title: Ionic multilayers at the free surface of an ionic liquid, trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide, probed by x-ray reflectivity measurements.
abstract: The presence of ionic multilayers at the free surface of an ionic liquid, trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide ([TOMA(+)][C(4)C(4)N(-)]), extending into the bulk from the surface to the depth of approximately 60 A has been probed by x-ray reflectivity measurements. The reflectivity versus momentum transfer (Q) plot shows a broad peak at Q approximately 0.4 A(-1), implying the presence of ionic layers at the [TOMA(+)][C(4)C(4)N(-)] surface. The analysis using model fittings revealed that at least four layers are formed with the interlayer distance of 16 A. TOMA(+) and C(4)C(4)N(-) are suggested not to be segregated as alternating cationic and anionic layers at the [TOMA(+)][C(4)C(4)N(-)] surface. It is likely that the detection of the ionic multilayers with x-ray reflectivity has been realized by virtue of the greater size of TOMA(+) and C(4)C(4)N(-) and the high critical temperature of [TOMA(+)][C(4)C(4)N(-)].
authors.affiliation: Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Nishi
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Yasui
authors.forename: Tomoya
authors.initials: T
authors.lastname: Uruga
authors.forename: Hajime
authors.initials: H
authors.lastname: Tanida
authors.forename: Tasuku
authors.initials: T
authors.lastname: Yamada
authors.forename: Shun-ichi
authors.initials: S
authors.lastname: Nakayama
authors.forename: Hideki
authors.initials: H
authors.lastname: Matsuoka
authors.forename: Takashi
authors.initials: T
authors.lastname: Kakiuchi