(86b) Interfacial Routes to Colloidal Gelation

Colloidal gelation is loosely defined as the emergence of arrested dynamics in a particulate suspension, and is typically due to attractive interparticle interactions that lead to clustering and the formation of a percolating particle network.  Such transitions are heavily exploited in a myriad of technological applications to enhance the microstructure and texture, rheology, or shelf life of colloidal suspensions.  In this talk, new routes to colloidal gelation will be discussed, which are based on particle assembly at liquid-liquid interfaces.  Two different systems will be presented, where gelation again results from the formation of a percolating colloid network.  However, particle trapping at fluid interfaces fundamentally changes the route to network formation and results in starkly dissimilar microstructures in the two systems.  In the first example, gelation is due to droplet bridging, which leads to the formation of a tenuous particle/droplet network in a continuous third phase.  In the second system, gelation is the result of particle jamming at fluid interfaces during spinodal decomposition, resulting in a co-continuous arrangement of uniform fluid domains separated by a jammed monolayer of colloidal particles.  Motivating the need to understand the rheology of these multiphase materials for their modern technological applications, we will discuss how the different kinetic pathways to gelation mediate the resultant microstructures and, in turn, the rheology of the mixtures. Finally, we will compare the results to the more familiar class of colloidal gels in which attractive interparticle interactions are a requirement for gelation.