Switchable Catalysis as a tool for the Synthesis of Novel Multiblock Copolymers

聚合物是由较小的分子（单体）在称为“聚合”的过程中连接在一起而形成的大分子。聚合物是在自然界中发现的，它已经进化出复杂的机制来精确地控制聚合。虽然自然系统仅限于从几种类型的单体制造聚合物，但合成化学提供了从本质上无限种类的单体制造聚合物的机会。这些人造聚合物构成了各种各样的材料。然而，人造催化剂不能像自然系统那样控制单体与生长中的聚合物的结合。因此，需要能够精确控制单体掺入和聚合物结构的方法。来自加州大学洛杉矶分校的Diaconescu教授正在设计一种金属催化剂，这种催化剂可以在两种状态下存在，并且可以在每种状态下产生不同的聚合物。通过改变催化剂的状态，Diaconescu基团可以制成不同的嵌段共聚物（即，由一个单体的“嵌段”和由不同单体组成的另一个嵌段组成的聚合物）。Diaconescu教授获得了来自大分子、超分子和纳米化学项目以及化学催化项目的奖项，他正在研究可切换催化剂的设计和反应性，并将这些催化剂应用于合成新的、可生物降解的聚合物材料。这些材料是了解多嵌段共聚物性质的极好候选材料。该项目通过培养博士后、研究生和本科生，促进科学、技术和工程人力资源的发展。该项目还为高中纳米科学项目的高中生提供暑期研究机会，该项目是加州大学洛杉矶分校和洛杉矶联合学区之间的合作项目，由加州纳米系统研究所组织。Diaconescu小组正在研究氧化还原可切换聚合催化剂的设计和作用机理，以形成可生物降解的共聚物。催化剂在多嵌段共聚物生产中的应用也在研究中。聚合方法依赖于能够进行环氧化物、丙交酯、内酯和碳酸盐、生物相容性、可生物降解和非免疫原性单体的氧化还原可切换共聚的金属催化剂。该小组正在使用实验和计算方法，包括主成分分析（PCA）指导下的定量构效关系（QSAR）来了解机理并改善催化剂功能。研究了生成的材料的性质，重点是表征多室胶束和序列定义的多嵌段共聚物。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。

Polymers are large molecules that are made up of smaller molecules (monomers) linked together in a process called "polymerization". Polymers are found in nature, which has evolved complex machinery for controlling polymerization in a precise manner. While natural systems are limited to making polymers from only a few types of monomers, synthetic chemistry offers the opportunity to create polymers from an essentially infinite variety of monomers. These man-made polymers make up a wide range of materials. Man-made catalysts, however, cannot control monomer incorporation into a growing polymer to the degree that natural systems can. As such, methods that can achieve precise control of monomer incorporation and polymer structure are needed. Professor Diaconescu from University of California Los Angeles is designing metal catalysts that can exist in two states and can create different polymers in each of these states. By switching the state of the catalyst, the Diaconescu group can make different block copolymers (i.e., polymers that consist of a "block" of one monomer followed by another block made of different monomers). With this award from the Macromolecular, Supramolecular and Nanochemistry Program and the Chemical Catalysis Program, Professor Diaconescu is studying the design and reactivity of switchable catalysts and is applying the catalysts to the synthesis of new, biodegradable polymeric materials. These materials are excellent candidates for understanding the properties of multiblock copolymers. The project contributes to the development of human resources in science, technology, and engineering through the education of postdoctoral fellows, graduate students, undergraduates. This project is also providing summer research opportunities for high school students from the High School Nanoscience Program, a partnership between UCLA and the Los Angeles Unified School District, organized by California NanoSystems Institute.The Diaconescu group is studying the design and mechanism of action of redox switchable polymerization catalysts for the formation of biodegradable copolymers. Applications of the catalysts to the production of multiblock copolymers are also being pursued. The polymerization methods rely on metal catalysts capable of carrying out the redox switchable copolymerization of epoxides, lactide, lactones, and carbonates, monomers that are biocompatible, biodegradable, and nonimmunogenic. The group is using experimental and computational approaches, including quantitative structure-activity relationships (QSAR) guided by principal component analysis (PCA) to understand the mechanism and improve catalyst function. The properties of the generated materials are investigated with an emphasis on characterizing multi-compartment micelles and sequence-defined multiblock copolymers.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.