Ionic-Bond Regulated Cross-Linking Polyurethane with Multilevel Energy Dissipation, Enhanced Chain Rearrangement and Solvent Reprocessability

Highly cross-linked thermosetting polyurethanes based on covalent adaptable networks (CANs) have limitations in network rearrangement due to reduced polymer chain mobility. Herein, the strategy of multilevel dynamic nanodomains ( MDND ) based on ionic-bond regulation was proposed for constructing a series of ionic polyurethane (Ionic-PU) with high mechanical properties, self-healing and solvent reprocessing ability. Specifically, three ionic chain extenders were synthesized using mercaptopropionate (SH(CH 2 ) 2 COO – ) as the anion part and N-substituted 1,4-bis(imidazol-1-yl)-butane ( IC 4 I ) containing different carbon chain length in a pendant group as the cation part, which were then polymerized into the main chain. Ionic-PUs exhibited customizable mechanical properties and multilevel energy dissipation due to the steric hindrance, the magnitude of electrostatic force, and the type of noncovalent interaction on the construction of MDND . Ionic-PUs had enhanced chain rearrangement and even solvent reprocessing due to the fact that ionic bonds break and reorganize efficiently at elevated temperatures or in highly polar solvents.