AGGREGATING BLOCK-COPOLYMERS AS MODEL SYSTEMS TO STUDY POLYMER BRUSH DYNAMICS

A-B block copolymers in a selective solvent-good for the B-species and bad for the A-species-form micellar aggregates with a compact A-core with a corona (brush) of B <<hairs>> reaching into the solvent. Wherea s polystyrene(PS)-polyisoprene(PI) in decane forms spherical micelles with a PS core of about 10 nm radius, polyethylene(PE)-polyethylenepro pylene(PEP) forms micellar platelets, the shape of which is goverend b y the habitus of PE crystallites forming the core. These planar aggreg ates have large (several hundred nanometers) lateral extension and a c ore thickness in the range of 10 nm. Both systems are model systems fo r polymer brushes, either on a spherical surface or planar. Neutron sp in-echo experiments allow for the investigation of the dynamics of the brushes which reflects their viscoelastic properties. Results of neut ron small-angle and spin-echo investigations are reported. The brush d ynamics is explained using a model based on an idea of de Gennes descr ibing the brush properties in terms of scaling relations for osmotic p ressure and viscosity of a semi-dilute solution with inhomogeneous den sity.