Synthesis and Study of Covalently Bonded Self-Assembled Polymer Gel Nanoparticles

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The search for novel macromolecular structures is at the core of innovation in macromolecular science and engineering and is the long-term goal of our research. Polymer gels are a unique class of macromolecular networks that contain a large fraction of solvent such as water within their structure. Most current research on structures of polymer gels has focused on either bulk gels or microgels. The objective of this work is to create nanostructured bulk polymer gels and correlate such structures to their physical properties. The central idea is to first synthesize monodispersed polymer gel nanoparticles, then self-assemble them into 3D networks, and eventually covalently bond them. The covalent bonding contributes to the structural stability, while self-assembly provides the with crystal structures that diffract light, resulting in colors. The self-assembled structure of the PI's systems are further enriched by their two-level structural hierarchy: the primary network consists of crosslinked polymer chains inside each nanoparticle, while the secondary network is a crosslinked system of the nanoparticles. As a feasibility study, the PI's synthesized such a material that contains 97 wt% water, displays a striking iridescence but is soft and flexible. The PI's approach consists of four components. First, several representative polymer gel nanoparticles such as N-isopropylacrylamide and hydroxypropyl cellulose will be synthesized and characterized by light scattering methods as model building blocks. Second, the nanoparticles will be self-assembled into various structures. Third, various reaction schemes will be used to covalently bond these assemblies. Fourth, the physical properties of the networks, including covalent bonding, mesh size, two-level structural hierarchy, periodic structures, and elasticity, will be investigated using Fourier transform infrared (FTIR) spectroscopy, chromatography, UV-visible spectroscopy, and light scattering methods.%%%This work, if successful, will provide a framework to generate stable periodic 3D structures with varying feature sizes in macromolecular materials. It allows us to obtain useful functionality not only from the constituent building blocks but also from the long-range ordering that characterizes these structures. Creating such nanostructured material may also be of importance in technological applications including controlled drug delivery, biomaterials, sensors, devices, chromatography, bio-adhesives, and displays. Both undergraduate and graduate students will participate in this research. They will gain valuable skills in interdisciplinary research and development in macromolecular science and nanotechnology.