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Published on: April 12, 2019
Probing selected morphological models of hydrated Nafion using large-scale molecular dynamics simulations
1Department of Chemistry and Center for Biophysical Modeling and Simulation, Room 2020, 315 South 1400 East, University of Utah, Salt Lake City, Utah 84112-0850, USA.
The Journal of Physical Chemistry. B
|February 18, 2010
Summary
Atomistic molecular dynamics simulations reveal fast network percolation in hydrated Nafion, driven by sulfonate groups within intercluster bridges. These findings are crucial for understanding Nafion
Area of Science:
- Polymer Science
- Materials Science
- Computational Chemistry
Background:
- Nafion is a perfluorinated sulfonic acid polymer widely used in fuel cells and electrochemical applications.
- Understanding the morphology of Nafion's hydrophilic domains is critical for optimizing its ionic conductivity and performance.
- Existing models of Nafion morphology vary, necessitating computational studies to validate their structural and dynamic implications.
Purpose of the Study:
- To investigate the molecular-level dynamics and morphology of hydrated Nafion using atomistic molecular dynamics simulations.
- To compare six prominent morphological models of Nafion under hydrated conditions.
- To elucidate the role of sulfonate groups and cluster interfaces in Nafion's network formation.
Main Methods:
- Atomistic molecular dynamics (MD) simulations of hydrated Nafion systems (approx. 2 million atoms, 30 nm box length).
- Simulation of six distinct Nafion morphological models: cluster-channel, parallel cylinder, local order, lamellar, rod network, and a random model.
- Analysis of intercluster bridge formation, sulfonate aggregation, cluster surface properties, and scattering data (radial distribution functions, structure factors).
Main Results:
- Fast intercluster bridge formation and network percolation were observed in all simulated Nafion models.
- Sulfonate groups were identified within the bridges, playing a key role in network percolation and aggregating within clusters.
- Simulations showed significant increases in interfacial area and cluster volume, with cluster surfaces being dynamic.
- All non-random models reproduced the characteristic experimental scattering peak, indicating its insensitivity to specific domain structures.
Conclusions:
- The dynamic nature of Nafion's hydrophilic domains and the critical role of sulfonate groups in network formation are confirmed.
- The study highlights the limitations of current experimental scattering techniques in distinguishing between different Nafion morphological models.
- Further research is needed to develop more sensitive methods for characterizing Nafion's complex morphology at the molecular level.
