Cationic-Catalyst Strategy Enabling Ultrafast and Controlled Polymerization and Efficient Depolymerization Toward a...

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.