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NMR Studies of Colloidal Systems in and out of Equilibrium
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
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 [en]
stopped-flow NMR, temperature-jump NMR, crossrelaxation, NMR, NMR probe, fluorosurfactant, micellar kinetics, micellar structure
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-3898ISBN: 91-7178-310-5 (print)OAI: oai:DiVA.org:kth-3898DiVA: diva2:9930
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
List of papers
1. A rapid-mixing design for conventional NMR probes
Open this publication in new window or tab >>A rapid-mixing design for conventional NMR probes
2005 (English)In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 175, no 2, 264-270 p.Article in journal (Refereed) Published
Abstract [en]

A simple stopped-flow design for rapid mixing of two liquids within the NMR probe is presented. The device uses no switches or relays but exploits instead the torque exerted by the magnetic field on a current-leading-coil to open and close the start and stop valves. Two serially arranged tangential jet mixer blocks provide a homogeneous mixture with, depending on conditions and requirements, a filling time in the 50-100 ms range and a subsequent stabilization time in the range of 10-40 ms as tested by mixing various combinations of liquids and observing their 1H NMR spectrum. Factors influencing the mixing process are analyzed.

Keyword
Alanine; Ethanol; Ethylene glycol; Homogeneous mixture; Mixing time; Pressure; Stopped-flow; Torque; Turbulent flow; Water
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5530 (URN)10.1016/j.jmr.2005.04.012 (DOI)000231082900011 ()2-s2.0-21244460805 (Scopus ID)
Note
QC 20100825Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
2. Micellar kinetics of a fluorosurfactant through stopped-flow NMR
Open this publication in new window or tab >>Micellar kinetics of a fluorosurfactant through stopped-flow NMR
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.

Keyword
Kinetic theory, Nuclear magnetic resonance spectroscopy, Relaxation processes, Surface active agents
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5531 (URN)10.1021/la0529660 (DOI)000235744500013 ()2-s2.0-33644911175 (Scopus ID)
Note
QC 20100922Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
3. A temperature-jump design for conventional NMR probes
Open this publication in new window or tab >>A temperature-jump design for conventional NMR probes
2006 (English)In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 181, no 1, 148-153 p.Article in journal (Refereed) Published
Abstract [en]

 The design and performance of a simple probe insert for temperature-jump experiments in conventional NMR probes is described. The insert uses the output from conventional NMR amplifiers for heating conductive aqueous samples with a rate of 30-80 K/s for 200 W radiofrequency power. The observed dependence of the heating rate on sample conductivity is explained by the dominance of dielectric heating. Factors governing the temperature gradient within the sample are discussed.

Keyword
radiofrequency heating; radiofrequency coil; inductive heating; aqueous solution; liquid crystal; thermoresponsive polymer; phase transition; ethylene glycol; 59Co; cesium perfluorooctanoate
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5532 (URN)10.1016/j.jmr.2006.04.006 (DOI)000238548000016 ()
Note
QC 20100825Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
4. Kinetics of demixing and remixing transitions in aqueous solutions of poly(N-isopropylacrylamide):  A temperature-jump H-1 NMR study
Open this publication in new window or tab >>Kinetics of demixing and remixing transitions in aqueous solutions of poly(N-isopropylacrylamide):  A temperature-jump H-1 NMR study
2006 (English)In: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 207, no 21, 1972-1979 p.Article in journal (Refereed) Published
Abstract [en]

The time course of the coil-to-globule collapse and intermolecular aggregation of poly(N-isopropylacrylamide) in aqueous solution upon exceeding the lower critical solution temperature (LCST) are investigated by temperature-jump 1H NMR spectroscopy. After the temperature jump, we record the time dependences of (i) the mobile fraction of the polymer chain as revealed by the intensity of the liquid-like NMR signal, (ii) the local mobility of those chains as revealed by the transverse relaxation time T2, and (iii) their self-diffusion coefficient D. The same data are also reported at their temperature-dependent long-time limits. The results suggest a sudden, faster than one second, collapse and intermolecular aggregation into globules and a slower reorganization/redistribution of the individual chains among and within the globular and mobile states. We found that all molecular changes are reversible if the temperature remains less than ca. 6-8 K above the LCST for less than a few minutes; under those conditions, experiments upon sudden temperature quench below the LCST show that the aggregates disintegrate and swell into coils in less than a few seconds.

Keyword
Aggregation, Miscibility, NMR, Temperature jump, Turbidity
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-5533 (URN)10.1002/macp.200600394 (DOI)000242249500008 ()2-s2.0-33751082937 (Scopus ID)
Note
QC 20100921. Uppdaterad från Submitted till Published (20100921).Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
5. Solute-Solvent Contact by Intermolecular Cross Relaxation: I. The Nature of the Water-Hydrophobic Interface
Open this publication in new window or tab >>Solute-Solvent Contact by Intermolecular Cross Relaxation: I. The Nature of the Water-Hydrophobic Interface
2006 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 125, no 7, 074704- p.Article in journal (Refereed) Published
Abstract [en]

Intermolecular cross-relaxation rates between solute and solvent were measured by {H-1} F-19 nuclear magnetic resonance experiments in aqueous molecular solutions of ammonium perfluoro-octanoate and sodium trifluoroacetate. The experiments performed at three different magnetic fields provide frequency-dependent cross-relaxation rates which demonstrate clearly the lack of extreme narrowing for nuclear spin relaxation by diffusionally modulated intermolecular interactions. Supplemented by suitable intramolecular cross-relaxation, longitudinal relaxation, and self-diffusion data, the obtained cross-relaxation rates are evaluated within the framework of recent relaxation models and provide information about the hydrophobic hydration. In particular, water dynamics around the trifluoromethyl group in ammonium perfluoro-octanoate are more retarded than that in the smaller trifluoroacetate

Keyword
molecular-dynamics simulation, overhauser effect measurements, nuclear-spin relaxation, pair correlation-functions, low ionic-strength, nmr relaxation, magnetic-resonance, carboxylic-acids, translational diffusion, electronic relaxation
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-5689 (URN)10.1063/1.2336199 (DOI)000239914800046 ()2-s2.0-33747624412 (Scopus ID)
Note
Uppdaterad från submitted till published: 20100914 QC 20100914Available from: 2006-05-10 Created: 2006-05-10 Last updated: 2012-03-22Bibliographically approved
6. Solute-Solvent Contact by Intermolecular Cross Relaxation: II. The Water-Micelle Interface and the Micellar Interior
Open this publication in new window or tab >>Solute-Solvent Contact by Intermolecular Cross Relaxation: II. The Water-Micelle Interface and the Micellar Interior
2006 (Swedish)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 51, 25775-25781 p.Article in journal (Refereed) Published
Abstract [en]

The intermolecular dipole-dipole cross-relaxation is measured between F-19 nuclei of sodium perfluorooctanoate in micelles and H-1 nuclei of the water solvent. The cross-relaxation rates for fluorines in the different moieties along the surfactant vary strongly by the resonance frequency in the investigated range of 188-470 MHz. This frequency dependence indicates that the cross-relaxation between water and amphiphilic aggregates is not controlled solely by the fast local water dynamics but significantly contributed to by the long-range translational diffusion of water. The cross-relaxation rates, analyzed in the framework of a model (Nordstierna, L.; Yushmanov, P. V.; Furo, I. J. Chem. Phys. 2006, 125, 074704), provide information about the dynamic retardation of water molecules by the micellar headgroup region and the location of the various moieties along the hydrophobic tail with respect to the water-micelle interface. Both intermolecular cross-relaxation and aggregation-induced F-19 chemical shift changes indicate no direct water contact to fluorines except for those closest to the head group.

Keyword
nuclear-magnetic-resonance, overhauser effect measurements, molecular-dynamics simulation, ionic surfactant micelles, order-parameter profile, sodium dodecyl-sulfate, spin relaxation, magic-angle, translational diffusion, conformational-analysis
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-5690 (URN)10.1021/jp0647885 (DOI)000242974300038 ()2-s2.0-33846400071 (Scopus ID)
Note
Uppdaterad från submitted till published: 20100914 QC 20100914Available from: 2006-05-10 Created: 2006-05-10 Last updated: 2012-03-22Bibliographically approved
7. Stopped-flow F-19 NMR studies of surfactant precipitation
Open this publication in new window or tab >>Stopped-flow F-19 NMR studies of surfactant precipitation
2006 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, Vol. 291, no 1-3, 59-62 p.Article in journal (Refereed) Published
Abstract [en]

The kinetics of the phase change in surfactant solutions is studied by F-19 stopped-flow NMR. In the aqueous solution of sodium perfluooctanoate, we observe precipitation and crystal growth induced by the addition of NaCl solution to the system. The time dependences of the NMR signal intensity and chemical shift, evaluated in the framework of a single model, narrow the range of possible scenarios, the most plausible of which is monomer incorporation into the growing crystals. In accordance to existing models of crystallization, both the nucleation rates and the crystal growth rates are strongly dependent on the magnitude of supersaturation.

Keyword
F-19 NMR, chemical shift, stopped-flow, kinetics, fluorosurfactant, supersaturation, precipitation, crystal growth, sodium perfluorooctanoate, ammonium perfluorooctanoate, micellar dissolution
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-24887 (URN)10.1016/j.colsurfa.2006.06.040 (DOI)000242873900009 ()
Note
QC 20100929Available from: 2010-09-29 Created: 2010-09-29 Last updated: 2010-09-29Bibliographically approved

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  • nn-NB
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Output format
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