Unclicking the Click: A Depolymerizable Clicked Polymer via Two Consecutive Single‐Crystal‐to‐Single‐Crystal Reactions

Abstract We report here a clicked polymer that can be depolymerized by a declicking reaction. A designed dipeptide monomer, upon heating its crystals, underwent a single‐crystal‐to‐single‐crystal topochemical ene‐azide cycloaddition polymerization to form a triazoline‐linked polymer, which upon further heating, underwent a remarkable SCSC denitrogenation, resulting in an imine‐linked polymer quantitatively. As both the TEAC polymerization and the denitrogenation occurred in SCSC fashion, the structures of the triazoline‐linked polymer and the imine‐linked polymer could be determined at atomic resolution by SCXRD. Acid hydrolysis of the imine‐linked polymer leads to quantitative depolymerization, yielding a dipeptide, showcasing the degradability and depolymerizability of such polymers. This solid‐state click polymerization and denitrogenation yielding depolymerizable polymer is attractive over the usual click polymers that cannot be unclicked.