Influence of different substituents on the surface composition of ionic liquids studied using ARXPS.
Angle resolved X-ray photoelectron spectroscopy has been used to study the surface composition of various nonfunctionalized and functionalized 1,3-dialkylimidazolium ionic liquids. For [CnC1Im][Tf2N] (where n = 2-16), an enrichment of the aliphatic carbon was observed for longer chains (n > or = 4). Enrichment of the aliphatic carbon also occurs for alkyl chains attached to the anion, as observed for [C2C1Im][OcOSO3]. Oligo(ethyleneglycol)ether (PEG) functionalities in the cation lead to a surface composition close to bulk stoichiometry and thus a loss in enrichment of the chains. This effect is attributed to attractive interactions between the oxygen atoms on the cation to the hydrogen atoms on the imidazolium ring for [Et(EG)2MIm] [Tf2N] and [Me(EG)3MIm][Tf2N].
Lovelock
K R J
KR
Lehrstuhl für Physikalische Chemie II, Lehrstuhl für Chemische Reaktionstechnik, Erlangen Catalysis Resource Center (ECRC), Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany.
Kolbeck
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C
Cremer
T
T
Paape
N
N
Schulz
P S
PS
Wasserscheid
P
P
Maier
F
F
Steinrück
H-P
HP