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

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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.