Orientational and translational dynamics in room temperature ionic liquids

Abstract

The authors investigate the dynamics of a series of room temperature ionic liquids, based on the same 1-butyl-3-methylimidazolium cation with different anions, by means of broadband (10(-6)-10(9) Hz) dielectric spectroscopy and depolarized light scattering in the temperature range from 400 K down to 35 K. Typical ionic conductivity is observed above the glass transition temperature Tg. Below Tg the authors detect relaxation processes that exhibit characteristics of secondary relaxations, as typically observed in molecular glasses. At high temperatures, the characteristic times of cation reorientation, deduced from the light scattering data, are approximately equal to the electric modulus relaxation times related to ionic conductivity. In the supercooled regime and close to Tg, the authors observe decoupling of conductivity from structural relaxation. Overall, room temperature ionic liquids exhibit typical glass transition dynamics, apparently unaltered by Coulomb interactions.

Molecular dynamics and the translational–rotational coupling of an ionically conducting glass-former: amlodipine besylate

“…25,29,35,39 The t of the data at 334 and 337 K is presented in Fig. S3 † with b KWW h (1 À n s ) ¼ 0.56, indicating broad frequency dispersion, which may have some connection to the unstable nature of amorphous AMB.…”

Cation and anion dynamics in supercooled and glassy states of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate: Results from13C,31P, andEndo1, Widgeon2, Yu3 et al. 2012Phys. Rev. B220150View full textAdd to dashboardCite

“…The maximum FWHM values of the 19 F and 31 P NMR spectra around T g are estimated to be ~ 13 kHz and 5 kHz, respectively. For a rigid lattice NMR line shape with Gaussian dipolar broadening, the FWHM can be expressed in the form of its second moment M 2 as, …”

Low Frequency Mechanical Spectroscopy Study of Three Pyrrolidinium Based Ionic Liquids

“…Information regarding the molecular dynamic behavior of each ion forming an IL is especially important because several of the basic properties of ILs are determined by their behaviors on a molecular level. The nature of the relaxation processes taking place in some ILs, in particular on those based on imidazolium cations, has been studied, mainly by means of nuclear magnetic resonance and broadband dielectric spectroscopy [3][4][5]. Since a low melting point is central in ILs, an understanding of the crystallization phenomena is extremely important.…”