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DRG: Deutsche Rheologische Gesellschaft

DRG 12: Poster Strukturierte Materialien

DRG 12.5: Poster

Dienstag, 2. März 1999, 14:00–16:00, Foyer

Viscoelastic behavior of polymer melts tethered to the air/water interface — •Clarisse Luap and Werner A. Goedel — Max-Planck-Institut für Kolloid- und Grenzflächenforschung,
Rudower Chaussee 5 , D-12489 Berlin.

We present a new experimental approach to get some more insight into the dynamics of polymer chains tethered by one end to an interface. We investigate the linear viscoelastic behavior of solvent-free polymer brushes as monolayers at the air/water interface, depending on the surface concentration and chain length. These brush-like monolayers, 20 to 50 nm thick, are obtained by spreading hydrophobic polymers with a hydrophilic head group onto the water surface[1]. The tethering density can be easily varied by lateral compression of the film with the movable barrier of a Langmuir trough. Their linear viscoelastic properties are determined directly at the air/water interface by applying a small amplitude oscillatory shear flow within the interface plane. We will present here our results obtained on monolayers of polyisoprenes terminated by a sulfonated head group. When increasing the chain length, we observe a transition from a liquid-like to a temporary network behavior typical of an entangled polymer melt. Their zero shear viscosity as well as their terminal relaxation time increase significantly when increasing the tethering density. Both quantities are 2 to3 orders of magnitude higher than those of a bulk polymer melt of equivalent molecular weight.
[1] R. Heger, W.A. Goedel, Macromolecules 1996, 29, p8912.