(484a) Mxene-Stabilized Emulsions, Foams, and Composites

Structured polymer composites have gained increasing attention due to their superior property enhancement (e.g., thermal, electrical conductivity) compared to their homogeneous counterparts, by designing the internal filler structures in the polymer matrix. The fabrication and design of structured polymer composites are still challenging and the common methods (e.g., solution casting, melt blending) have limited control over the internal filler structures. Pickering emulsion templating, in contrast, is an attractive approach to creating structured composites due to their well-defined interfaces, manageable structure and dimensions, and ease of scale-up. Among the common Pickering particles, MXenes are of great interest as they have the ability to not only stabilize emulsions but also introduce functional properties into structures, such as high electrical conductivity, high EMI shielding, and rapid radio frequency (RF) heating.

In this work, we focus on the development of MXene Ti3C2 Pickering emulsions in diverse fluid-fluid systems (e.g., oil-water and oil-oil) and their use as templates for fabrication of functional structured MXene-polymer composites. Pickering emulsions drive nanosheets to the fluid-fluid interfaces and subsequent localized polymerization creates diverse structured polymer composites (e.g., capsules, armored particles, and porous monoliths). The ability to access both aqueous and non-aqueous emulsion systems largely expands the possible polymer compositions. The Ti3C2 nanosheets are organized in these composites instead of being randomly distributed throughout. For instance, polymerization of the emulsion interfaces gives polymer shells with nanosheets embedded, polymerization of the dispersed phase gives polymer particles armored with nanosheets, and polymerization of the continuous phase gives porous monoliths with polymer struct and nanosheets coated pores. The incorporation of MXenes imparts functional properties into their structures for additional applications. For example, the MXene armored particles can be used as feedstock to fabricate segregated films for efficient EMI shielding applications at low MXene loadings due to the templated network within the polymers. MXene-polymer capsules and porous monoliths show excellent RF heating performance due to the highly locally conductive regions in these structures. The research work in this dissertation provides a simple platform to produce diverse structured MXene-polymer composites with well-controlled filler distribution, versatile compositions, and functional properties for potential advanced applications.