Mechanically robust, creep-resistant, intrinsic antibacterial and reprocessable dynamic polyurethane networks based on azine moieties

Abstract

Thermoset polyurethanes have been applied in various fields by virtue of their outstanding properties. However, the thermosets cannot be recycled due to their permanent crosslinking structure, which exerts a detrimental influence on the environment. Recently, the upsurge in the field of covalent adaptable networks (CANs) has attracted tremendous attention. Despite many efforts being dedicated to the design of CANs, the creep resistance of CANs holds much room for further improvement at high temperature. Here, we designed a kind of azine chain extender and prepared a series of dynamic polyurethane networks in varying azine proportions. The azine-containing CANs possess high creep temperature of ∼100 °C attributed to the stability of the azine moieties. Besides, the azine-containing polyurethanes also exhibit outstanding mechanical properties and reprocessability due to the conjugated structure and exchangeability of the azine moieties. The azine-containing polyurethanes also present good antibacterial properties as the azines are a special category of Schiff base. This work demonstrated that azine moieties could enhance the creep resistance, which is a long-term and crucial issue for dynamic covalent polyurethanes and endows the dynamic covalent polyurethane networks with excellent mechanical properties and intrinsic antibacterial properties.