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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 22: Poster: Charged Soft Matter

CPP 22.7: Poster

Mittwoch, 28. März 2012, 11:00–13:00, Poster A

Polyelectrolyte coupling to a charged lipid monolayer: relating lattice and domain structures — •Thomas Ortmann, Heiko Ahrens, Andreas Gröning, Frank Lawrenz, and Christiane A. Helm — Institut für Physik, Uni Greifswald, Felix-Hausdorff-Str. 6, 17487 Greifswald, Germany

Polystyrene sulfonate (PSS) is adsorbed from dilute solution (0.01 mM with respect to the monomer concentration) onto oppositely charged dioctadecyldimethylammonium bromide (DODAB) lipid monolayers. The PSS molecular weight is varied. With grazing incidence X-ray diffraction (GID) the two-dimensional lamellar phase of adsorbed PSS is observed, when DODAB is in the condensed phase. The same ordered PSS phase is also found when the lipids are in the fluid phase and PSS molecular weight exceeds 6.5 kDa. A large spacing between short stretched chains hinders the two-dimensional lamellar phase, presumably the short chains gain rotational entropy.

With Brewster Angle Microscopy (BAM) the nucleation and growth of domains is observed on clean water, but only when low molecular weight PSS (< 8 kDa) is used. For high molecular weight PSS no domains of DODAB with coupled PSS are found, even though GID indicates the nucleation of condensed lipid domains. The domains do not grow, which is attributed to hindered lipid diffusion due to the adsorbed macromolecules.