Temperature dependence of multilayering at the free surface of ionic liquids probed by X-ray reflectivity measurements

Naoya Nishi; Tomoya Uruga; Hajime Tanida; Takashi Kakiuchi

doi:10.1021/la200252z

Temperature dependence of multilayering at the free surface of ionic liquids probed by X-ray reflectivity measurements

Langmuir. 2011 Jun 21;27(12):7531-6. doi: 10.1021/la200252z. Epub 2011 May 19.

Authors

Naoya Nishi¹, Tomoya Uruga, Hajime Tanida, Takashi Kakiuchi

Affiliation

¹ Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan. Naoya.Nishi@z05.mbox.media.kyoto-u.ac.jp

PMID: 21595446
DOI: 10.1021/la200252z

Abstract

The effect of the temperature on the surface layering of ionic liquids has been studied for two ionic liquids, trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide([TOMA(+)][C(4)C(4)N(-)]) and trihexyltetradecylphosphonium bis(nonafluorobutanesulfonyl)amide ([THTDP(+)][C(4)C(4)N(-)]), using X-ray reflectivity measurements at 285, 300, and 315 K. Both [TOMA(+)][C(4)C(4)N(-)] and [THTDP(+)][C(4)C(4)N(-)] develop multilayers at the surface. The structure of the multilayers at the [TOMA(+)][C(4)C(4)N(-)] surface shows little temperature-dependent change, whereas that at the [THTDP(+)][C(4)C(4)N(-)] surface clearly becomes diffused with increasing temperature. The different temperature dependence seems to be related to the difference in the recently reported ultraslow dynamics of the interfacial structure of [TOMA(+)][C(4)C(4)N(-)] and [THTDP(+)][C(4)C(4)N(-)] at the ionic liquid|water interface.