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Bilayers with Surfactant-induced Pores and Demixing in Micelles: Studies of Segregation in Amphiphile Systems
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry.
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The focus of this thesis has been on the effects of segregation in mixtures of amphiphilic molecules. Two different systems were investigated: fluorocarbon-hydrocarbon surfactant mixtures and lipid-surfactant mixtures.

In fluorocarbon-hydrocarbon surfactant mixtures the repulsive interactions between the chains can lead to a demixing into different types of coexisting micelles, fluorocarbon rich and hydrocarbon rich. From NMR self-diffusion measurements such a demixing was found to occur in the mixture of the partially fluorinated surfactant HFDePC and C16TAC. We furthermore suggested a demixing also within the micelles to explain 19F-NMR line width data and results from neutron scattering.

In lipid-surfactant mixtures, a segregation of the molecules may instead be caused by a difference in the preferred curvature of the lipid and the surfactant residing within the same aggregate. Using a surfactant selective electrode, binding isoterms of four different cationic surfactants (C12TAC, C14TAC, C16TAC and HFDePC) to preformed lipid (GMO) vesicles were determined. Perforated vesicles were observed by cryo-TEM in the mixture with C16TAC. To explain the results from the binding isoterms, the formation of pores in the bilayer was regarded as a cooperative process, similar to micelle formation. The surfactant accumulates at the edges of the pores, and increasing the surfactant concentration results in an increased number of pores with a constant surfactant/lipid ratio at the edges.

The lipid-surfactant mixtures were also studied at the solid/solution interface using AFM. An adsorbed mesh structure, a counterpart to the bulk perforated lamellar phase, was observed for the first time.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2003. , p. 55
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 884
Keywords [en]
Physical chemistry, fluorocarbon surfactants, amphiphile mixtures, perforated bilayers, segregation, NMR, surfactant selective electrode, cryo-TEM, SANS, AFM
Keywords [sv]
Fysikalisk kemi
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-3565ISBN: 91-554-5728-2 (print)OAI: oai:DiVA.org:uu-3565DiVA, id: diva2:163285
Public defence
2003-10-03, B7:113a, BMC, Uppsala, 14:00
Opponent
Supervisors
Available from: 2003-09-12 Created: 2003-09-12Bibliographically approved
List of papers
1. Molecular Mechanism of Lateral Diffusion of Fluorosurfactants. A 19F NMR Study
Open this publication in new window or tab >>Molecular Mechanism of Lateral Diffusion of Fluorosurfactants. A 19F NMR Study
2002 In: Langmuir, Vol. 18, no 12, p. 5015-5018Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-90803 (URN)
Available from: 2003-09-12 Created: 2003-09-12Bibliographically approved
2. Demixing of Fluorinated and Hydrogenated Surfactants into Distinct Aggregates and into Distinct Regions Within Aggregates. A Combined NMR, Fluorescence Quenching and Cryo-TEM Study
Open this publication in new window or tab >>Demixing of Fluorinated and Hydrogenated Surfactants into Distinct Aggregates and into Distinct Regions Within Aggregates. A Combined NMR, Fluorescence Quenching and Cryo-TEM Study
2002 In: Langmuir, Vol. 18, no 24, p. 9243-9249Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-90804 (URN)
Available from: 2003-09-12 Created: 2003-09-12Bibliographically approved
3. Mixed Micelles of Fluorocarbon and Hydrocarbon Surfactants. A Small Angle Neutron Scattering Study
Open this publication in new window or tab >>Mixed Micelles of Fluorocarbon and Hydrocarbon Surfactants. A Small Angle Neutron Scattering Study
Show others...
Manuscript (Other academic)
Identifiers
urn:nbn:se:uu:diva-90805 (URN)
Available from: 2003-09-12 Created: 2003-09-12 Last updated: 2010-01-13Bibliographically approved
4. Determination of Isoterms for Binding of Surfactants to Vesicles Using a Surfactant Selective Electrode
Open this publication in new window or tab >>Determination of Isoterms for Binding of Surfactants to Vesicles Using a Surfactant Selective Electrode
Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:uu:diva-90806 (URN)
Available from: 2003-09-12 Created: 2003-09-12Bibliographically approved
5. Direct Visualization of Mesh Phases at Solid/Solution Interfaces by AFM
Open this publication in new window or tab >>Direct Visualization of Mesh Phases at Solid/Solution Interfaces by AFM
Show others...
Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:uu:diva-90807 (URN)
Available from: 2003-09-12 Created: 2003-09-12Bibliographically approved

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