Influence of different substituents on the surface composition of ionic liquids studied using ARXPS

K R J Lovelock; C Kolbeck; T Cremer; N Paape; P S Schulz; P Wasserscheid; F Maier; H-P Steinrück

doi:10.1021/jp810637d

Influence of different substituents on the surface composition of ionic liquids studied using ARXPS

J Phys Chem B. 2009 Mar 5;113(9):2854-64. doi: 10.1021/jp810637d.

Authors

K R J Lovelock¹, C Kolbeck, T Cremer, N Paape, P S Schulz, P Wasserscheid, F Maier, H-P Steinrück

Affiliation

¹ Lehrstuhl für Physikalische Chemie II, Lehrstuhl für Chemische Reaktionstechnik, Erlangen Catalysis Resource Center (ECRC), Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany.

PMID: 19708216
DOI: 10.1021/jp810637d

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 [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].