Catenated, Singlet Fission, and Semi-conducting Cyclic Polymers

在化学系大分子、超分子和纳米化学项目的支持下，佛罗里达大学的Adam S. Veige教授和Brent S. Sumerlin教授正在开发新的合成方法来制备功能共轭聚合物。共轭聚合物是一类独特的聚合物，含有长碳链，其重复单元由带有碳-碳键的烯烃基团组成。这些基团使化合物不饱和，在许多天然产物中很常见，如胆固醇和脂肪酸。在共轭聚合物的情况下，当这些键被破坏时，它们会沿着聚合物链产生正电荷和负电荷，从而使它们能够导电。由于共轭聚合物含有数以万计的pi键，它们的导电性有时可以超过铜或铝等普通金属。在这项研究中，钨催化剂将首先用于制备共轭环状聚合物，这种聚合物具有像串珠一样在内部互锁的能力。然后，这些聚合物将进一步进行合成改性，以研究和改善其光学和电子性能。本研究制备的高分子材料在分子电子学和吸能材料等领域具有潜在的应用前景。与该奖项相关的研究活动也旨在扩大参与，并使高中生、本科生和研究生能够接受聚合物化学方面的培训。外展活动“万圣节分子狂热”提供了一个有吸引力的策略，以激发参与的高中生，当地教师和他们的父母对科学的兴趣。本项目主要研究利用钨催化扩环复分解聚合合成各种类型的环状聚合物。在第一个目标中，将制备和表征聚乙炔的链式（pi键互锁）环类似物。特别的重点将放在详细的反应动力学和使用成像（原子力显微镜）和流变学研究，以提供确凿的证据的catenation。第二个目标是通过将共轭发色团连接到环状聚合物上来诱导长寿命单线态裂变。单线态裂变是一种允许自旋的过程，它可以使这些线性共轭聚合物的光转换效率得到长期的提高。最后，研究小组的目标是在制备的环状聚合物中实现低配置异构化障碍。这将探索通过分子内键移位来合成半导体环状聚合物。这项研究有可能在环聚合物领域产生新的知识，并为进一步的催化剂设计提供机理理解。此外，获得半导体环状聚合物将为探索有机材料导电性的基本原理提供重要的新机会。这项研究对太阳能收集和能量转换领域也有潜在的长期科学影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Professors Adam S. Veige and Brent S. Sumerlin of University of Florida are developing new synthetic approaches for the preparation of functional conjugated polymers. Conjugated polymers are a unique class of polymers that contain long carbon chains with the repeating unit consisting of an olefin group bearing a carbon-carbon pi-bond. Such groups bring unsaturation to a chemical compound and are very commonly found in many natural products, such as cholesterol and fatty acids. In the case of conjugated polymers, when these pi-bonds are broken they create positive and negative charges along the polymer chain allowing them to conduct electricity. Since conjugated polymers contain tens of thousands of pi-bonds, their conductivity can sometimes surpass that of common metals such as copper or aluminum. In this research, a tungsten catalyst will first be used to prepare conjugated cyclic polymers which have the ability to interlock within themselves like beads on a string. These polymers will then be further modified synthetically in order to study and improve their optical and electronic properties. Polymeric materials prepared in this research have potential applications in the areas of molecular electronics and energy absorbing materials. The research activities associated with this award are also directed at broadening participation and enabling the training of high school, undergraduate, and graduate students in polymer chemistry. The outreach event “Halloween Molecular Mania” provides an attractive strategy to generate interest in science to participating high school students, local teachers and their parents.This project focuses on the use of tungsten-catalyzed ring expansion metathesis polymerization for the synthesis of various types of cyclic polymers. In the first goal, catenated (pi-bond interlocked) cyclic analogues of polyacetylene will be prepared and characterized. Special focus will be placed on detailed reaction kinetics and on the use of imaging (atomic force microscopy) and rheological studies to provide conclusive evidence of catenation. Induction of a long-lived singlet fission is to be achieved by attaching conjugated chromophores to cyclic polymers in the second goal. Singlet fission is a spin-allowed process, which could lead to long sought improved photo-conversion efficiencies with these linear pi-conjugated polymers. Lastly, the research team aims to achieve low barriers to configuration isomerization in the prepared cyclic polymers. This will be explored to synthesize semi-conducting cyclic polymers via an intramolecular pi-bond shift. This research has the potential to yield new knowledge in the area of cyclic polymers and provide mechanistic understanding for further catalyst design. Furthermore, access to semi-conducting cyclic polymers would provide important new opportunities to probe the fundamental principles of electrical conductivity in organic materials. This research also has the potential for long term scientific broader impacts on the fields of solar energy-harvesting and energy conversion.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.