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Morphological and Interaction Characteristics of Surface‐Active Ionic Liquids and Palmitic Acid in Mixed Monolayers
Author(s) -
Eftaiha A. F.,
Qaroush Abdussalam K.,
Kayed Ghada G.,
Abdel Rahman Abdel Rahman K.,
Assaf Khaleel I.,
Paige Matthew F.
Publication year - 2020
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000359
Subject(s) - alkyl , brewster's angle , monolayer , surface pressure , ionic liquid , chemistry , langmuir , chemical engineering , analytical chemistry (journal) , crystallography , organic chemistry , aqueous solution , optics , biochemistry , physics , brewster , mechanics , engineering , catalysis
A series of water soluble, surface‐active ionic liquids (SAILs), namely, 1‐alkyl‐3‐methyl imidazolium chlorides ([C n ‐ mim ]Cl) and their mixtures with palmitic acid (PA) are investigated in Langmuir monolayers and Langmuir–Blodgett films. It is inferred from the surface pressure‐area isotherms that C 16 ‐ mim ‐IL mixes non‐ideally with PA and stabilizes the binary mixed films. In addition, the residence of mim ‐IL at the water surface is enhanced as a function of the increasing alkyl side chain length. Generally, the compressional moduli values decrease upon increasing the content of the mim ‐ILs over a wide range of compositions. Furthermore, film relaxation measurements indicate that the IL component is selectively excluded from the mixed films upon achieving a certain target pressure. Brewster angle microscope images demonstrate minimal changes on the PA domains in the presence of either C 4 ‐ and C 8 ‐ mim ‐ILs, whereas presence of the hexadecyl counterpart results in the formation of condensed sheets. Atomic force microscopy imaging of deposited films show the formation of propeller‐like aggregates when C 8 ‐ or C 16 ‐ mim ‐IL is present in the mixed films.