Abstract
The self-diffusion of three 128-arm polybutadiene star solutions in
toluene was investigated over a broad concentration range from dilute to
the ordering region with pulsed field gradient NMR (PFG-NMR). The strong
concentration dependence of the self-diffusion coefficient in the fluid
state is distinguished clearly from that of linear chains and can be
described by a non-Arrhenius VFT-like equation with the concentration
playing the role of inverse temperature. In the concentrated regime, the
observation of two dynamic phases reflects the coexistence of
crystalline and liquid phases over a limited concentration region. The
concentration dependences of both the ordinary (fluid-like) diffusion
and the completely restricted in-cage motion of these hyper stars are in
agreement with the behavior of concentrated colloidal suspensions. (C)
2000 Elsevier Science B.V. All rights reserved.