Self-folding enhanced mechanical and self-healing polyurethane elastomer for stretchable electronic devices

Polymer elastomers are playing an ever-more crucial for the advancement of flexible electronic devices, highlighting their significance in the field. They need to showcase not just outstanding mechanical traits but also a variety of other features, such as significant toughness and quick self-repairing abilities. Nevertheless, achieving a balance between high mechanical strength and robust dynamic self-healing presents a significant issue in material design and engineering. In this study, a novel polyurethane (PU) supramolecular elastomer was developed with incorporating alternating donor (D) and acceptor (A) groups along its main polymer chain. This innovative strategy leveraged supramolecular interactions to tackle the inherent difficulties associated with molecular design, effectively facilitating the self-folding of molecular chains through intra- and inter-chain donor-acceptor (D-A) self-assembly processes. The introduction of fluorine atoms into the polymer chain enhances the electron-withdrawing properties, strengthening D-A interactions and self-assembly density, while increasing the free volume of the polymer chain segments. This optimizes interchain interactions, thereby conferring exceptional properties to the material. The resulting material, PU-NF, exhibited exceptional mechanical attributes, achieving a break elongation of 1680 %, a tensile strength of 9.32 MPa, and a toughness of 56.97 MJ/m³. Beyond these figures, the material also showcased remarkable features, including notch insensitivity and an outstanding self-healing efficiency of 94.42 %. Its reprocessability was noted to be an impressive 96.6 %, and after four months, the remaining mass of the material was 78.9 %. In addition to these beneficial properties, the PU-NF elastomer demonstrated exceptional resistance to fatigue and stress relaxation. This was validated through cyclic tensile and stress relaxation tests, where the material achieved stress retention of 92.16 % and a dissipation efficiency of 9.87 % after enduring 10 tensile cycles under 100 % strain. This work represents a pioneering and versatile approach in the design and construction of high-performance elastomers, which could greatly enhance the development of various electronic devices, opening up possibilities for better applications in stretchable electronics.