Self-Healable, Recyclable, and Reprocessable Poly(urethane–urea) Elastomers with Tunable Mechanical Properties Constructed by Incorporating Triple Dynamic Bonds

Abstract

Elastomers that are self-healable, recyclable, reprocessable, and customizable in mechanical properties are desired for numerous industries but remain challenging to achieve. Herein, we develop novel poly(urethane–urea) (PUU) elastomers involving triple dynamic bonds in a convenient and efficient manner. Briefly, a prepolymer based on polyetheramine terminated by asymmetric alicyclic diisocyanate was synthesized and chain-extended with two diamines to generate a PUU elastomer containing dynamic hydrogen bonds (H bonds) and disulfide bonds, followed by incorporation with Zn2+ ions for Zn2+–urea coordination. The coordination bonds were proved to augment the microphase separation leading the hard segment domains to be homogeneously distributed in the soft phase and serve as nanoscale reinforcements for the simultaneous improvement of the mechanical modulus, strength, and toughness, which were facilely tunable by varying the zinc content. In the meantime, self-healing could be achieved at room temperature or no higher than 40 °C owing to the dynamic exchangeable bonds. Impressively, the elastomers can be reprocessed by hot pressing and recycled by solvent dissolution. This work, combining the macromolecular structure design with metal–urea coordination bonds, adds a new strategy to the toolbox of constructing elastomers with tunable and advanced performances.