POLYELECTROLYTE BRUSHES GRAFTED AT THE AIR WATER INTERFACE/

A new approach for the study of grafted polyelectrolytes is investigat ed: monolayers at the air/water interface of block copolymers consisti ng of a liquid hydrophobic and a polyelectrolyte block. The lateral in teractions between the molecules is extremely long-ranged; a lateral p ressure can be measured, while the grafting density is varied by a fac tor of 10. Furthermore, the isotherms show a phase transition. With sp ecular X-ray reflectivity the segment density profile along the isothe rm in the compressed phase is determined. The hydrophobic block shows features characteristic of a melt: constant electron density and a lin ear relationship between length and grafting density. In contrast, the length of the polyelectrolyte block amounts to 66% of the contour len gth and remains constant while the grafting density is varied by a fac tor 2. These features are typical for an osmotic brush phase.