Efficient and selective closed-loop recycling of poly(L-lactic acid) to L-lactide enabled by catalyst/solvent cooperative effects

Chemical recycling to monomer (CRM) represents a crucial approach to achieving the circular plastic economy. This study systematically investigates the design principles of a highly efficient and selective depolymerization system for the closed-loop recycling of poly(L-lactic acid) (PLLA) to its monomer, L-lactide (L-LA). Using commercially available diethyl zinc (ZnEt2) as the catalyst in synergy with acetonitrile (MeCN) as the solvent, the system achieves high depolymerization activity while suppressing the formation of meso-lactide. Further mechanistic studies reveal that this catalytic system promotes rapid transesterification, which is key to its exceptional performance. The scalability and reusability of the system have also been further validated. Meanwhile, the easy post-treatment characteristics of the catalytic system have also been considered, ensuring high yield and purity of the recovered L-LA monomer. This work will provide theoretical support for the design of a CRM depolymerization system for polyester materials.