Direct Correlation of Surface Tension and Surface Composition of Ionic Liquid Mixtures-A Combined Vacuum Pendant Drop and Angle-Resolved X-ray Photoelectron Spectroscopy Study.
Molecules
; 27(23)2022 Dec 05.
Article
in En
| MEDLINE
| ID: mdl-36500653
ABSTRACT
We investigated the surface tension and surface composition of various mixtures of the two ionic liquids (ILs) 1-methyl-3-octyl-imidazolium hexafluorophosphate [C8C1Im][PF6] and 1,3-bis(polyethylene glycol)imidazolium iodide [(mPEG2)2Im]I in the temperature range from 230 to 370 K under ultraclean vacuum conditions. The surface tension was measured using a newly developed apparatus, and the surface composition was determined by angle-resolved X-ray photoelectron spectroscopy (ARXPS). In the pure ILs, the alkyl chains of [C8C1Im][PF6] and the PEG chains of [(mPEG2)2Im]I are enriched at the IL/vacuum interface. In the mixtures, a strong selective surface enrichment of the alkyl chains occurs, which is most pronounced at low [C8C1Im][PF6] contents. For the surface tension, strong deviations from an ideal mixing behaviour take place. By applying a simple approach based on the surface composition of the mixtures as deduced from ARXPS, we are able to predict and reproduce the experimentally measured temperature-dependent surface tension values with astonishingly high accuracy.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Ionic Liquids
Language:
En
Journal:
Molecules
Journal subject:
BIOLOGIA
Year:
2022
Document type:
Article
Affiliation country:
Germany