Self-diffusion of multiarm star polymers in solution far from and near theordering transition

The self-diffusion of three 128-arm polybutadiene star solutions in toluene was investigated over a broad concentration range from dilute to the order ing region with pulsed field gradient NMR (PFG-NMR). The strong concentrati on dependence of the self-diffusion coefficient in the fluid state is disti nguished clearly from that of linear chains and can be described by a non-A rrhenius VFT-like equation with the concentration playing the role of inver se temperature. In the concentrated regime, the observation of two dynamic phases reflects the coexistence of crystalline and liquid phases over a lim ited concentration region. The concentration dependences of both the ordina ry (fluid-like) diffusion and the completely restricted in-cage motion of t hese hyper stars are in agreement with the behavior of concentrated colloid al suspensions. (C) 2000 Elsevier Science B.V. All rights reserved.