Telechelic polyolefins for recyclable crosslinked thermosets and tough nanoporous membranes

PART 1: NON-TECHNICAL SUMMARY Polyolefins like polyethylene found in packaging and polypropylene found in nearly all automobiles are ubiquitous and essential to modern society. The remarkable array of properties they offer has enabled numerous technologies that include lightweight transportation, food packaging, membrane materials for clean water and energy applications. However, a long-standing challenge has been the incorporation of chemical functional groups into polyolefins that would enable explosive growth in potential applications thus fostering economic growth in this class of materials. Moreover, while polyethylene has enjoyed some recycling success, such functional polyolefins would enable new recycling strategies that would bring important benefits to this immensely useful class of polymers especially in terms of promoting a self-sustaining circular polyolefin economy. This includes reuse and recycling of locally prepared and utilized plastics. The work described in this proposal will significantly advance our understanding of how to readily prepare the target functional polyolefins using the modern tools of polymer synthesis, which will in turn clear the path for implementation of new technologies. This work will emphasize new materials applications for next generation thermally, mechanically, and chemically robust polyethylenes as high performance plastics and membranes. The proposed activities will benefit society in several ways. These activities will improve the well-being of individuals given the urgent need to solve our pressing plastics predicament: society depends on these polymeric materials and continually expects increased performance but suffers consequences from the associated pollution that can result. PART 2: TECHNICAL SUMMARY The work described in this proposal will focus on how to efficiently prepare functional telechelic polyolefins with high atom economy using an approach that combines metathesis polymerization and catalytic hydrogenation using a dual function catalyst. Specifically, Project 1 will establish a wholly new strategy to create crosslinked polyethylene using an unprecedented reactive precursor approach that will lead to the material benefits of established crosslinked polyethylenes while adding chemical recyclability and highly tunable molecular features that include molar mass between crosslinks, crystallinity, and functional group concentration. A separate strategy to create high stability PEX materials by eliminating tertiary carbons that are susceptible to oxidative degradation will also be pursued. Project 2 will spearhead the generation and development of new nanostructures and mechanically robust nanoporous materials that have utility in, for example, separation membranes and in the formation of nanobubbles for water treatment and biomedical applications. Importantly, the work proposed will uncover methods that allow for the generation of mechanically robust materials through molecular engineering of the block polymer structure. 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.