On the Nature of Freezing/Melting Water in Ionic Polysulfones

Vondrasek, Britannia; Wen, Chengyuan; Cheng, Shengfeng; Riffle, Judy S.; Lesko, John J.

doi:10.1021/acs.macromol.1c00591

Cited by 4 publications

(13 citation statements)

References 45 publications

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“…MD simulations are performed as described elsewhere. [43] Both disulfonated and monosulfonated polymers are simulated at an ion content of 50% (consistent with the dBPS25 and mBPS50 polymers). Each MD system consists of 64 tetramers (comprising 128 fixed sulfonate ions and 256 sulfone groups), 128 sodium counterions, and 128λ water molecules.…”

Section: E MD Modelingsupporting

confidence: 59%

“…This difference in behavior between the monosulfonated and disulfonated polysulfones is related to the difference in the ion spacing along the polysulfone backbone but the molecular-scale understanding of the connection is still lacking. [43] The interpretation of the experimental data should be carefully considered. The shape of the OH stretch region from FTIR measurements may be sensitive to the hydrogenbonding environment of water molecules and their inter- actions with ions.…”

Section: B Ftir Resultsmentioning

confidence: 99%

“…Finally, there is no experimental or theoretical evidence of microscale ionic aggregation or phase separation in sulfonated polysulfones. [42,43] As a result, analysis of the absorbed water is not likely to be impacted by phase inhomogeneities.…”

Section: A Materialsmentioning

confidence: 99%

“…Ionic polysulfone samples are prepared as described elsewhere. [3,43] To measure the equilibrium water uptake (W eq ), three samples, each approximately 3 cm by 3 cm, are cut from a hydrated film. The samples are blotted with a laboratory wipe to remove surface water, and then quickly weighed.…”

Section: B Water Uptake and λEqmentioning

confidence: 99%

“…From a computational point of view, it is much more straightforward to simulate a sulfonated polysulfone at a fixed ion content and vary the amount of water in the simulation. [43] To obtain experimental data that can be directly compared to such simulations, we focus on two disulfonated polymers, dBPS33 and dBPS40, which show a distinct amount of melting water at their equilibrium water uptake. We hydrate these polymers at various water contents and then run DSC measurements as described in Section II C. The DSC curves and the resulting melting enthalpy, similar to those shown in Fig.…”

Section: Comparison To MD Simulationsmentioning

confidence: 99%

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On the Nature of Freezing/Melting Water in Ionic Polysulfones

Vondrasek,

Wen,

Cheng

et al. 2021

Preprint

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We investigate the behavior of hydrated sulfonated polysulfones over a range of ion contents through differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and molecular dynamics (MD) simulations. Experimental evidence shows that at comparable ion contents, the spacing between the ionic groups along the polymer backbone can significantly impact the amount of melting water present in the polymer. When we only consider water molecules that can hydrogen bond to four neighboring water molecules as the melting water, the MD simulation results are found to agree with the experimental data. The states of water measured by DSC can therefore be described as "aggregated" (or bulk-like) for the melting component, and "isolated" for the nonmelting part. Using this physical picture, a polymer with more aggregated ions has a higher content of melting water, while a polymer at the same ion content but with more dispersed ions has a lower content of melting water. Therefore, ions should be well dispersed to minimize the amount of bulk-like water in ionic polymer membranes.

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Section: E MD Modelingsupporting

confidence: 59%

Section: B Ftir Resultsmentioning

confidence: 99%

Section: A Materialsmentioning

confidence: 99%

Section: B Water Uptake and λEqmentioning

confidence: 99%

Section: Comparison To MD Simulationsmentioning

confidence: 99%

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On the Nature of Freezing/Melting Water in Ionic Polysulfones

Vondrasek,

Wen,

Cheng

et al. 2021

Preprint

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Manning condensation in ion exchange membranes: A review on ion partitioning and diffusion models

Kitto

Kamcev

2022

Journal of Polymer Science

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The rational design of ion exchange membranes (IEMs) is becoming more pertinent as their usage becomes broader and as their staple applications (i.e., electrodialysis, flow batteries, and fuel cells) improve in commercial viability. Such efforts would be catalyzed by an improved fundamental understanding of ion transport in IEMs. This review discusses recent progress in modeling ion partitioning and diffusion in IEMs in an effort to relate IEM performance metrics to fundamental membrane properties over which researchers and membrane manufacturers possess direct and sometimes precise control. Central focus is given to the Donnan‐Manning model for ion partitioning and the Manning‐Meares model for ion diffusion in IEMs. These two frameworks, which are derived from Manning's counter‐ion condensation theory for polyelectrolyte solutions, have been widely used within the IEM literature since their recent introduction. To explore this topic, the mathematical derivation of both models is revisited, followed by a survey of experimental and computational discussions of counter‐ion condensation in IEMs. Alternative models which fulfill similar roles in predicting IEM transport properties are compared. This review concludes by highlighting the uniquely favorable positions of the Donnan‐Manning and Manning‐Meares models and discussing their prospects as leading predictors of IEM partitioning and diffusive properties.

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Sulfonated Polybenzothiazoles Containing Hexafluoroisopropyl Units for Proton Exchange Membrane Fuel Cells

et al. 2023

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A sulfonated dicarboxylic monomer containing hexafluoroisopropyl, i.e., 3,3′-disulfonate-2,2-bis(4-carboxyphenyl)hexafluoropropane (SCFA), was prepared via sulfonation and oxidation to synthesize novel sulfonated polybenzothiazoles (sPBT-F) through polycondensation of 2,2-bis(4-carboxyphenyl)hexafluoropropane (CFA), SCFA, and 2,5-diamino-1,4-benzenedithiol dihydrochloride (DABDT). These sPBT-F series polymers exhibited excellent solubility due to the incorporation of a flexible hexafluoroisopropyl group. Meanwhile, the sPBT-F series polymers displayed high thermal stability and were used to prepare tough and soft membranes by solution casting. Interestingly, sPBT-F series membranes exhibited excellent water uptake and low swelling ratio, indicating excellent dimensional stability. AFM images displayed a region of obvious separation of light/dark phases, indicating high proton conductivity of sPBT-F series membranes. The sPBT-F82.5 membrane with a high degree of sulfonation demonstrated a conductivity of 0.14 S cm −1 at 80 °C and 100% RH, superior to the results of Nafion 117. Furthermore, the sPBT-F82.5 membrane displayed a maximum power density of 344.33 mW cm −2 and superb durability at a current density of 0.2 A cm −2 for 20 h. In summary, the sPBT-F polymers are potential matrix materials for PEMs.

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On the Nature of Freezing/Melting Water in Ionic Polysulfones

Cited by 4 publications

References 45 publications

On the Nature of Freezing/Melting Water in Ionic Polysulfones

On the Nature of Freezing/Melting Water in Ionic Polysulfones

Manning condensation in ion exchange membranes: A review on ion partitioning and diffusion models

Sulfonated Polybenzothiazoles Containing Hexafluoroisopropyl Units for Proton Exchange Membrane Fuel Cells

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