Polymer and Liquid Crystal Assembled Nanomaterials

本研究计划的主题是将纳米材料组装成有组织的、刺激响应的结构，并辅以固态核磁共振表征。1. 片状纳米颗粒（NPs）。本课题涉及基于聚合物的“片状纳米颗粒”的制备、表征和组装，定义为具有至少一个明确定义的斑块的颗粒，以允许与其他颗粒或表面定向相互作用。斑片状粒子是光子胶体晶体、多室药物传递剂和催化剂的研究热点。障碍包括缺乏大规模的制备和合适的表征工具。具有混合聚合物外壳的NPs的理论研究预测相分离的电晕会提供柔软的、可变形的“斑块”。最近，我们开发了一种易配体交换方法，用混合聚合物刷制备NPs，并通过NMR对纳米相分离进行了表征。将通过改变NP的大小和形状以及聚合物配体的比例和链长来测试将片状NP控制组装成分层上层结构。2. 聚合物功能化NPs在lc中的应用。第二个主题融合了我的团队的两个专业领域，聚合物功能化np和np -液晶分散体。主要目标将是开发合适的聚合物配体，以取代通常用于形成稳定的NP- lc分散体的定制合成介系配体，将聚合物和NP添加剂的优势结合到lc中。NP掺杂剂可以增强LC的电光性能，相反，LC可以将NP模板成规则的空间结构。lc -聚合物共混物广泛用于显示应用，但lc -聚合物界面仍然知之甚少。lc -聚合物共混物的理论/实验研究，随后是与NPs相连的相同聚合物的研究，将检查链的构象和动力学，以了解分子水平的聚合物- lc相互作用。由于聚合物在LCs中的混相性与链刚度密切相关，因此将研究柔性和刚性棒聚合物。3. 通过表面化学调整NP特性。第三个主题着重于表面化学对无机NPs性质的影响。由于表面原子构成了NP的很大一部分，配体壳的组成可以决定NP的结构。卤化铅钙钛矿是一类很有前途的新型半导体纳米晶体。在这些纳米材料用于太阳能电池或光电器件之前，需要一种有效的表面化学物质来防止潮湿、光或热的降解。另一种新的纳米材料，铁电BaTiO3 （BTO）纳米立方体，将被研究，以了解为什么它仍然是铁电的，尺寸小于理论预测，这对非易失性存储器和其他应用至关重要。核磁共振实验将允许通过配体交换反应以及配体与特定表面结合位点的匹配来检测表面重建。

The main theme of this research program is the assembly of nanomaterials into organized, stimuli-responsive structures, assisted by solid-state NMR characterization. 1. Patchy Nanoparticles (NPs). This topic concerns the preparation, characterization and assembly of polymer-based "patchy nanoparticles", defined as particles with at least one well defined patch to allow directional interactions with other particles or surfaces. Patchy particles are of interest for photonic colloidal crystals, multi-compartmental drug delivery agents and catalysts. Obstacles include a lack of large-scale preparations and suitable characterization tools. Theoretical studies of NPs with mixed polymer shells predict phase separated coronas that provide soft, deformable "patches". We recently developed a facile ligand exchange method to produce NPs with mixed polymer brushes and characterized the nanophase separation by NMR. Controlled assembly of patchy NPs into hierarchical superstructures will be tested by varying the NP size and shape and the ratios and chain lengths of the polymer ligands. 2. Polymer Functionalized NPs in LCs. The second topic merges two areas of expertise of my group, polymer functionalized NPs and NP-liquid crystal dispersions. The main goal will be to develop suitable polymer ligands to replace custom-synthesized mesogenic ligands typically used to form stable NP-LC dispersions, combining the advantages of polymer and NP additives to LCs. NP dopants can enhance LC electro-optical properties and conversely LCs can template NPs into regular spatial structures. LC-polymer blends are widely used for display applications but the LC-polymer interface remains poorly understood. Theoretical/experimental studies of LC-polymer blends, followed by studies of the same polymers tethered to NPs, will examine the chain conformation and dynamics to understand the molecular level polymer-LC interactions. Since the miscibility of polymers in LCs is strongly correlated with the chain stiffness, both flexible and rigid rod polymers will be studied. 3. Tuning NP Properties via Surface Chemistry. A third topic focuses on the effect of the surface chemistry on the properties of inorganic NPs. Since the surface atoms make up a significant fraction of a NP, the ligand shell composition can determine the NP structure. Lead halide perovskites are a promising new class of semiconductor nanocrystals (NCs). Before these NCs can be used for solar cells or opto-electronic devices, an effective surface chemistry is needed to prevent degradation from moisture, light or heat. Another new nanomaterial, ferroelectric BaTiO3 (BTO) nanocubes, will be studied to understand why it remains ferroelectric down to sizes smaller than theoretical predictions, critical for non-volatile memory and other applications. NMR experiments will allow detection of surface reconstruction by ligand exchange reactions as well as matching of ligands to specific surface binding sites.