Molecular dynamics simulations of EMI-BF4 in nanoporous carbon actuators

Abstract   An artificial muscle composite material consisting of carbide derived carbon (CDC) and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF₄) ionic liquid was modeled using molecular dynamics (MD) simulations, in order to determine the molecular structural rearrangements causing actuation. CDC was represented as separate curved graphene-like flakes with charges of +2, 0 or −2 on each flake, with 24–27 aromatic rings each. The charge distribution in the flakes was determined by PM6 semi-empirical optimization. The pore size distribution of CDC and the density of the material were comparable to experimental data. Molecular structure analysis revealed a preferential parallel orientation for the cations over the negatively charged CDC surfaces, while cationic rotations and reorientations could be observed for positively charged CDC. Changes in the pore occupancy for each ionic type were observed for pore sizes between 4 and 7 Å, which, together with the replacement of large cations with smaller anions, could explain the volume decrease in the anodes (and, vice versa, the volume increase in the cathodes) in this type of actuator. Figure Carbide derived carbon flakes and EMI-BF4 in molecular dynamics simulation box

• Content Type Journal Article
• Pages 1-12
• DOI 10.1007/s00894-011-1182-5
• Authors
  • Endel Soolo, IMS Lab, Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia
  • Daniel Brandell, Department of Materials Chemistry, Uppsala University, Box 538, 75121 Uppsala, Sweden
  • Anti Liivat, Department of Materials Chemistry, Uppsala University, Box 538, 75121 Uppsala, Sweden
  • Heiki Kasemägi, IMS Lab, Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia
  • Tarmo Tamm, IMS Lab, Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia
  • Alvo Aabloo, IMS Lab, Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia

• Journal Journal of Molecular Modeling
• Online ISSN 0948-5023
• Print ISSN 1610-2940