RUI: Investigations of the cybotactic nematic phase in bent-core liquid crystals

非技术概述液晶显示器(LCD)可在手机、电视和计算机屏幕等设备中找到。这些装置是使用呈现液晶相的化合物构建的。在电场的作用下，这个相中的分子可以重新定向，从而改变它们的光学性质。在固态和材料化学计划的资助下，化合物的制备和研究显示了一种独特的液晶相，在这种液晶相中，分子可能会经历更快的重新定向。这可能会导致液晶显示速度更快，从而提高设备的光学质量，并降低设备的能耗。普吉特湾大学的本科生直接参与了NSF资助的研究的方方面面。参与研究为学生提供了一个极好的机会来提高他们的批判性思维能力。这些经验为学生提供了强大的技术培训，这些培训将为他们在科学领域进入劳动力大军或攻读化学或相关领域的研究生课程提供很好的服务。在普吉特湾大学，57%的学生是女性，25%的学生认为自己是有色人种学生。NSF的这种支持帮助PI为STEM领域中代表性较低的群体的学生提供研究机会。自从双轴向列相(Nb)在高熔点弯曲芯化合物中被报道以来，人们对它产生了浓厚的兴趣；使用这种相制造的液晶显示器有可能经历更快的电光开关。然而，对于这一相是否真的是双轴向列相存在争议；最近的证据表明，该相由层状(近晶)结构域(环状簇合物)组成，仅在较大的长度尺度上显示向列相。这笔来自固态和材料化学计划的赠款支持合成各种恶二唑类化合物，并分析它们的液晶行为。这些研究对各种结构因素如何影响弯芯化合物中向列相的稳定性和性质提供了重要的见解。具有1)各种侧基、2)高极性取代基和3)酰胺键的一系列化合物的制备允许Pi和他的学生建立结构-性质关系，目的是了解哪些结构特征能够产生低起始温度的向列相。目标化合物的合成和相行为的初步分析(使用偏光显微镜和差示扫描量热法)是在普吉特海湾大学进行的。PI的合作者通过X射线衍射来研究化合物，它提供了关于向列相中分子组织的详细信息。他们还对具有高极性基团的衍生物进行电光实验，因为这些衍生物是铁电开关的候选者。具有低温向列相的衍生物将有利于物理学家的基础研究和可能的应用研究。来自NSF的这种支持帮助PI为来自STEM领域通常代表性不足的本科生提供研究机会。

Non-technical summaryLiquid crystal displays (LCD) are found in devices such as cell phones and television and computer screens. These devices are constructed using compounds that exhibit a liquid crystal phase. Molecules in this phase can be reoriented in the presence of an electric field, which changes their optical properties. With support from this grant by the Solid State and Materials Chemistry Program compounds are prepared and studied that exhibit a unique type of liquid crystal phase in which the molecules can potentially undergo faster reorientation. This could lead to faster liquid crystal displays, which would improve the optical quality of the devices, and lower the amount of energy consumed by the devices. Undergraduate students at the University of Puget Sound are directly involved in all aspects of the NSF-funded research. Participation in research offers an excellent opportunity for students to enhance their critical thinking skills. These experiences provide students with strong technical training that will serve them well as they enter the workforce in a scientific field or pursue graduate studies in Chemistry or a related area. At the University of Puget Sound, 57% of the students are women, and 25% of the students identify as students of color. This support from NSF helps the PI to provide research opportunities to students from groups who are typically underrepresented in STEM fields. Technical summaryThere has been intense interest in the biaxial nematic phase (Nb) since it was reported in high melting bent-core compounds; liquid crystal displays fabricated using this phase have the potential to undergo faster electro-optic switching. However, there is controversy as to whether this phase is truly a biaxial nematic phase; recent evidence suggests the phase consists of layered (smectic) domains (cybotactic clusters) that show nematic order only across larger length scales. This grant from the Solid State and Materials Chemistry Program supports the synthesis of a variety of oxadiazole-based compounds, and analysis of their liquid crystalline behavior. These studies provide critical insight into how various structural factors affect the stability and nature of the nematic phase in bent-core compounds. The preparation of series of compounds with 1) various lateral groups, 2) highly polar substituents, and 3) amide linkages allow the PI and his students to generate structure-property relationships, with the intention to learn what structural features yield a nematic phase with a low onset temperature. Synthesis of the target compounds and initial analysis of phase behavior (using polarizing microscopy and differential scanning calorimetry) are carried out at the University of Puget Sound. Collaborators of the PI study the compounds by X-ray diffraction, which provides detailed information about the molecular organization within the nematic phase. They also carry out electro-optic experiments on the derivatives with highly polar groups as these are candidates for ferroelectric switching. Having derivatives with low temperature nematic phases would facilitate both fundamental study by physicists and investigation of possible applications. This support from NSF helps the PI to provide research opportunities to undergraduate students from groups who are typically underrepresented in STEM fields.