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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Poster Session I

CPP 24.7: Poster

Montag, 16. März 2020, 17:30–19:30, P3

Supermolecular ordering in monolayers of lipids with extended polymer head groups - DSPE-PEG — •Heiko Ahrens, Olaf Soltwedel, Jens-Uwe Günther, and Christiane A. Helm — Institut für Physik, Uni-Greifswald, 17489 Greifswald

Depending on area per molecule, lipid monolayers - like Distearoylphosphatidyl-ethanolamine (DSPE) - at the air-water interface exhibit a phase transition form a liquid expanded to a condensed phase with tilted alkyl tails. On further compression the tilt angle decreases. Larger head groups increase the tilt angle and disturb the crystalline order.

DSPE with chemically attached short PEG (poly ethylene glycol) to the head group was investigated with GID and x-ray reflection. DSPE with longer PEG chains show a transition from fluid molecules to heterogeneous monolayer consisting of domains with condensed tilted lipid chains immersed in PEG chains adsorbed into the hydrophobic moiety of the lipid monolayer. These domains are then arranged in a hexagonal super structure with lattice constants up to 16 nm.

With a short PEG chain (8 monomers) an incompressible condensed phase with coherence length in the 10 nm range is found. The alkyl tails are strongly tilted - 39°- in a strongly distorted oblique lattice. Perpendicular to the tail axis they are arranged in the dense herring bone structure. Additional diffraction peaks due to an extended unit cell consisting of four alky tails were observed.