Berlin 2005 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 4: SYMPOSIUM: Dynamics of multi-component fluids IV

CPP 4.2: Vortrag

Freitag, 4. März 2005, 16:15–16:30, TU C243

Dynamics of structural transitions in amphiphilic systems followed by small-angle scattering experiments — •Gradzielski Michael — Lehrstuhl Physikalische Chemie I, Universität Bayreuth, D-95440 Bayreuth

Morphological transitions in amphiphilic systems can be induced by mixing with other surfactants or additives. In our experiments fast mixing phenomena were investigated by means of coupling the stopped-flow technique with the observation by means of SANS/SAXS, whereby detailed structural information can be obtained with a time resolution of 5-50 ms. Different types of structural investigations were studied, e. g. formation of unilamellar or multilamellar vesicles by mixing with oppositely charged surfactant or a cosurfactant. For instance the slow formation of monodisperse unilamellar vesicles was observed, that is driven purely by diffusive processes, and proceeds via a well-defined disk state. In general kinetics, intermediately formed structures and final state depend subtlely on the electrostatic conditions of the amphiphilic system and the molecular composition. In other experiments the disintegration of micelles initiated by mixing with a bad solvent was studied. Interestingly this this process does not proceed via a simple dissolution step by through a minimum aggregation state, which is followed by the reformation of small micellar structures. In general, it can be stated that the dynamics of amphiphilic systems can be complex but its detailed knowledge is pivotal for using self-aggregation as a tool for forming complex nanostructured materials.