Strain-Promoted Azide-Alkyne Cycloaddition-Mediated Step-Growth Polymerization

The development of new polymerization techniques enables the preparation of new polymers with unique functionalities, structures, and architectures. Here, we report a bifunctional monomer based on the strained dibenzoazacyclooctyne (DBCO) structure that efficiently polymerizes with several bifunctional azide comonomers. The reactions proceed to full conversion in under 5 min and routinely results in polymers with molecular weights above 50 kDa, as determined by size-exclusion chromatography and 1H NMR. The polymers were found to retain reactive chain ends, enabling control of molecular weight via monomer addition or titration of monomer stoichiometry. The DBCO-based monomer was further investigated in the synthesis of cross-linked polymers using a trifunctional azide cross-linker, which formed gels at concentrations in excess of 50 mM, as suppression of intramolecular cyclization was necessary. This strategy allows for the rapid and efficient preparation of polymers and cross-linked gels without heat, light, catalysts, initiators, or any by-products.