Novel Molar Design Concept for Low Molar Mass Glass-Forming Liquid Crystals

低摩尔质量玻璃形成液晶的新颖摩尔设计概念

• 批准号: 9500737
• 负责人: Shaw Chen
• 金额: $ 17万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-02-01 至 1998-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9500737&HistoricalAwards=false
• 关键词: Novel; Molar; Design; Concept; Low

ABSTRACT Proposal NO. CTS-9500737 University of Rochester Shaw H. Chen Liquid crystals have found potential applications to various optical and optelectronic technologies. With the exception of active components based on the change in molecular orientation in response to an applied field, practical applications of liquid crystals are limited by the intrinsic fluid nature and tendency to crystallize. To provide mesophase stability and environmental durability, liquid crystalline polymers have been explored as an alternative in view of the potential for vitrification with a glass transition temperature above the ambient. However, polymeric materials are inherently difficult to process into uniform films because of a generally high melt viscosity. It is most desirable to combine the attributes of these two classes of materials, i.e., ease of material processing and ability to preserve a high degree of mesomorphic ordering in a glassy environment. To achieve this ultimate goal, a two-year program is proposed for research on low molar mass glass-forming liquid crystals. In principle, all liquids should vitrify given a sufficiently rapid cooling rate. Nevertheless, the question of why some materials are more prone to glass formation than others has remained unanswered to date. Since theoretical or computational approaches do not appear to promise a rational molecular design tool in the foreseeable future, it is proposed that a molecular design concept be pursued from an empirical standpoint. In essence, low molar mass liquid crystals represent a subtle balance between two seemingly opposing factors: one to encourage liquid crystal mesomorphism and the other to discourage crystallization. It is proposed that two diametrically different structural features, mesogenic moiety and excluded-volume core, be chemically bonded to each other via a flexible spacer. The idea is to enable the chemically combined system to form and optically anisotropic, morphologically stable glass, even though both mesogenic moiety and excluded-volume core may crystallize on their own. Our technical approach consists of molecular design, chemical synthesis, and relevant characterizations including morphology, theology, and the kinetics of thermally activated phase transformation. In addition, characterizations with a direct bearing on practical applications will also be performed. Results from the proposed research will furnish new insight into vitrification, liquid crystallinity, morphology and processing of low molar mass compounds. In addition, through judicious molecular design, multifunctional materials capable of optical and optoelectronic applications are expected to come forth. Specific examples may include light polarization, nonlinear optical activity, photochromizm, and electroluminescence, which constitute a broad base for emerging display, imaging, and communications technologies.

摘要提案编号：CTS-9500737罗切斯特大学肖H。陈 液晶在各种光学和光电技术中具有潜在的应用。 除了基于分子取向响应于所施加的场的变化的活性组分之外，液晶的实际应用受到固有流体性质和结晶倾向的限制。 为了提供中间相稳定性和环境耐久性，考虑到玻璃化转变温度高于环境温度的玻璃化的可能性，已经探索了液晶聚合物作为替代物。 然而，聚合物材料由于通常高的熔体粘度而固有地难以加工成均匀的膜。 最理想的是将这两类材料的属性联合收割机结合起来，即，易于材料加工和在玻璃环境中保持高度介晶有序的能力。 为了实现这一最终目标，提出了一个为期两年的计划，研究低摩尔质量玻璃形成液晶。 原则上，所有的液体都应该在足够快的冷却速度下玻璃化。 然而，为什么一些材料比其他材料更容易形成玻璃的问题至今仍未得到解答。 由于理论或计算方法似乎并不承诺在可预见的未来一个合理的分子设计工具，它提出了一个分子设计的概念，从经验的角度来追求。 本质上，低摩尔质量液晶代表了两个看似相反的因素之间的微妙平衡：一个是鼓励液晶介晶性，另一个是阻碍结晶。 提出了介晶部分和排斥体积核这两种完全不同的结构特征通过柔性间隔基彼此化学键合。 该想法是使化学组合的系统能够形成光学各向异性的、形态稳定的玻璃，即使介晶部分和排除体积核都可以自己结晶。 我们的技术方法包括分子设计，化学合成和相关表征，包括形态，流变学和热活化相变动力学。 此外，还将进行与实际应用直接相关的表征。 从拟议的研究结果将提供新的洞察玻璃化，液晶性，形态和低摩尔质量化合物的加工。 此外，通过合理的分子设计，有望出现具有光学和光电应用能力的多功能材料。 具体示例可以包括光偏振、非线性光学活性、光致变色和电致发光，其构成了新兴显示、成像和通信技术的广泛基础。