CAS: Rubber Functionalization, Upcycling, and Circularity Enabled by Allylic C-H Amination

With the support of the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry, Professors Forrest Michael and Matthew Golder of the University of Washington will investigate new ways to generate novel plastic and elastic materials with tunable properties and develop new methods for these materials to be chemically recycled. Synthetic plastics and rubbers are essential and ubiquitous products in everyday life, serving as important materials for a wide variety of applications. Though many of these materials find alternative end-of-life uses, our current ability to recycle these materials is very limited. This proposal will investigate novel ways of transforming simple petroleum byproducts into functionalized plastics and rubbers with higher levels of control over the microscopic chemical structure and its tunability. The key to this approach is the use of a unique catalytic functionalization of commodity polymers that can add a wide range of functionality in controllable proportions. Using this catalytic reaction, this project will prepare a variety of new plastics and rubbers and investigate their physical properties. Additionally, this project will develop methods that allow the initial transformation to be chemically reversed, thus regenerating the original material and allowing its reuse in new applications. This functionalization/defunctionalization process will enable a circular life-cycle for these materials, in which they can continually be restored to their original state and then subsequently re-functionalized and reused for novel purposes. The broader impacts of this work will be to allow more sustainable, predictable, and tunable access to plastic and rubber materials, and to greatly improve those materials’ usability and reusability at a fundamental chemical level. This technology stands to change how rubber materials are used and re-used across diverse industries. Additionally, Professors Michael and Golder will provide invaluable cross-disciplinary training for students, and design and implement outreach activities to educate homeschooled students on the use and importance of sustainable plastics. Professors Michael and Golder will develop general synthetic strategies for the reversible introduction of novel functionality and crosslinks into synthetic elastomers. In this project, they will study structure-function relationships and develop fundamental design principles for the generation of novel functionalized thermoplastic and thermoset elastomers using a catalytic amination of polydiene feedstocks. Using this catalytic method, this project will also develop methods for generating thermoset materials from synthetic thermoplastic rubbers that retain the parent alkene microstructure. Additionally, a novel method for deamination of the functionalized thermoplastic and thermoset materials based on the formation and elimination of hydrazides will be developed, thus allowing the functionalized materials to be chemically reverted to their original state in a traceless fashion. This approach will advance our fundamental understanding of elastomer recycling and enable the use of synthetic elastomers as reusable and recoverable building blocks for a variety of materials applications. This technology aims to enable a new circular life cycle for elastomeric building blocks across a diverse range of applications and industries. 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.