Spherical polymeric brushes viewed as soft colloidal particles: zero-shearviscosity

We examine the concentration dependence of the zero-shear viscosity of two chemically distinct classes of spherical brushes, multiarm star polymers an d giant diblock copolymer micelles. We show that the effective volume fract ion based on the hydrodynamic, rather than the static, size of these object s is the appropriate scaling parameter for obtaining a generic description of the relative viscosity for systems of varying size and softness. We demo nstrate that it is possible to span the whole range from polymeric behavior to that of hard colloidal spheres by tuning the sphere softness at the mol ecular level (arm size and functionality). (C) 2001 Elsevier Science B.V. 4 11 rights reserved.