InterplayBetween Hydrophobic Aggregation and Charge Transport in the IonicLiquid Methyltrioctylammonium Bis(trifluoromethylsulfonyl)imide.

Inorder to understand the nature of the exceedingly low ionic conductivityof aprotic ammonium ionic liquids (ILs), we have measured the chargetransport and structural dynamics of methyltrioctylammonium bis(trifluoromethylsulfonyl)imide[m3oa][ntf2] over a broad temperature range using broadband dielectricspectroscopy, depolarized dynamic light scattering (DDLS), rheology,and pulsed field gradient nuclear magnetic resonance. We demonstratethat the low level of ionic conductivity in this material is due tothe combined effects of reduced ion mobility as well as reduced freeion concentration relative to other types of ILs. Furthermore, detailedanalysis of the DDLS spectra reveals a slow process in addition tothe structural α relaxation that we attribute to reorientationalmotion of alkyl aggregates. These findings indicate that hydrophobicaggregation strongly influences the charge transport mechanism ofaprotic ammonium ionic liquids with long aliphatic side chains. [ABSTRACT FROM AUTHOR]