title: Amphiphile micelle structures in the protic ionic liquid ethylammonium nitrate and water.
abstract: Micelles formed by amphiphiles in a protic ionic liquid (PIL), ethylammonium nitrate (EAN), were investigated using synchrotron small-angle X-ray scattering and contrasted with those that formed in water. The amphiphiles studied were cationic hexadecyltrimethylammonium chloride (CTAC) and hexadecylpyridinium bromide (HDPB) and nonionic poly(oxyethylene) (10) oleyl ether (Brij 97) and Pluronic ethylene oxide-propylene oxide-ethylene oxide block copolymer (P123). The scattering patterns were analyzed using spherical, core-shell, and cylindrical scattering models. The apparent micelle shape and size of the surfactants and the block copolymer in the PIL have been reported. At low amphiphile concentrations (<10 wt %) spherical micelles were preferentially formed for all the amphiphiles in EAN. The micelles formed by the two cationic amphiphiles in EAN and water were similar, though different scattering models were required predominantly due to the ionic nature of EAN. The two nonionic amphiphiles formed micelles with similar core radii in water and in EAN. However, the micelle shells composed of ethylene oxide groups fitted to a significantly thicker layer in water compared to EAN. At high concentrations (>10 wt %) in EAN and water, there was a preference for cylindrical micelles for CTAC, HDPB, and Brij 97; however, the P123 micelles remained spherical.
authors.affiliation: Particulate Fluids Processing Centre (PFPC), School of Chemistry, The University of Melbourne , Melbourne, Victoria 3010, Australia.
authors.forename: Zhengfei
authors.initials: Z
authors.lastname: Chen
authors.forename: Tamar L
authors.initials: TL
authors.lastname: Greaves
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Caruso
authors.forename: Calum J
authors.initials: CJ
authors.lastname: Drummond
mesh_terms: D008725:Bis-Trimethylammonium Compounds / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D008823:Micelles; D015394:Molecular Structure; D010938:Plant Oils / Q000737:chemistry; D011060:Poloxalene / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011726:Pyridinium Compounds / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D053838:Scattering, Small Angle; D013501:Surface-Active Agents / Q000737:chemistry*; D017356:Synchrotrons; D014867:Water / Q000737:chemistry*
chemical_list: D008725:Bis-Trimethylammonium Compounds; D052578:Ionic Liquids; D008823:Micelles; D010938:Plant Oils; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; C525618:cethyltrimethylammonium chloride; C521901:hexadecylpyridinium bromide; D014867:Water; C421484:ethylammonium; C464484:pluronic block copolymer P123; D011092:Polyethylene Glycols; D011060:Poloxalene; C033084:polyethylene glycol oleyl ether