Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 29: Crystallisation, Nucleation and Self assembly

CPP 29.12: Talk

Wednesday, March 28, 2012, 18:30–18:45, C 243

Kinetics of vesicle formation: A SAXS-stopped-flow study — •Katharina Bressel¹, Michael Muthig¹, Jeremie Gummel², Theyencheri Narayanan², and Michael Gradzielski¹ — ¹Stranski-Laboratorium, Institut für Chemie, TU Berlin, Germany — ²European Synchrotron Radiation Facility (ESRF), France

Vesicle formation processes often pass through an intermediate state of disc-like micelles that grow to a maximum size and than close to form vesicles. The driving force for the disc growth is controlled by the line tension of the disc-rim. The balance between the line tension of the discs and the bending elasticity of the vesicle bilayers determines the size and polydispersity of the initially formed vesicles.

In our study we modified the previously studied TDMAO (tetradecyldimethylamine oxide)/LiPFOS (lithium perfluorooctylsulfonate) system by addition of amphiphilic copolymers. The hydrophobic part of these copolymers is incorporated into the surfactant bilayers and is assumed to accumulate in the disc-rim and therefore lower the line tension. That leads to an increase in the maximum size of the disc-like micelles and to a slower vesicle formation. By means of the stopped-flow technique with SAXS detection we studied in situ the kinetics of the vesicle formation process. This rapid-mixing technique allows the observation of kinetic processes in the ms time range and gives excess to detailed structural information about size, shape, and polydispersity of the aggregates. We compared the analysis of these measurements to a coagulation simulation. This simulation is based on a disc growth process that follows a Smoluchowski mechanism.