Microphase regulation via benzotriazine-siloxane synergistic construction realizes highly stretchable and self-extinguishing polyurethane elastomers for flexible sensors

Abstract

Currently, polyurethane (PU) elastomers are widely utilized in various industrial fields, but their weak recyclability and flammable nature hinder the further development. To overcome these challenges, we develop a novel molecular design strategy via introducing dual chain extenders of benzotriazine (BGA) and 1,3‑bis(3‑aminopropyl)tetramethyldisiloxane (siloxane) to the PU main chains. This synergistic interaction between the newly-developed BGA and siloxane induces micro-phase separation in the polymer matrix, overcoming the limitations of conventional single-chain extenders. Here, the rigid BGA segments effectively enhance the intermolecular interactions, thereby reinforcing the molecular framework. Simultaneously, the flexible siloxane chains promote the micro-phase separation and result in a characteristic aggregated morphology on the PU surface. This strategy yields a new elastomer of PU-BGA/Si4% with a tensile strength of 15.08 MPa and an elongation at break of 1608%, achieving a remarkable balance between strength and flexibility. Moreover, PU-BGA/Si4% demonstrates excellent recyclability, retaining significant mechanical properties after recycling. Significantly, the existence of nitrogen (N) and silicon (Si) elements imparts the self-extinguishing properties to the PU-BGA/Si4%, making it suitable for use in fire-prone environments. Benefiting from this reliable self-extinguishing behavior, PU-BGA/Si4% has also been successfully used as an encapsulation material for electronic pressure-sensing films, where flame suppression is essential for device safety and stability. Therefore, this approach offers a promising strategy for developing high-performance, recyclable, and self-extinguishing PU elastomers for future applications in advanced materials.