TY - JOUR
T1 - Heterogeneous Nature of Relaxation Dynamics of Room-Temperature Ionic Liquids (EMIm)2[Co(NCS)4] and (BMIm)2[Co(NCS)4]
AU - Hensel-Bielowka, Stella
AU - Wojnarowska, Zaneta
AU - Dzida, Marzena
AU - Zorębski, Edward
AU - Zorębski, Michał
AU - Geppert-Rybczyńska, Monika
AU - Peppel, Tim
AU - Grzybowska, Katarzyna
AU - Wang, Yangyang
AU - Sokolov, Alexei P.
AU - Paluch, Marian
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/8/11
Y1 - 2015/8/11
N2 - Dynamic crossover above Tg 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. Moreover, 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.
AB - Dynamic crossover above Tg 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. Moreover, 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.
UR - http://www.scopus.com/inward/record.url?scp=84940823510&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.5b07123
DO - 10.1021/acs.jpcc.5b07123
M3 - Article
AN - SCOPUS:84940823510
SN - 1932-7447
VL - 119
SP - 20363
EP - 20368
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 35
ER -