Research

Particles at Interfaces

Interest in understanding the behavior of colloidal particles near interfaces has grown in recent years. Among motivations for such studies is the attraction of colloids to interfaces, which is of considerable importance for many applications such as foam and emulsion stabilization, oil recovery, and self-assembly processes. Analogous to surfactants, colloidal particles are surface-active materials as they can spontaneously accumulate at the fluid interfaces, either liquid-vapor or liquid-liquid, a behavior first reported by Ramsden at the beginning of the last century. This phenomenon was further explored by Pickering after whom solid-stabilized emulsions are named, so-called Pickering Emulsions. Despite their surface activity, colloidal particles with homogeneous chemical composition and surface properties are not amphiphilic in nature. In contrast to homogeneous particles with uniform wettability, Janus particles with anisotropic surface wettability, described by de Gennes on the occasion of the 1991 noble prize lecture as a "new animal", possess the typical Pickering character coupled with the amphiphilicity of a classical surfactant. Consequently, an enhanced surface activity is expected for these Janus colloids in comparison to homogeneous particles. Our research is focused on studying the behavior of Janus particles near and at the interface of two immiscible liquids using both simulation and experimentaltools with the goal of gaining insight into their stabilizing impact on fluid interfaces. In other words, we are interested in investigating the dynamics of particle adsorption to a liquid-liquid interface and the particle-particle interactions at the interface in order to comprehend their influence on emulsion stability.

Figure 1. Molecular Dynamics simulation of a particle entering an interface.

City College of New York

Nanomaterials at City College of New York

Department of Chemical Engineering

City University of New York

CHUST

Sweden

Colombia

REU

Conatct Ilona Kretzschmar at:

kretzschmar@ccny.cuny.edu

212-650-6769