Cationic‐Catalyst Strategy Enabling Ultrafast and Controlled Polymerization and Efficient Depolymerization Toward a Circular Polymer Economy

The development of chemically recyclable polymers is considered one of the ideal solutions to alleviate the growing polymer waste. Fast, controlled synthesis and closed-loop recycling of amino acid (AA) polymers, as an important class of polyamides, are highly important for applications and circular polymer economy. Strong base-initiated N-carboxyanhydrides (NCAs) polymerization can prepare AA polymers very quickly, however, has the long-standing challenge of poor molecular weight controllability and numerous side reactions. Herein, we develop a highly efficient cationic-catalyst strategy that enables both "ultrafast, controlled AA polymer synthesis" and "closed-loop AA polymer recycling". This robust and easily scalable cationic-catalyst strategy is compatible with various organic strong bases as initiators, and enables the synthesis of molecular weight well-controlled AA polymers on a hectogram scale (∼120 g) within minutes. Moreover, the cationic catalyst facilitates the efficient depolymerization of AA polymers into environmentally friendly amino acids, with a recovery rate of 85.9%. In addition, the catalyst itself can be recycled quantitatively. In short, the highly efficient cationic-catalyst strategy implies practical and promising applications in polymerization and depolymerization chemistry, demonstrating great potential for the circular polymer economy and sustainable management of polymer waste.