Connecting Short Range Order to Macroscopic Properties in Complex Structured Fluids

非技术摘要细长的小有机分子是今天每年1000亿美元的液晶显示器产业背后的原型材料。当这些分子的形状变得不那么对称时--例如，通过在它们的中心核心引入一个扭结或一个本来是线性结构的分支--它们通常自发地形成纳米尺寸的区域，这些区域比整体的宏观材料更有序，后者仍然表现出本质上类似流体的行为。这种有趣的长度范围的二分法可以被用来生产新型的、易于加工的结构化流体，具有比光电显示器更广泛的新技术的潜力-从独特的软执行器到个人规模的绿色发电。这个项目将加强现有的，并开发和展示新的实验和分析工具和程序，以将低对称性分子系统中的短程有序与具有潜在重大技术影响的更大规模的性质联系起来。它还将致力于合成和表征一类全新的还原对称络合流体，该流体将DNA双链体的精细长度可调与近年来重振液晶领域研究的弯曲型分子结构相结合。本科生和研究生将通过难得的跨学科接触(物理、化学物理和化学)、定期参与国际研究合作的机会以及前沿小规模和大型(国家)实验室经验的平衡来指导学生。在凝聚态物理(CMP)和固态与材料化学(SSMC)计划的支持下，该项目将致力于由复杂形状的分子组成的定向有序流体的材料合成和实验研究，范围从降低对称性的液晶单体和二聚体到溶致溶液，其中可调长度的DNA双链与弯曲形状的芳香族核心结构相结合，以一种新的方法制备降低对称性的向列相流体。该项目将测试这一概念的普遍性，即降低粒子的对称性显著提高它们之间纳米尺度有序性的性质和程度(影响例如双轴、极性或手性纳米结构)，而整个系统在宏观尺度上保持更高的(类流体)对称性。对于潜在的技术应用，将评估这些材料对外场的响应(特别是光电和机电响应)。这项研究将采用各种技术，旨在：i)利用同步辐射X射线设备(包括NSLS-II)和通过低温电子显微镜方法的直接成像来详细描述纳米结构，以及ii)利用灵敏的光学探头和外部电场和磁场将短程结构与宏观性质联系起来。本科生和研究生将通过跨学科接触(物理、化学物理和化学)、平衡尖端的小型和大型(国家)实验室经验以及定期参与国际研究合作的机会来获得指导。

Non-Technical AbstractSmall, elongated organic molecules are the archetypal materials behind today's $100 billion/yr liquid crystal display industry. When the shape of these molecules is made less symmetrical - e.g., by introducing a kink in their central core or a branching of an otherwise linear structure - they often spontaneously form nanometer size domains that are more ordered than the overall, macroscopic material, which still exhibits an essentially fluid-like behavior. This interesting dichotomy across length scales can be exploited to produce novel, easily processible structured fluids with potential for new technologies much broader than electro-optical displays - technologies ranging from unique soft actuators to personal-scale green power generation. This project will enhance existing, and develop and demonstrate new, experimental and analytical tools and procedures to connect short-range order in low symmetry molecular systems to larger scale properties of potentially significant technological impact. It will also aim to synthesize and characterize a completely new class of reduced-symmetry complex fluids based on combining the exquisite length tunability of DNA duplexes with the bent-shaped molecular structures that have revitalized research in the liquid crystal field in recent years. Undergraduate and graduate students will be mentored through a rare 'trifecta' of cross-disciplinary exposure (physics, chemical physics, and chemistry), regular opportunities for participation in international research collaboration, and a balance of cutting-edge small and large (national) scale laboratory experience. Technical AbstractThis project, supported by the Condensed Matter Physics (CMP) and Solid State and Materials Chemistry (SSMC) Programs will pursue materials' synthesis and experimental studies of orientationally-ordered fluids composed of complex-shaped molecular constituents, ranging from reduced-symmetry liquid crystal monomers and dimers to lyotropic solutions in which tunable-length DNA duplexes are combined with a bent-shaped aromatic core structure in a novel approach to produce a reduced-symmetry nematic fluid. The project will test the generality of the concept that reducing the symmetry of particles significantly enhances the nature and degree of nanoscale ordering among them (effecting, e.g., a biaxial, polar, or chiral nanostructure), while the overall system maintains higher (fluid-like) symmetry at the macroscopic scale. The response of these materials to external fields (electro-optical and electro-mechanical responses in particular) will be assessed for potential technological applications. The investigation will employ a variety of techniques aimed at: i) detailing the nanostructure, using synchrotron X-ray facilities (including NSLS-II) and direct imaging via cryo-TEM methods, and ii) connecting short-range structure to macroscopic properties, utilizing sensitive optical probes and external electric and magnetic fields. Undergraduate and graduate students will be mentored through a combination of cross-disciplinary exposure (physics, chemical physics, and chemistry), a balance of cutting-edge small and large (national) scale laboratory experience, and regular opportunities for participation in international research collaboration.