Catanionic and chain-packing effects on surfactant self-assembly in the ionic liquid ethylammonium nitrate

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:540

Article

Bryant, Saffron J.^1,2  Jafta, Charl J.³  Atkin, Rob⁴  Gradzielski, Michael⁵  Warr, Gregory G.^1,2 

[1] Univ Sydney, Sch Chem, Sydney, NSW 2006, Australia

[2] Univ Sydney, Nano Inst, Sydney, NSW 2006, Australia

[3] Helmholtz Zentrum Berlin, D-14109 Berlin, Germany

[4] Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia

[5] Tech Univ Berlin, Inst Chem, Str 17 Juni 124, D-10623 Berlin, Germany

关键词: Catanionic surfactant;    Ionic liquid;    Mixed micelle;    Cosurfactant;    Neutron scattering;   

DOI  :  10.1016/j.jcis.2019.01.048

来源: Elsevier

【 摘 要 】

Hypothesis: Micelle formation, particularly the formation of compact, globular micelles in the high ionic strength environment of an ionic liquid, seems to be at odds with the principle of opposing forces and the concept of the surfactant packing parameter. Here we examine how interactions between polar head-groups, with solvent ions, and chain packing affect self-assembly structure in ionic liquids. Experiments: The self-assembly of pure cationic and anionic surfactants, their catanionic mixtures, and the effect of the cosurfactant tetradecanol in the ionic liquid ethylammonium nitrate (EAN) is investigated by small-angle neutron scattering (SANS). Findings: The critical micelle concentrations of cationic surfactants are much higher and micelles much smaller in EAN than in water, whereas anionic micelles are less dramatically affected. Catanionic surfactant mixtures form small micelles in EAN at all compositions, unlike their counterparts in water which form vesicle dispersions or precipitates near 1:1 mol ratios. This contrasts with the behavior of cationic surfactants when mixed with double-chained analogs or alkanol cosurfactants, which induce micelle growth and shape transitions to rod-like and bilayer aggregates through chain packing effects similar to aqueous systems. This enables the aggregate morphology in the ionic liquid to be controlled through the composition of the surfactant mixtures. (C) 2019 Elsevier Inc. All rights reserved.

【 授权许可】

Free