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We present a study of equilibrium chain-exchange kinetics of a well-defined model system for starlike polymeric micelles. The results show that the kinetics follows a logarithmic time dependence. The same feature has been confirmed for two other micellar systems. This is in sharp contrast to theoretical predictions and hints towards strongly coupled chain dynamics within the micellar cores induced by geometrical constraints.

The micellar behaviour of the amphiphilic block copolymer poly-(ethylene-propylene)-poly-(ethylene oxide) (PEP-PEO) in aqueous solution has been studied with smallangle neutron scattering. The polymer was studied over a wide range of molecular weights, always keeping the volume of the blocks equal. The scattering behaviour of the solutions showed that a morphological transition takes place upon lowering the molecular weight. The high molecular weight block copolymers all build spherical, monodisperse micelles with large aggregation numbers. At low molecular weights, however, cylindrical micelles are formed. An interesting intermediate case is represented by the PEP2-PEO2 system, in which a morphological transition occurs upon dilution. [ABSTRACT FROM AUTHOR]