A generalised phenomenological dynamic order–disorder model for polymer electrolytes

Oliveira, A.L. de; Silva, P.R.

doi:10.1016/s0013-4686(97)00199-0

Cited by 4 publications

(8 citation statements)

References 19 publications

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“…Important for polymer electrolyte applications, the order present in the triblock copolymer with y < 9 decreases the segmental mobility, increases the tortuosity, and reduces the ionic conductivity. These results support the use of an order-disorder model 4,5 to explain the previously reported dependence of ionic conductivity on Li + concentration in these samples. 1…”

Section: Discussionsupporting

confidence: 90%

“…This order-disorder transition around y ) 9 occurs at the same lithium concentration as the previously observed peak in ionic conductivity at 50 °C. [1][2][3][4][5] Figure 4 shows the temperature dependence of the SAXS diffraction intensities around 2.1°for the pure and doped samples (y ) 5, 7, 9, 12, and 16). As can be seen for samples with y g 9, the SAXS patterns show weak and broad lines (disorder) well above the melting temperature (35 °C).…”

Section: Resultsmentioning

confidence: 99%

“…4 The alkali metal ion (Li + or Na + ) concentration dependence of the ionic conductivity at 50 °C (above the polymer melting point) goes through a very sharp peak, where the ionic conductivity reaches values of approximately 8.0 × 10 -4 S/cm (for Li + -PEGD) and 1.3 × 10 -4 S/cm (for Na + -PEGD) for y ) 9. 1,4,5 For these ABA triblock ionic conducting copolymers, a special model was proposed on the basis of the order-disorder transition to explain the ionic conductivity behavior as a function of the alkali metal ion concentration above the melting point. 4,5 To further explore this model, we have performed 1 H, 7 Li, 13 C, and 23 Na solid-state NMR measurements on PEGD doped with Li + and Na + with several O/Me + ratios.…”

Section: Introductionmentioning

confidence: 99%

“…1,4,5 For these ABA triblock ionic conducting copolymers, a special model was proposed on the basis of the order-disorder transition to explain the ionic conductivity behavior as a function of the alkali metal ion concentration above the melting point. 4,5 To further explore this model, we have performed 1 H, 7 Li, 13 C, and 23 Na solid-state NMR measurements on PEGD doped with Li + and Na + with several O/Me + ratios. The temperature dependencies further elucidate the relationships between the cation-polymer interaction and the bulk properties.…”

Section: Introductionmentioning

confidence: 99%

“…The alkali metal ion doped ABA triblock copolymer poly(ethylene glycol) distearate (PEGD), CH 3 (CH 2 ) 16 CO(OCH 2 CH 2 ) n O 2 C(CH 2 ) 16 CH 3 , average M n ca . 930, has been studied during the past few years by several experimental techniques including ionic conductivity, thermal analysis (DSC), Raman spectroscopy, viscometry, and NMR. − The PEGD structure consists of two nonpolar aliphatic stearate sections that have fairly rigid crystalline structures and a more mobile phase composed of the polar ethylene glycol segments. Undoped material has the consistency of a soft wax at room temperature, undergoing a glass transition at −68 °C and a melting transition to a viscous liquid around 35 °C.…”

Section: Introductionmentioning

confidence: 99%

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Phase Behavior and Dynamics of the ABA Triblock Copolymer Poly(ethylene glycol) Distearate Doped with Alkali Metal Salts

et al. 2002

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The ABA triblock copolymer poly(ethylene glycol) distearate (PEGD), average M n ca. 930, complexed with lithium and sodium perchlorates has been studied by 1H, 7Li, 13C, and 23Na solid-state nuclear magnetic resonance (NMR), SAXS, DSC, and polarized-light optical microscopy. Unlike other solid polymer electrolytes, highly Li+-doped PEGD samples exhibit sharp 7Li NMR quadrupolar powder patterns even at temperatures well above the melting point, indicating that this triblock copolymer is microphase separated and the dynamics in the PEG phase are anisotropic. Measurements of the 7Li central transition line width in highly doped samples show three distinct line narrowings, due to the poly(ethylene glycol) glass transition (∼−20 °C), the stearate melting point of the polymer (∼35 °C), and an order−disorder transition (∼72 °C). 23Na NMR measurements yield similar results. SAXS, DSC, and optical microscopy with polarized light confirm the presence of a microphase-separated state up to ∼72 °C. 13C and 1H NMR show that the segmental mobility in the ordered state is reduced compared to the isotropic melt. The results confirm the previously proposed order−disorder model to explain the dependence of the ionic conductivity on the lithium concentration for Li+-doped PEGD samples.

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Section: Discussionsupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase Behavior and Dynamics of the ABA Triblock Copolymer Poly(ethylene glycol) Distearate Doped with Alkali Metal Salts

et al. 2002

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Microstructure of Catalyst Layers in PEM Fuel Cells Redefined: A Computational Approach

2011

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This work comprises an extensive coarse-grained molecular dynamics study of self-organization processes that define the mesoscopic structure of catalyst layers used in polymer electrolyte fuel cells. The detailed structural analysis focuses on agglomeration of Pt-decorated primary particles of graphitized carbon black, formation of ionomer domains, emergence of the porous network, and formation of interfaces between the distinct phases. Insights obtained enable us to decisively redraw the existing structural picture of the catalyst layer. As a key result, we found that ionomer forms a thin adhesive film, which partially covers agglomerates of Pt/carbon. Densely arranged charged side chains of ionomer form a highly ordered array on the ionomer film surface. The preferential orientation of these charged side chains depends on the surface wetting properties of the agglomerates. As a major consequence, results on ionomer structure and distribution, presented in this work, seem to invalidate the classical electrolyte-flooded agglomerate model that has been widely applied to catalyst layers in polymer electrolyte fuel cells. Instead, the structural analysis provided defines a need for novel models of proton transport, water distribution, and Pt effectiveness that account for the thin-film morphology of ionomer and the specific arrangement of surface groups.

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7Li NMR diffusion coefficient measurements on the Li+-doped ABA triblock copolymer poly(ethylene glycol) distearate

Alves-Santos¹,

deAzevedo²,

Vidoto³

et al. 2005

Solid State Ionics

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A generalised phenomenological dynamic order–disorder model for polymer electrolytes

Cited by 4 publications

References 19 publications

Phase Behavior and Dynamics of the ABA Triblock Copolymer Poly(ethylene glycol) Distearate Doped with Alkali Metal Salts

Phase Behavior and Dynamics of the ABA Triblock Copolymer Poly(ethylene glycol) Distearate Doped with Alkali Metal Salts

Microstructure of Catalyst Layers in PEM Fuel Cells Redefined: A Computational Approach

7Li NMR diffusion coefficient measurements on the Li+-doped ABA triblock copolymer poly(ethylene glycol) distearate

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