Solid-State NMR of Polymer and Liquid Crystalline Nanocomposites

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Liquid crystalline materials form the basis of many of our current display technologies such as computer screens, TVs, and cell phones. The properties of liquid crystals (LCs) can be controlled and enhanced by dispersing a second material to form a LC composite. While polymer-LC composites have been studied for several decades and have been incorporated into devices, nanoparticles (NPs) dispersed in LCs form a new class of smart materials, combining the optical and electronic properties of both components along with the self-healing properties of fluid LCs. Metal oxide NPs have recently been reported to favorably modify the LC properties such as lowering the voltage required to change the orientation of the LC molecules as well as the response times, parameters that will enhance the performance of LC based devices. The tendency of NPs to phase separate is the major obstacle to producing stable NP-LC dispersions. This proposal builds on our recent success in synthesizing gold NPs that are highly miscible in LC solvents and previous work on functionalizing metal oxide NPs with phosphonic acids. These materials will be characterized by nuclear magnetic resonance (NMR) spectroscopy and other methods to understand the LC-NP molecular interactions and the effect of the NPs on the LC structure. The goal will be to control the spatial distribution of the NPs to form homogeneous dispersions or to template regular structures.Polymer nanocomposites will be made with metallic and metal oxide NPs to add functionality to polymer films (optical, magnetic, electronic). Polymers which change chain conformation in response to an external trigger (heat, pH, solvent, light) can be used to vary the spacing between NPs and thus the film properties. Likewise, NPs can be functionalized with stimuli-responsive polymers for applications in various technologies (pharmaceutical, cosmetic, coatings etc.). This proposal focus on pH responsive interpolymer complexes consisting of a H-bond donor (polyacids) and acceptor (polypyridines,polyethers) polymers. The structure and dynamics of the polymer coated NPs and matrix will be characterized separately first and then as a nanocomposite, primarily by solids NMR methods, to understand how to chemically tune the macroscopic properties.