Emulsions have long been a foundational technology for the solution-phase synthesis of functional particles and materials. More recently, methods to create emulsions with complex internal droplet structure and assembly have opened up an entire new design space of complex droplets and soft solids with potential advantages for medicine, additive manufacturing and functional materials. However, limitations on current emulsification methods have prevented these advances from being translated to the nanoscale, where their true advantages lie. Nanoemulsions – metastable suspensions of nanoscale droplets – overcome these limitations through their scalable processing and metastability. However, their engineering is complicated by emergent colloidal and interfacial behavior when droplets are driven to the nanoscale. In this seminar, I will summarize our recent work to show how interfacial molecular self-assembly can be used to control this emergent behavior to create complex nanodroplets, and exploit it for nanomaterials synthesis and assembly. In one example, we demonstrate the production of double nanoemulsions (i.e. nanodroplets in nanodroplets) whose morphology can be tuned by fluid composition through the selection of co-surfactants with frustrated interfacial mechanics. In another example, we develop nanoemulsions with thermoresponsive droplet linkers that self-assemble into hierarchically structured soft solids, whose morphology and mechanical properties can be controlled through thermal processing in a similar as in biphasic hard materials. These complex emulsions provide new opportunities for templating colloidal particles, gels and soft solids with tailored structure and properties.
Matt Helgeson is an Assistant Professor in the Department of Chemical Engineering and a faculty member of the Materials Research Laboratory at UC Santa Barbara. He received his B.S. in Chemical Engineering at Carnegie Mellon University in 2004, and his Ph.D. in Chemical Engineering at the University of Delaware in 2009. He performed postdoctoral research at MIT before joining the faculty at UCSB. Prof. Helgeson’s research focuses on designing and processing complex fluids with well-specified mesostructure, especially those involving colloids (nanoparticles, emulsions, proteins, etc.) in self-assembling & structured liquids. Prof. Helgeson’s research has been recognized with a number of awards, including Early Career Awards from both the National Science Foundation (2013) and Department of Energy (2015), a Hellman Foundation Faculty Fellowship (2016), and both the Victor K. LaMer Award (2011) and Unilever Award (2016) from the American Chemical Society.