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CPP: Chemische Physik und Polymerphysik

CPP 7: SYMPOSIUM Disperse Polymer Systems I

CPP 7.2: Vortrag

Dienstag, 28. März 2006, 10:00–10:15, ZEU 160

The Influence of Triblock Copolymers and Low Molecular Weight Homopolymers on the Structure of Microemulsions — •Tinka Spehr and Bernd Stühn — Institute of Condensed Matter Physics, Technical University Darmstadt, D-64289 Darmstadt

We use small angle X-ray scattering (SAXS) to study a microemulsion consisting of water droplets coated by the anionic surfactant AOT dispersed in decane. At a constant water-to-AOT ratio the dependence of droplet radius, polydispersity and structure factor of the pure microemulsion on droplet density and temperature were investigated. Unexpectedly the radius of the water core decreases with increasing droplet volume fraction. At a volume fraction of droplets of ten percent we added different amounts of the amphiphilic triblock copolymer PEO-PI-PEO, which has hydrophilic headgroups and a hydrophobic middle part (PEO: polyethyleneoxide, PI: polyisoprene). There is clear evidence for an increasing crosslinking of the droplets with increasing polymer concentration. Already a low number of polymer molecules per droplet causes network formation as opposed to the complementary system (o/w-microemulsion with nonionic surfactant) for which the interconnection of the droplets via an amphiphilic triblock copolymer has previously been shown [1]. Structure factors were extracted from the SAXS profiles. Furthermore the effect on droplet structure caused by the incorporation of low molecular weight PEO homopolymers will be discussed. [1] M. Schwab and B. Stühn; J. Chem. Phys. 14, 6461 (2000)