ABSTRACT

Bulk properties of particle stabilized Pickering Emulsions are determined by dispersed drops’ behavior. In Pickering emulsions, particle laden interfaces create steric repulsion and interfacial viscoelasticity, altering drop behavior. By controlling these interfacial properties, emulsions can also be manipulated. However, to do this requires understanding the relationship between interfacial mechanical properties and contact angle, interface composition, and inter-particle interactions. In the Christopher lab, we have created a suite of unique techniques that allow us to characterize such relationships.

Using Bessel Beam microscopy, we have found that even monodisperse particle populations at oil/water interfaces have large contact angle distributions due to normal diffusion and particle variation. Using Stokesian Dynamic simulations, we have found that increasingly random initial particle order and stronger hydrodynamic interactions create denser networks when particles aggregate at an interface. Finally, using simultaneous interfacial rheology and microscopy, we have found that inter-particle attraction sets interfacial moduli magnitude but microstructure deformation determines global properties such as relative elasticity and yield strain. Our results indicate that it is possible to manipulate particle laden interfaces so that in the future we may manipulate bulk emulsions.

BRIEF ACADEMIC/EMPLOYMENT HISTORY:

Gordon Christopher is an Associate Professor in the Department of Mechanical Engineering at Texas Tech University where he has worked since 2011. He received a BS in Mechanical Engineering (2002) and a BA in Film (2003) from Columbia University.  He attended Carnegie Mellon and graduated with a PhD in Mechanical engineering and a MS in Chemical Engineering in 2008.  Afterwards, he spent 2 years in the Polymers Division of the National Institute of Standards and Technology as a NRC Postdoc