Recycling-privileged plastic polymers

Jules Harings, Hendrik Ballerstedt, Lars M. Blank

The plastic crisis is in full swing, requiring our collective attention to limit its adverse impact on the environment and human health. Here in, we argue that the high recycling quota required can be more easily achieved when using recycling-privileged plastics, for examplem i.e., plastics that, at the end of their life, are in a technological environment readily depolymerized into their monomers or building blocks of higher, but controlled order (chemistry). Incidentally, recycling rates or recycling quotas are mandated targets, expressed as a percentage, for the amount of waste that must be collected and recycled, often by governments and regulatory bodies. These quotas, such as the EU's overall 65% packaging recycling goal by 2025, aim to promote a circular economy, reduce landfill waste, conserve resources, and decrease pollution. They are calculated as an output-oriented rate, meaning only waste that is successfully reused is counted towards the target. Once degradation pathways are understood, this can be achieved by crossing multiple length scales down to the molecular level to intercept them on time. These recycling-privileged plastics typically contain heteroatomic bonds and are classified as polycondensates, such as polyesters or polyamides. These plastics can consist of novel monomers and/or of modified material, tailored not only for the application but also for recycling. It goes without saying that any future plastic economy relies on alternative carbon sources (biomass, CO 2 , plastic waste). We state the challenges, present the state-of-the-art of recycling-privileged polymers, and discuss the many possibilities at the end-of-life when polymer physics is used to tailor material properties during and after the utilization phase. • Recycling-privileged polymers required for reaching high recycling quotas. • Recycling-privileged polymers accessible by physical and molecular design. • Enzyme-based recycling complements chemical recycling.