Oligopeptide-Grafted Styrene Butadiene Rubber with Enhanced Mechanical Properties and Recyclability via a Tetrazine Click Reaction

Enhancing the mechanical properties of commercial rubbers while preserving favorable processability and recyclability is of great significance for sustainable development. Styrene–butadiene rubber (SBR), a widely utilized commercial elastomer with C═C bonds in its main chain and excellent processability, is an ideal raw material for thermoplastic elastomers. Herein, we designed a molecular structure (Tz4A) integrating both tetrazine and tetra-alanine moieties, and achieved chemical modification of SBR by leveraging the inverse electron-demand Diels–Alder (IEDDA) reaction between tetrazine and the cis-double bonds of SBR, thereby effectively introducing tetra-alanine onto the SBR backbone. The quadruple hydrogen bonding of tetra-alanine formed a dynamic cross-linked network, whose density could be conveniently regulated by adjusting the Tz4A content to tailor the mechanical performance of the supramolecular materials. Notably, the entanglements of SBR main chains and the robust hydrogen-bonding networks constructed by the Tz4A peptide side chains synergistically enabled the fabrication of high-strength, tough, and recyclable SBR elastomers─an innovative strategy that differs from conventional modification methods. Experimental results indicated that the SBR-Tz4A-2 sample (2 mol % Tz4A) exhibited a tensile strength of 14.15 MPa, an elongation at break of 1031%, and a toughness of 81.1 kJ/m3. After recycling, the SBR-Tz4A-0.5 sample retained a tensile strength of 4.75 MPa and an elongation at break of 1150%, with recovery rates of 93.5 and 97.4%, respectively. This work demonstrates the feasibility and superiority of peptide-based SBR modification via IEDDA click chemistry, providing valuable insights for the development of high-performance-rubber materials.