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Micellar kinetics of a fluorosurfactant through stopped-flow NMR
KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.ORCID iD: 0000-0002-0231-3970
KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
2006 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 5, 2002-2004 p.Article in journal (Refereed) Published
Abstract [en]

 F-19 NMR chemical shifts and transverse relaxation times T, were measured as a function of time after quick stopped-flow dilution of aqueous solutions of sodium perfluorooctanoate (NaPFO) with water, Different initial concentrations of micellar solution and different proportions of mixing were tested. Previous stopped-flow studies by time-resolved small-angle X-ray scattering (TR-SAXS) detection indicated a slow (similar to 10 s) micellar relaxation kinetics in NaPFO solutions. In contrast, no evidence of any comparable slow (> 100 ms) relaxation process was found in our NMR studies. Possible artifacts of stopped-flow experiments are discussed as well as differences between NMR and SAXS detection methods. Upper bounds on the relative weight of a slow relaxation process are given within existing kinetic theories of micellar dissolution.

Place, publisher, year, edition, pages
2006. Vol. 22, no 5, 2002-2004 p.
Keyword [en]
Kinetic theory, Nuclear magnetic resonance spectroscopy, Relaxation processes, Surface active agents
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-5531DOI: 10.1021/la0529660ISI: 000235744500013Scopus ID: 2-s2.0-33644911175OAI: oai:DiVA.org:kth-5531DiVA: diva2:9927
Note
QC 20100922Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
In thesis
1. NMR Studies of Colloidal Systems in and out of Equilibrium
Open this publication in new window or tab >>NMR Studies of Colloidal Systems in and out of Equilibrium
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The Thesis describes (i) the development of add-on instrumentation extending the capabilities of conventional NMR spectrometers and (ii) the application of the designed equipments and techniques for investigating various colloidal systems. The new equipments are:

Novel designs of stopped-flow and temperature–jump inserts intended for conventional Bruker wide-bore superconductive magnets. Both inserts are loaded directly from above into the probe space and can be used together with any 10 mm NMR probe with no need for any auxiliary instruments.

A set of 5 mm and 10 mm 1H – 19F – 2H NMR probes designed for heteronuclear 1H – 19F cross-relaxation experiments in Bruker DMX 200, AMX 300 and DMX 500 spectrometers, respectively.

A two–stage low-pass filter intended for suppressing RF noise in electrophoretic NMR experiments.

The kinetics of micellar dissolution and transformation in aqueous solutions of sodium perfluorooctanoate (NaPFO) is investigated using the stopped-flow NMR instrument. The sensitivity of NMR as detection tool for kinetic processes in micellar solutions is clarified and possible artefacts are analysed. In the NaPFO system, the micellar dissolution is found to proceed faster than 100 ms while surfactant precipitation occurs on the time scale of seconds-to-minutes. The kinetics of the coil-to–globule transition and intermolecular aggregation in a poly (Nisopropylacrylamide) solution are investigated by the temperature-jump NMR instrument. As revealed by the time evolution of the 1H spectrum, the T2 relaxation time and the self-diffusion coefficient D, large (>10 nm) and compact aggregates form in less than 1 second upon fast temperature increase and dissolve in less than 3 seconds upon fast temperature decrease.

The intermolecular 1H – 19F dipole-dipole cross-relaxation between the solvent and solute molecules, whose fast rotational diffusion is in the extreme narrowing limit, is investigated. The solutes are perfluorooctanoate ions either in monomeric or in micellar form and trifluoroacetic acid and the solvent is water. The obtained cross-relaxation rates are frequency-dependent which clearly proves that there is no extreme narrowing regime for intermolecular dipole-dipole relaxation. The data provide strong constraints for the dynamic retardation of solvent by the solute.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 55 p.
Series
Trita-FYK, 0601
Keyword
stopped-flow NMR, temperature-jump NMR, crossrelaxation, NMR, NMR probe, fluorosurfactant, micellar kinetics, micellar structure
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-3898 (URN)91-7178-310-5 (ISBN)
Public defence
2006-04-20, Sal F3, Lindstedtsvägen 26, 10:00
Opponent
Supervisors
Note
QC 20100929Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2010-09-29Bibliographically approved

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Furó, István

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