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| Item type: | Article | ||||
|---|---|---|---|---|---|
| Date: | 2004 | ||||
| Institutions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry VI - Physical Chemistry (Solution Chemistry) > Prof. Dr. Werner Kunz | ||||
| Identification Number: |
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| Keywords: | nonionic surfactant micelle structure water alc | ||||
| Dewey Decimal Classification: | 500 Science > 540 Chemistry & allied sciences | ||||
| Status: | Published | ||||
| Refereed: | Yes, this version has been refereed | ||||
| Created at the University of Regensburg: | Yes | ||||
| Item ID: | 24590 |
Abstract
Small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) techniques have been used to study the structural properties of nonionic surfactant dodecyl-poly(ethylene oxide-23) ether (C12E23, com. name Brij 35) in water and in various alcs. from ethanol to 1-decanol. All measurements were performed at 25 °C. SAXS exptl. data were put on abs. scale using water as a secondary std. and ...
Abstract
Small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) techniques have been used to study the structural properties of nonionic surfactant dodecyl-poly(ethylene oxide-23) ether (C12E23, com. name Brij 35) in water and in various alcs. from ethanol to 1-decanol. All measurements were performed at 25 °C. SAXS exptl. data were put on abs. scale using water as a secondary std. and evaluated using the generalized indirect Fourier transformation method (GIFT), which is based on the simultaneous detn. of the intra- and interparticle scattering contributions. In this way, the size and shape of interacting scattering particles in real space could be deduced. In the Brij 35/water binary system (surfactant concns. from 0.5 to 25 mass %) globular micelles with max. dimensions ranging from 9 to 10.5 nm and radii of the hydrophobic core around 1.7 nm were found. At low surfactant concns. the micelles were more or less spherical, whereas slight elongation of the micelles was obsd. at concns. above 10 mass %. Dynamic light scattering (DLS) measurements confirmed SAXS results. SAXS spectra of Brij 35/alc. binary systems showed strong alc. interaction peaks at higher values of the scattering vector q that represented the structure of the solvent itself and were therefore eliminated during the evaluation procedure. Two populations of scattering particles were found in these systems: globular particles with max. dimension around 2.5 nm (solvated Brij 35 monomers) and large quite polydisperse Brij 35 objects with dimensions well above the resoln. of SAXS measurements, thus detd. by the DLS method. Accordingly, these samples were found to be very close to the limit of phase sepn., which could be actually obsd. with the naked eye, if the samples were left resting for longer period of time. With substitution of only 2 % of the alc. by water in the Brij 35/alc. binary systems the samples became stable. The SAXS data of these ternary systems indicated the transformation of the large objects into smaller structures that resembled the smaller population found in binary systems. However, the structures in the ternary systems were slightly larger and swollen into a more spherical shape. The obsd. structuration of pure alcs., which were used as solvents in the Brij 35/alc. binary system samples, was also explored.
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