJ mol-1) and entropy (48-79 kJ mol-1 K-1) of water exchanging from low to high frequency states.
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Affiliation(s)
- Chikaodinaka I Eneh
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77840, USA.
| | - Matthew J Bolen
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77840, USA.
| | - Pilar C Suarez-Martinez
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77840, USA.
| | - Adam L Bachmann
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Tawanda J Zimudzi
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Michael A Hickner
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Piotr Batys
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, PL-30239 Krakow, Poland
| | - Maria Sammalkorpi
- Department of Chemistry and Materials Science, Aalto University, PO Box 16100, 00076 Aalto, Finland and Department of Bioproducts and Biosystems, Aalto University, PO Box 16100, 00076 Aalto, Finland
| | - Jodie L Lutkenhaus
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77840, USA. and Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77840, USA
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9
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Roget SA, Kramer PL, Thomaz JE, Fayer MD. Bulk-like and Interfacial Water Dynamics in Nafion Fuel Cell Membranes Investigated with Ultrafast Nonlinear IR Spectroscopy. J Phys Chem B 2019; 123:9408-9417. [PMID: 31580076 DOI: 10.1021/acs.jpcb.9b07592] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The water confined in the hydrophilic domains of Nafion fuel cell membranes is central to its primary function of ion transport. Water dynamics are intimately linked to proton transfer and are sensitive to the structural features and length scales of confinement. Here, ultrafast polarization-selective pump-probe and two-dimensional infrared vibrational echo (2D IR) experiments were performed on fully hydrated Nafion membranes with sodium counterions to explicate the water dynamics. Like aerosol-OT reverse micelles (AOT RMs), the water dynamics in Nafion are attributed to bulk-like core water in the central region of the hydrophilic domains and much slower interfacial water. Population and orientational dynamics of water in Nafion are slowed by polymer confinement. Comparison of the observed dynamics to those of AOT RMs helps identify local interactions between water and sulfonate anions at the interface and among water molecules in the core. This comparison also demonstrates that the well-known spherical cluster morphology of Nafion is not appropriate. Spectral diffusion of the interfacial water, which arises from structural dynamics, was obtained from the 2D IR experiments taking the core water to have dynamics similar to bulk water. Like the orientational dynamics, spectral diffusion was found to be much slower at the interface compared to bulk water. Together, the dynamics indicate slow reorganization of weakly hydrogen-bonded water molecules at the interface of Nafion. These results provide insights into proton transport mechanisms in fuel cell membranes, and more generally, water dynamics near the interface of confining systems.
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Affiliation(s)
- Sean A Roget
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Patrick L Kramer
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Joseph E Thomaz
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Michael D Fayer
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
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10
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Non-invasive macroscopic and molecular quantification of water in Nafion® and SPEEK Proton Exchange Membranes using terahertz spectroscopy. J Memb Sci 2019. [DOI: 10.1016/j.memsci.2019.117183] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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11
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Dunkelberger AD, Fears KP, Davidson II RB, Dressick WJ, Simpkins BS, Owrutsky JC. Vibrational relaxation of small anions in a polymer film. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.03.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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12
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Biswas S, Santra S, Yesylevskyy S, Maiti J, Jana M, Das R. Picosecond Solvation Dynamics in Nanoconfinement: Role of Water and Host-Guest Complexation. J Phys Chem B 2018. [PMID: 29527896 DOI: 10.1021/acs.jpcb.7b10376] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The dynamics of solvation of an excited chromophore, 5-(4″-dimethylaminophenyl)-2-(4'-sulfophenyl)oxazole, sodium salt (DMO), has been explored in confined nanoscopic environments of β-cyclodextrin (βCD) and heptakis(2,6-di- O-methyl)-β-cyclodextrin (DIMEB). Solvation occurs on a distinctly slower time scale (τS3 ∼ 47 ps, τS4 ∼ 517 ps) in the host cavity of DIMEB than in that of βCD (τS3 ∼ 20 ps, τS4 ∼ 174 ps). The calculated equilibrium solvation response of DMO was characterized by four relaxation components (τS1 ∼ 0.46-0.48 ps, τS2 ∼ 3.2-3.4 ps, τS3 ∼ 32.3-37.7 ps, and τS4 ∼ 232-485 ps), of which the longer ones (τS3, τS4) are well-consistent with experiments, whereas the ultrafast components (τS1, τS2) are unresolved. The observed time constant (τS3) within the ∼20-47 ps range arises from slow water molecules in the primary hydration layers of the host CDs and is slower for DIMEB than for βCD presumably due to longer-lived and stronger hydrogen bonds that water forms with the former host relative to the latter. Decomposition of the calculated solvation response of DMO has revealed that conformational fluctuations of the macrocyclic hosts give rise to the observed long-time relaxation component (τS4), which is much slower for the inclusion complexes with DIMEB than for those with βCD because of slower conformational dynamics of the former host than that of the latter.
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Affiliation(s)
- Suman Biswas
- Department of Chemistry , West Bengal State University , Barasat, Kolkata 700126 , India
| | - Santanu Santra
- Molecular Simulation Laboratory, Department of Chemistry , National Institute of Technology , Rourkela 769008 , Orissa , India
| | - Semen Yesylevskyy
- Institute of Physics , National Academy of Sciences of Ukraine , 03028 Kyiv , Ukraine
| | - Jyotirmay Maiti
- Department of Chemistry , West Bengal State University , Barasat, Kolkata 700126 , India
| | - Madhurima Jana
- Molecular Simulation Laboratory, Department of Chemistry , National Institute of Technology , Rourkela 769008 , Orissa , India
| | - Ranjan Das
- Department of Chemistry , West Bengal State University , Barasat, Kolkata 700126 , India
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13
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14
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Barique MA, Tsuchida E, Ohira A, Tashiro K. Effect of Elevated Temperatures on the States of Water and Their Correlation with the Proton Conductivity of Nafion. ACS OMEGA 2018; 3:349-360. [PMID: 31457896 PMCID: PMC6641407 DOI: 10.1021/acsomega.7b01765] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 12/27/2017] [Indexed: 06/10/2023]
Abstract
For the first time, we report the effects of elevated temperatures, from 80 to 100 °C, on the changes in the states of water and ion-water channels and their correlation with the proton conductivity of Nafion NR212, which was investigated using a Fourier transform infrared spectroscopy study. Experimentally, three types of water aggregates, protonated water (H+(H2O) n ), nonprotonated hydrogen (H)-bonded water (H2O···H2O), and non-H-bonded water, were found in Nafion, and the existence of those three types of water was confirmed through ab initio molecular dynamics simulation. We found that the proton conductivity of Nafion increased for up to 80 °C, but from 80 to 100 °C, the conductivity did not increase; rather, all of those elevated temperatures showed identical conductivity values. The proton conductivities at lower relative humidities (RHs) (up to 50%) remained nearly identical for all elevated temperatures (80, 90, and 100 °C); however, from 60% RH (over λ = 4), the conductivity remarkably jumped for all elevated temperatures. The results indicated that the amount of randomly arranged water gradually increased and created more H-bonded water networks in Nafion at above 60% RH. From the deconvolution of the O-H bending band, it was found that the volume fraction f i (i=each deconvoluted band) of H-bonded water for elevated temperatures (>80-100 °C) increased remarkably higher than for 60 °C.
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Affiliation(s)
- Mohammad A. Barique
- Fuel
Cell Cutting-Edge Research Center TRA, National
Institute of Advanced Industrial Science and Technology Main Building, 2-3-26 Aomi, Koto-ku, Tokyo 135-0064, Japan
| | - Eiji Tsuchida
- Research
Center for Computational Design of Advanced Functional Materials, National Institute of Advanced Industrial Science
and Technology, Tsukuba
Central 2, 1-1-1 Umezono, Tsukuba 305-8568, Japan
| | - Akihiro Ohira
- Fuel
Cell Cutting-Edge Research Center TRA, National
Institute of Advanced Industrial Science and Technology Main Building, 2-3-26 Aomi, Koto-ku, Tokyo 135-0064, Japan
- Research
Institute for Energy Conservation, National
Institute of Advanced Industrial Science and Technology, Tsukuba Central 2, 1-1-1 Umezono, Tsukuba 305-8568, Japan
| | - Kohji Tashiro
- Toyota
Technological Institute, 2-12-1, Hisakata, Tempaku, Nagoya 468-8511, Japan
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15
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Smedley SB, Zimudzi TJ, Chang Y, Bae C, Hickner MA. Spectroscopic Characterization of Sulfonate Charge Density in Ion-Containing Polymers. J Phys Chem B 2017; 121:11504-11510. [DOI: 10.1021/acs.jpcb.7b06904] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sarah B. Smedley
- Department
of Material Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Tawanda J. Zimudzi
- Department
of Material Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Ying Chang
- Department
of Chemistry and Chemical Biology, New York State Center for Polymer
Synthesis, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Chulsung Bae
- Department
of Chemistry and Chemical Biology, New York State Center for Polymer
Synthesis, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Michael A. Hickner
- Department
of Material Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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16
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Gong C, Pinatti L, Lavigne G, Shaw MT, Scola DA. Thermal stability of end-capped and linear sulfonated polyimides, sulfonated polystyrene, and Nafion 117. J Appl Polym Sci 2017. [DOI: 10.1002/app.45694] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Chenliang Gong
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering; Lanzhou University; Lanzhou 730000 People's Republic of China
| | - Laura Pinatti
- Polymer Science Program, Institute of Materials Science; University of Connecticut; 97 North Eagleville Road, U-3136, Storrs Connecticut 06269-3136
| | - Gary Lavigne
- Polymer Science Program, Institute of Materials Science; University of Connecticut; 97 North Eagleville Road, U-3136, Storrs Connecticut 06269-3136
| | - Montgomery T. Shaw
- Polymer Science Program, Institute of Materials Science; University of Connecticut; 97 North Eagleville Road, U-3136, Storrs Connecticut 06269-3136
| | - Daniel A. Scola
- Polymer Science Program, Institute of Materials Science; University of Connecticut; 97 North Eagleville Road, U-3136, Storrs Connecticut 06269-3136
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17
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Kundu A, Verma PK, Cho M. Role of Solvent Water in the Temperature-Induced Self-Assembly of a Triblock Copolymer. J Phys Chem Lett 2017; 8:3040-3047. [PMID: 28613892 DOI: 10.1021/acs.jpclett.7b01008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Water-soluble triblock copolymers have received much attention in industrial applications and scientific fields. We here show that femtosecond mid-IR pump-probe spectroscopy is useful to study the role of water in the temperature-induced self-assembly of triblock copolymers. Our experimental results suggest two distinct subpopulations of water molecules: those that interact with other water molecules and those involved in the hydration of a triblock copolymer surface. We find that the vibrational dynamics of bulk-like water is not affected by either micellation or gelation of triblock copolymers. The increased population of water interacting with ether oxygen atoms of the copolymer during the unimer to micelle phase transition is important evidence for the entropic role of water in temperature-induced micelle formation at a low copolymer concentration. In contrast, at the critical gelation temperature and beyond, the population of surface-associated water molecules interacting with ether oxygen atoms decreases, which indicates important enthalpic control by water. The present study on the roles of water in the two different phase transitions of triblock copolymers sheds new light on the underlying mechanisms of temperature-induced self-aggregation behaviors of amphiphiles that are ubiquitous in nature.
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Affiliation(s)
- Achintya Kundu
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS) , Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University , Seoul 02841, Republic of Korea
| | - Pramod Kumar Verma
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS) , Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University , Seoul 02841, Republic of Korea
| | - Minhaeng Cho
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS) , Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University , Seoul 02841, Republic of Korea
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18
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Thomaz JE, Lawler CM, Fayer MD. Proton Transfer in Perfluorosulfonic Acid Fuel Cell Membranes with Differing Pendant Chains and Equivalent Weights. J Phys Chem B 2017; 121:4544-4553. [PMID: 28398064 DOI: 10.1021/acs.jpcb.7b01764] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proton transfer in the nanoscopic water channels of polyelectrolyte fuel cell membranes was studied using a photoacid, 8-hydroxypyrene-1,3,6-trisulfonic acid sodium salt (HPTS), in the channels. The local environment of the probe was determined using 8-methoxypyrene-1,3,6-trisulfonic acid sodium salt (MPTS), which is not a photoacid. Three fully hydrated membranes, Nafion (DuPont) and two 3M membranes, were studied to determine the impact of different pendant chains and equivalent weights on proton transfer. Fluorescence anisotropy and excited state population decay data that characterize the local environment of the fluorescent probes and proton transfer dynamics were measured. The MPTS lifetime and anisotropy results show that most of the fluorescent probes have a bulk-like water environment with a relatively small fraction interacting with the channel wall. Measurements of the HPTS protonated and deprotonated fluorescent bands' population decays provided information on the proton transport dynamics. The decay of the protonated band from ∼0.5 ns to tens of nanoseconds is in part determined by dissociation and recombination with the HPTS, providing information on the ability of protons to move in the channels. The dissociation and recombination is manifested as a power law component in the protonated band fluorescence decay. The results show that equivalent weight differences between two 3M membranes resulted in a small difference in proton transfer. However, differences in pendant chain structure did significantly influence the proton transfer ability, with the 3M membranes displaying more facile transfer than Nafion.
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Affiliation(s)
- Joseph E Thomaz
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Christian M Lawler
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Michael D Fayer
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
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19
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Kim SH, Mehmood A, Ahn Y, Kim HS, Ha HY, Kim D, Han OH. Proton conductivity improvement of polymer electrolyte membrane using nano-scale explosion of water in the membrane. J Electroanal Chem (Lausanne) 2016. [DOI: 10.1016/j.jelechem.2016.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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20
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Prakash M, Subramanian V. Ab initio and density functional theory (DFT) studies on triflic acid with water and protonated water clusters. J Mol Model 2016; 22:293. [PMID: 27888404 DOI: 10.1007/s00894-016-3158-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 11/08/2016] [Indexed: 02/04/2023]
Abstract
The structure, stability and infrared spectral signatures of triflic acid (TA) with water clusters (Wn) and protonated water clusters (TAH+Wn, n = 1 - 6) were computed using DFT and MP2 methods. Our calculations show that a minimum of three water molecules are necessary to stabilize the dissociated zwitterionic form of TA. It can be seen from the results that there is no significant movement of protons in smaller (n = 1 and 2) and linear (n = 1 - 6) types of water clusters. Further, the geometries of TAWn clusters first form a neutral pair (NP) to contact ion pair (CIP), then form a solvent separated ion pair (SSIP) in a water hexamer. These findings reveal that proton transfer may take place through NP to CIP and then CIP to SSIP. The calculated binding energies (BEs) of ion pair clusters is always higher than that of NP clusters (i.e., more stable than the NP). Existing excess proton linear chain clusters transfer a proton to adjacent water molecules via a Grotthuss mechanism, whereas the same isomers in the branched motifs do not conduct protons. Examination of geometrical parameters and infrared frequencies reveals hydronium ion (H3O+ also called Eigen cation) formation in both TAWn and protonated TAWn clusters. The stability of Eigen water clusters is three times higher than that of other non-Eigen water clusters. Our study shows clearly that formation of ion pairs in TAWn and TAH+Wn clusters greatly favors proton transfer to neighboring water molecules and also enhances the stability of these complexes.
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Affiliation(s)
- M Prakash
- Department of Chemistry and Research Institute, SRM University, Kattankulathur, 603203, Tamil Nadu, India
- Chemical Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai, 600 020, India
| | - V Subramanian
- Chemical Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai, 600 020, India.
- Academy of Scientific and Innovative Research (AcSIR), CSIR-CLRI Campus, Chennai, 600 020, India.
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21
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Singh RK, Kunimatsu K, Miyatake K, Tsuneda T. Experimental and Theoretical Infrared Spectroscopic Study on Hydrated Nafion Membrane. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b00999] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Raman K. Singh
- Fuel Cell
Nanomaterials Centre, University of Yamanashi, Kofu 400-0021, Japan
| | - Keiji Kunimatsu
- Fuel Cell
Nanomaterials Centre, University of Yamanashi, Kofu 400-0021, Japan
| | - Kenji Miyatake
- Fuel Cell
Nanomaterials Centre, University of Yamanashi, Kofu 400-0021, Japan
| | - Takao Tsuneda
- Fuel Cell
Nanomaterials Centre, University of Yamanashi, Kofu 400-0021, Japan
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22
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Plazanet M, Torre R, Sacchetti F. Confinement, entropic effects and hydrogen bond network fluctuations of water in Nafion membrane. J Mol Liq 2016. [DOI: 10.1016/j.molliq.2016.01.079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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23
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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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24
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Shimoaka T, Wakai C, Sakabe T, Yamazaki S, Hasegawa T. Hydration structure of strongly bound water on the sulfonic acid group in a Nafion membrane studied by infrared spectroscopy and quantum chemical calculation. Phys Chem Chem Phys 2015; 17:8843-9. [DOI: 10.1039/c5cp00567a] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The hydration structure of the ‘strongly bound water’ around the sulfonic acid (SA) groups in Nafion is studied using infrared spectroscopy with the aid of quantum chemical (QC) calculations.
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Affiliation(s)
- T. Shimoaka
- Laboratory of Solution and Interface Chemistry
- Division of Environmental Chemistry
- Institute for Chemical Research
- Kyoto University
- Uji
| | - C. Wakai
- Laboratory of Solution and Interface Chemistry
- Division of Environmental Chemistry
- Institute for Chemical Research
- Kyoto University
- Uji
| | - T. Sakabe
- Analysis and Simulation Center
- Asahi Kasei Corporation
- Fuji-shi
- Japan
| | - S. Yamazaki
- Analysis and Simulation Center
- Asahi Kasei Corporation
- Fuji-shi
- Japan
| | - T. Hasegawa
- Laboratory of Solution and Interface Chemistry
- Division of Environmental Chemistry
- Institute for Chemical Research
- Kyoto University
- Uji
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25
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Venkatesan SV, Lim C, Rogers E, Holdcroft S, Kjeang E. Evolution of water sorption in catalyst coated membranes subjected to combined chemical and mechanical degradation. Phys Chem Chem Phys 2015; 17:13872-81. [DOI: 10.1039/c5cp01641j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Ionomer water sorption is altered with combined chemical and mechanical degradation.
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Affiliation(s)
| | - Chan Lim
- School of Mechatronic Systems Engineering
- Simon Fraser University
- Surrey
- Canada
| | | | | | - Erik Kjeang
- School of Mechatronic Systems Engineering
- Simon Fraser University
- Surrey
- Canada
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26
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Kabrane J, Aquino AJA. Electronic Structure and Vibrational Mode Study of Nafion Membrane Interfacial Water Interactions. J Phys Chem A 2014; 119:1754-64. [DOI: 10.1021/jp5084339] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Joseph Kabrane
- Department
of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
| | - Adelia J. A. Aquino
- Department
of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
- Institute
of Soil Research, University of Natural Resources and Applied Life Sciences Vienna, Peter-Jordan-Strasse 82b, A 1190 Vienna, Austria
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27
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Singhal N, Datta A. Reversible Tuning of Chemical Structure of Nafion Cast Film by Heat and Acid Treatment. J Phys Chem B 2014; 119:2395-403. [DOI: 10.1021/jp506911w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Nancy Singhal
- Department
of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
| | - Anindya Datta
- Department
of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
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28
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Clark II JK, Paddison SJ. Ab initio molecular dynamics simulations of water and an excess proton in water confined in carbon nanotubes. Phys Chem Chem Phys 2014; 16:17756-69. [DOI: 10.1039/c4cp00415a] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Black SB, Chang Y, Bae C, Hickner MA. FTIR Characterization of Water–Polymer Interactions in Superacid Polymers. J Phys Chem B 2013; 117:16266-74. [DOI: 10.1021/jp406242h] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sarah B. Black
- Department
of Material Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Ying Chang
- Department
of Chemistry and Chemical Biology, New York State Center
for Polymer Synthesis, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Chulsung Bae
- Department
of Chemistry and Chemical Biology, New York State Center
for Polymer Synthesis, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Michael A. Hickner
- Department
of Material Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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30
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Sokolowsky KP, Fayer MD. Dynamics in the isotropic phase of nematogens using 2D IR vibrational echo measurements on natural-abundance 13CN and extended lifetime probes. J Phys Chem B 2013; 117:15060-71. [PMID: 24156524 DOI: 10.1021/jp4071955] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The long time scale orientational relaxation of nematogens in the isotropic phase is associated with the randomization of pseudonematic domains, which have a correlation length that grows as the isotropic-to-nematic phase transition temperature is approached from above. Here we begin to address the fast dynamics of the nematogen molecules within the domains using two-dimensional infrared (2D IR) vibrational echo experiments. The problems of performing ultrafast IR experiments in pure liquids are discussed, and solutions are presented. In addition, the issue of short vibrational lifetimes, which limit the ability of 2D IR experiments to examine dynamics over a wide range of times, is addressed. The experiments were performed on the nematogen 4-cyano-4'-pentylbiphenyl (5CB), with the CN stretch initially used as the vibrational probe. Although the CN stretch has a small transition dipole, because the sample is a pure liquid it is necessary to use an exceedingly thin sample to perform the experiments. The small sample volume leads to massive heating effects that distort the results. In addition, the high concentration in the pure liquid can result in vibrational excitation transfer that interferes with the measurements of structural dynamics, and the CN vibrational lifetime is very short (3.6 ps). These problems were overcome by performing the experiments on the natural-abundance (13)CN stretch (5(13)CB), which greatly reduced the absorbance, eliminating the heating problems; also, this stretch has a longer lifetime (7.9 ps). Experiments were also performed on benzonitrile, which showed that the heating problems associated with pure liquids are not unique to 5CB. Again, the problems were eliminated by conducting measurements on the (13)CN stretch, which has an even longer lifetime (20.2 ps) compared with the (12)CN stretch (5.6 ps). Finally, to extend the range of the dynamical measurements, 4-pentyl-4'-thiocyanobiphenyl (5SCB) was synthesized and studied as a dilute solute in 5CB. The CN stretch of 5SCB has a vibrational lifetime of 103 ps, which permits dynamical measurements to 200 ps, revealing the full range of fast structural dynamics in the isotropic phase of 5CB. It is shown that the 5SCB probe reports essentially the same dynamics as 5(13)CB on the short time scale that is observable with the 5(13)CB vibrational probe.
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Affiliation(s)
- Kathleen P Sokolowsky
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
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31
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Liu S, Aquino AJA, Korzeniewski C. Water-ionomer interfacial interactions investigated by infrared spectroscopy and computational methods. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:13890-13897. [PMID: 24111660 DOI: 10.1021/la402497w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Structures for interfacial water condensed in pores and channels of the fluorinated ionomer Nafion from low relative humidity atmosphere were probed through the use of Fourier transform infrared (FTIR) spectroscopy and support from classical and quantum chemical calculations. Modern FTIR spectra of H2O and the O-H stretching region for the deuterium-substituted HOD species interacting at the water-ionomer interface in Nafion exchanged by sodium cations are reported and compared to characteristics observed in the earlier studies that employed a dispersive infrared spectrometer and unspecified spectral resolution. Molecular simulations that examine the orientations of water molecules in the vicinity of ionomer were applied to understand the appearance of multiple free O-H stretching bands and the effect of HOD addition. One computational approach was based on a classical force field model, and the other employed density functional theory (DFT) to investigate atomic-scale interactions of water with regions of different hydrophobicity and charge on a perfluorosulfonate ionomer segment. The results suggest hydrogen bonding stabilizes the types of water-ionomer environments that can lead to multiple free O-H stretching vibrational features in experimental spectra. The studies shed light on the structure of H2O at interfaces inside ion conducting membrane materials and have potential for application in elucidating structure at different types of water interfaces.
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Affiliation(s)
- Shu Liu
- Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States
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32
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Yuan D, Liu Z, Tay SW, Fan X, Zhang X, He C. An amphiphilic-like fluoroalkyl modified SiO2 nanoparticle@Nafion proton exchange membrane with excellent fuel cell performance. Chem Commun (Camb) 2013; 49:9639-41. [DOI: 10.1039/c3cc45138k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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33
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Byun CK, Parker T, Liang C, Kendrick I, Dimakis N, Smotkin ES, Jin LM, Zhuang D, DesMarteau DD, Creager SE, Korzeniewski C. Thermal Processing as a Means to Prepare Durable, Submicron Thickness Ionomer Films for Study by Transmission Infrared Spectroscopy. Anal Chem 2012; 84:8127-32. [DOI: 10.1021/ac301662f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Chang Kyu Byun
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock,
Texas 79409-1061, United States
| | - Tifani Parker
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock,
Texas 79409-1061, United States
| | - Chunchao Liang
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock,
Texas 79409-1061, United States
| | - Ian Kendrick
- Department of Chemistry and
Chemical Biology, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Nicholas Dimakis
- Department of Physics and Geology, University of Texas Pan American, 1201 West University
Drive, Edinburg, Texas 78539, United States
| | - Eugene S. Smotkin
- Department of Chemistry and
Chemical Biology, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Li-Mei Jin
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973,
United States
| | - Dongqing Zhuang
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973,
United States
| | - Darryl D. DesMarteau
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973,
United States
| | - Stephen E. Creager
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973,
United States
| | - Carol Korzeniewski
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock,
Texas 79409-1061, United States
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34
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Gruenbaum SM, Pieniazek PA, Skinner JL. Vibrational spectroscopy of water in hydrated lipid multi-bilayers. II. Two-dimensional infrared and peak shift observables within different theoretical approximations. J Chem Phys 2012; 135:164506. [PMID: 22047251 DOI: 10.1063/1.3655671] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In a previous report, we calculated the infrared absorption spectrum and both the isotropic and anisotropic pump-probe signals for the OD stretch of isotopically dilute water in dilauroylphosphatidylcholine (DLPC) multi-bilayers as a function of the lipid hydration level. These results were then compared to recent experimental measurements and are in generally good agreement. In this paper, we will further investigate the structure and dynamics of hydration water using molecular dynamics simulations and calculations of the two-dimensional infrared and vibrational echo peak shift observables for hydration water in DLPC membranes. These observables have not yet been measured experimentally, but future comparisons may provide insight into spectral diffusion processes and hydration water heterogeneity. We find that at low hydration levels the motion of water molecules inside the lipid membrane is significantly arrested, resulting in very slow spectral diffusion. At higher hydration levels, spectral diffusion is more rapid, but still slower than in bulk water. We also investigate the effects of several common approximations on the calculation of spectroscopic observables by computing these observables within multiple levels of theory. The impact of these approximations on the resulting spectra affects our interpretation of these measurements and reveals that, for example, the cumulant approximation, which may be valid for certain systems, is not a good approximation for a highly heterogeneous environment such as hydration water in lipid multi-bilayers.
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Affiliation(s)
- Scott M Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave., University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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35
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Pismenskaya ND, Nikonenko VV, Melnik NA, Shevtsova KA, Belova EI, Pourcelly G, Cot D, Dammak L, Larchet C. Evolution with time of hydrophobicity and microrelief of a cation-exchange membrane surface and its impact on overlimiting mass transfer. J Phys Chem B 2012; 116:2145-61. [PMID: 22176351 DOI: 10.1021/jp2101896] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Surface properties were measured together with electrochemical characteristics of a CMX (Neosepta, Tokuyama Corp.) cation-exchange membrane. Relative hydrophobicity was controlled by the contact angle; XPS and SEM were used for characterizing chemical composition and microrelief of the surface, respectively. Voltammetry, chronopotentiometry, and mass transfer rate measurements were made as well. A "fresh" membrane and samples after 10, 25, 100, and 150 h of operation in an electrodialysis cell at an overlimiting current equal to 3 theoretical limiting currents, in a 0.02 M NaCl solution, were characterized. Some electrochemical properties were also measured for a Neosepta cation-exchange membrane, aged 2 years, in an industrial food process. It was found that the hydrophobicity of the CMX membrane has increased after the first 10 h of operation; more and more cavities of the dimension of the order of 1 μm have appeared with time testifying electrochemical erosion of the surface. The limiting current density (i(lim)) and the overlimiting transfer rate through the CMX membrane increased with time of its operation under overlimiting current. In the case of new CMX, i(lim) was very close to the theoretical value i(lim)(theor) calculated by the Lévêque equation. After 10 h of operation, i(lim) increased by 5%, and after 25, 100, and 150 h, the increase was by 30%, 70%, and 100%, respectively. Similarly, the mass transfer rate was found to increase up to 5 times (when desalting 0.005 M NaCl under 3 V) in comparison with the theoretical value. The ensemble of data was explained by the hypothesis that the passage of intensive current produces erosion of the ion-exchange polymer forming a continuous phase in CMX. This erosion results in exposure at the surface of the other constituent of CMX: small (about 100 nm) particles of relatively hydrophobic polyvinylchloride. Increasing surface hydrophobicity facilitates the slip of electroconvective vortexes along the surface. Besides, the geometry of the cavities gives rise to appearing tangential electric force applied to the extended space charge density at cavity's walls. As the local limiting current density within a cavity is lower than at the flat surface, electroconvective vortices arise at current densities lower than i(lim)(theor). With time, the number and the size of cavities increase (apparently, due to paired electroconvective vortices occurring inside them) that seems the main reason for overlimiting transfer increase.
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36
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Abstract
Water is a critical component of many chemical processes, in fields as diverse as biology and geology. Water in chemical, biological, and other systems frequently occurs in very crowded situations: the confined water must interact with a variety of interfaces and molecular groups, often on a characteristic length scale of nanometers. Water's behavior in diverse environments is an important contributor to the functioning of chemical systems. In biology, water is found in cells, where it hydrates membranes and large biomolecules. In geology, interfacial water molecules can control ion adsorption and mineral dissolution. Embedded water molecules can change the structure of zeolites. In chemistry, water is an important polar solvent that is often in contact with interfaces, for example, in ion-exchange resin systems. Water is a very small molecule; its unusual properties for its size are attributable to the formation of extended hydrogen bond networks. A water molecule is similar in mass and volume to methane, but methane is a gas at room temperature, with melting and boiling points of 91 and 112 K, respectively. This is in contrast to water, with melting and boiling points of 273 and 373 K, respectively. The difference is that water forms up to four hydrogen bonds with approximately tetrahedral geometry. Water's hydrogen bond network is not static. Hydrogen bonds are constantly forming and breaking. In bulk water, the time scale for hydrogen bond randomization through concerted formation and dissociation of hydrogen bonds is approximately 2 ps. Water's rapid hydrogen bond rearrangement makes possible many of the processes that occur in water, such as protein folding and ion solvation. However, many processes involving water do not take place in pure bulk water, and water's hydrogen bond structural dynamics can be substantially influenced by the presence of, for example, interfaces, ions, and large molecules. In this Account, spectroscopic studies that have been used to explore the details of these influences are discussed. Because rearrangements of water molecules occur so quickly, ultrafast infrared experiments that probe water's hydroxyl stretching mode are useful in providing direct information about water dynamics on the appropriate time scales. Infrared polarization-selective pump-probe experiments and two-dimensional infrared (2D IR) vibrational echo experiments have been used to study the hydrogen bond dynamics of water. Water orientational relaxation, which requires hydrogen bond rearrangements, has been studied at spherical interfaces of ionic reverse micelles and compared with planar interfaces of lamellar structures composed of the same surfactants. Water orientational relaxation slows considerably at interfaces. It is found that the geometry of the interface is less important than the presence of the interface. The influence of ions is shown to slow hydrogen bond rearrangements. However, comparing an ionic interface to a neutral interface demonstrates that the chemical nature of the interface is less important than the presence of the interface. Finally, it is found that the dynamics of water at an organic interface is very similar to water molecules interacting with a large polyether.
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Affiliation(s)
- Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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37
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38
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Habenicht BF, Paddison SJ. Ab Initio Simulations of the Effects of Nanoscale Confinement on Proton Transfer in Hydrophobic Environments. J Phys Chem B 2011; 115:10826-35. [DOI: 10.1021/jp205787f] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Bradley F. Habenicht
- 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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39
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Gruenbaum SM, Skinner JL. Vibrational spectroscopy of water in hydrated lipid multi-bilayers. I. Infrared spectra and ultrafast pump-probe observables. J Chem Phys 2011; 135:075101. [PMID: 21861584 PMCID: PMC3172989 DOI: 10.1063/1.3615717] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 07/02/2011] [Indexed: 11/15/2022] Open
Abstract
The vibrational spectroscopy of hydration water in dilauroylphosphatidylcholine lipid multi-bilayers is investigated using molecular dynamics simulations and a mixed quantum/classical model for the OD stretch spectroscopy of dilute HDO in H(2)O. FTIR absorption spectra, and isotropic and anisotropic pump-probe decay curves have been measured experimentally as a function of the hydration level of the lipid multi-bilayer, and our goal is to make connection with these experiments. To this end, we use third-order response functions, which allow us to include non-Gaussian frequency fluctuations, non-Condon effects, molecular rotations, and a fluctuating vibrational lifetime, all of which we believe are important for this system. We calculate the response functions using existing transition frequency and dipole maps. From the experiments it appears that there are two distinct vibrational lifetimes corresponding to HDO molecules in different molecular environments. In order to obtain these lifetimes, we consider a simple two-population model for hydration water hydrogen bonds. Assuming a different lifetime for each population, we then calculate the isotropic pump-probe decay, fitting to experiment to obtain the two lifetimes for each hydration level. With these lifetimes in hand, we then calculate FTIR spectra and pump-probe anisotropy decay as a function of hydration. This approach, therefore, permits a consistent calculation of all observables within a unified computational scheme. Our theoretical results are all in qualitative agreement with experiment. The vibrational lifetime of lipid-associated OD groups is found to be systematically shorter than that of the water-associated population, and the lifetimes of each population increase with decreasing hydration, in agreement with previous analysis. Our theoretical FTIR absorption spectra successfully reproduce the experimentally observed red-shift with decreasing lipid hydration, and we confirm a previous interpretation that this shift results from the hydrogen bonding of water to the lipid phosphate group. From the pump-probe anisotropy decay, we confirm that the reorientational motions of water molecules slow significantly as hydration decreases, with water bound in the lipid carbonyl region undergoing the slowest rotations.
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Affiliation(s)
- S M Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave. University of Wisconsin, Madison, Wisconsin 53706, USA
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40
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Kunimatsu K, Bae B, Miyatake K, Uchida H, Watanabe M. ATR-FTIR Study of Water in Nafion Membrane Combined with Proton Conductivity Measurements during Hydration/Dehydration Cycle. J Phys Chem B 2011; 115:4315-21. [DOI: 10.1021/jp112300c] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Keiji Kunimatsu
- Fuel Cell Nanomaterials Center and ‡Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu 400-8510, Japan
| | - Byungchan Bae
- Fuel Cell Nanomaterials Center and ‡Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu 400-8510, Japan
| | - Kenji Miyatake
- Fuel Cell Nanomaterials Center and ‡Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu 400-8510, Japan
| | - Hiroyuki Uchida
- Fuel Cell Nanomaterials Center and ‡Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu 400-8510, Japan
| | - Masahiro Watanabe
- Fuel Cell Nanomaterials Center and ‡Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu 400-8510, Japan
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Heinzelmann G, Figueiredo W, Girardi M. Orientational dynamics for an amphiphilic-solvent solution. J Chem Phys 2011; 134:064901. [PMID: 21322728 DOI: 10.1063/1.3537737] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In this work, we performed Monte Carlo simulations on a lattice model for spontaneous amphiphilic aggregation, in order to study the orientational and hydrogen-bonding dynamics of water on different regions inside the micellar solution. We employed an associating lattice gas model that mimics the aqueous solvent, which presents a rich phase diagram with first- and second-order transition lines. Even though this is a simplified model, it makes possible to investigate the orientational dynamics of water in an equilibrium solution of amphiphiles, as well as the influence of the different phases of the solvent in the interfacial and bulk water dynamics. By means of extensive simulations, we showed that, at high temperatures, the behavior of the orientational relaxation and hydrogen bonding of water molecules in the bulk, first, and second hydration shells are considerable different. We observe the appearance of a very slow component for water molecules in the first hydration shell of micelles when the system reaches a high-density phase, consistent with previous theoretical and experimental studies concerning biological water. Also, at high temperatures, we find that water molecules in the second hydration shell of micelles have an orientational decay similar to that of bulk water, but with a generally slower dynamics. Otherwise, at low temperatures, we have two components for the orientational relaxation of bulk water in the low density liquid phase, and only a single component in the high density liquid (HDL) phase, which reflect the symmetry properties of the different phases of the solvent model. In the very dense region of water molecules in the first hydration shell of micelles at low temperatures, we find two components for the orientational relaxation on both liquid phases, one of them much slower than that in the single component of bulk water in the HDL phase. This happens even though our model does not present any hindrance to the water rotational freedom caused by the presence of the amphiphiles.
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Affiliation(s)
- G Heinzelmann
- School of Physics, University of Sydney, New South Wales 2006, Australia.
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Fayer MD, Levinger NE. Analysis of water in confined geometries and at interfaces. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2010; 3:89-107. [PMID: 20636035 DOI: 10.1146/annurev-anchem-070109-103410] [Citation(s) in RCA: 198] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The properties of water depend on its extended hydrogen bond network and the continual picosecond-time scale structural evolution of the network. Water molecules in confined environments with pools a few nanometers in diameter or at interfaces undergo hydrogen bond structural dynamics that differ drastically from the dynamics they undergo in bulk water. Orientational motions of water require hydrogen bond network rearrangement. Therefore, observations of orientational relaxation in nanoscopic water systems provide information about the influence of confinement and interfaces on hydrogen bond dynamics. Ultrafast infrared polarization- and wavelength-selective pump-probe experiments can measure the orientational relaxation of water and distinguish water at an interface from water removed from an interface. These experiments can be applied to water in reverse micelles (spherical nanopools). The results provide quantitative determination of the dynamics of water as a function of the size and nature of the confining structure.
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Affiliation(s)
- Michael D Fayer
- Department of Chemistry, Stanford University, California 94305, USA.
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Abstract
The orientational dynamics of water at a neutral surfactant reverse micelle interface are measured with ultrafast infrared spectroscopy of the hydroxyl stretch, and the results are compared to orientational relaxation of water interacting with an ionic interface. The comparison provides insights into the influence of a neutral vs. ionic interface on hydrogen bond dynamics. Measurements are made and analyzed for large nonionic surfactant Igepal CO-520reverse micelles (water nanopool with a 9-nm diameter). The results are compared with those from a previous study of reverse micelles of the same size formed with the ionic surfactant Aerosol-OT (AOT). The results demonstrate that the orientational relaxation times for interfacial water molecules in the two types of reverse micelles are very similar (13 ps for Igepal and 18 ps for AOT) and are significantly slower than that of bulk water (2.6 ps). The comparison of water orientational relaxation at neutral and ionic interfaces shows that the presence of an interface plays the dominant role in determining the hydrogen bond dynamics, whereas the chemical nature of the interface plays a secondary role.
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45
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Spry DB, Fayer MD. Proton Transfer and Proton Concentrations in Protonated Nafion Fuel Cell Membranes. J Phys Chem B 2009; 113:10210-21. [DOI: 10.1021/jp9036777] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- D. B. Spry
- Department of Chemistry, Stanford University, Stanford, California 94305
| | - M. D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305
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46
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Fenn EE, Moilanen DE, Levinger NE, Fayer MD. Water dynamics and interactions in water-polyether binary mixtures. J Am Chem Soc 2009; 131:5530-9. [PMID: 19323522 PMCID: PMC2889155 DOI: 10.1021/ja809261d] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Poly(ethylene) oxide (PEO) is a technologically important polymer with a wide range of applications including ion-exchange membranes, protein crystallization, and medical devices. PEO's versatility arises from its special interactions with water. Water molecules may form hydrogen-bond bridges between the ether oxygens of the backbone. While steady-state measurements and theoretical studies of PEO's interactions with water abound, experiments measuring dynamic observables are quite sparse. A major question is the nature of the interactions of water with the ether oxygens as opposed to the highly hydrophilic PEO terminal hydroxyls. Here, we examine a wide range of mixtures of water and tetraethylene glycol dimethyl ether (TEGDE), a methyl-terminated derivative of PEO with 4 repeat units (5 ether oxygens), using ultrafast infrared polarization selective pump-probe measurements on water's hydroxyl stretching mode to determine vibrational relaxation and orientational relaxation dynamics. The experiments focus on the dynamical interactions of water with the ether backbone because TEGDE does not have the PEO terminal hydroxyls. The experiments observe two distinct subensembles of water molecules: those that are hydrogen bonded to other waters and those that are associated with TEGDE molecules. The water orientational relaxation has a fast component of a few picoseconds (water-like) followed by much slower decay of approximately 20 ps (TEGDE associated). The two decay times vary only mildly with the water concentration. The two subensembles are evident even in very low water content samples, indicating pooling of water molecules. Structural change as water content is lowered through either conformational changes in the backbone or increasing hydrophobic interactions is discussed.
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Affiliation(s)
- Emily E. Fenn
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | | | | | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, CA 94305
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47
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Byun CK, Sharif I, DesMarteau DD, Creager SE, Korzeniewski C. Infrared Spectroscopy of Bis[(perfluoroalkyl)sulfonyl] Imide Ionomer Membrane Materials. J Phys Chem B 2009; 113:6299-304. [DOI: 10.1021/jp900164x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chang Kyu Byun
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - Iqbal Sharif
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - Darryl D. DesMarteau
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - Stephen E. Creager
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
| | - Carol Korzeniewski
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, and Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973
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Zhao W, Moilanen DE, Fenn EE, Fayer MD. Water at the surfaces of aligned phospholipid multibilayer model membranes probed with ultrafast vibrational spectroscopy. J Am Chem Soc 2008; 130:13927-37. [PMID: 18823116 PMCID: PMC2648527 DOI: 10.1021/ja803252y] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dynamics of water at the surface of artificial membranes composed of aligned multibilayers of the phospholipid dilauroyl phosphatidylcholine (DLPC) are probed with ultrafast polarization selective vibrational pump-probe spectroscopy. The experiments are performed at various hydration levels, x = 2 - 16 water molecules per lipid at 37 degrees C. The water molecules are approximately 1 nm above or below the membrane surface. The experiments are conducted on the OD stretching mode of dilute HOD in H 2O to eliminate vibrational excitation transfer. The FT-IR absorption spectra of the OD stretch in the DLPC bilayer system at low hydration levels shows a red-shift in frequency relative to bulk water, which is in contrast to the blue-shift often observed in systems such as water nanopools in reverse micelles. The spectra for x = 4 - 16 can be reproduced by a superposition of the spectra for x = 2 and bulk water. IR Pump-probe measurements reveal that the vibrational population decays (lifetimes) become longer as the hydration level is decreased. The population decays are fit well by biexponential functions. The population decays, measured as a function of the OD stretch frequency, suggest the existence of two major types of water molecules in the interfacial region of the lipid bilayers. One component may be a clathrate-like water cluster near the hydrophobic choline group and the other may be related to the hydration water molecules mainly associated with the phosphate group. As the hydration level increases, the vibrational lifetimes of these two components decrease, suggesting a continuous evolution of the hydration structures in the two components associated with the swelling of the bilayers. The agreement of the magnitudes of the two components obtained from IR spectra with those from vibrational lifetime measurements further supports the two-component model. The vibrational population decay fitting also gives an estimation of the number of phosphate-associated water molecules and choline-associated water molecules, which range from 1 to 4 and 1 to 12, respectively, as x increases from 2 to 16. Time-dependent anisotropy measurements yield the rate of orientational relaxation as a function of x. The anisotropy decay is biexponential. The fast component is almost independent of x, and is interpreted as small orientational fluctuations that occur without hydrogen-bond rearrangement. The slower component becomes very long as the hydration level decreases. This component is a measure of the rate of complete orientational randomization, which requires H-bond rearrangement and is discussed in terms of a jump reorientation model.
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Affiliation(s)
| | | | - Emily E. Fenn
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, CA 94305
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Korzeniewski C, Adams E, Liu D. Responses of hydrophobic and hydrophilic groups in Nafion differentiated by least squares modeling of infrared spectra recorded during thin film hydration. APPLIED SPECTROSCOPY 2008; 62:634-639. [PMID: 18559150 DOI: 10.1366/000370208784658075] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Least squares modeling was applied to gain insights into changes that occur in the structure of Nafion polymer membrane during hydration. Transmission infrared spectra followed changes in the strong polymer bands in the range of 1400-950 cm(-1) during water uptake by initially dry membrane upon exposure to 100% relative humidity atmosphere. Spectra recorded during hydration were fit to a rate equation that modeled the loss of a dry state accompanied by the development of a hydrated state. The evolution of the two states was described by an equation for diffusion in a cylindrical pore in the long time limit. Comparison of the experimental spectra in a data set to spectra calculated from the pure components derived by least squares modeling gave an excellent match for bands of the -CF2 and C-O-C group modes, but agreement was not as close for bands arising from modes of the hydrophilic -SO3(-) group and (modeled separately) water. The differences are discussed in terms of the likelihood that the -SO3(-) groups have stronger interactions with bulk-like water condensed in the membrane and therefore undergo more complex changes than do more hydrophobic polymer regions during hydration. A different model is necessary to describe the evolution of spectral features for water and -SO3(-) end groups during water uptake into Nafion thin films.
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Affiliation(s)
- Carol Korzeniewski
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
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50
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Lin J, Wu PH, Wycisk R, Pintauro PN, Shi Z. Properties of Water in Prestretched Recast Nafion. Macromolecules 2008. [DOI: 10.1021/ma800194z] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jun Lin
- Department of Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, and Institute for Fuel Cell Innovation, National Research Council Canada, 3250 East Mall, Vancouver, British Columbia V6T IW5, Canada
| | - Pin-Han Wu
- Department of Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, and Institute for Fuel Cell Innovation, National Research Council Canada, 3250 East Mall, Vancouver, British Columbia V6T IW5, Canada
| | - Ryszard Wycisk
- Department of Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, and Institute for Fuel Cell Innovation, National Research Council Canada, 3250 East Mall, Vancouver, British Columbia V6T IW5, Canada
| | - Peter N. Pintauro
- Department of Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, and Institute for Fuel Cell Innovation, National Research Council Canada, 3250 East Mall, Vancouver, British Columbia V6T IW5, Canada
| | - Zhiqing Shi
- Department of Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, and Institute for Fuel Cell Innovation, National Research Council Canada, 3250 East Mall, Vancouver, British Columbia V6T IW5, Canada
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