Open AccessProbing the Surface Tension of Ionic Liquids Using the Langmuir Principle
Author(s) -
Karina Shimizu,
Bettina S. J. Heller,
Florian Maier,
HansPeter Steinrück,
José N. Cagia Lopes
Publication year - 2018
Publication title -
langmuir
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.042
H-Index - 333
eISSN - 1520-5827
pISSN - 0743-7463
DOI - 10.1021/acs.langmuir.7b04237
Subject(s) - ionic liquid , surface tension , molecular dynamics , chemistry , homologous series , x ray photoelectron spectroscopy , alkyl , imide , langmuir , computational chemistry , thermodynamics , crystallography , polymer chemistry , organic chemistry , physics , nuclear magnetic resonance , adsorption , catalysis
At 298 K, the surface tension of ionic liquids (ILs) of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide series, [C n C 1 Im][NTf 2 ], ranges from around 35 mN·m -1 for [C 2 C 1 Im][NTf 2 ] to just below 30 mN·m -1 for [C 12 C 1 Im][NTf 2 ]. However, the decrease rate along the series is not constant: a large decrease from [C 2 C 1 Im][NTf 2 ] to [C 8 C 1 Im][NTf 2 ] is followed by almost constant values from [C 8 C 1 Im][NTf 2 ] to [C 12 C 1 Im][NTf 2 ]. Such behavior is hard to interpret from a molecular point of view without suitable information about the free-surface structure of the different ILs. In this work, we have successfully used the Langmuir principle in combination with structural data obtained from angle-resolved X-ray photoelectron spectroscopy experiments and molecular dynamics simulations, to predict the correct surface tension trend along the IL series. The concepts unveiled for this particular homologous IL family can be easily extended to other systems.
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