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(CH2)2COO–) as the anion part and N-substituted 1,4-bis(imidazol-1-yl)-butane (IC4I) 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.