CAREER: CAS: Chemically Recyclable Polyolefins with Tunable Ceiling Temperatures and Thermomechanical Properties

NON-TECHNICAL SUMMARY Synthetic polymers are used everywhere in our daily lives, with applications ranging from packaging and construction materials to electronics and medical devices. However, the lack of efficient recycling for polymer waste has resulted in its accumulation in the environment, causing negative impacts on ecosystems. Depolymerization, which involves breaking down polymer waste into its building blocks (monomers), has emerged as a promising solution for reducing the environmental burden of plastics. Nevertheless, extremely high temperatures (and thus energy) are typically needed for the depolymerization process of commodity polymers. This project aims to address these challenges by designing novel recyclable polymer materials that can be easily depolymerized back to monomers under mild conditions. In addition, the project will systematically investigate the relationship between polymer structures and their depolymerization performance. This knowledge will aid in the design of next-generation polymer materials with enhanced sustainability and eco-friendliness. Through this project, the next generation of polymer scientists will be trained in contemporary polymer research. Furthermore, a Summer Polymer Academy will be established for local middle and high school students to inspire their interest in STEM education and polymer science. TECHNICAL SUMMARY Depolymerization, which transforms polymers back into their constituent monomers, offers an ideal approach for the infinite recycling of polymer materials. The regenerated monomers can be repolymerized to produce recycled polymers with properties similar to those of the original products. However, the inherently high ceiling temperatures of most commodity polymers make depolymerization a highly energy-intensive process, compromising its economic viability for recycling post-consumer polymer waste. The goal of this CAREER project is to develop novel sustainable polymers that can be reverted to their monomers under mild conditions. A library of low-strain cyclic olefin monomers, including monocyclic and bridged bicyclic olefins, will be designed for the production of chemically recyclable polymers via ring-opening metathesis polymerization. To elucidate the structure-depolymerization relationship, the project will investigate the influence of monomer functional groups on the ceiling temperatures of their corresponding polymers by examining the thermodynamic parameters of polymerization. The project will provide hands-on training to undergraduate and graduate students in the emerging fields of polymer and materials science. Additionally, a Summer Polymer Academy program will be developed for local students in grades 6-12 and their parents to raise awareness of STEM research opportunities and polymer sustainability. 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.