In this project we investigate how steric interactions, by surface-grafted PEG polymer on colloidal particles, translates into effective attractions and its effect on the static structure, phase behavior and dynamics. PEGylated particles differ from the commonly used non-aqueous systems for which crystallization in the polymer shell acts to trigger the attractions. This water-based system offers a more controlled approach where the solvent quality for PEG is varied and found to smoothly regulate the interactions (Zackrisson Oskolkova et al., RCS Advances, 2015). From a quantitative analysis of small-angle neutron scattering data we can extract the effective attraction. In contrast to what is commonly assumed, the effective attraction is found to depend on particle concentration at high volume fractions and the attraction is no-longer pairwise additive. This aspect should serve as impetus for further studies of graft-mediated interactions.

Furthermore, Core-shell particles with a fluorinated core are now being synthesized and characterized using Cryo-TEM. The fluorination serves to match the index of refraction of the solvent i.e. water, cancelling or minimizing the attractive Van der Waals (VdW) forces, normally always present in common systems. Now instead, the steric contribution to the interactions is dominating. This facilitates the study of the detailed nature of steric stabilization and destabilization and the role of VdW interactions.

People: Jeanette Ulama (Physical Chemistry, Göteborg University), Johan Bergenholtz (Physical Chemistry, Göteborg University and Physical Chemistry, Lund University), Giuseppe Foffi (University of Paris-Syd) and Malin Zackrisson Oskolkova

Contact person: Malin Zackrisson Oskolkova