Journal of Chemical Physics vol:136 issue:12 pages:1-9
A direct consequence of the finite compressibility of a swollen microgel is that it can shrink and deform
in response to an external perturbation. As a result, concentrated suspensions of these particles
exhibit relaxation dynamics and rheological properties which can be very different with respect to
those of a hard sphere suspension or an emulsion.We study the reduction in size of ionic microgels in
response to increasing number of particles to show that particle shrinkage originates primarily from
steric compression, and that the effect of ion-induced de-swelling of the polymer network is negligible.
With increasing particle concentration, the single particle dynamics switch from those typical
of a liquid to those of a super-cooled liquid and finally to those of a glass. However, the transitions
occur at volume fractions much higher than those characterizing a hard sphere system. In the supercooled
state, the distribution of displacements is non-Gaussian and the dependence of the structural
relaxation time on volume fraction is describable by a Volger-Fulcher-Tammann function.