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

RUI：弯核液晶中胞规向列相的研究

• 批准号: 1709148
• 负责人: Eric Scharrer
• 金额: $ 12.42万
• 依托单位: University of Puget Sound
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1709148&HistoricalAwards=false
• 关键词: RUI; Investigations; cybotactic; nematic; phase

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.

非技术概述液晶显示器（LCD）存在于诸如蜂窝电话和电视以及计算机屏幕的设备中。这些装置是使用呈现液晶相的化合物构造的。在这个阶段的分子可以在电场的存在下重新取向，这改变了它们的光学性质。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出一种独特的液晶相，其中分子可能会经历更快的重新取向。这可能导致更快的液晶显示器，这将提高设备的光学质量，并降低设备消耗的能量。普吉湾大学的本科生直接参与NSF资助研究的各个方面。参与研究为学生提供了一个很好的机会，以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，这将有助于他们进入科学领域的劳动力或在化学或相关领域攻读研究生课程。在普吉湾大学，57%的学生是女性，25%的学生认为自己是有色人种。 NSF的这种支持有助于PI为来自STEM领域代表性不足的群体的学生提供研究机会。 技术概述自从在高熔点双晶核化合物中报道了双轴双晶相（Nb）以来，人们对它产生了浓厚的兴趣;使用该相制造的液晶显示器具有经历更快电光切换的潜力。然而，有争议的是，这个阶段是否是一个真正的双轴晶相;最近的证据表明，该阶段包括分层（近晶）域（cybotactic集群），显示晶序只在较大的长度尺度。固态与材料化学项目的这项资助支持多种恶二唑基化合物的合成及其液晶行为的分析。这些研究为了解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见解。制备一系列具有1）各种侧基，2）高极性取代基和3）酰胺键的化合物，使PI和他的学生能够产生结构-性质关系，目的是了解什么结构特征产生具有低起始温度的双相。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）在普吉特海湾大学进行。PI的合作者通过X射线衍射研究这些化合物，这提供了关于在α相内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物。 具有低温相变的衍生物将有利于物理学家的基础研究和可能应用的研究。NSF的这种支持有助于PI为来自STEM领域代表性不足的群体的本科生提供研究机会。