Here - Institute for Building Materials - ETH Zürich

Cooperative processes in restructuring gel networksJader Colombo and Emanuela Del GadoMicrostructure and Rheology, Institute for Building Materials,ETH Zurich, CH-8093 Zurich, SwitzerlandColloidal gel networks are disordered elastic solids that can form also via reversibleaggregation and even in extremely diluted particle suspensions. The possibility ofinternal restructuring underlies their smart mechanics and being able to design it atthe level of the nanoscale components would be ground-breaking for severaltechnological applications. This is challenging, especially because there is limitedunderstanding of how local breaking and recombination change the mesoscaleorganization of the network and the stress transmission through it.We have carried out a comparative study of restructuring and non-restructuring gelnetworks, by means of molecular dynamics. The networks arise from self-assembly ofcolloidal particles, whose effective interactions yields local rigidity necessary tomake thin network structures at low volume fractions mechanically stable. Thelocalization of particles in the network, akin to some extent to caging in denseglasses, appears to be determined only by the network topology and displays thesame features in restructuring and non-restructuring networks. Nevertheless, bondbreakinginduces cooperative processes that are not present in the non-restructuringnetworks and we are able to relate them to the presence of regions where bondbreakingis more likely to occur. Interestingly, such regions are not characterized bymore mobile particles: because the mesoscale organization of the network is notdisrupted by single bond-breaking events, such events can instead changesignificantly the mobility of regions further away.Spatial map of particle mobility.Spatial map of propensity to bond breaking.51