title: Coalescence control of elastomer clusters by fixed surface charges.
abstract: We studied the coalescence behavior of a fluorinated elastomer colloid, stabilized by fixed surface charges, with a glass transition temperature of about -20 degrees C, as a function of temperature under diffusion-limited cluster-cluster aggregation (DLCA) conditions. We first measured the aggregation kinetics by in situ dynamic light scattering and then simulated it through the Smoluchowski approach (i.e., population balance equations) using the only unknown parameter, the fractal dimension D(f) of the clusters, as the fit parameter. It was found that the estimated D(f) value increased as the temperature increased, starting from 1.7 at 25 degrees C and reaching the upper limit of 3.0 for T > or = 55 degrees C. These results indicate that the coalescence extent increases as the temperature increases. Such temperature-dependent coalescence behavior cannot be explained by thermodynamic considerations, and it must be related to a certain kinetic resistance. We explain this effect by considering the resistance of the fixed charges to relocation on the particle surface, which decreases as the temperature increases.
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland.
authors.forename: Cornelius
authors.initials: C
authors.lastname: Gauer
authors.forename: Hua
authors.initials: H
authors.lastname: Wu
authors.forename: Massimo
authors.initials: M
authors.lastname: Morbidelli
mesh_terms: D003102:Colloids / Q000737:chemistry; D020724:Elastomers / Q000737:chemistry*; D007700:Kinetics; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics
chemical_list: D003102:Colloids; D020724:Elastomers