Polymerizations at Interfaces and in Interphases

PART 1: NON-TECHNICAL SUMMARY

This research proposal will develop the knowledge required to create capsules with liquid core and polymers shells, in which the liquid core is pure, and the properties of the shell can be fine-tuned for a desired application. Capsules are used in a broad range of technologies including those for medicine, food science, energy discovery, textiles and the like.

The fundamental issue that the proposed research will address is how to localize precursors to the polymer shell (monomers and initiators) such that the shell is grown around the liquid droplet, essentially shrink wrapping it. To this end, emulsions will be used as a platform for capsule formation, with droplets of one liquid in a continuous phase of the other (the droplet will become the core liquid).

The ability to produce such capsules is important for creating new materials that meet societal needs; for example, capsules with a protective polymer shell and core of a salt hydrate solid-liquid phase change material can be used to passively manage heat, so that air conditioning does not have to be used as often. An important component to consider is that for these capsules to be used multiple times, the shell must be strong enough to prevent leakage but also impermeable so that the composition does not change.

Notably, this research can be applied to different core liquids and polymer shells relevant to other applications, such as for carbon capture, pesticide delivery, or additive manufacturing, to name a few. Through this research, graduate and undergraduate students will be trained in how to design and implement research; how to collect, organize, and report data; and how to collaborate across disciplines.

PART 2: TECHNICAL SUMMARY

This proposal addresses the critical need to understand how confinement of initiators and monomers in emulsions impacts the production of capsules and their properties. Limitations to an interfacial polymerization approach are that the liquid core is contaminated and that only a few polymer chemistries can be used, thus restricting composition and performance-related properties such as permeability.

To overcome this, the proposed research will (i) use modified particles as both surfactant and initiator for radical polymerization of monomers located in the emulsion continuous phase; and (ii) leverage double emulsions in which the interphase contains monomers to polymerize around the inner droplet. For this purpose, the interface is defined as the zone where two domains touch and the interphase as a self-contained region between two domains (thus flanked by two interfaces).These two distinct approaches are supported by initial results from the PI’s lab and will provide unprecedented control of capsule composition (both shell and core) such that structure-property-application relationships can be defined.

The PI has access to all resources and infrastructure required to complete this work, and the research component is complemented by the training and professional development of undergraduate and graduate student researchers, as well as development of a hands-on module to be incorporated into the undergraduate laboratory curriculum.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.