"Hairy" Colloids Collaboration with Dr. Jan Vermant at the Katholieke Universiteit Leuven, Heverlee, Belgium and Prof. Dieter Richter at the Forschungszentrum Jülich, Neutron Scattering

The attractive van-der-Waals interaction between colloids can be shielded by grafting or absorbing polymers onto the colloid surface. This leads to a stabilization of the colloidal suspension. Depending on the layer thickness, the solvent quality and the grafting density the interaction potential can be easily varied between hard-sphere interaction and the longer ranged (softer) potential of star polymers. Our interest in "hairy" colloids which include polymer coated colloids [1] and diblock-copolymer micelles [2] is multifolded: In the frame of the project "Hard to Ultra soft Colloids" (HUSC) which is funded by the European Community we are in particular interested in the phenomenon of shear-band formation [3]. The shear induced instability might have its origin in the shear induced polymer brush deformation that might render the van der Waals attractions in certain directions unshielded. Current measurements for the determination of the shape and structural investigations in the high concentration range include insitu-rheological experiments with neutron-, light- and X-ray scattering. We also wish to investigate ordering phenomena and collective dynamics in the high concentration range without applied shear. [1] J. Vermant; J. Coll. Int. Sci. 211 (1999) 221. [2] L. Willner et al.; Europhys. Lett. 51 (2000) 628. [3] J.K.G. Dhont; Phys. Rev. E 60 (1999) 8804.