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Direct Visualization of Mesh Phases at Solid/Solution Interfaces by AFM
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Article in journal (Refereed) Submitted
URN: urn:nbn:se:uu:diva-90807OAI: oai:DiVA.org:uu-90807DiVA: diva2:163284
Available from: 2003-09-12 Created: 2003-09-12Bibliographically approved
In thesis
1. Bilayers with Surfactant-induced Pores and Demixing in Micelles: Studies of Segregation in Amphiphile Systems
Open this publication in new window or tab >>Bilayers with Surfactant-induced Pores and Demixing in Micelles: Studies of Segregation in Amphiphile Systems
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. 55 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 884
Physical chemistry, fluorocarbon surfactants, amphiphile mixtures, perforated bilayers, segregation, NMR, surfactant selective electrode, cryo-TEM, SANS, AFM, Fysikalisk kemi
National Category
Physical Chemistry
urn:nbn:se:uu:diva-3565 (URN)91-554-5728-2 (ISBN)
Public defence
2003-10-03, B7:113a, BMC, Uppsala, 14:00
Available from: 2003-09-12 Created: 2003-09-12Bibliographically approved

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