Using a Molecular Stopwatch to Study Particle Uptake in Pickering Emulsions.
Colloidal PMMA particles and an interfacially assembled, pH-switchable lipid film (tetradecylammonium hydrogen phosphate, TAHP) were combined to form emulsion droplets with composite interfaces. Two time scales govern the interfacial structure and droplet size of the system: the rate of particle adsorption and the rate of film assembly. We tune these two time scales by varying the particle size (in the case of the particles) and aqueous pH (in the case of the lipid film). Three rates of film assembly are studied: rapid (pH 5), slow (pH 7), and inactive (pH 9). At pH 5, small droplets coated with a mixed interfacial structure are formed, and increasing particle volume fraction does not change the droplet size. At pH 7, the slowed kinetics of TAHP film assembly results in the particle size having a systematic effect upon droplet size: the smaller the particles, the smaller the droplets. At pH 9, TAHP plays no role in the system, and more familiar Pickering emulsions are observed. Finally, we show that at pH 5 both the interfacial particle density and droplet size can be readily tuned in our system. This suggests potential applications in the rational design of capsules and emulsion droplets with tunable interfacial structure.
School of Physics and Astronomy, University of Edinburgh , James Clerk Maxwell Building, Edinburgh EH9 3FD, United Kingdom.
Joe
J
Forth
School of Physics and Astronomy, University of Edinburgh , James Clerk Maxwell Building, Edinburgh EH9 3FD, United Kingdom.
Paul S
PS
Clegg