Ionomer Self-Assembly in Dilute Solution Studied by Coarse-Grained Molecular Dynamics

Ghelichi, Mahdi; Malek, Kourosh; Eikerling, Michael

doi:10.1021/acs.macromol.5b02158

Cited by 47 publications

(76 citation statements)

References 107 publications

(241 reference statements)

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“…This value is very close to the chain separation of 5.6 Å in crystalline phase of Nafion with an orthorhombic unit cell ( a = 9.9 Å, b = 5.6 Å, and c = 2.8 Å) . This implies that the backbones can be aligned in parallel in the short rod‐like particles, which is in accordance with recent simulations showing association of short Nafion chains in polar solvents …”

Section: Discussionsupporting

confidence: 92%

“…23 This implies that the backbones can be aligned in parallel in the short rod-like particles, which is in accordance with recent simulations showing association of short Nafion chains in polar solvents. 24,25 The outer surface area of this cylinder is 107 nm 2 and the specific surface, that is, the area per one charge is 0.89 nm 2 . This value is close to the estimated values of the rod-like particles in most of the polar solvents but larger than the value of about 0.6 nm 2 in H 2 O.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Size and shape of Nafion particles in water after high‐temperature treatment

Yamaguchi¹,

Terao²,

Ohira

et al. 2019

J Polym Sci B Polym Phys

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Perfluorosulfonic acid ionomers have been widely used as proton‐conducting materials in polymer‐electrolyte membrane fuel cells and their dispersions in polar solvents are used to prepare proton‐conducting membranes as well as catalyst layers. While it has been known that the dispersed particles become monodisperse after heating to 230 °C or above, their size and shape have not been fully characterized yet. Cryogenic transmission electron microscopy images and small‐angle X‐ray scattering profiles of the dilute aqueous dispersions before and after heating to 240 °C have clearly shown that rod‐like particles became significantly shorter cylinders without changing their radii. Particle length distributions were lognormal and average molar mass and dispersity after heating to 240 °C were consistent with the values from size exclusion chromatography. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 813–818

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Size and shape of Nafion particles in water after high‐temperature treatment

Yamaguchi¹,

Terao²,

Ohira

et al. 2019

J Polym Sci B Polym Phys

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“…Significant attention has been focused on understanding how perfluorosulfonic ionomer (PFSI) interacts in different solvent systems because of its complex structure. 13,14 PFSA is characterized by a hydrophobic backbone and a hydrophilic side chain and does not form a true solution but instead has the tendency to form a colloid structure when dispersed in a solvent. Uchida et al demonstrated that PFSA properties were fundamentally a function of the solvents dielectric constant.…”

mentioning

confidence: 99%

Catalyst Layer Ink Interactions That Affect Coatability

Dixit

Harkey

Shen

et al. 2018

J. Electrochem. Soc.

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Catalyst layer inks are examples of biphasic material systems composed of a solid material, a polymer, and a solvent. Nanoscale interactions between the individual constituents can alter macroscopic properties that are relevant for coating and manufacturing processes (i.e. viscosity, surface tension, aggregation, and rheology). Control over these macroscale properties are important for controlled electrode formation during scalable roll-to-roll manufacturing. The underlying interactions include polymer|particle, particle|solvent, and polymer|solvent interactions. In this work we systematically investigate polymer|particle interactions via studying a range of formulated inks composed of different solvents (methanol, isopropyl alcohol, octanol, and water), varying polymer loadings, and particles with different surface charges. Ink aging is also addressed and over short time periods (<1 hr shelf life) the addition of a perfluorosulfonic acid ionomer was shown to stabilize the ink and also decrease the aggregation size. However, over long time periods (168 hrs) the aggregation size is independent of polymer loading, and approaches a steady state aggregation size around 350 nm. This equilibrium point suggests that the polymer is free to diffuse, adsorb, and relax within the excluded volume region. Furthermore, these results suggest that primary aggregates can be broken up with the addition of very low polymer loadings (15% I:C). A semi-empirical model is used to describe polymer|particle interactions within the ink, and the polymer coverage at the surface of the carbon was found to be the most sensitive parameter dictating ink stability. Finally, coating and rheology experiments are completed on all inks.

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“…Their size and shape depends on the solvent and the equivalent weight of the ionomer. Ghelichi and Eikerling reported from a general modelling approach including a variety of different ionomer architectures that the particle size depends on the detailed molecular structure and the properties of the solvent (24). The bundles have a dense hexagonal packing consisting of ionomer backbones, the sulfonic acid groups are oriented to the sides.…”

Section: Dispersion Particlesmentioning

confidence: 99%

Structure, Properties, and Degradation of Ultrathin Ionomer Films in Catalytic Layers of Fuel Cells

et al. 2018

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The structure of electrodes for proton-exchange membrane fuel cells and electrolysers has an important impact on performance and degradation. Ionomer films covering Pt/C agglomerates in fuel cell electrodes have a thickness in the range of 4 to 15 nm and differ from the bulk structure with their mostly lamellar films. The formation of such nanothin films deposited by drop-casting and self-assembly was studied by atomic force microscopy. For different equivalent weights and different solvents of Aquivion® and Nafion® dispersions, the size and structure of the dispersion particles, of sub-monolayers, single and multilayers was investigated on graphene, platinum, mica, and silicon. The size of dispersion particles strongly depends on the solvent. On hydrophobic graphene, the height of ionomer bundles and layers measures 1.5 nm, significantly less than the 2.5 nm height found on hydrophilic Pt, Si, and mica. 10.1149/08613.0179ecst ©The Electrochemical Society ECS Transactions, 86 (13) 179-191 (2018) 179 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 141.58.18.225 Downloaded on 2018-09-24 to IP

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Ionomer Self-Assembly in Dilute Solution Studied by Coarse-Grained Molecular Dynamics

Cited by 47 publications

References 107 publications

Size and shape of Nafion particles in water after high‐temperature treatment

Size and shape of Nafion particles in water after high‐temperature treatment

Catalyst Layer Ink Interactions That Affect Coatability

Structure, Properties, and Degradation of Ultrathin Ionomer Films in Catalytic Layers of Fuel Cells

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