Janus particles are biphasic colloids that have two sides with distinct chemistry and wettability. Because of their amphiphilic nature, Janus particles present a unique opportunity for stabilizing multiphasic mixture such as emulsions. Inspired by a special class of molecular amphiphiles that are responsive to environmental stimuli, we synthesize stimuli-responsive Janus particles that drastically change their shape and in turn their surfactant properties. We show that these Janus particles can stabilize different types of emulsions depending on the solution pH and composition of the multiphasic mixtures. We demonstrate that these emulsions can be inverted to the opposite type by inducing transitional phase inversion via pH change. We also demonstrate that multiple emulsions can be stabilized with these Janus particles in one-step emulsification. These multiple emulsions exhibit triggered release behavior in response to changes in the solution pH. Our study not only presents a new class of colloidal materials that will further widen the functionality and properties of Janus particles as dynamically tunable solid surfactants but also shows the versatility of Janus particles in stabilizing multiphasic mixtures.

Janus particles as dynamically tunable solid surfactants

249th National Meeting (2015)

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