Dresden 2017 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 47: Fluids and Interfaces I
CPP 47.3: Vortrag
Mittwoch, 22. März 2017, 17:00–17:15, ZEU 255
Ultra-thin Polymer Films at the Air/Water Interface: Lateral and vertical structure of poly (butyl acrylate) during compression — •Christian Appel and Bernd Stühn — Institut für Festkörperphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany
The behaviour of poly (butyl acrylate), PBA, spread readily at the a/w interface is well studied. It forms stable films that become elastic at high surface pressures (20-30 mN/m).[1] We prepare Langmuir monolayers of PBA and the diblock copolymer poly(ethylene glycol)-PBA with different molecular weights from 5 kg/mol to 20 kg/mol. The PEG block acts as a small hydrophilic anchor (NM < 10).
We perform in-situ Brewster-Angle-Microscopy (BAM) and in-situ X-Ray reflectometry (XRR) to get a thorough understanding of the film structure. For the dilute and semi-dilute regime the surface pressure and coverage follows the expected scaling laws. In the concentrated regime there is a transition from a continuous water-free monolayer to a more complex structure. At first in the semi-dilute regime, XRR and BAM show a single monolayer structure of the film. During the compression to the concentrated regime the lateral structure of the film changes to 2D-disks of PBA within the monolayer. This is complementarily observed by XRR (Yoneda peak and off-specular intensity) and BAM. Hysteresis experiments indicate that a part of the monolayer is irreversible deformed within the concentrated regime.
[1] K. Witte et al., Macromolecules 43, 2990-3003 (2010)