The AnnaLab Website

From the CCFE Website: CFE faculty Anna and Walker have intitated a new project to quantify the interfacial aspects of dispersants used to treat oil spills in marine environments. A three year project will characterize the impact of components of dispersants on model oil-water systems.

The project is funded through the  Consortium for the Molecular Engineering of Dispersant Systems (C-MEDS) awarded to Tulane University.

Our paper entitled “Interfacial Dynamics and Rheology of Polymer-Grafted Nanoparticles at Air-Water and Xylene-Water interfaces,” by N.J. Alvarez, S.L. Anna, T. Saigal, R.D. Tilton, and L.M. Walker, was published in Langmuir, 28 (2012) 8052 – 8063.

Dynamics of polymer grafted nanoparticles adsorbing at oil/water and air/water interfaces are characterized along with mechanics of the resulting particle‐laden interfaces.

Abstract: Particle-stabilized emulsions and foams offer a number of advantages over traditional surfactant-stabilized systems, most notably a greater stability against coalescence and coarsening. Nanoparticles are often less effective than micrometer-scale colloidal particles as stabilizers, but nanoparticles grafted with polymers can be particularly effective emulsifiers, stabilizing emulsions for long times at very low concentrations. In this work, we characterize the long-time and dynamic interfacial tension reduction by polymer-grafted nanoparticles adsorbing from suspension and the corresponding dilatational moduli for both xylene–water and air–water interfaces. The dilatational moduli at both types of interfaces are measured by a forced sinusoidal oscillation of the interface. Surface tension measurements at the air–water interface are interpreted with the aid of independent ellipsometry measurements of surface excess concentrations. The results suggest that the ability of polymer-grafted nanoparticles to produce significant surface and interfacial tension reductions and dilatational moduli at very low surface coverage is a key factor underlying their ability to stabilize Pickering emulsions at extremely low concentrations.