Berlin 2005 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 30: POSTER: Chemical physics

CPP 30.43: Poster

Dienstag, 8. März 2005, 16:30–18:30, Poster TU D

Polymer-induced transient networks in water-in-oil(w/o)-microemulsions — •Tinka Spehr, Thomas Blochowicz, Ahmed Sayeed, and Bernd Stühn — Technische Universität Darmstadt, Institut für Festkörperphysik, Hochschulstr. 8, 64289 Darmstadt

We study water in oil microemulsions which are dispersions of water droplets coated with a monolayer of surfactant in a continuous oil phase. Of particular interest for the present work is the system consisiting of water, n-decane and the anionic surfactant AOT, which we investigate by small-angle X-ray scattering (SAXS) and photon correlation spectroscopy (PCS). Below room temperature the structure of our one phase microemulsion is characterized by water droplets with a well defined radius in an oil matrix. In a former study of a complementary system (o/w-microemulsion with nonionic surfactant) the addition of a triblock copolymer led to the interconnection of the micelles. [1] In our case the polymer used is PEO(polyethylenoxide)-PI(polyisoprene)-PEO which has hydrophilic headgroups and a hydrophobic middle part.

We are monitoring the formation and structure of the network with SAXS to determine the structure factor and the domain form factor. Furthermore PCS is used to observe the dynamics of concentration fluctuations comprising the translational diffusion of the droplets and the relaxation of the network. Compared to the earlier study our system shows a remarkable increase of the viscosity at a much lower number of polymers per droplet. This effect is either caused by a higher degree of crosslinking or a longer lifetime of the junctions in our system.

[1] M. Schwab and B.Stühn, J. Chem. Phys. 14, 6461, (2000)