Self-Assembly of Multinuclear Catalysts for the Direct Synthesis of Functionalized Polyolefins

聚乙烯是一种在日常生活中随处可见的塑料，它被用于从包装膜和牛奶罐到机械部件和人造关节的无数应用。聚乙烯是在金属催化剂的帮助下，通过一种称为聚合的过程，将两个碳单元的小气体分子(乙烯)连接成长链而制成的。理查德·乔丹教授的研究小组正在开发新一代金属催化剂，这种催化剂可以在聚乙烯链中加入其他类型的小分子，以生产具有更好性能的塑料，包括更高的韧性、出色的抗气体和化学物质渗透以及增强的生物降解性。该项目通过博士后、研究生、本科生和高中生的教育，为科学、技术、工程和数学领域的人力资源开发做出贡献。该项目还通过芝加哥大学学者计划为芝加哥公立学校(CPS)系统的高中生提供暑期研究机会，并通过邻里学校计划向CPS高中生提供辅导和其他支持。该项目专注于钯-双芳烃配体(OPO2-)的化学，这些配体自组装成四聚体结构，其中四个(OPO-Li)PDR单元排列在立方锂-磺酸盐笼子的外围。“Pd笼形”催化剂将乙烯聚合成超高相对分子质量的线性聚乙烯(Mw 10^6 Da)，并与氟乙烯共聚，共聚单体的掺入量比单核催化剂高10倍。这项研究正在利用程序化分子自组装的力量来合成异常坚固的Pd笼形结构，这些结构在高温下保持其完整性，并作为单位聚合催化剂发挥作用。靶标包括基于OPO2-配体的组合物，其包含具有增强的碱性以加强笼内Li&A；O相互作用的磺酸盐基团；加入额外离子以提供补充成键作用的“扩展”笼；其中OPO2-配体之间的共价键提供高稳定性的“捆绑”笼；以及基于锌-膦酸笼的催化剂，其固有地比Li-磺酸盐笼更坚固。该研究小组正在建立控制笼形催化剂自组装的因素和通过这些催化剂进行乙烯聚合的关键机理特征，并利用这些知识开发用于乙烯/乙烯-氟化物共聚的高性能催化剂。

Polyethylene, a plastic that is ubiquitous in everyday life, is used in innumerable applications ranging from packaging films and milk jugs to machine parts and artificial joints. Polyethylene is made by linking small 2-carbon-unit gas molecules (ethylene) together into long chains with the aid of metal catalysts in a process known as polymerization. The research group of Professor Richard Jordan is developing a new generation of metal catalysts that can incorporate other kinds of small molecules into the polyethylene chains, to produce plastics with improved properties, including increased toughness, superior resistance to penetration by gases and chemicals, and enhanced biodegradability. This project is contributing to the development of human resources in science, technology, engineering and mathematics through the education of postdoctoral fellows, graduate students, undergraduates and high school students. This project is also providing summer research opportunities to high school students from the Chicago Public Schools (CPS) system through the University of Chicago Collegiate Scholars Program and mentoring and other support to CPS high school students through the Neighborhood Schools Program.This project is focused on the chemistry of palladium alkyl complexes with phosphine-bis-arenesulfonate ligands (OPO2-) that self-assemble into tetrameric structures in which four (OPO-Li)PdR units are arranged around the periphery of a cubic Li-sulfonate cage. "Pd cage" catalysts polymerize ethylene to ultra-high-molecular-weight linear polyethylene (MW 10^6 Da) and copolymerize ethylene with vinyl fluoride with tenfold-higher comonomer incorporation than can be achieved with mononuclear catalysts. This research is harnessing the power of programmed molecular self-assembly to synthesize exceptionally robust Pd cage structures that maintain their integrity at high temperature and function as single-site polymerization catalysts. The targets include assemblies based on OPO2- ligands that contain sulfonate groups with enhanced basicity to strengthen the Li─O interactions in the cage, "expanded" cages that incorporate additional ions to provide supplementary bonding interactions, "strapped" cages in which covalent links between OPO2- ligands provide high stability, and catalysts based on Zn-phosphonate cages that are inherently more robust than Li-sulfonate cages. The research team is establishing the factors that control the self-assembly of cage catalysts and the key mechanistic features of ethylene polymerization by these catalysts, and is exploiting this knowledge to develop high-performance catalysts for ethylene/vinyl-fluoride copolymerization.