Revisiting Acetoacetyl Chemistry to Build Malleable Cross-Linked Polymer Networks via Transamidation.

Covalent adaptable networks (CANs) have various potential applications for their dynamic features benefiting from the existence of dynamic covalent bonds (DCBs). Here we exploit acetoacetyl chemistry to design CANs in which acetoacetyl formed amides (AFAs) act as a type of DCBs. We first illuminate that the transamidation of AFAs is ascribed to a "proton-switch" mechanism via model study and DFT calculations. When such AFA linkages are incorporated into cross-linked polymer networks, the malleability and recyclability are demonstrated. After recycling the polymer networks for three times, there are no significant mechanical changes or degradations observed. The study reveals that the transamidation is an economic and efficient exchange reaction in the preparation of CANs.