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Title: Enhanced ionic diffusion in ionomer-filled nanopores

Coarse-grained simulations in the united-atom-model approximation are used to investigate confinement-induced morphological changes in Nafion-like ionomers. The system we study models a cylindrical pore in a hydrophobic matrix of supporting material with pore diameters that vary from 0.7 to 3.96 nm. Simulation results indicate a strong dependence of the equilibrium ionomer structures both on the pore diameter and on the sulfonate concentration in the pore. In the case of larger pores, the ionic clustering has the shape of a branched wire-like network oriented parallel to the pore axis. In the case of narrow pores, the ionic clusters occupy the pore center and exhibit strong density modulations both along the pore axis and across the pore diameter. The calculated diffusion coefficients for the ions indicate a sharp increase within the narrow pores. This finding is explained by ballistic-type ionic motion at shorter times and by the collective motion of ions in hydrophilic clusters. The influence of the hydrophobic walls on the distribution of ions and solvent molecules is discussed.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1]
  1. Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine Universität Düsseldorf, Universitätstrasse 1, 40225 Düsseldorf (Germany)
  2. (United States)
  3. (IVTAN), 13/19 Izhorskaya Street, Moscow 125412 (Russian Federation)
  4. (Azerbaijan)
  5. Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079 (United States)
Publication Date:
OSTI Identifier:
22493373
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 24; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABUNDANCE; ATOMS; COMPUTERIZED SIMULATION; CONCENTRATION RATIO; CONFINEMENT; CYLINDRICAL CONFIGURATION; DENSITY; DIFFUSION; EQUILIBRIUM; IONS; MATRICES; MODULATION; MOLECULES; MORPHOLOGICAL CHANGES; SOLVENTS; SULFONATES