CAREER: Design Principles for Controlled Cyclic Polymer Synthesis

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。在化学系大分子、超分子和纳米化学项目的支持下，华盛顿大学的Matthew R. Golder教授正在开发新的合成方法来制备环状聚合物。与其他种类的聚合物相比，环状聚合物是独特的，因为它们没有链端。目前，人们正在探索环状聚合物作为下一代药物递送剂、导电材料和热塑性树脂的潜在候选者。高纯度和大量环状聚合物的合成仍然是聚合物化学中的一个挑战，因为目前的方法通常产生线性和环状大分子的混合物，难以分离。在本研究中，基于钌的金属引发剂将被开发并用于控制环状聚合物的合成。将进行详细的动力学和机理研究，以将引发剂的结构与其在聚合反应中的反应性联系起来。最终，开发的引发剂将能够调节反应动力学和分子量或环状聚合物的大小。如果成功，这项工作将使具有结构的环状聚合物材料的制备成为可能，否则很难实现。与该奖项相关的研究活动将增加更广泛的参与，并使高中生、本科生和研究生在合成聚合物化学方面得到培训。“哈士奇在家学习科学”的推广项目将覆盖并吸引整个华盛顿州在家学习的学生。该活动将开发一个虚拟的动手程序和一本以聚合物科学为中心的儿童故事书。本项目将重点发展钌介导的扩环复分解聚合，用于控制合成环状聚合物。在第一个目标中，将制备拴系钌苄基引发剂并用于研究聚合反应动力学。计算模型将用于补充实验合成和机理研究。重点将放在确定引发剂结构在整个反应剖面上的作用。在第二个目标中，将进行系统的研究，以控制环钌相对于插入的闭合环（即背面咬）。从闭合环中插入单体解耦可以实现活性聚合，其中环聚合物的分子量将由单体与引发剂的比例决定。最后，将开发一种方法，以更准确地测定环膨胀复分解聚合中环聚合物中的无环杂质。这项新技术将涉及到体积庞大的硅醚单体的结合，作为单添加可降解的连接，允许两个聚合物块的结合和分离。如果成功，这项研究将促进对如何控制金属介导的环膨胀复分解聚合中的反向反应的基本理解，从而使使用现有方法难以制备的环状聚合物的合成成为可能。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Professor Matthew R. Golder of the University of Washington is developing new synthetic approaches for the preparation of cyclic polymers. Compared to other polymer classes, cyclic polymers are unique because they lack chain ends. Cyclic polymers are currently being explored as potential candidates for next generation of drug-delivery agents, conductive materials, and thermoplastic resins. The synthesis of cyclic polymers in high purity and large quantities remains a challenge in polymer chemistry because current methodologies typically yield mixtures of linear and cyclic macromolecules which are difficult to separate. In this research, metal initiators based on ruthenium will be developed and used to control the synthesis of cyclic polymers. Detailed kinetic and mechanistic studies will be conducted to correlate the initiator structure with its reactivity in polymerization reactions. Ultimately, the developed initiators will be able to regulate reaction kinetics and molecular weight or size of cyclic polymers. If successful, this work will enable the preparation of cyclic polymeric materials with architectures that are otherwise very challenging to achieve. The research activities associated with this award will increase broadening participation and enable training of high school, undergraduate, and graduate students in synthetic polymer chemistry. The outreach program “Husky at Home Science” will reach and engage homeschooled students across the state of Washington. This activity will develop a virtual hands-on program and a children’s storybook centered around polymer science. This project will focus on the development of ruthenium-mediated ring expansion metathesis polymerization for the controlled synthesis of cyclic polymers. In the first goal, tethered ruthenium benzylidene initiators will be prepared and used to study polymerization reaction kinetics. Computational modeling will be utilized to complement the experimental synthetic and mechanistic studies. Emphasis will be placed on determining the role of initiator structure on the overall reaction profile. In the second goal, systematic studies will be conducted to gain control over the ring-closing (i.e., back-biting) of the cyclic ruthenium species relative to insertion. Decoupling monomer insertion from ring-closure could enable living polymerization in which the molecular weights of cyclic polymers will be predetermined by the ratio of monomer to the initiator. Lastly, a methodology will be developed for more accurate determination of acyclic impurities amongst cyclic polymers in ring expansion metathesis polymerization. The new technique will involve incorporation of bulky silyl ether monomers that act as single-addition degradable junctions, allowing for the union and separation of two polymer blocks. If successful, this research will advance fundamental understanding of how to control back-biting reactions in metal-mediated ring expansion metathesis polymerization, enabling the synthesis of cyclic polymers that are otherwise difficult to prepare using existing methodologies.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.