Structure and Dynamics of Ultra‐Low‐Crosslinked Microgels

ABSTRACT Concentrated suspensions of small ultra‐low crosslinked microgels are investigated with scattering and steady shear rheology to capture their equilibrium dynamics. We combine viscosimetry, dynamic light scattering, and small‐angle neutron and x‐ray scattering in dilute suspensions and show that the synthesis without the addition of any crosslinker agent and in presence of high concentrations of surfactants led to small ultra‐soft microgels. Although the slow relaxation time increases exponentially with the generalized packing fraction, , the relative viscosity follows a power‐law dependence on , with . The interplay between characteristic lengths (mesh size vs. overall size of the microgel) and the enhanced polymeric contributions of the shell make these microgels ultra‐soft, enabling the formation of viscoelastic fluids even in overcrowded conditions.