title: Polymer-Graft-Mediated Interactions between Colloidal Spheres.
abstract: Aqueous dispersions of fluorinated colloidal spheres bearing grafted poly(ethylene glycol) (PEG) are studied as a function of salt and particle concentration with the aim of improving the understanding of interactions among polymer-grafted particles. These dispersions can sustain large concentrations of salt, but crystals nucleate in dilute dispersions when a sufficient Na2CO3 concentration is reached, which is attributed to the presence of attractions between particles. On further increasing the Na2CO3 concentration, the solvent is rapidly cleared of particles. Small-angle X-ray scattering and cryogenic transmission electron microscopy are employed in order to quantify the attractions. The former is used to extract a second virial coefficient, and the latter shows that the PEG-graft contracts as a function of increasing salt concentration. The contraction not only leads to a reduction in excluded volume but also is accompanied by attractions of moderate magnitude. In contrast, dispersion of the particles in ethanol, in which bulk PEG solutions crystallize, lead to fractal structures caused by strong attractions.
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg , SE-41296 Göteborg, Sweden.
authors.forename: Jeanette
authors.initials: J
authors.lastname: Ulama
authors.affiliation: Division of Physical Chemistry, Center of Chemistry and Chemical Engineering, Lund University , SE-22100 Lund, Sweden.
authors.forename: Malin Zackrisson
authors.initials: MZ
authors.lastname: Oskolkova
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg , SE-41296 Göteborg, Sweden.|Division of Physical Chemistry, Center of Chemistry and Chemical Engineering, Lund University , SE-22100 Lund, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Bergenholtz