Functionalization of C=C bonds in Polycyclooctene: Progress in a Two-Step Approach to Polyolefin Valorization

Polyolefins comprise a majority of plastic waste generated globally, and much of it ends up occupying landfills or polluting the environment as a result of low recycling rates. Here, we propose a two-step approach to chemical recycling of polyolefins by dehydrogenating to create C=C bonds in the backbone and then attaching functional groups via these bonds. In this study, we report hydrocarboxylation with cobalt-based catalysts of polycyclooctene (PCOE), a polymer used to model dehydrogenated polyethylene. An optimization study enabled the development of high-yield reaction conditions to add carboxylic acid functionalities to PCOE, as confirmed with infra-red and nuclear magnetic resonance spectroscopy. This reaction avoids deleterious crosslinking side-reactions and uses catalysts based on earth abundant metals. We compared the physical properties of these functionalized PCOEs to poly(ethylene-co-acrylic acid), a valuable material in the packaging industry, using contact angle and lap joint shear tests. Thus, we report progress in developing a reaction to functionalize dehydrogenated polyolefins, the second step of our proposed two-step approach to chemical recycling of polyolefins.