  The dynamics of soft colloids in solutions is characterized by internal
collective motion as well as center-of-mass diffusion. Using neutron scattering
we demonstrate that the competition between the relaxation processes associated
with these two degrees of freedom results in strong dependence of dynamics and
structure on colloid concentration, c, even well below the overlap
concentration c*. We show that concurrent with increasing inter-particle
collisions, substantial structural dehydration and slowing-down of internal
dynamics occur before geometrically defined colloidal overlap develops. While
previous experiments have shown that the average size of soft colloids changes
very little below c*, we find a marked change in both the internal structure
and internal dynamics with concentration. The competition between these two
relaxation processes gives rise to a new dynamically-defined dilute threshold
concentration well below c*.
