Solid-State NMR of Polymer and Liquid Crystalline Nanocomposites

液晶材料构成了我们当前许多显示技术的基础，如计算机屏幕、电视和手机。通过分散第二种材料形成液晶复合材料，可以控制和提高液晶的性能。聚合物-液晶复合材料已经被研究了几十年，并被应用到器件中，分散在液晶中的纳米颗粒形成了一类新的智能材料，它结合了这两个组分的光学和电学性质以及流体液晶的自愈特性。最近有报道称，金属氧化物纳米颗粒可以很好地改变液晶的性能，例如降低改变液晶分子取向所需的电压以及响应时间，这些参数将提高基于液晶的器件的性能。纳米粒子的相分离倾向是制备稳定的NP-LC分散体的主要障碍。这项建议建立在我们最近成功地合成了在LC溶剂中高度相容的金纳米颗粒，以及之前用膦酸官能化金属氧化物纳米颗粒的工作基础上。这些材料将通过核磁共振波谱等方法进行表征，以了解LC-NP之间的分子相互作用以及NPs对LC结构的影响。目标将是控制NPs的空间分布，以形成均匀的分散或模板规则结构。聚合物纳米复合材料将由金属和金属氧化物纳米颗粒制成，以增加聚合物薄膜的功能(光学、磁性、电子)。响应外部触发(热、pH、溶剂、光)而改变链构象的聚合物可用于改变纳米粒子之间的间距，从而改变薄膜的性能。同样，NPs可以用刺激响应型聚合物功能化，用于各种技术(制药、化妆品、涂料等)。这项建议侧重于由氢键供体(多酸)和受体(聚吡啶、聚醚)聚合物组成的pH响应性聚合物间络合物。聚合物包覆纳米颗粒和基质的结构和动力学将首先单独表征，然后作为纳米复合材料，主要通过固体核磁共振方法来了解如何通过化学方法调节宏观性能。

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.