Polymer and Liquid Crystal Assembled Nanomaterials

该研究计划的主题是将纳米材料组装成有组织的刺激响应结构，并辅以固态NMR表征。1.片状纳米颗粒（NP）。本主题涉及基于聚合物的“片状纳米颗粒”的制备、表征和组装，所述片状纳米颗粒被定义为具有至少一个良好限定的补丁以允许与其他颗粒或表面定向相互作用的颗粒。斑片状粒子在光子胶体晶体、多室药物传递剂和催化剂等方面具有重要的应用价值。障碍包括缺乏大规模的准备和合适的表征工具。具有混合聚合物壳的NP的理论研究预测相分离的电晕，其提供柔软的、可变形的“补丁”。我们最近开发了一种简便的配体交换方法来生产具有混合聚合物刷的纳米颗粒，并通过NMR表征了纳米相分离。将通过改变NP的大小和形状以及聚合物配体的比率和链长来测试片状NP到分级超结构中的受控组装。2. LC中的聚合物官能化NP。第二个主题融合了我的团队的两个专业领域，聚合物功能化纳米粒子和纳米粒子-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晶配体，将聚合物和NP添加剂的优点结合到LC中。NP掺杂剂可以增强LC电光性质，并且相反地LC可以将NP模板化为规则的空间结构。LC-聚合物共混物广泛用于显示器应用，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NP连接的相同聚合物的研究，将检查链构象和动力学，以了解分子水平的聚合物-LC相互作用。由于液晶中聚合物的亲水性与链刚度密切相关，因此将研究柔性和刚性棒状聚合物。3.通过表面化学调节NP性质。第三个主题集中在无机纳米粒子的性能上的表面化学的效果。由于表面原子构成NP的重要部分，配体壳组成可以决定NP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NC可用于太阳能电池或光电器件之前，需要有效的表面化学来防止水分，光或热的降解。另一种新的纳米材料，铁电BaTiO 3（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，非易失性存储器和其他应用的关键。NMR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.