  We investigate the dynamics of kinetically frozen block copolymer micelles of
different softness across a wide range of particle concentrations, from the
fluid to the onset of glassy behavior, through a combination of rheology,
dynamic light scattering and pulsed field gradient NMR spectroscopy. We
additionally perform Brownian dynamics simulations based on an ultrasoft
coarse-grained potential, which are found to be in quantitative agreement with
experiments, capturing even the very details of dynamic structure factors S(Q,
t) on approaching the glass transition. We provide evidence that for these
systems the Stokes-Einstein relation holds up to the glass transition; given
that it is violated for dense suspensions of hard colloids, our findings
suggest that its validity is an intriguing signature of ultrasoft interactions.
