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

聚乙烯是一种在日常生活中无处不在的塑料，从包装薄膜、牛奶壶到机器零件和人工关节，它被用于无数的应用领域。聚乙烯是在金属催化剂的帮助下，通过聚合的过程将小的2碳单元气体分子（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的金属催化剂，这种催化剂可以将其他种类的小分子结合到聚乙烯链中，从而生产出性能更好的塑料，包括更强的韧性，更强的抗气体和化学物质渗透能力，以及更强的生物可降解性。该项目通过培养博士后、研究生、本科生和高中生，为发展科学、技术、工程和数学方面的人力资源做出贡献。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，并通过社区学校计划为CPS高中学生提供指导和其他支持。这个项目的重点是钯烷基配合物与膦-双芳烃磺酸配体（OPO2-）的化学性质，这种配合物可以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笼的外围。“钯笼”催化剂将乙烯聚合成超高分子量线性聚乙烯（分子量为10^6 Da），并将乙烯与氟乙烯共聚，共聚单体的加入量比单核催化剂高10倍。这项研究利用程序化分子自组装的能力来合成异常坚固的Pd笼结构，该结构在高温下保持其完整性，并具有单位点聚合催化剂的功能。靶标包括基于OPO2-配体的组装，这些配体含有碱度增强的磺酸基，以增强Li&amp；笼中的O相互作用，“扩展”笼中包含额外的离子以提供补充键相互作用，“束缚”笼中OPO2-配体之间的共价键提供高稳定性，以及基于膦酸锌笼的催化剂，其本质上比锂-硫酸盐笼更坚固。研究小组正在建立控制笼型催化剂自组装的因素和这些催化剂聚合乙烯的关键机理特征，并利用这些知识开发乙烯/氟乙烯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.