Ordering and dynamics of soft spheres in melt and solution

Abstract

Multiarm star polymers, consisting of a high number of linear homopolymer arms, are viewed as ideal core-shell type of spheres with soft colloidal character. Owing to their non-uniform monomer density distribution (in solution) and non-uniform arm interpenetration (in the melt), these spheres order both in solution (above the overlap concentration) and in the melt. The structure reflects a rich dynamic response, featuring both polymeric (shell) and colloidal (core) characteristics. In the melt it manifests itself as a two-step viscoelastic relaxation in the terminal region. In solution, concentration and number density fluctuations relax via polymeric cooperative diffusion and colloidal self-diffusion and structural relaxation. Blend solutions involving mixtures of stars with linear homopolymers or different stars are used as the vehicle to explore the dynamics of composites in the mesoscopic regime.