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Title: Communication: Influence of nanophase segregation on ion transport in room temperature ionic liquids

In this paper, we report measurements of the ionic conductivity, shear viscosity, and structural dynamics in a homologous series of quaternary ammonium ionic liquids (ILs) and a prototypical imidazolium-based IL over a wide range of temperatures down to the glass transition. We find that the ionic conductivity of these materials generally decreases, while the shear viscosity correspondingly increases, with increasing volume fraction of aliphatic side groups. Upon crossing an aliphatic volume fraction of ~0.40, we observe a sharp, order-of-magnitude decrease in ionic conductivity and enhancement of viscosity, which coincides with the presence of long-lived, nanometer-sized alkyl aggregates. These strong changes in dynamics are not mirrored in the ionicity of these ILs, which decreases nearly linearly with aliphatic volume fraction. Finally, our results demonstrate that nanophase segregation in neat ILs strongly reduces ionic conductivity primarily due to an aggregation-induced suppression of dynamics.
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Material Science and Engineering
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences
  3. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
  4. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry
Publication Date:
Grant/Contract Number:
AC05-00OR22725; CHE-1213444
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 144; Journal Issue: 15; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Pennsylvania, Philadelphia, PA (United States); Univ. of Tennessee, Knoxville, TN (United States)
Sponsoring Org:
USDOE; National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Ionic conductivity; Viscosity; Ionic liquids; Shear rate dependent viscosity; Aggregation
OSTI Identifier:
1347336

Griffin, Philip J., Wang, Yangyang, Holt, Adam P., and Sokolov, Alexei P.. Communication: Influence of nanophase segregation on ion transport in room temperature ionic liquids. United States: N. p., Web. doi:10.1063/1.4947552.
Griffin, Philip J., Wang, Yangyang, Holt, Adam P., & Sokolov, Alexei P.. Communication: Influence of nanophase segregation on ion transport in room temperature ionic liquids. United States. doi:10.1063/1.4947552.
Griffin, Philip J., Wang, Yangyang, Holt, Adam P., and Sokolov, Alexei P.. 2016. "Communication: Influence of nanophase segregation on ion transport in room temperature ionic liquids". United States. doi:10.1063/1.4947552. https://www.osti.gov/servlets/purl/1347336.
@article{osti_1347336,
title = {Communication: Influence of nanophase segregation on ion transport in room temperature ionic liquids},
author = {Griffin, Philip J. and Wang, Yangyang and Holt, Adam P. and Sokolov, Alexei P.},
abstractNote = {In this paper, we report measurements of the ionic conductivity, shear viscosity, and structural dynamics in a homologous series of quaternary ammonium ionic liquids (ILs) and a prototypical imidazolium-based IL over a wide range of temperatures down to the glass transition. We find that the ionic conductivity of these materials generally decreases, while the shear viscosity correspondingly increases, with increasing volume fraction of aliphatic side groups. Upon crossing an aliphatic volume fraction of ~0.40, we observe a sharp, order-of-magnitude decrease in ionic conductivity and enhancement of viscosity, which coincides with the presence of long-lived, nanometer-sized alkyl aggregates. These strong changes in dynamics are not mirrored in the ionicity of these ILs, which decreases nearly linearly with aliphatic volume fraction. Finally, our results demonstrate that nanophase segregation in neat ILs strongly reduces ionic conductivity primarily due to an aggregation-induced suppression of dynamics.},
doi = {10.1063/1.4947552},
journal = {Journal of Chemical Physics},
number = 15,
volume = 144,
place = {United States},
year = {2016},
month = {4}
}