Regensburg 2002 – scientific programme

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SYPF: Struktur und Dynamik in dünnen Polymerfilmen

SYPF 2: Poster Session

SYPF 2.28: Poster

Thursday, March 14, 2002, 09:00–18:00, Poster B

The enhanced lateral diffusion and ethanol-induced phase coexistence in lipid monolayers coupled to polyelectrolytes investigated by pattern photobleaching — •Liying Wang, Monika Schönhoff, and Helmuth Möhwald — MPI für Kolloid- und Grenzflächenforschung, D-14424 Potsdam-Golm, Deutschland

The lateral diffusion in lipid monolayers attached to a polymer cushion is studied by fluorescence recovery after pattern photobleaching. The polymer support is formed by layer-by-layer self-assembly. Lipid diffusion coefficients are very small as measured in air, indicating strong electrostatic coupling. Comparing phosphatidylcholine lipids with different chains (DMPC, DOPC) to phosphatidic acid (DOPA), the lipid head group is determining the lateral diffusion, with negligible influence of the chain. The dependence of charge in the last polyelectrolyte layer on diffusion can not be detected, which is attributed to the flexibility of the lipid binding to extending loops of internal layers or to the long-range electrostatic interaction. Temperature dependent diffusion is performed at 20-61^∘C, a slow kinetics of chain rearrangement of polymer is observed above 45^∘C. In spite of strong electrostatic interactions at the internal interface, evidence of molecular flexibility is provided. In systems swollen with 0-50% ethanol solution, diffusion coefficients are increased by a factor of 40-250 for PC lipids. As experiments carried out up to 75-100% [ethanol], phase coexistence is observed at room temperature in all above lipids/polymer coupling systems. The enhanced lateral diffusion and phase coexistence can be only due to the reduced interfacial interaction by increasing the interfacial distance.