Hybrid IEG–ISG Synthesis of Sequence-Defined Polymers via Orthogonal CuAAC and Acyl Azide Esterification

Sequence-defined polymers demand synthetic strategies that deliver high sequence fidelity, structural complexity, and access to high–molar mass in a limited number of operations. Here we report a hybrid growth platform that combines an IEG-type Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) backbone with a protecting-group-free ISG step based on acyl azide esterification. In this orthogonal pairing, acyl azides and alcohols serve as built-in acyl-transfer partners, enabling clean ester formation under mild conditions without external activating agents, while CuAAC provides a robust triazole-forming step with excellent chemoselectivity. Using two bifunctional monomers bearing hydroxyl/alkynyl and azide/acyl-azide motifs, we construct sequence-defined oligotriazoles with high–molar mass in a small number of iterative cycles. Expansion to diversified monomers further demonstrates the modularity of the approach and its capacity to encode more complex architectures. Tandem mass spectrometry reveals characteristic and diverse cleavage patterns associated with ester and triazole linkages, underscoring the potential of this acyl azide/CuAAC platform for digital polymer synthesis and readout.