(201f) Superacid-Assisted Polystyrene Upcycling

Amongst the recycling technologies for end-of-life polystyrene (PS) products, chemical upcycling is a promising way to build a profitable circular plastic economy for PS. Acid-catalyzed conversion of PS requires a relatively milder reaction environment and has the potential to produce high-value chemical compounds in a low-cost environment. We investigated the superacid-assisted degradation of PS chains at 20 °C using time-resolved characterizations to understand how the PS chains transform into small compounds. The following stages are identified: i) topological changes in the PS chains by intra-chain crosslinking that forms nanoparticles and simultaneous transformation of styrene to indan units, ii) breakdown of the crosslinked polymer nanoparticles into a range of small compounds such as benzene and indan/indene derivatives, and iii) and formation of the polycyclic aromatic hydrocarbons by the Scholl reaction. Our findings elucidate the precise degradation process of PS and will help design effective and economically competitive upcycling strategies for end-of-life polymers.