Universität zu Köln

Puetz, Y., Grassberger, L., Lindner, P., Schweins, R., Strey, R. and Sottmann, T. (2015). Unexpected efficiency boosting in CO2-microemulsions: a cyclohexane depletion zone near the fluorinated surfactants evidenced by a systematic SANS contrast variation study. Phys. Chem. Chem. Phys., 17 (8). S. 6122 - 6135. CAMBRIDGE: ROYAL SOC CHEMISTRY. ISSN 1463-9084

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Abstract

Microemulsions with supercritical CO2 are promising alternatives for organic solvents, especially if both polar and non-polar components need to be dissolved. However, only fluorinated surfactants, which are known to be environmentally unfriendly, are appropriate to formulate well-structured microemulsions. While most approaches to increase the environmental performance of CO2-microemulsions deal with the design of new surfactants with a reduced degree of fluorination, we discovered that the partial substitution of CO2 by cyclohexane enables a considerable reduction of fluorinated surfactants. Thereby, the most efficient solubilization of the CO2/cyclohexane mixture, which turned out to be pressure-dependent, was found at a cyclohexane-to-CO2 mass ratio between 1 : 6 and 1 : 4. In order to elucidate this unexpected effect a systematic Small Angle Neutron Scattering (SANS) contrast variation study was performed. The analysis of the recorded scattering curves by the Generalized Indirect Fourier Transformation (GIFT) clearly shows that the scattering length density profiles differ considerably from CO2-microemulsions without cyclohexane. Instead of a nearly constant scattering length density, a density profile that varies systematically over half of the droplet radius was detected. These results clearly indicate that the observed efficiency boosting is caused by the formation of a depletion zone of cyclohexane close to the fluorinated amphiphilic film.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Puetz, Y. UNSPECIFIED UNSPECIFIED UNSPECIFIED Grassberger, L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lindner, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schweins, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Strey, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sottmann, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-417267
DOI:	10.1039/c4cp05435k
Journal or Publication Title:	Phys. Chem. Chem. Phys.
Volume:	17
Number:	8
Page Range:	S. 6122 - 6135
Date:	2015
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; CARBON-DIOXIDE MICROEMULSIONS; INDIRECT FOURIER TRANSFORMATION; NEUTRON-SCATTERING; SUPERCRITICAL CO2; PHASE-BEHAVIOR; NONIONIC MICROEMULSIONS; INTERACTING PARTICLES; WATER-IN-CO2 MICROEMULSION; CO2-PHILIC SURFACTANTS Multiple languages Chemistry, Physical; Physics, Atomic, Molecular & Chemical Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/41726