Glasses with Tunable Liquid Crystalline Order

液晶和玻璃是现代技术中的重要材料。lc能够通过外部控制快速调整分子组织，使其用于显示器和传感器。玻璃将液体的无序性和空间均匀性与固体的机械强度结合在一起，在光学、电子和无定形药物中都有应用。该项目由美国国家科学基金会固态和材料化学项目以及凝聚态物理项目支持，创造了结合LC和玻璃优点的新材料-具有连续可变LC顺序的玻璃材料。这些材料显示的分子包装在LC的有序和玻璃的无序之间可调，同时保持了普通玻璃的优点。它们有望在有机电子学和光电子学中找到应用。例如，在广泛应用于手机显示屏的有机发光二极管（oled）的有源层中控制发射体分子组织的能力，可以显著提高此类显示屏的效率。考虑到这些设备的数量，这是全球规模的好处。总的来说，这些新材料是理想的应用，其性能取决于分子取向和包装，但可能会受到晶体材料中常见缺陷的影响。此外，制药科学家将能够利用这些材料来优化溶解度和物理稳定性。此外，该项目通过整合材料研究和教育，促进了研究生，本科生和高中生的培训。外展活动包括每年夏天通过威斯康星大学麦迪逊分校PEOPLE项目向代表性不足的高中生提供材料化学课程，每年5月通过威斯康星大学扩展服务向工业科学家提供名为“非晶药物”的短期课程，以及由亚利桑那州立大学科学家领导并在整个凤凰城都会区提供的外展项目“科学是乐趣”中关于晶体和玻璃材料的新演示。技术概述：液晶以其快速可逆的相变而闻名。这些转变发生的速度导致了快速冷却不会抑制LC有序的概念，但最近的工作发现，LC转变可以在实际冷却速率下动态阻止，从而允许形成具有可变LC顺序的玻璃或访问不同的LC相。该项目由美国国家科学基金会固态和材料化学项目以及凝聚态物理项目支持，建立了通过玻璃制备条件控制分子组织的原理。该团队测试了一个假设，即被困在玻璃中的LC秩序的数量是由棒状LC分子的端对端旋转的动力学停止决定的。通过实验室和同步加速器源进行的x射线散射，评估了LC顺序作为温度和冷却速率的函数。介电光谱测定了分子在不同轴上旋转的时间尺度和动力学停止的温度。采用时效实验研究了LC序在玻璃态下的稳定性。该项目预计将为选择工艺条件以控制玻璃中的LC顺序提供通用配方，从而产生具有增强有机电子和药物配方性能潜力的材料。目前的LC跃迁理论通常不包括时间作为一个变量，有效地假设瞬时跃迁仅由热力学控制。这个项目的结果将支持转化动力学发挥重要作用的理论的发展。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARY Liquid crystals (LCs) and glasses are important materials in modern technologies. LCs enable rapid adjustment of molecular organization by external control, making them useful for displays and sensors. Glasses merge liquid-like disorder and spatial uniformity with the mechanical strength of a solid, finding applications in optics, in electronics, and as amorphous pharmaceuticals. This project, supported by the Solid State and Materials Chemistry program as well as the Condensed Matter Physics program at NSF, creates new materials that combine the advantages of both LCs and glasses - glassy materials with continuously variable LC order. These materials display molecular packing that is tunable between the order of a LC and the disorder of a glass, while maintaining the advantages of ordinary glasses. They are expected to find applications in organic electronics and optoelectronics. For example, the ability to control the organization of emitter molecules in the active layers of organic light emitting diodes (OLEDs), which are widely used in cell phone displays, can significantly enhance the efficiency of such displays. Given the number of these devices this is a benefit of global scale. In general, these new materials are ideal for applications where performance depends on molecular orientation and packing and but can be compromised by defects commonly present in crystalline materials. Additionally, pharmaceutical scientists will be able to employ these materials to optimize solubility and physical stability. Furthermore, the project advances the training of graduate, undergraduate, and high school students by integrating materials research and education. Outreach activities include the offering of a materials chemistry course each summer to high school seniors from under-represented groups through the UW-Madison PEOPLE program, a short course titled Amorphous Pharmaceuticals to industrial scientists each May through UW Extension Services, and new demonstrations on crystalline and glassy materials for Science Is Fun, an outreach program led by ASU scientists and delivered throughout the Phoenix Metro Area.TECHNICAL SUMMARYLiquid crystals are known for their fast and reversible phase transitions. The speed at which these transitions occur has led to the notion that fast cooling will not suppress LC ordering, but recent work has discovered that LC transitions can be dynamically arrested at practical cooling rates, thus allowing the formation of glasses with variable LC order or the access to different LC phases. This project, supported by the Solid State and Materials Chemistry program as well as the Condensed Matter Physics program at NSF, establishes the principles by which molecular organization can be controlled through conditions of glass preparation. The team tests the hypothesis that the amount of LC order trapped in a glass is determined by the kinetic arrest of the end-over-end rotation of rod-like LC molecules. LC order is evaluated as a function of temperature and cooling rate by X-ray scattering conducted using both laboratory and synchrotron sources. Dielectric spectroscopy determines the timescales of molecular rotations about the different axes and the temperatures of kinetic arrest. Aging experiments are used to study the stability of LC order in the glassy state. This project is expected to provide a general recipe for selecting process conditions to control LC order in a glass, leading to materials that have the potential to enhance the performance of organic electronics and pharmaceutical formulations. Current theories of LC transitions generally do not include time as a variable, effectively assuming instantaneous transitions controlled by thermodynamics alone. Results from this project will support development of theories in which transformation kinetics play an important role.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.