Densities and expansion coefficients of nafion polymers

Takamatsu, T.; Eisenberg, A.

doi:10.1002/app.1979.070241102

Cited by 73 publications

(62 citation statements)

References 2 publications

(2 reference statements)

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“…2). This effect is far greater than expected from thermal expansion alone since the thermal strain of PFSA membranes in this temperature range is on the order of 0.01 [41]. Therefore, the results suggest that the water sorption behavior of PFSA membranes is affected directly by humidity and temperature.…”

Section: Resultsmentioning

confidence: 66%

Constitutive response and mechanical properties of PFSA membranes in liquid water

Kusoglu

Tang

Lugo

et al. 2010

Journal of Power Sources

103

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Section: Resultsmentioning

confidence: 66%

Constitutive response and mechanical properties of PFSA membranes in liquid water

Kusoglu

Tang

Lugo

et al. 2010

Journal of Power Sources

103

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“…The simulations for the blocky system leads to a density 5% smaller than the experimental value (∼1.75 g/cm 3 at 300 K) for the H form of Nafion 117 with the same water content (15 water molecules per sulfonate group). 57,58 A part of the explanation for our calculated density being smaller than experiment could be because our simulations considered purely amorphous systems, whereas the experimental systems are thought to have ∼3-8% crystallinity. 52,[71][72][73] We find that all sulfonate groups are in the water phase, which is consistent with the experimental observation of complete dissociation of the sulfonate groups in hydrated Nafion.…”

Section: Resultsmentioning

confidence: 80%

Nanophase-Segregation and Transport in Nafion 117 from Molecular Dynamics Simulations: Effect of Monomeric Sequence

et al. 2004

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Nafion polyelectrolyte is widely used in polymer electrolyte membrane fuel cells (PEMFC) due to its high proton conductivity. The properties of hydrated Nafion are attributed to its nanophase-segregated structure in which hydrophilic clusters are embedded in a hydrophobic matrix. However, there has been little characterization of how the monomeric sequence of the Nafion chain affects the nanophase-segregation structure and transport in hydrated Nafion. To study such properties, we carried out molecular dynamics (MD) simulations of Nafion 117 using two extreme monomeric sequences: one very blocky and other very dispersed. Both produce a nanophase-segregated structure with hydrophilic and hydrophobic domains. However, the blocky Nafion leads to a characteristic dimension of phase-segregation that is ∼60% larger than for the dispersed system. We find that the water-polymer interface is heterogeneous, consisting of hydrophilic patches (water contacting sulfonate groups of Nafion) and hydrophobic patches (water contacting fluorocarbon group). The distribution of the hydrophilic and the hydrophobic patches at the interface (i.e., the heterogeneity of interface) is much more segregated for blocky Nafion. This leads to a water diffusion coefficient for the dispersed case that is ∼25% smaller than for the blocky case (0.46 × 10 -5 vs 0.59 × 10 -5 cm 2 /s at 300 K). The experimental value (0.50 × 10 -5 cm 2 /s) is within the calculated range. On the other hand, we find that the vehicular diffusion of hydronium is not affected significantly by the monomeric sequence. These results should be useful in optimizing the properties of Nafion and as targets for developing other membranes to replace Nafion in PEMFC and other applications.

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“…9À11, 23 The concept of membrane free volume is adopted to characterize the porous 31 Oberbroeckling et al, 32 and Takamatsu and Eisenberg. 33 Note that one data point from Takamatsu and Eisenberg is overlapped with that from Oberbroeckling et al at λ = 15. The Journal of Physical Chemistry B ARTICLE structure of hydrated Nafion.…”

Section: Simulation Methodsmentioning

confidence: 96%

Molecular Simulation of Gas Adsorption, Diffusion, and Permeation in Hydrated Nafion Membranes

et al. 2011

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Molecular simulations were performed to characterize hydrated Nafion membranes in terms of gas adsorption, diffusion, and permeation. The experimental results validate the molecular model of Nafion with respect to material density, morphology, free volume, and water diffusivity. Nafion’s adsorption property is examined in terms of the solubility and adsorption isotherms for gases, including H2, O2, and N2. The adsorption capacity of hydrated Nafion is shown to be strong for O2 and N2 but not for H2. Due to the dilution effect, N2 is able to suppress the loading of O2 and protect the fuel cell from fuel crossover. The dynamic behaviors of H2 and O2 are represented by self-diffusion coefficients, with the results showing that H2 diffusion in Nafion membranes is nearly 1 order of magnitude faster than O2 diffusion. The effects of water content and the concentration of adsorbed gases were verified, and a close correlation of Nafion free volume to gas transport properties was revealed. On the basis of the solution-diffusion mechanism, the permeabilities of H2 and O2 in hydrated Nafion membranes are calculated and compared with corresponding experiments, and the permeability of H2 is found to be approximately twice that of O2.

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Densities and expansion coefficients of nafion polymers

Cited by 73 publications

References 2 publications

Constitutive response and mechanical properties of PFSA membranes in liquid water

Constitutive response and mechanical properties of PFSA membranes in liquid water

Nanophase-Segregation and Transport in Nafion 117 from Molecular Dynamics Simulations: Effect of Monomeric Sequence

Molecular Simulation of Gas Adsorption, Diffusion, and Permeation in Hydrated Nafion Membranes

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