Abstract
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 C(n)C(1)ImTf2N (where
n = 2-16), an enrichment of the aliphatic carbon was observed for
longer chains (n >= 4). Enrichment of the aliphatic carbon also occurs
for alkyl chains attached to the anion, as observed for
C2C1IMOcOSO(3). 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)(2)MImTf2N and Me(EG)(3)MImTf2N.
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