(328i) Dynamic Arrest of Adhesive Hard Sphere Dispersions Following a Thermal Quench

In this work, we address the fundamental questions concerning the interplay between particle interactions, dynamical arrest and phase behavior by rheology and neutron scattering measurements on a model, thermoreversible, colloidal adhesive hard sphere (AHS) suspension. The model AHS dispersion shows a unique anomalous rheological behavior in the form of a reproducible drop in shear modulus during aging at a deep thermal quenched state. After this drop in the modulus, AHS gel evolves toward a quench-path-independent state over the experimental timescale. To provide a mechanistic understanding, small angle neutron scattering measurements under rheological shear flow (Rheo-SANS) are used to interrogate the microstructure on the particle scale. SANS measurements of colloidal suspension as a function of time during various thermal quench is characterized in terms of an effective interaction strength and a Mason number. The systematic differences in the effective interaction strength provide insights into the different landscapes in the phase diagram explored by the colloidal suspension upon varying the extent of thermal quench. The insight form the rheological and scattering study connects homogeneous gelation with heterogeneous gel formation due to phase separation and shows that the extent of quench can be used as an independent parameter to govern the rheological response of the arrested gel.