Confinement Effects in Dynamics of Ionic Liquids with Polymer-Grafted Nanoparticles

Ionic liquid mixed with poly(methyl methacrylate)-grafted Fe₃ O₄ nanoparticle aggregates at low particle concentrations was found to exhibit different dynamics and ionic conductivity than that of pure ionic liquid in our previous studies. In this work, we report on the quasi-elastic neutron scattering results of ionic liquid containing polymer-grafted Fe₃ O₄ nanoparticles at higher particle concentrations. The diffusivity of imidazolium (HMIM⁺ ) cations of 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIM-TFSI) in the presence of poly(methyl methacrylate)-grafted Fe₃ O₄ nanoparticles is discussed through the confinement. Analysis of the elastic incoherent structure factor revealed that the confinement radius decreased with the addition of grafted particles in HMIM-TFSI/solvent mixture. We propose the confinement that is induced by the high concentration of grafted particles shrinks the HMIM-TFSI restricted volume. We further conjecture that this enhanced diffusivity occurs as a result of the local ordering of cations within aggregates of poly(methyl methacrylate)-grafted Fe₃ O₄ nanoparticles.