Amphidynamic Crystalline Materials Based on Inertial Rotors and Dipolar Arrays

本提案描述了一项研究计划，该计划以基于其分子单元运动的新型功能材料的设计为中心。这些材料被称为双动力材料，因为它们具有存在于分子动力学光谱两个极端的建筑元素。该项目的长期愿景是创建密集的多组件组件，具有智能材料和人工分子机器所期望的复杂性和可寻址性。通过形式和功能，本研究选择的建筑单元类似于宏观的指南针或陀螺仪，选择的名称取决于它们的运动状态和对外部场响应的偶极子的存在。它们的结构由一个旋转体或旋转器组成，旋转体通过轴连接到一个刚性框架上，刚性框架将整个总成固定在一起，起到定子的作用。基于惯性转子和偶极阵列的双动力材料有望在电光和介电应用中具有可寻址的力学、偶极和光学特性。与液晶类似，新材料将具有双折射、二色性和二阶非线性光学响应，可以通过外场开关。然而，分子罗盘不需要整个分子和体畴重新定向，因此具有适当对称性的偶极晶格将具有铁电基态和响应时间，接近由重新定向单元的转动惯量给出的响应时间，约为1012 s-1（太赫兹）。在材料化学系的固态和材料化学项目以及化学系的大分子、超分子和纳米化学项目的支持下，加州大学洛杉矶分校的团队将测试用于显示固态惯性旋转的结构，这是一种新的分子罗盘和陀螺仪家族，具有对热和光化学刺激作出反应的旋转运动。并将研究一类基于线性共轭发色团之间取向变化的新型电致变色材料。为了对从事材料研究工作的少数族裔学生数量产生影响，PI与贸易技术学院（Trade Technical College）的教员建立了合作关系，该学院位于洛杉矶市中心，拥有非常多的西班牙裔和非洲裔美国人。PI和他的学生已经概述了向公众传播他们的研究的计划。该项目由材料化学学部的固态和材料化学项目以及化学学部的大分子、超分子和纳米化学项目支持，其主要目标是开发一种新型的响应材料，这种材料可以通过开关来操纵光和电信号。这将通过改变构成材料的分子的方向和运动来实现。值得注意的是，当我们想到固体时，首先想到的不是分子运动。然而，PI实验室最近的进展表明，这种材料可以用分子转子来构建，分子转子通过分子轴和轴承连接到刚性框架上，类似于宏观机器中的分子轴和轴承。在这个项目中研究的具体结构唤起了一个宏观的指南针。它们有一个杆针，或“偶极子”，绕轴旋转，以指向最强的磁场或电场。在强外场存在的情况下，通过集体改变它们的方向，材料中的许多分子罗盘可以改变透射光的强度、颜色和偏振。加州大学洛杉矶分校的研究小组利用设计来改变旋转速度的元件，旨在改变信号传输的速度，以改进目前用于手机和其他设备的技术。对这些所谓的“两动力”材料的研究将为PI提供教育和培训有才华的材料化学家的机会，并开展旨在增加贫困背景的学生进入材料化学领域的研究活动。通过保持高度支持和创造性的环境，促进材料科学和科学教育领域的职业发展，PI非常成功地吸引了女性和少数民族学生加入他的研究小组。作为该项目的一部分，PI与贸易技术学院的教师合作开展了几项外展活动，该学院位于洛杉矶市中心，拥有非常多的西班牙裔和非洲裔美国人。希望最有才华的学生能够转学到加州大学洛杉矶分校和其他研究型大学，从事化学和材料科学方面的职业。

TECHNICAL SUMMARYThis proposal describes a research plan centered on the design of a novel class of functional materials based on the motion of their molecular units. These materials are said to be amphidynamic in reference to the fact that they have architectural elements that exist at the two extremes of the molecular dynamics spectrum. The long-term vision of this project is to create dense multi-component assemblies with the complexity and addressability that is expected of smart materials and artificial molecular machines. By form and function, the building units selected for this study resemble macroscopic compasses or gyroscopes, with the designation of choice depending on their state of motion and the presence of dipoles that respond to external fields. Their structures consist of a rotary mass, or rotator, that is connected by an axle to a rigid frame that holds the assembly together and plays the role of a stator. Amphidynamic materials based on inertial rotors and dipolar arrays are expected to have addressable mechanic, dipolar, and optical properties for electro-optic and dielectric applications. In analogy to liquid crystals, the new materials will possess birefringence, dichroism, and second-order non-linear optical responses that can be switched on and off with external fields. However, molecular compasses will not require the entire molecule and the bulk domain to reorient so that dipolar lattices with suitable symmetries will have a ferroelectric ground state and response times approaching those given by the moment of inertia of the reorienting units, on the order of 1012 s-1 (THz). With the support of the Solid-State and Materials Chemistry program in the Division of Materials Chemistry and the Macromolecular, Supramolecular, and Nanochemistry program in the Division of Chemistry , the UCLA team will test structures design to display inertial rotation in the solid state, a new family of molecular compasses and gyroscopes with rotary motion that responds to thermal and photochemical stimuli, and will investigate a new class of electrochromic materials based on changes in orientation between linearly conjugated chromophores. Hoping to make an impact on the number of underrepresented minority students who pursue materials research careers, the PI has established a collaboration with Faculty at Trade Technical College, which is located in downtown Los Angeles and has a very large Hispanic and African American population. The PI and his students have outlined plans to disseminate their research to the general public. NON-TECHNICAL SUMMARYThe primary objective of this project, supported by the Solid-State and Materials Chemistry program in the Division of Materials Chemistry and the Macromolecular, Supramolecular, and Nanochemistry program in the Division of Chemistry, is to develop a new class of responsive materials that can be switched on-and-off to manipulate light and electrical signals. This will be accomplished by altering the orientation and motion of the molecules that constitute the material. Notably, molecular motion is not the first thing that comes to mind when thinking about solids. However, recent advances in the PI laboratory have shown that such materials can be built with molecular rotors linked to rigid frameworks by molecular axles and bearings akin to those found in macroscopic machines. The specific structures studied in this project are evocative of a macroscopic compass. They have a bar needle, or "dipole", that rotates about an axle in order to point towards the strongest magnetic or electric field. By collectively changing their orientation in the presence of strong external fields many such molecular compasses within the material can change the intensity, color, and polarization of transmitted light. Using elements designed to change the speed of rotation, the UCLA group aims at changing the speed of signal transmission in order to improve technologies currently used in cell phones and other devices. Research on these so-called "amphidynamic" materials will provide the PI with opportunities to educate and train talented materials chemists and to carry out research activities aimed at increasing the number of students from underprivileged backgrounds that enter the field of materials chemistry. The PI has been very successful attracting women and minority students to his research group by maintaining a highly supportive and creative environment that fosters careers in materials science and in science education. As part of this project, the PI has established several outreach activities in collaboration with Faculty at Trade Technical College, which is located in downtown Los Angeles and has a very large Hispanic and African American population. It is hoped that the most talented students will transfer to UCLA and other research universities to pursue careers in chemistry and materials sciences.