CAREER: Multi-Functional Particle Assemblies in Polymer Nanocomposites

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TECHNICAL SUMMARY:The PI will design multi-functional polymer composites displaying self-assembled nanostructures with tunable mechanical and electrical properties in this CAREER project. The project aims to construct equilibrium magnetic nanostructures in which their multi-functional properties can be varied and optimized with the intermolecular forces. Polymer decorated iron oxide nanoparticles are a comprehensive model system offering both anisotropic and isotropic interactions that can be tuned with particle size, particle functionality (e.g. length and density of grafted chains, ions or bioligands) and external magnetic fields. This research plan will explain the role of various interactions and elucidate the formation of thermodynamically equilibrium self-assembled structures through non-linear rheology, scattering and microscopy. The PI proposes to investigate the fundamentals of the self-assembly mechanism for three-dimensional structures and their novel reversible self-assembly behavior. The role of conformational entropy of polymer chains on the assembly mechanism will be also examined. In addition, the phase diagram for a mixture of particles with different sizes will be studied to achieve complex novel structures other than obtained from monomodal particle sizes. Cluster organization kinetics and transition from disordered to ordered structures will be measured in-situ to underpin the stability of equilibrium states and reversibility of complex architectures.NON-TECHNICAL SUMMARY:The proposed research will offer a promising and simple synthesis and processing method to make multi-functional nanomaterials which can be used for applications requiring enhanced mechanical and electrical properties. This CAREER project will open new routes to the self-assembly of magnetic nanoparticles which can be applied to self-healing membranes and composites with tunable properties. The results will have an impact on design of new polymeric composites as they behave akin to smart materials, such as stimuli-responsive copolymers sensitive to pH and temperature or materials in which the conductivity and transduction properties change with the arrangement of particles. Moreover, the reversible self-assembly concept will have potential applications in biocompatible materials, mechanical sensors, highly reinforced compounds and new energetic materials. The fundamental nanoscale interactions and their impact on the mesoscale properties (e.g. combined mechanical and conductive properties in one material) of flexible polymer nanocomposites will be explored. Within the course of this project, the PI plans to educate and train high school science teachers by offering research experiences in her laboratory to develop a collaborative science project for high school science curricula. To foster the interest of underrepresented students in science, research and engineering, she will work with the Society of Women Engineers and disseminate her research findings in their local and regional meetings and outreach activities. The PI will integrate her research activities into teaching of polymer science and will also actively engage undergraduate students in research.