Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 50: Wetting, Nano- and Microfluidics I (joint session CPP/DY, organized by CPP)
CPP 50.11: Vortrag
Donnerstag, 10. März 2016, 12:30–12:45, H42
Stability of emulsions against coalescence and transport: Influence of surfactants — •Birte Riechers1,2, Philipp Gruner2, Florine Maes1,2, and Jean-Christophe Baret1,2 — 1CNRS, Univ. Bordeaux, CRPP, UPR 8641, Pessac, France — 2Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
Monodisperse aqueous droplets within emulsions become evermore attractive for use as separate microreactors in pharmaceutical and biotechnological applications [Theberge et al., Angewandte 2010]. These applications need constant experimental conditions inside the droplets. To date stabilization against coalescence is mainly obtained using surfactants. Surfactants also affect the solubility of solutes inside the continuous oil phase, thereby restricting their use [Gruner et al., Curr. Opin. Colloid Interface Sci. 2015]. Microfluidic tools provide insight into the mechanisms of interfacial stabilization:
Here we perform a complete analysis of the adsorption kinetics of a surfactant typically used in droplet-based microfluidic applications. We combine pH measurements at the micronscale and coalescence experiments in droplet-based microfluidics with bulk measurements to show that the kinetics of the transport of molecules across interfaces directly relates to those of interfacial stabilisation. Combining all information, we derive a simple model of adsorption in the kinetic-limited regime and show that two interfaces are only stabilized against coalescence for surfactant concentrations which are close to or above the critical micellar concentration.