Simulation Study of the Correlation between Structure and Conductivity in Stretched Nafion

Allahyarov, Elshad; Taylor, Philip L.

doi:10.1021/jp8047746

Cited by 60 publications

(76 citation statements)

References 60 publications

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“…However, the in‐plane proton conductivity is slightly higher for the constrained membrane at 30 as well as at 80 °C. An increased in‐plane conductivity and a decreased through‐plane conductivity was reported by Allahyarov et al in a theoretical study on the influence of proton conductivity for an uniaxially stretched Nafion‐like membrane . According to this work, this effect is based on the rearrangement of polymer chains during the stretching process.…”

Section: Resultssupporting

confidence: 52%

“…A simulation about structure and conductivity in stretched Nafion revealed similar results. The authors report a strongly reduced proton diffusion perpendicular to the stretching axis and point out that the desired direction of proton transport for common applications is perpendicular to the stretching direction . For tetrabutylammonium ion exchanged and uniaxially oriented perfluorosulfonate ionomer an oriented morphology was reported and sodium ion exchanged perfluorosulfonate ionomers exhibit a higher surface conductivity parallel to the stretching direction …”

Section: Introductionmentioning

confidence: 96%

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Reduced In-Plane Swelling of Nafion by a Biaxial Modification Process

Hink

Henkensmeier

Jang

et al. 2015

Macromol. Chem. Phys.

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A biaxial modifi cation process to reduce the in-plane swelling of perfl uorosulfonic acid polymers is demonstrated for Nafi on 212 membranes. The process is based on the one-way shape memory effect of the polymer, which can be installed by drying under constrained conditions and observed by water swelling. The through-plane/in-plane swelling ratio at 30 °C for treated Nafi on 212 increases from 1.4 to 5.8 (ex situ) and ≈25 (after humidity cycling in a fuel cell). Young modulus and tensile strength increase. X-ray diffraction analysis shows an increase of crystallinity. The infl uence on through-and in-plane proton conductivity is studied. Finally, fuel cell tests are presented. The results suggest that the process enhances the durability of fuel cell systems under changing humidity conditions.

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Section: Resultssupporting

confidence: 52%

Section: Introductionmentioning

confidence: 96%

Reduced In-Plane Swelling of Nafion by a Biaxial Modification Process

Hink

Henkensmeier

Jang

et al. 2015

Macromol. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…One of the major technical barriers is the slow electrode dynamics of methanol and thus high operational temperature is preferred. [23][24][25][26][27][28] In this study, the intermolecular momentum transfer in PFSA systems will be studied in terms of center of mass velocity cross-correlation functions ͑VCCFs͒. [11][12][13] In the quest for better DMFCs, methanol crossover in poly͑perfluorosulfonic acid͒ ͑PFSA͒ membrane has been extensively investigated by use of both experimental [14][15][16][17][18][19] and theoretical methods.…”

Section: Intermolecular Momentum Transfer In Poly"perfluorosulfonic Amentioning

confidence: 99%

Intermolecular momentum transfer in poly(perfluorosulfonic acid) membrane hydrated by aqueous solution of methanol: A molecular dynamics simulation study

Shao

Yan

et al. 2009

The Journal of Chemical Physics

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Intermolecular momentum transfer in methanol-water mixture solvated poly(perfluoro-sulfonic acid) membrane is studied in terms of center of mass velocity cross-correlation functions between molecular mass centers in their first coordination shells based on molecular dynamics simulations. Moreover, the center of mass velocity cross-correlation functions are also decomposed into longitudinal and transversal contributions. The fastest momentum transfer is observed between hydronium cation and water molecule due to the strong hydrogen bond interaction. The center of mass velocity cross-correlation functions reach peak value in about 36 fs, corresponding to a single collision with a neighboring molecule. For the momentum transfer between the water molecule and methanol molecule, the peaking time is 70 fs or about twice of that between hydronium cation and water molecule. Oscillation of the center of mass velocity cross-correlation functions between hydronium cation and water molecule is also observed due to the cage effect in their equilibrium positions.

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“…Within this context, some atomistic computer simulation studies have been reported to stablish relationships between the structure and transport phenomena in ion-exchange membranes. [20][21][22][23][24][25][26][27][28] However, such studies were essentially focused on the controlled diffusion of small molecules (e.g. protons and water) across the membranes rather than on structural aspects for the application of the material in catalysis.…”

Section: Introductionmentioning

confidence: 99%

Atomistic simulations of the structure of highly crosslinked sulfonated poly(styrene-co-divinylbenzene) ion exchange resins

et al. 2015

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The microscopic structure of highly crosslinked sulfonated poly(styrene-codivinylbenze) resins have been modeled by generating atomistic microstructures using stochastic-like algorithms that are , subsequently, relaxed using molecular dynamics.Two different generation algorithms have been tested. Relaxation of the microstructures generated by the first algorithm, which is based on a homogeneous construction of the resin, leads to a significant overestimation of the experimental density as well as to an unsatisfactory description of the porosity. In contrast, the generation approach that combines algorithms for the heterogeneous growing and branching of the chains enables the formation of crosslinks with different topologies. In particular, the intrinsic heterogeneity observed in these resins is well reproduced when topological loops, which are defined by two or more crosslinks closing a cycle, are present in their microscopic description. Thus, the apparent density, porosity and pore volume estimated using microstructures with these topological loops, called super-crosslinks, are in very good agreement with experimental measures. Although the backbone dihedral angle distribution of the generated and relaxed models is not influenced by the topology, the number and type of crosslinks affect the medium-and long-range atomic disposition of the backbone atoms and the distribution of the sulfonic groups. Analysis of the distribution of the local density indicates that super-crosslinks are responsible of the heterogeneous homogenization observed during the MD relaxation. Finally, - stacking interactions between aromatic phenyl groups have been analyzed, those in which the two rings adopt a T-shaped disposition being considerably more abundant than those with the rings co-facially oriented, independently of the resin topology.3

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Simulation Study of the Correlation between Structure and Conductivity in Stretched Nafion

Cited by 60 publications

References 60 publications

Reduced In-Plane Swelling of Nafion by a Biaxial Modification Process

Reduced In-Plane Swelling of Nafion by a Biaxial Modification Process

Intermolecular momentum transfer in poly(perfluorosulfonic acid) membrane hydrated by aqueous solution of methanol: A molecular dynamics simulation study

Atomistic simulations of the structure of highly crosslinked sulfonated poly(styrene-co-divinylbenzene) ion exchange resins

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