Dynamic Multi-state Living Coordination Polymerization for Next Generation Polyolefins

在化学催化（CAT）和化学系大分子、超分子和纳米化学（MSN）项目的支持下，马里兰大学帕克分校的Lawrence Sita教授正在开发新的聚合催化剂，这种催化剂可以通过编程从一个引发剂产生多种产物。这种“一种催化剂-多种材料”的模式正在研究中，以扩大新型聚烯烃材料的范围，这些材料具有技术上有用的物理特性，对社会和经济有益，例如可回收性，并可替代不太环保的传统塑料。第4组催化剂正被调整为在通常被认为是非选择性的体系中进行选择性聚合。正在进行的活动还为培训下一代科学家提供了一个极好的论坛，以便他们从事与科学和工程有关的教育、工业和科学政策方面的职业，重要的是，培训那些代表性不足的群体的成员。传统上，均相烯烃聚合催化剂被优化为从单一单体生产单一类型的聚合物。相比之下，Sita教授和他的研究小组正在设计和制备由环戊二烯基和氨基酸盐配体支持的4d(0)族配合物，这些配合物可以作为烯烃活性配位链转移聚合的引发剂，生成多种新型聚烯烃产品。通过对可逆动态反应的相对速率进行控制，从而与链生长繁殖相竞争，高度通用的多态聚合过程被编程为在其他相同条件下从单一引发剂产生不同产物的光谱。正在探索的系统的不同控制因素包括：氨基酸配体的结构和手性，安装在氨基酸配体上的配位基团的影响，以及反应混合物对聚合物组成的时间控制。这些研究正在朝着具有理想物理性能的聚烯烃材料的进步而努力，同时在复杂系统中建立催化控制的新元素。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 Chemical Catalysis (CAT) and the Macromolecular, Supramolecular, and Nanochemistry (MSN) Programs in the Division of Chemistry, Professor Lawrence Sita of the University of Maryland, College Park is developing new polymerization catalysts that can be programmed to deliver multiple products from a single initiator. This ‘one catalyst – many materials’ paradigm is being investigated to expand the range of new polyolefin materials that possess technologically-useful physical properties that are of benefit to society and the economy, such as recyclability and serving as replacements for less environmentally benign legacy plastics. Group 4 catalysts are being tuned to undergo selective polymerization in systems that would typically be assumed to be unselective. The activities that are being pursued also provide an excellent forum for training the next generation of scientists for science- and engineering-related careers in education, industry, and science policy, and importantly, those who are members of underrepresented groups.Homogeneous olefin polymerization catalysts are traditionally optimized to produce a single type of polymer from a single monomer. In contrast, Professor Sita and his research team are designing and preparing Group 4 d(0)-complexes supported by cyclopentadienyl and amidinate ligands that can serve as initiators for the living coordinative chain transfer polymerization of olefins into multiple new classes of polyolefin products. By exerting control over the relative rates of reversible dynamic reactions that are competitive with chain-growth propagation, highly versatile multi-state polymerization processes are being programmed to deliver a spectrum of different products from a single initiator under otherwise identical conditions. Different controlling elements of the system being explored include: the structure and chirality of the amidinate ligands, the effect of coordinative groups installed on the amidinate ligands, as well as reaction mixture temporal control over polymer composition. These studies are working towards the advance of polyolefin materials with desirable physical properties while establishing new elements of catalytic control in complex systems.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.