Elucidating the microstructural transition behind shear-induced gelation in model colloid-polymer mixtures using rheo-SAXS

Colloidal Gels (CGs), composed of particles and polymers, are used in industries such as food, personal care, and construction. Their properties are determined by the attractive interactions and volume fraction of their subunits. CGs' microstructure and mechanical properties can be adjusted through moderate shear. Here, the studied CGs consist of colloid-polymer mixtures (PAM & fumed silica particles in water/glycerol mixtures) that either (i) spontaneously aggregate into gels or (ii) undergo shear-induced gelation via irreversible colloid flocculation due to polymer bridging. This research explores shear-assisted aggregation by Rheo-SAXS -XPCS to determine the range of mechanical properties and microstructures that can be generated. It also compares these properties with those created by varying the volume fraction for a fixed shear history. Additionally, it seeks to identify shear sequences that can "freeze" structural anisotropy in CGs upon cessation of flow.