hide
Free keywords:
polymer-grafted nanoparticles, ionic liquid, zwitterionic liquid, solvation, dynamic coupling, quasi-elastic neutron scattering, translational diffusion.
Abstract:
We incorporated polymer-grafted nanoparticles into ionic and zwitterionic liquids to explore the solvation
and confinement effects on their heterogeneous dynamics using quasi-elastic neutron scattering (QENS).
1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIM-TFSI) mixed with deuterated
poly(methyl methacrylate) (d-PMMA)-grafted nanoparticles is studied to unravel how dynamic coupling
between PMMA and HMIM-TFSI influence the fast and slow diffusion characteristics of the HMIM+
cations. The zwitterionic liquid, 1-butyl-3-methyl imidazole-2-ylidene borane (BMIM-BH3) is critically
selected and mixed with PMMA-grafted nanoparticles for comparison in this work as its ions do not selfdissociate
and it does not couple with PMMA through ion-dipole interactions as HMIM-TFSI does. We
find that long-range unrestricted diffusion of HMIM+ cations is higher in well-dispersed particles than in
aggregated particle systems, whereas the localized diffusion of HMIM+ is measured to be higher in closepacked
particles. Translational diffusion dynamics of BMIM-BH3 is not influenced by any particle
structures suggesting that zwitterions do not interact with PMMA. This difference between two ionic
liquid types enables us to decouple polymer effects from the diffusion of ionic liquids, which is integral to
understand the ionic transport mechanism in ionic liquids confined in polymer-grafted nanoparticle
electrolytes.
