Universität zu Köln

Thater, Jan C., Stubenrauch, Cosima, Glatter, Otto, Klemmer, Helge ORCID: 0000-0001-6818-465X and Sottmann, Thomas (2019). Microstructure of ionic liquid (EAN)-rich and oil-rich microemulsions studied by SANS. Phys. Chem. Chem. Phys., 21 (1). S. 160 - 171. CAMBRIDGE: ROYAL SOC CHEMISTRY. ISSN 1463-9084

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Abstract

In a previous study we investigated the phase behavior of microemulsions consisting of the ionic liquid ethylammonium nitrate (EAN), an n-alkane and a nonionic alkyl polyglycolether (CiEj). We found the same general trends as for the aqueous counterparts, i.e. a transition from an oil-in-EAN microemulsion via a bicontinuous microemulsion to an EAN-in-oil microemulsion with increasing temperature. However, unlike what happens in the corresponding aqueous systems, in EAN-in-oil microemulsions only a very small amount of EAN was detected by NMR-measurements. This is why we investigated the phase behavior and microstructure of EAN-rich n-dodecane-in-EAN microemulsions and oil-rich EAN-in-n-octane microemulsions. We found that the ionic liquid emulsification failure boundary has an extraordinarily small slope, which suggests that the amphiphilic film loses its ability to solubilize EAN with an increase in temperature by only a few degrees. The analysis of the small angle neutron scattering (SANS) curves unambiguously shows that this behavior is due to the fact that the EAN molecules form a substructure with a characteristic length scale of approximate to 8 angstrom inside the EAN-in-oil droplets. In more detail, the analysis of the SANS data with the GIFT method revealed a transition from spherical to cylindrical structures approaching the respective critical endpoint temperatures. By using the respective form factors and combining them with a Gaussian spatial intensity distribution to account for the EAN sub-structure we were able to describe the scattering curves nearly quantitatively.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Thater, Jan C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Stubenrauch, Cosima UNSPECIFIED UNSPECIFIED UNSPECIFIED Glatter, Otto UNSPECIFIED UNSPECIFIED UNSPECIFIED Klemmer, Helge UNSPECIFIED orcid.org/0000-0001-6818-465X UNSPECIFIED Sottmann, Thomas UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-159497
DOI:	10.1039/c8cp06228e
Journal or Publication Title:	Phys. Chem. Chem. Phys.
Volume:	21
Number:	1
Page Range:	S. 160 - 171
Date:	2019
Publisher:	ROYAL SOC CHEMISTRY
Place of Publication:	CAMBRIDGE
ISSN:	1463-9084
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SMALL-ANGLE SCATTERING; INDIRECT FOURIER TRANSFORMATION; AMPHIPHILIC BLOCK-COPOLYMERS; PHASE-BEHAVIOR; INTERACTING PARTICLES; NEUTRON-SCATTERING; ETHYLAMMONIUM NITRATE; WATER; MIXTURES; MICELLES Multiple languages Chemistry, Physical; Physics, Atomic, Molecular & Chemical Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/15949