Mechanically Robust, Moisture-Resistant Poly(thioether-thiourea) Elastomers with Glassy-State Self-Healing Capability

Conventional elastomers irreversibly embrittle below their glass transition temperature (Tg), causing service failures that cannot self-heal in the glassy state and may escalate to catastrophic accidents. Herein, we develop a novel class of poly(thioether-thiourea) elastomers (PTUEs) capable of autonomous self-healing in the glassy state. Building on the intrinsic asymmetry of thiourea-thiourea hydrogen bonds, the introduction of thioether units into thiourea-rich backbones further reduces the cohesive energy density (CED) and creates additional asymmetric, loosely packed thiourea-thioether hydrogen bonds. These integrated hydrogen-bonds paradoxically retain high mobility despite segmental chain immobilization below Tg. This enables the dynamic reconfiguration of the hydrogen-bond network for self-repair in the glassy state. By tailoring the CED through regulating the number of methylene units between thioether moieties, we can optimize physical-mechanical properties. The optimized material achieves a tensile strength of 9.6 MPa while demonstrating exceptional glassy-state healing: 97.2% autonomous repair efficiency after 36 h at −10 °C (below its Tg of 7.3 °C) and 100% efficiency within 90 min at −35 °C under mild compression. Furthermore, PTUEs exhibit outstanding moisture resistance due to hydrophobic thiourea/thioether moieties, retaining >93% of both strength and Young's modulus after 120 h at 80% relative humidity (25 °C). This unique combination of glassy-state self-healing and environmental stability makes PTUEs promising for advanced sealing and insulation applications.