Phase behaviour and structure of zwitanionic mixtures of perfluorocarboxylates and tetradecyldimethylamine oxide-dependence on chain length of the perfluoro surfactant

Bressel, K.; Koetz, J.; Gradzielski, M.; Appavou, M.-S.; Tiersch, B.; Prevost, S.

doi:10.1039/c1sm05618b

Journal Article

Phase behaviour and structure of zwitanionic mixtures of perfluorocarboxylates and tetradecyldimethylamine oxide-dependence on chain length of the perfluoro surfactant

Bressel, K. ; Prevost, S. ; Appavou, M.-S.FZJ* ; Tiersch, B. ; Koetz, J. ; Gradzielski, M.

2011
Royal Society of Chemistry (RSC) Cambridge

Soft matter 7, 11232 - 11242 (2011) [10.1039/c1sm05618b]

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Please use a persistent id in citations: http://hdl.handle.net/2128/7360 doi:10.1039/C1SM05618B

Abstract: Phase behaviour and the mesoscopic structure of zwitanionic surfactant mixtures based on the zwitterionic tetradecyldimethylamine oxide (TDMAO) and anionic lithium perfluoroalkyl carboxylates have been investigated for various chain lengths of the perfluoro surfactant with an emphasis on spontaneously forming vesicles. These mixtures were studied at a constant total concentration of 50 mM and characterised by means of dynamic light scattering (DLS), electric conductivity, small-angle neutron scattering (SANS), viscosity, and cryo-scanning electron microscopy (Cryo-SEM). No vesicles are formed for relatively short perfluoro surfactants. The extension of the vesicle phase becomes substantially larger with increasing chain length of the perfluoro surfactant, while at the same time the size of these vesicles increases. Head group interactions in these systems play a central role in the ability to form vesicles, as already protonating 10 mol% of the TDMAO largely enhances the propensity for vesicle formation. The range of vesicle formation in the phase diagram is not only substantially enlarged but also extends to shorter perfluoro surfactants, where without protonation no vesicles would be formed. The size and polydispersity of the vesicles are related to the chain length of the perfluoro surfactant, the vesicles becoming smaller and more monodisperse with increasing perfluoro surfactant chain length. The ability of the mixed systems to form well-defined unilamellar vesicles accordingly can be controlled by the length of the alkyl chain of the perfluorinated surfactant and depends strongly on the charge conditions, which can be tuned easily by pH-variation.

Keyword(s): Polymers, Soft Nano Particles and Proteins (1st) ; Key Technologies (1st) ; Soft Condensed Matter (2nd) ; J

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Note: This research work was financially supported by the German Research Council (DFG) within the frame of the priority program SPP 1273 Kolloidverfahrenstechnik (GR1030/7-1 and 2). The SANS measurements on V4 at the HZB have been supported by the European Commission under the 6th Framework Programme through the Key Action: Strengthening the European Research Infrastructures (Contract no: RII3-CT-2003-505925 (NMI 3)). The SANS measurements on KWS-2 of JCNS (operating at FRMII, Munich) have been supported by the European Commission under the 7th Framework Programme through the 'Research Infrastructures' action of the 'Capacities Programme' Contract no.: 226507 (NMI3). M. G. would like to thank the Institute Laue-Langevin (ILL, Grenoble, France) and the DFG (project GR1030/10) for hospitality and funding of his sabbatical stay during which this manuscript was produced. Fruitful discussions with T. Narayanan are gratefully acknowledged. Finally we would like to thank the referees for their constructive comments that helped to improve the manuscript.

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