Solvent relaxation of a room-temperature ionic liquid [bmim][PF6] confined in a ternary microemulsion

In this paper we have reported the solvent and rotational relaxation of 1-butyl-3-methyl-imidazolium hexafluorophosphate (bmim]PF₆]) confined in tween 20/(bmim]PF₆]/water microemulsion using coumarin 153 (C-153) as probe. The most interesting feature of our experiment was that we observed an increase in solvent relaxation time with increase in R (R = tween 20-to-bmim]PF₆] molar ratio). This is due to the fact that with increase in bmim]PF₆] content of the microemulsions, the microviscosity of the pool of the microemulsions increases, and motion of ions of bmim]PF₆] is hindered in the pool of microemulsions. Since motion of ions is responsible for solvation in room-temperature ionic liquids (RTILs), solvent-relaxation time increases with increase in R.