CAREER: Novel Approaches to Hyperbranched Polymers

在化学系大分子、超分子和纳米化学项目的支持下，弗吉尼亚理工学院和州立大学的Michael D. Schulz正在开发自凝开环复分解聚合（ROMP）来制备超支化聚合物。高度和超支化聚合物是树状的3D大分子，与线性聚合物相比，具有非常不同的粘度特性。因此，超支化聚合物已被应用于各种应用，从涂料添加剂和传感器，到组合化学中的高负载支撑，再到均相催化剂。在这项研究中，首先合成的是既可以作为引发剂又可以作为单体的小分子。还将进行结构修饰以优化聚合活性。然后将成功制备的引发剂用于自凝聚聚合，以制备几种具有有趣结构和机械性能的超支化聚合物。本研究有可能为合成具有可控大分子结构的新型塑料奠定基础。该项目还将作为训练学生在聚合物化学和催化方面的一个很好的工具。在西弗吉尼亚科学博物馆举行的以化学为主题的教育推广活动将重点关注现代世界中的聚合物，以及它们的特性如何依赖于化学结构。还将开发一个旅行包，用于访问科学教育资源不足的农村社区。该项目将重点研究利用钌催化自缩合开环复分解聚合（ROMP）控制合成超支化聚合物。核心方法将包括用修饰的苄基配体制备潜在引发的烯烃复分解催化剂，这些配体将与ROMP单体偶联，产生烯烃复分解聚合物。我们将系统地研究合成的预聚物，以检验结构修饰对延迟控制、活化和聚合性能的影响。然后，成功的候选物将用于制备超支化聚合物。重点将是研究聚合条件、聚合动力学、超支化结构和端基修饰策略之间的相互作用。最后，系统地研究了合成聚合物的结构-性能关系。该项目有可能产生一种强大的策略来合成具有控制分支，重复单元功能和端基的超支化ROMP聚合物。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, Michael D. Schulz of Virginia Polytechnic Institute and State University is developing self-condensing ring opening metathesis polymerization (ROMP) to prepare hyperbranched polymers. Highly and hyperbranched polymers are tree-like 3D macromolecules that have very different viscosity characteristics when compared to linear polymers. As a result, hyperbranched polymers have been applied in various applications ranging from their use as additives to coatings and as sensors, as high loading supports in combinatorial chemistry, and as homogeneous catalysts. In this research, inimers—small molecules that can act as both an initiator and a monomer—will first be synthesized. Structural modifications will also be conducted to optimize polymerization activity. Successfully prepared inimers will then be used in self-condensing polymerization to prepare several hyperbranched polymers with interesting structural and mechanical properties. This research has the potential to lay the foundation for the synthesis of new class of plastics with controlled macromolecular structures. The project will also serve as an excellent vehicle for training students in polymer chemistry and catalysis. A chemistry-themed educational outreach with demonstrations at the Science Museum of West Virginia will focus on polymers in the modern world and how their properties are dependent on chemical structure. A travelling kit will also be developed for visits to rural communities that are under-resourced in science education. The project will focus on controlled synthesis of hyperbranched polymers using ruthenium-catalyzed self-condensing ring opening metathesis polymerization (ROMP). The central approach will involve the preparation of latent-initiating olefin metathesis catalysts with modified benzylidene ligands that will be coupled to a ROMP monomer, producing an olefin metathesis inimer. The synthesized inimers will be systematically investigated to examine the effects of structural modification on latency control, activation, and polymerization properties. Successful candidates will then be used to prepare hyperbranched polymers. A strong focus will be on investigating the interplay among polymerization conditions, polymerization kinetics, hyperbranched structures, and strategies for end-group modification. Lastly, structure-property relationships in the synthesized polymers will be systematically investigated. This project has the potential to produce a powerful strategy to synthesize hyperbranched ROMP polymers with controlled branching, repeat-unit functionality, and end-groups.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.