Regensburg 2016 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 48: Focus: The Physics of Water Interactions with Biological Matter (joint session BP/CPP, organized by CPP)

CPP 48.7: Hauptvortrag

Donnerstag, 10. März 2016, 12:00–12:30, H37

Controlling Water Evaporation: self-assembly at air/liquid interfaces — •Emma Sparr¹ and Kevin Roger² — ¹Physical chemistry, Lund University, Sweden — ²Université de Toulouse, France

Land-living organisms face the challenge that the ambient air is much drier than what is found in a living cell. One strategy to counter this drying-out threat is through lipid-protein barrier membranes, like the human skin. One important property of the skin is that the evaporation rate across skin is nearly independent of the air humidity, which implies that skin is a responding membrane and its permeability depends on its boundary conditions.

Using aqueous solutions of amphiphilic molecules, we show that the response can be explained by changes in self-assembly structures in the water gradient across the interfacial layer. We have designed an experimental device coupled to a variety of characterization techniques (X-ray scattering, polarized & IR microscopy) to study the non-equilibrium time evolution at an air- liquid interface. Using this device we demonstrate for two model systems how multilayer interfacial structures are formed, and how these structures influence the water transport. We show that a dry phase with low water permeability forms at the air/liquid interface and adapts its thickness to counter changes in the air humidity. This responsive shield is a universal feature of systems for which the structure/permeability changes with the water content. Our findings can unveil mechanism of responding membrane in biological systems, for example, the skin, and it can lead to new possibilities to design robust and homogeneous coatings of amphiphilic molecules.