Dynamic response crosslinking units endow polyurethane elastomers with synergistic mechanical robustness, multiphase pH sensing capability, and recyclability for sustainable environmental monitoring

Abstract

Polyurethane (PU) elastomers suffer from a long-standing critical trade-off between mechanical reinforcement and functionalization, severely limiting their applications. To address this, this study proposes an innovative design paradigm based on Dynamic Responsive Crosslinking Units (DRCUs)—achieving precise control over material properties by integrating structural connectivity, responsiveness, and dynamic reversible mechanisms. By incorporating tetra(p-hydroxyphenyl)ethylene (TPE-TOH) into a PU matrix, a supramolecular elastomer (TTPU-3) with exceptional performance was fabricated: a true fracture stress of 69.9 MPa, a toughness of 367.7 MJ m⁻³, an elongation at break of up to 1873%, an optical transmittance of 97%, and excellent recyclability (retaining 94% of mechanical properties after 3 cycles) via dynamic hydrogen bonds. The reversible protonation/deprotonation of DRCU sites enables solvent-triggered activation of TTPU-3, producing fast, reversible color changes across the pH range of 1–14. An RGB-pH model realizes quantitative correlation between color variation and the pH value for non-destructive, accurate multiphase pH detection. TTPU-3 was also developed into a controllably activated multimodal anti-counterfeiting label. This paradigm overcomes the bottleneck in balancing mechanical reinforcement and functionalization of PU elastomers, endows the material with sustainability, and offers a promising pathway for advanced environmental monitoring and high-safety applications.