title: Effects of Coalescence on Shear-Induced Gelation of Colloids.
abstract: Shearing lyophobic colloidal suspensions can lead to aggregation, followed by gelation, if the formed clusters grow to sizes large enough to percolate. If the temperature is set over the glass transition temperature of the suspended material, the particles embedded in the same aggregate start to coalesce with one another. Coalescence occurs to the finite viscosity of the particles' material, which leads to material diffusion from particle to particle. The driving force of this process is the reduction of the particle-dispersant interface and, as a consequence, the decrease the center-to-center separation of the particles. This leads to decreased cluster size, and hence a delayed gelation. Simultaneously, coalescence reinforces the particle-particle bonds formed upon aggregation, leading to clusters that are able to resist higher hydrodynamic forces before breaking up, hence leading to faster gelation. These two competing effects, combined with the natural complexity of colloidal aggregation makes it rather difficult to understand and predict which trend becomes dominant. In the present work, the shear-induced gelation of model polymeric colloidal systems with different glass transition temperatures has been studied. Starting with their interaction potential we investigate the impact of temperature on the gel time in concentrated suspensions (φ = 5%) under steady shear, followed by the effect of temperature on the stress-resistance of fully destabilized clusters under agitation. The results of the present work allow for a systematic view and deepened understanding of the factors governing shear-induced gelation in the presence of coalescence.
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich , Vladimir-Prelog-Weg 1, 8093 Zurich, Switzerland.
authors.forename: Baptiste
authors.identifier: 0000-0002-3920-9173
authors.initials: B
authors.lastname: Jaquet
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors.forename: Stefano
authors.initials: S
authors.lastname: Lazzari
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich , Vladimir-Prelog-Weg 1, 8093 Zurich, Switzerland.
authors.forename: Luca
authors.initials: L
authors.lastname: Colonna
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich , Vladimir-Prelog-Weg 1, 8093 Zurich, Switzerland.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Colombo
authors.affiliation: Department of Chemical Engineering, University of Chemistry and Technology Prague , Technicka 5, 16628 Prague 6, Czech Republic.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Soos
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich , Vladimir-Prelog-Weg 1, 8093 Zurich, Switzerland.
authors.forename: Massimo
authors.initials: M
authors.lastname: Morbidelli