8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P6.28Fri 911:10-14:00Concentration dependent pathways in spontaneousself-assembly of unilamellar vesiclesTheyencheri Narayanan, 1 Jeremie Gummel, 1 Michael Sztucki, 1 and MichaelGradzielski 21 European Synchrotron Radiation Facility, 6 Jules Horowitz, 38043, Grenoble,France2 Technische Universitat Berlin, Berlin, GermanyWhile the equilibrium microstructure of a large variety of self-assembled soft matter systems iswidely studied, the transient intermediate states in the self-assembly process are only beginningto be explored [1]. Understanding the pathways of self-assembly is key to achieving control andpredictive capabilities in the fabrication of well-defined nanostructures. In this respect, unilamellarvesicles are interesting systems as they are often formed under non-equilibrium conditions. Here,we report on the structural dynamics underlying the formation of unilamellar vesicles uponrapid mixing of dilute solutions of anionic (lithium perfluorooctanoate) and zwitterionic (tetradecyldimethylamineoxide) surfactants using a stopped-flow device [2]. The transient intermediatestructures were probed by time-resolved small-angle X-ray scattering with millisecond resolution[3] While disk-like transient mixed micelles are formed at higher concentrations, more elongatedstructures such as cylinder-like and torus-like micelles are involved at lower concentrations wellbelow the critical micellar concentration of the more soluble component [4]. These differencesare attributed to monomer addition mechanism dominating the self-assembly process at lowconcentration range where as at higher concentrations, the process is governed by fusion ofdisk-like mixed micelles. The results reveal that the same final structure can be reached bydifferent routes indicating the thermodynamic driving force for the formation of unilamellarvesicles in this type of mixed surfactant systems.[1] M. Gradzielski, J. Phys. Condens. Matter, 15, R655 (2003).[2] T. M. Weiss, T. Narayanan, and M. Gradzielski, Langmuir, 24, 3759 (2008).[3] T. Narayanan, Cur. Opin. Coll. Interface Sci. , 14, 409 (2009).[4] J. Gummel, M. Sztucki, T. Narayanan, and M. Gradzielski, Soft Matter, DOI: 10.1039/c1sm05354j (2011).28