US-Ireland R&D Partnership: Structure-property relationships of new polar liquid crystalline phases through synthesis and characterization using a range of analytical techniques

非技术解释：众所周知的液晶显示器通常是基于棒状的分子，并可能被模拟为两端削尖的铅笔。在过去的10-15年里，人们对由弯曲的分子形成的液晶产生了重大的科学兴趣，这种分子被模拟为曲棍球杆，这也与它们的镜像相吻合。对具有这两种结构性质的分子的研究导致了具有独特性质的新的液晶相的发现，这些相在很大程度上是未知的。本研究的目的是用化学方法合成具有这些结构的新分子，展示这些新的相，然后研究它们的物理性质，以更好地了解分子结构和液晶性质之间的关系，并促进这些材料在未来作为光子、能量存储和开关器件的应用。这些目标是通过汇集分别来自北爱尔兰、美国和爱尔兰共和国的合成化学家、物理学家和工程师的互补专业知识来实现的。这为学生和博士后研究员提供了一个独特的多学科和多国环境，通过合作、在其他主要研究人员的实验室进行科学派驻和获得单一实验室无法获得的技能来丰富科学、专业和文化。技术描述：目前的液晶技术几乎完全基于形成向列相和/或近晶相的棒状(钙质)分子。然而，在过去的10-15年里，人们对非棒状的非手性分子产生了极大的兴趣。这导致了新的向列相的发现和相应的向列相-向列相相变。这些新阶段被称为扭弯、张弯、张展和铁质向列相。这些相及其相变和物理性质在很大程度上是一个未被探索的前沿。这种几何结构的分子有时会形成极性近晶相，如果发现了这样的相，我们也会对其进行研究。本研究的目的是合成和研究由弯曲分子形成的新型液晶材料的物理性质，目的是更好地了解和促进分子结构、由此产生的液晶相以及由此产生的极性向列相和近晶中间相的物理化学性质之间的关系。这是通过系统地合成形成所需相的新介元来实现的；确定液晶相及其转变温度；使用电光和互补光谱技术(x射线散射、拉曼散射、红外、双折射、宽带介电光谱和二次谐波产生)来研究这些相的结构和物理性质。最后，将制造具有良好取向的液晶分子的测试单元。这些将被用来调查各种(电场、磁场、表面锚定和流动)场的影响，以调查这些阶段的应用，并促进物理性质的测量。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。

Nontechnical Explanation:The well-known liquid crystal display is generally based on molecules that are rod-like and may be modeled as a pencil sharpened at both ends. In the past 10-15 years there has been significant scientific interest in liquid crystals formed from bent molecules, modeled as a hockey stick, which also coincide with their mirror image. The study of molecules with these two structural properties has led to the discovery of new liquid crystalline phases with unique properties that are largely unexplored. The purpose of this research is to chemically synthesize new molecules that have these structures and exhibit these new phases and then study their physical properties with the dual goals of better understanding the relationships between molecular structure and liquid crystal properties and facilitating future applications of these materials as photonic, energy storage, and switching devices. These goals are accomplished by the pooling of the complementary expertise of a synthetic chemist, a physicist, and an engineer, from Northern Ireland, the US, and the Republic of Ireland respectively. This provides students and post-doctoral fellows a unique multidisciplinary and multinational environment for scientific, professional, and cultural enrichment through collaboration, scientific residencies in other Principal Investigator’s laboratories and the acquisition of skills that are not obtainable by working in a single laboratory. Technical Description:Current liquid crystal technologies are almost exclusively based on rod-like (calamitic) molecules that form nematic, and/or smectic phases. However, over the past 10-15 years there has been great interest in non-chiral molecules that are not rod-like. This led to the discovery of new nematic phases and corresponding nematic-nematic phase transitions. These new phases are called the twist-bend, the splay-bend, the splay, and the ferro nematic. These phases and their phase transitions and physical properties are a largely unexplored frontier. Molecules of this geometry sometimes form polar smectic phases, and should such phases be found; they too will be studied. The goal of this research is to synthesize and study the physical properties of new liquid crystalline materials that form from “bent” molecules with the objective of better understanding and advancing the relationship between molecular structure, the resulting liquid crystalline phases, and the physical and chemical properties of the resulting polar nematic and smectic mesophases. This is achieved through systematic synthesis of new mesogens that form the desired phases from bent core, bimesogen, and twisted core moieties; determination of liquid crystal phases and their transition temperatures; use of electro-optical and complementary spectroscopic techniques (x-ray scattering, Raman scattering, infrared, birefringence, wideband dielectric spectroscopy, and second harmonic generation) to investigate the structure and physical properties of these phases. Finally, test cells with well oriented liquid crystal molecules will be fabricated. These will be used to investigate the effect of various (electric, magnetic, surface anchoring, and flow) fields to investigate applications of these phases as well as to facilitate measurements of physical properties.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.