Main-Chain Zwitterionic Supramolecular Polymers Derived from N‑Heterocyclic Carbene–Carbodiimide (NHC–CDI) Adducts

Polyzwitterions have found extensive applications in biological and materials sciences. Despite this success, most polyzwitterions have nondegradable polyolefin backbones with pendant zwitterionic groups. Transcension of this structural paradigm via the formation of main-chain zwitterionic supramolecular polymers could lead to readily processable, as well as self-healing and/or degradable, polyzwitterions. Herein, we report the synthesis and characterization of poly­(azolium amidinate)­s (PAzAms), which are a new class of supramolecular main-chain polyzwitterions assembled via the formation of N-heterocyclic carbene–carbodiimide (NHC–CDI) adducts. These polymers exhibit a wide range of tunable dynamic properties due to the highly structure-sensitive equilibrium between the NHC–CDI adduct and its constituent NHCs and CDIs: e.g., PAzAms derived from N-aryl-N′-alkyl CDIs are dynamic at lower temperatures than those derived from N,N′-diaryl CDIs. We develop a versatile synthetic platform that provides access to PAzAms with control over the main-chain charge sequence and molecular weight. In addition, block copolymers incorporating PAzAm and poly­(ethylene glycol) (PEG) blocks are water soluble (>30 mg mL–1) and self-assemble in aqueous environments. This work defines structure–property relationships for a new class of degradable main-chain zwitterionic supramolecular polymers, setting the stage for the development of these polymers in a range of applications.