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BP: Fachverband Biologische Physik

BP 5: Membranes, Vesicles and Synthetic Life-like Systems I

BP 5.4: Vortrag

Montag, 9. März 2026, 15:45–16:00, BAR/0205

Hexagonal and Lamellar Superstructure in DSPE-PEG1000 Monolayers at the Air/Water Interface — •Issam Assi, Heiko Aherns, and Christiane A. Helm — Institute of Physics, University of Greifswald, Germany

Inspired by diblock copolymer self-assembly, we investigate lipopolymer monolayers at the air/water interface. We studied DSPE-PEG1000 monolayers with alkyl chains in the liquid-condensed phase in dependence of the molecular area. Due to its conformational entropy, the moderately hydrophilic PEG has a larger area requirement than the alkyl chains in all-trans conformation. Small-angle grazing incidence X-ray diffraction (GID) measurements identified a hexagonal superstructure. The ordered alkyl chains form hydrophobic domains that are embedded in dissolved PEG. These domains consist of the alkyl chains of ca. 200 PEGylated lipid molecules. During monolayer compression, the number of alkyl chains in a domain remains constant, while their area fraction increases. At an area fraction of 50%, a transition to a lamellar superstructure occurs. During this transition, the alkyl chain domains merge. This transition is attributed to the entropy loss of the laterally compressed PEG chains. Wide-angle GID reveals that the alkyl chains in the liquid-condensed phase possess the same small cross-sectional area, as those in DSPE monolayers, indicating that PEG has little influence on the liquid-condensed phase. The hexagonal superstructure was confirmed with AFM images.

Keywords: lipopolymer; lipid monolayer; x-ray; superstructure; AFM