Tail-Free Discotic Liquid Crystals

无尾盘状液晶

• 批准号: 1809536
• 负责人: Brett Ellman
• 金额: $ 49.93万
• 依托单位: Kent State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1809536&HistoricalAwards=false
• 关键词: Tail; Free; Discotic; Liquid; Crystals

Non-technical abstract:Liquid crystals are compounds that display "phases" (states of matter) that are more ordered than liquids, but less ordered than crystalline arrangements. LCs are the basis of a huge display industry as well as potential game changers as semiconductors, enabling cheap flexible electronics, organic photovoltaics, and sensors. This project, funded by the Solid State and Materials Chemistry Program in the Division of Materials Research at NSF, breaks a paradigm in liquid crystal (LC) molecular design and drives a transformation in the understanding and use of these important materials. Liquid crystal molecules, and especially discotic (disc-like) LCs, are nearly always built of a rigid central "core" surrounded by long, flexible "tails", which constantly change shape. These highly dynamic tails represent a challenge to computer modeling of LCs and also often compromise conduction in LC semiconductors. How can society better reap the benefits of materials like LC semiconductors while avoiding the limitations imposed by tails? A new light-driven synthesis offers a way out of this conundrum, revealing multiple families of tail-free discotic LCs based on simple building blocks with a few added fluorine atoms. Besides offering LCs of technological interest, these materials promise to shine light on a difficult question: Why do some molecules form LCs while other closely related ones do not? To answer this question and gain insights into the design and synthesis of new semiconductors, the researchers tightly couple experiment and theory. Using computational modeling of the molecules to understand the details of their interaction with each other, new chemical syntheses and measurements of structural and electronic properties the researchers identify new tail-free LCs and increase the understanding of what drives liquid crystallinity in these fascinating systems. Additionally, this project supports a public outreach project, "What?s in the Box?", in which everyday electronics will be deconstructed in a guided, fun atmosphere. Through this activity the public gets an opportunity to better understand everyday electronic technology, and children might become more interested in STEM education.Technical abstract:The importance of liquid crystals (LCs) in the display industry is well known, and discotic LCs are promising organic semiconductors. Liquid crystals, and especially discotic LCs, are nearly always comprised of a rigid core surrounded by flexible, highly dynamic, often saturated tails. Families of discotic LCs are usually found empirically, with limited theoretical guidance, partly due to the complexity of modeling the tails. Recent work on fluorinated triphenylene and other fused-ring aromatics demonstrates that there are multiple families of tail-free discotic LCs (TFDLCs). These new materials promise to illuminate a difficult question: Why do some molecules form LCs while other closely related ones do not? TFDLCs are structurally rigid, simple model systems much closer to idealized models of LCs than conventional discotic LCs with tails. In this project, funded by the Solid State and Materials Chemistry Program in the Division of Materials Research at NSF, TFDLCs' small size and rigidity are leveraged to perform quantum ab-initio calculations of intermolecular potentials and enable realistic simulations to discover what forces drive liquid crystallinity. These simulations are built on literature methods, enabling efficient Monte Carlo and molecular dynamics for real molecules including effects of anisotropic potentials and steric interactions. Experimentally, all of TFLDCs are comprehensively characterized, including time-of-flight charge transport and x-ray diffraction in the crystal and discotic phases. The researchers correlate experimental results with the simulations. Design principles, resulting from this work are expected to lead to new classes of organic semiconductors to probe the role that disorder plays in transport, the use of fluorination to enhance electron mobility, and the effects of dimensionality due to strong intercolumn interactions in the absence of tails. Larger TFDLCs are studied to explore potential high mobility discotic semiconductors to enhance device design and performance.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.

非技术摘要：液晶是一种化合物，它显示出比液体更有序、但比晶体排列更不有序的“相”(物质状态)。液晶显示器是一个巨大的显示行业的基础，也是半导体行业潜在的游戏规则改变者，使廉价的柔性电子产品、有机光伏和传感器成为可能。该项目由NSF材料研究部的固态和材料化学计划资助，打破了液晶(LC)分子设计的范式，并推动了对这些重要材料的理解和使用的转变。液晶分子，尤其是盘状液晶，几乎总是由一个坚硬的中央“核心”组成，周围环绕着不断变化形状的长而灵活的“尾巴”。这些高度动态的尾巴对LC的计算机模拟提出了挑战，也经常影响LC半导体的导电性。社会如何才能更好地获得像LC半导体这样的材料的好处，同时避免尾巴带来的限制？一种新的光驱动合成提供了一种解决这一难题的方法，揭示了多个家族的无尾盘状LC，这些LC基于简单的构建块和几个添加的氟原子。除了提供具有技术价值的液晶，这些材料还有望解决一个难题：为什么一些分子形成液晶，而其他密切相关的分子不形成液晶？为了回答这个问题，并深入了解新半导体的设计和合成，研究人员将实验和理论紧密结合在一起。通过对分子的计算建模来了解它们相互作用的细节、新的化学合成以及结构和电子性质的测量，研究人员确定了新的无尾液晶，并增加了对这些迷人系统中驱动液晶性的因素的理解。此外，该项目还支持一个公共推广项目--“盒子里的S？”，在这个项目中，日常电子产品将在一种有指导的、有趣的氛围中被解构。通过这次活动，公众有机会更好地了解日常电子技术，孩子们可能会对STEM教育更感兴趣。技术摘要：液晶在显示产业中的重要性是众所周知的，盘状液晶是很有前途的有机半导体。液晶，尤其是盘状液晶，几乎总是由一个坚硬的核心组成，周围环绕着灵活的、高度动态的、通常是饱和的尾巴。盘状LC家族通常是经验性发现的，理论指导有限，部分原因是尾巴建模的复杂性。最近对氟化三苯和其他稠环芳烃的研究表明，存在多个无尾盘状液晶化合物(TFDLC)家族。这些新材料有望阐明一个棘手的问题：为什么一些分子会形成液晶，而其他密切相关的分子则不会？TFDLC是结构刚性的、简单的模型系统，比传统的带尾部的盘状LCS更接近LCS的理想化模型。在这个项目中，由NSF材料研究部的固态和材料化学计划资助，TFDLC的小尺寸和刚性被利用来执行分子间势的量子从头计算，并使现实的模拟能够发现是什么驱动力驱动液晶。这些模拟建立在文献方法的基础上，使得能够对真实分子进行高效的蒙特卡罗和分子动力学，包括各向异性势和空间相互作用的影响。在实验上，对所有的TFDC进行了全面的表征，包括飞行时间电荷输运和晶体和盘状相的X射线衍射。研究人员将实验结果与模拟结果联系起来。由这项工作产生的设计原则有望导致新的有机半导体类别，以探索无序在传输中所起的作用，使用氟化来增强电子迁移率，以及在没有尾巴的情况下由于强烈的柱间相互作用而产生的维度效应。研究较大的TFDLC是为了探索潜在的高迁移率盘状半导体，以改进器件设计和性能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Structure and dynamics of tail-free discotic liquid crystals: Simulations of fluorinated triphenylene

无尾盘状液晶的结构和动力学：氟化苯并菲的模拟

• DOI: 10.1063/5.0106722
• 发表时间: 2022
• 期刊: The Journal of Chemical Physics
• 作者: Powers, M.;Twieg, R. J.;Portman, J.;Ellman, B.
• 通讯作者: Ellman, B.

Fluorinated triphenylenes and a path to short tailed discotic liquid crystals: synthesis, structure and transport properties

氟化苯并菲和短尾盘状液晶的途径：合成、结构和传输特性

• DOI: 10.1039/d1ma00606a
• 发表时间: 2022
• 期刊: Materials Advances
• 影响因子: 5
• 作者: Li, Zhe;Powers, Mitchell;Ivey, Kayla;Adas, Sonya;Ellman, Brett;Bunge, Scott D.;Twieg, Robert J.
• 通讯作者: Twieg, Robert J.