Dynamic Covalent Polyurethane Network Materials: Synthesis and Self‐Healability

Abstract

Polyurethane (PU) has not only been widely used in the daily lives, but also extensively explored as an important class of the essential polymers for various applications. In recent years, significant efforts have been made on the development of self‐healable PU materials that possess high performance, extended lifetime, great reliability, and recyclability. A promising approach is the incorporation of covalent dynamic bonds into the design of PU covalently crosslinked polymers and thermoplastic elastomers that can dissociate and reform indefinitely in response to external stimuli or autonomously. This review summarizes various strategies to synthesize self‐healable, reprocessable, and recyclable PU materials integrated with dynamic (reversible) Diels–Alder cycloadduct, disulfide, diselenide, imine, boronic ester, and hindered urea bond. Furthermore, various approaches utilizing the combination of dynamic covalent chemistries with nanofiller surface chemistries are described for the fabrication of dynamic heterogeneous PU composites.

Sustainable, Malleable, and Recyclable Castor Oil-Derived Poly(urethane urea) Networks with Tunable Mechanical Properties and Shape Memory Performance Based on Dynamic Piperazine–Urea Bonds

“…In addition to introducing reprocessability and recyclability, dynamic covalent bonds can also introduce additional functionalities such as self-healing, reconfiguration, programmability, shape memory, and so forth. − Some dynamic covalent bonds such as disulfides, imines, phenol-carbamates, and vinylogous urethanes have been introduced to fabricate malleable CO-derived PU CANs. ,− They can be thermally reprocessed or recycled, but are still limited by their poor mechanical properties and/or high costs due to the use of expensive chemicals and lengthy fabrication procedures; therefore, it is highly desirable to develop CO-based PU CANs with high performances and commercial competitiveness by rationally designing their chemical structures, dynamic covalent bonds, and fabrication procedures.…”

Combination of Dynamic and Coordination Chemistry Achieving Two-Method Recycling of Polyurethane

“…Polyurethanes (PUs) are playing an important role in thermosets and composites due to their unique mechanical, physical, biological, and chemical properties with the ease of processing . Traditional crosslinked PUs cannot be recycled or remolded with heating or solvents owing to the strong covalently crosslinked three-dimensional network generated during curing, and their wastes become a significant environmental burden. , To reduce the negative environmental impact of the crosslinked PU, significant efforts have been undertaken to create innovative recycling systems. − Making them reprocessable by incorporating dynamic covalent bonds into the networks is one promising approach. At the experiment scale, typical dynamic linkages including Diels–Alder cycloadduct, − imine, − diselenide, , disulfide, − boronic ester bonds, − dynamic acetal, , allyl selenide, and so on have been successfully employed in the crosslinked network of PU to achieve the recyclability.…”

Sustainable cycloaliphatic polyurethanes: from synthesis to applications

“…Various recent reviews show that these properties can be introduced to PUs. [125][126][127] Besides, it also provides access to shape-memory materials, especially in the biomedical field. 128,129 In the particular case of PUs, the urethane group can show dynamic behavior depending on its nature and the urethane/ free alcohol ratio via tanscarbamoylation.…”