Heterogeneous nature of relaxation dynamics of room-temperature ionic liquids (EMIm)₂[Co(NCS)₄] and (BMIm)₂[Co(NCS)₄]

Journal Article · Tue Aug 11 04:00:00 EDT 2015 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.5b07123· OSTI ID:1342696

Hensel-Bielowka, Stella ^[1]; Wojnarowska, Zaneta E. ^[2]; Dzida, Marzena ^[1]; Zorebski, Edward ^[1]; Zorebski, Michal ^[1]; Geppert-Rybczynska, Monika ^[1]; Peppel, Tim ^[3]; Grzybowska, Katarzyna ^[1]; Wang, Yangyang ^[4]; Sokolov, Alexei P. ^[5]; Paluch, Marian W. ^[2]

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1. Univ. of Silesia, Katowice (Poland)
2. Univ. of Silesia, Katowice (Poland); Univ. of Silesia, Chorzow (Poland)
3. Leibniz Institute for Catalysis, Rostock (Germany)
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)

Dynamic crossover above T_g has been recognized as a characteristic feature of molecular dynamics of liquids approaching glass transition. Experimentally, it is manifested as a change in Vogel Fulcher Tammann dependence or a breakdown of the Stokes Einstein and related relations. In this paper, we report the exception from this rather general pattern of behavior. By means of dielectric, ultrasonic, rheological, and calorimetric methods, dynamics of two good ionic conductors (BMIm)₂[Co(NCS)₄] and (EMIm)₂[Co(NCS)₄] of less common stoichiometry (2:1) was studied in a very broad temperature range. However, none of the mentioned dynamic changes was observed in the entire studied temperature range. On the contrary, the single VFT and the same fractional Walden coefficient were found for conductivity and viscosity changes over 12 decades. Furthermore, ultrasonic studies revealed that the data at temperatures which cover the normal liquid region cannot be fitted by a single exponential decay, and the Cole Cole function should be used instead.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1342696
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 35 Vol. 119; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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