Polymer-Grafted Nanoparticles in Ionic Liquids

The newly synthesized zwitterionic liquid (ZIL) 1-butyl-3-methyl imidazole-2-ylidene borane, has superior properties to existing ionic liquids such as good stability in ambient environment. Because it is a zwitterion, there is no self-dissociation of ions, the ion transport and conductivity measured will be due to dynamics of zwitterionic molecule. In this work, deuterated PMMA-grafted nanoparticles with two grafting densities were synthesized. Their dispersion in aprotic ZIL and protic ionic liquid (1-hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide) (IL) were investigated in high resolution electron microscopy. We measured dynamics of IL and ZIL with the addition of grafted particles in quasi-elastic neutron scattering experiments. We found translational ionic diffusion of IL slowed down as result of the good mixing and coupling of IL with grafted chains. With the aggregated system, diffusion was similar in bulk, which was due to the phase separation between IL and particles. Interestingly, diffusivity of ZIL increased with the inclusion of particles, particularly with the particles of higher graft density. The increased diffusivity is explained by the confinement of ZIL within structures of grafted nanoparticles.