CAREER: Understanding the Interfacial Rheology of Carbon Nanotubes at the Fluid-Fluid Interfaces for Creating Ultra-stable Emulsions and Microcapsules

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1253613MaIt has been known for more than a century that particles can stabilize emulsions by adsorbing at the fluid-fluid interface and lowering the interfacial energy. Thermodynamics and earlier experimental studies indicate that controlling the particle size and wetability are two key factors to stabilize emulsions. However, the effect of particle shape has remained largely unexplored and unexploited. The hypothesis of this proposal is that particle shape matters and that rod-like and high-aspect-ratio particles will increase the number of particle-particle contacts, leading to the formation of a stronger layer at the interface and consequently more stable emulsions relative to spheres. To examine this hypothesis, carbon nanotubes (CNTs) with high aspect ratio (1000) will be investigated as a model system. The objective is to establish a fundamental understanding of the physics of an interface decorated with CNTs. The microstructure and the interfacial rheology will be carefully examined and further linked to the mechanical integrity and stability of a CNT-laden interface. The intellectual merit of this proposal involves: (1) exploring the complex physics of CNTs at the fluid-fluid interface, and (2) connecting the rheology with interfacial phenomena. Broader Impact: Exploiting the particle shape could be the missing key to unlocking the full potential of nanoparticle-stabilized emulsions. The proposed research may offer a general and yet relatively simple strategy to improve the stability of emulsions and prolong the shelf life of widely used pharmaceutical, agricultural, and personal care products. Secondly, the findings may revolutionize the use of nanoparticles for enhanced oil recovery, essential to ensuring national energy independence and addressing the world's energy challenge. Thirdly, understanding the interfacial behavior of nanoparticles will help comprehend the fate of both naturally occurring and engineered nanoparticles in the environment and wastewater treatment processes, such as flotation, which could have an impact on the sustainable use of nanoparticles. Finally, the proposed research may also impact the creation of technologically important materials such as: (1) novel microcapsules with controllable permeability for drug encapsulation and delivery, (2) scrims and polymer blends for composite and membrane applications, and (3) metamaterials that can be further used in cloaking devices and light-based circuits that may ultimately outperform electron-based computers in terms of speed, power consumption, and costs.Education and Outreach: The proposed research will be integrated with educational and outreach activities at all levels to maximize its impact. The graduate and undergraduate students involved in this project will receive cross-discipline training across the fields of rheology, interfacial phenomena, and carbon nanotubes. To engage the younger generation and the local community, culinary foams and emulsions will be used as the theme for the outreach plan. With the support of the CAREER award, the PI and his team will continue their outreach efforts through several programs (e.g., UConn's Mentor Connection Program and da Vinci project) and will attempt a new initiative on introducing basic scientific concepts through debunking cooking myths at high schools in inner-city Hartford and Willimantic with high minority populations.