Origin of de-swelling and dynamics of dense ionic microgel suspensions

Giovanni Romeo, Luna Imperiali, Jin-Woong Kim, Alberto Fernández-Nieves, David A. Weitz
2012 Journal of Chemical Physics  
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
more » ... 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.
doi:10.1063/1.3697762 pmid:22462893 fatcat:cpvqnq55onbwdelnl72snidlti