Double Modification of Poly(urethane-urea): Toward Healable, Tear-Resistant, and Mechanically Robust Elastomers for Strain Sensors

Polyurethane elastomers with mechanical robustness, tear resistance, and healing efficiency hold great potential in wearable sensors and soft robots. However, achieving excellent mechanical properties and healable capability simultaneously remains highly desirable but exclusive. Herein, we propose a straightforward procedure for double modification of poly(urethane-urea) (PUU) via thiolactone chemistry, and two different dynamic cross-linking bonds (disulfide linkages and Zn2+/imidazole coordination) are successively incorporated into the side chain of PUU, producing double cross-linking elastomers (PUU-I/Zn-S). The synergy between disulfide linkages and Zn2+/imidazole coordination forms a robust and dynamic network, endowing PUU-I/Zn-S with excellent mechanical and healing properties. The tensile stress, elongation at break, and toughness of the resultant elastomer can reach 44.06 MPa, 1000%, and 181.93 MJ m(-3), respectively. Meanwhile, PUU-I/Zn-S exhibits outstanding tearing resistance with a tearing energy of 42.1 kJ m(-2). The PUU-I/Zn-S can restore its mechanical robustness after self-healing at room temperature (25 +/- 2 degrees C) or 60 degrees C and even maintain 91% of its original tensile strength after reprocessing two times. Additionally, PUU-I/Zn-S-based strain sensors are fabricated by introducing conductive nanofillers and demonstrate remarkable sensing capability to diverse human body motions. This work demonstrates a simple and feasible method for the postfunctionalization and enhancement of polyurethane and provides some insights into reconciling the traditional contradictory properties of mechanical robustness and healing efficiency.

Automated summary

In this study, a simple and feasible method for the modification of poly(urethane-urea) (PUU) was proposed. Two different dynamic cross-linking bonds (disulfide linkages and Zn2+/imidazole coordination) were incorporated into the side chain of PUU, resulting in double cross-linking elastomers (PUU-I/Zn-S) with excellent mechanical and healing properties. The PUU-I/Zn-S elastomer exhibited high tensile stress, elongation at break, toughness, and tearing resistance, and could restore its mechanical robustness after self-healing at room temperature or higher temperatures. Furthermore, strain sensors based on PUU-I/Zn-S showed remarkable sensing capability to diverse human body motions.