(691d) Towards Stimulus-Responsive Control of Foam and Emulsion Stability Using Nanoparticles

The physics and engineering of switchable stability in foams and emulsion systems depends of active control of the fluid/fluid interface. We utilize nanoparticles with designed surface chemistry to control the contact angle of the nanoparticle at the fluid/fluid interface, the free energy of attachment, ultimately the interfacial elasticity. Interrogation of the aggregation kinetics and rheology of the fluid/fluid interface enables elucidation into fundamental mechanisms of foam and emulsion stabilization.

Here, we discuss a new class of thermosensitive polymeric materials based on random copolymers  which display a lower critical solution temperature (LCST) in water that is dependant on co-polymer ratio and ionic strength. Gold nanoparticles grafted with thermosensitive polymer brushes of these copolymers have switchable aggregation kinetics (k11) and interfacial elasticity (E*).  We show the dependence of k11 and the complex interfacial modulus (E*) on environmental conditions such as salt concentration and temperature; it is demonstrated that switchable stabilization is controlled by bulk aggregation rate, rather than interfacial rheology.