Plastic pollution is a major global challenge. Since the 1950s, over 9 billion tons of plastic have been produced, with less than 8% having been recycled. Chemical recycling aims to depolymerize plastics into monomers or other valuable chemical derivatives (molecules, gases, etc.). Although still underdeveloped, this approach holds promise for reducing fossil resource consumption, limiting greenhouse gas emissions, and advancing toward a circular economy.
In this thesis, I developed a novel method for cleaving C‒O bonds in oxygenated plastics such as polyesters (PCL, PBT, PET, PES, PLA) and polycarbonates (PCC, PCHC) using iodosilanes Me₃SiI and SiH₂I₂. Depolymerization proceeds without the need for a catalyst and under relatively mild conditions, leading to various reactive silyl esters and/or acyl iodides with high yields. This method is effective on both pure plastics and household waste-derived materials. The reaction can be selective depending on the conditions, and products were isolated in good yields.
Compared to Me₃SiI, the SiH₂I₂ derivative allows for reductive depolymerization with complete deoxygenation of the products. HI is also capable of depolymerizing PCL, PBT, and PET, yielding crystalline depolymerized products.
Me₃SiCl can also cleave σ(C–O) bonds in monocarbonates ROCOR’ into RX and Me₃SiOR’, but only in the presence of catalytic amounts of metal salts such as LiI. A catalytic mechanism is proposed, and this approach has been successfully applied to the depolymerization of polycarbonate.