Temperature dependence of transport coefficients and cooperativity in ionic liquids

The temperature dependence of the molecular motion cooperativity in imidazolium-basedroom temperature ionic liquids with bis(trifluoromethane sulfonyl)amide anion,[Rmim][(CF3SO2)2N], where, R=e (ethyl), b (butyl), C6 (hexyl) and C8 (octyl), respectively,were evaluated by using a relation defined in the framework of the Bond Strength-Coordination Number Fluctuation (BSCNF) model. The degree of the cooperativity in ionicliquids was reflected in the quantity NB, which gave the number of structural units involved inthe thermally activated viscous flow. It was shown that by using the BSCNF model togetherwith both, the Nernst-Einstein and the Stokes-Einstein relations, NB was mutually related withthe transport coefficients, i.e., viscosity, diffusion coefficient and ionic conductivity