A permanent covalent bond-crosslinked thermosetting polymer with room-temperature autonomous self-healing performance

Abstract

Despite great progress having been made in realizing the intrinsic self-healing of thermosetting polymers based on dynamic bond crosslinking, it is difficult to achieve intrinsic self-healing of thermosetting polymers crosslinked by permanent covalent bonds due to the permanent crosslinked structures restricting the mobility of molecular chains. Herein, we present a new type of thermosetting polymer with room-temperature autonomous self-healing performance by crosslinking hydroxyl functionalized hyperbranched polymers with permanent covalent bonds. The phenomenon of swelling and insolubility in the solvent and up to 72.9% gel rate confirm the formation of a crosslinked structure; meanwhile, infrared spectroscopy and ¹³C nuclear magnetic resonance analysis results confirm that this thermosetting polymer retains the strong mobility characteristics of hyperbranched polymer chains, and the high density of hydrogen bonds formed by the hydroxyls at the ends of branching arms also have considerable dynamics at room temperature. As a result, the above combined effect promotes the realization of excellent autonomous self-healing properties at room temperature. Specifically, the polymer can recover to 24.2% of the original tensile strength within 2 min, and, as time goes by, the tensile strength gradually recovers and can eventually reach 51.9% of the original tensile strength within 4 h. Therefore, the proposed technology provides a new insight for the preparation of autonomous self-healing thermosetting polymers and broadens the range of autonomous self-healing materials to permanent covalent bond-crosslinked thermosetting polymers.