Self-Healable,\nRecyclable, and Reprocessable Poly(urethane–urea)\nElastomers with Tunable Mechanical Properties Constructed by Incorporating\nTriple Dynamic Bonds

Abstract

Elastomers that are self-healable, recyclable, reprocessable,\nand\ncustomizable in mechanical properties are desired for numerous industries\nbut remain challenging to achieve. Herein, we develop novel poly(urethane–urea)\n(PUU) elastomers involving triple dynamic bonds in a convenient and\nefficient manner. Briefly, a prepolymer based on polyetheramine terminated\nby asymmetric alicyclic diisocyanate was synthesized and chain-extended\nwith two diamines to generate a PUU elastomer containing dynamic hydrogen\nbonds (H bonds) and disulfide bonds, followed by incorporation with\nZn²⁺ ions for Zn²⁺–urea coordination.\nThe coordination bonds were proved to augment the microphase separation\nleading the hard segment domains to be homogeneously distributed in\nthe soft phase and serve as nanoscale reinforcements for the simultaneous\nimprovement of the mechanical modulus, strength, and toughness, which\nwere facilely tunable by varying the zinc content. In the meantime,\nself-healing could be achieved at room temperature or no higher than\n40 °C owing to the dynamic exchangeable bonds. Impressively,\nthe elastomers can be reprocessed by hot pressing and recycled by\nsolvent dissolution. This work, combining the macromolecular structure\ndesign with metal–urea coordination bonds, adds a new strategy\nto the toolbox of constructing elastomers with tunable and advanced\nperformances.