研究・研究者
研究会・セミナー
| 演 題 | 「Dynamics in Room Temperature Ionic Liquids: Theory and Simulations」 |
|---|---|
| 日 時 | 2012年02月27日(月) 16:00 |
| 講演者 | Dr. Ranjit Biswas, Associate Professor (S. N. Bose National Centre for Basic Sciences) |
| 場 所 | 研究棟201セミナー室 |
| 概 要 | Dynamic Stokes shift measurements using a polarity probe in imidazolium and pyridinium ionic liquids (ILs)1 have revealed sub-picosecond solvation response, followed by a much slower component that ranges between a few picoseconds to several hundred of picoseconds. Also, the magnitude of shift is quite large, often comparable to those measured for common polar solvents, such as, acetonitrile and methanol. Similar measurements with phosphonium ionic liquids, however, reveal no ultrafast component in the measured decays that fit to stretched exponentials with single relaxation time constants. Recently, we have developed a molecular theory that, by using the available experimental dielectric relaxation data, shows that solute-IL dipolar interaction and orientational relaxation of dipolar ionic species contributes significantly to the measured shift and solvation response in the imidazolium and pyridinium ILs.2-7 The slow component appears to arise from the relaxation of the isotropic ion dynamic structure factor. The above theory also explains cogently the absence of ultrafast dynamics in phosphonium ILs and suggests microscopic reason for the apparent break-down of the existing dynamic continuum model theories in explaining the measured dynamics in ILs. Upon comparison with measured solvation response in (IL+ polar solvent) mixtures,8 the molecular theory predicts separation of dynamics into pure IL and pure polar solvent contributions.9 Our simulations using 128 ion pairs interacting via all-atom potentials suggest that the hydrodynamic relation that connects single particle rotation to the collective orientational relaxation is nearly valid at high temperature.10 In this talk, some of these results will be presented and discussed. |
| お問合せ先 | 大峯 巖 |
