Ultra-strong, recyclable, self-healable and transparent polythiourethane-urea elastomer via physical–chemical dual-reversible networks synergy

Abstract

Thermosetting polyurethane elastomers exhibit excellent dimensional stability, thermal resistance, and mechanical strength, yet their permanent covalent cross-links hinder self-healing and recyclability. While dynamic cross-linking strategies address these limitations, they often compromise mechanical performance. Herein, we report an innovative polyurethane system with a synergistic dual reversible network: a physical network of multiple hydrogen bonds and π–π stacking, combined with a dynamic thiourethane covalent network. This dual-network system optimizes hard-domain dimensions and regulates microphase structure, endowing the elastomer with exceptional mechanical properties. The optimized elastomer (PTUU-C₂) achieves a tensile strength of 81.06 MPa (the highest reported for self-healing chemically cross-linked elastomers) and a toughness of 286.99 MJ m⁻³. Enabled by the dual-dynamic network, the elastomer exhibits efficient self-healing (≥80% recovery) and complete chemical recyclability via decross-linking, with the recycled thiol-terminated polymer having re-crosslinking potential via click chemistry. Additionally, it features high transparency (89.69% transmittance), low haze (1.23%), and suitable refractive index (1.49), showing promise in transparent protection, anti-counterfeiting and optical applications. This molecular-level strategy overcomes the traditional high performance-recyclability trade-off of cross-linked polyurethanes, offering a viable pathway toward advanced thermosets integrating excellent mechanical properties, self-healing, and full recyclability.