Berlin 2005 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 29: POSTER: Polymer physics

CPP 29.8: Poster

Dienstag, 8. März 2005, 16:30–18:30, Poster TU D

The Internal Interface of a Homogeneous Compressed PEE-PEO Diblock-Copolymer Monolayer — •Alexander Wesemann¹, Heiko Ahrens¹, Roland Steitz², Stephan Förster³, and Christiane A. Helm¹ — ¹Angewandte Physik, Uni Greifswald, 17487 Greifswald — ²Stranski-Laboratorium, TU Berlin, 10623 Berlin — ³Physikalische Chemie, Uni Hamburg, 20146 Hamburg

Amphiphilic block copolymers consisting of a fluid hydrophobic (Poly ethyl ethylene, PEE) and a hydrophyilic (Polyethyleneoxide, PEO) block form monolayers at the air/water interface. With X-ray and neutron reflectivity the density profile of PEE₄₃₂PEO₄₈₄ is investigated. It was found that the polymer adsorption layer consists of a homogeneous PEE and a homogenous PEO block, which can be compressed by a factor of three. The PEE thickness increases inversely proportional to the molecular area, and the PEO brush follows roughly the scaling law predicted for a brush in a good solvent. However, the stretching of the two blocks roughens the PEE-PEO interface, causing a transition from a PEO-monolayer adsorbed to a hydrophobic interface (0.8-1.1 nm thick) to a PEO/PEE/water interfacial layer of 3nm thickness. This transition of the interfacial layer highlights the rich phase behavior of amphiphilic block copolymers, which resembles that of lipids and non-ionic surfactants.