Polyolefin-based Multiblock Copolymers from Cascade ROMP-RAFT Polymerization

Plastic disposal has become a serious environmental and social problem. Mechanical recycling of waste plastics is the most widely adopted strategy to address this issue, but if used to recycle mixed plastics, it usually requires the addition of amphiphilic block copolymers. Polyolefins account for almost half of all synthetic plastics, making them ubiquitous in the plastic waste stream. Within this perspective, polyolefin-based multiblock copolymers are highly desirable, but they are difficult to access using traditional strategies. In this contribution, a cascade ring-opening metathesis polymerization (ROMP) and reversible addition-fragmentation chain transfer (RAFT) polymerization strategy was developed to prepare various polyolefin-based multiblock copolymers with tunable polar segments and microstructures. Using this strategy, tunable amounts of the trithiocarbonate RAFT agents were installed in the polyolefin main chain via ROMP. Subsequent chain extension of various polar vinyl monomers via controlled RAFT polymerization formed various polyolefin-based multiblock copolymers with high molecular weight and good physical properties. These multiblock copolymers were used to compatibilize and upcycle mixtures of high-density polyethylene/polymethyl methacrylate (HDPE/PMMA) and high-density polyethylene/polyethylene terephthalate (HDPE/PET).