Dual-Mode Recyclable Ethylene-Propylene Rubber Via Dynamic Structure Regulation

Abstract

Elastomers with dynamic covalent networks (DCNs) often undergo progressive mechanical degradation after thermal reprocessing mainly due to incidental backbone cleavage and chemical oxidation, whereas their chemical recycling typically relies on harsh conditions. Herein, we report a mechanically robust, dual-mode recyclable ethylene-propylene rubber (EPR) by engineering boronic ester-based dynamic cross-linking domains with tunable architectures. It is revealed that the mechanical performance and recyclability can be systematically tailored through two structural parameters, domain size and domain density, which govern the dynamic bond exchange kinetics, network rearrangement capability, and overall network connectivity. Rheological analysis decouples the distinct contributions of dynamic bond exchange and chain entanglement/disentanglement, revealing that relaxation behavior is governed by synergistic interplay between the architecture of dynamic domains and topological constraints. The optimized EPR exhibits excellent mechanical performance (EPDM-0.5H5I6 (5.18 MPa, 1407%) and dual-mode recyclability, in which the reprocessed rubber obtained via hot-pressing achieves high mechanical recovery (95% recovery in tensile strength), while mild alcoholysis-based chemical recycling enables selective network deconstruction with preserved backbone integrity for reconstruction. Our dynamic domain-based regulation strategy establishes a versatile platform for tuning mechanical robustness of sustainable rubbers with efficient recyclability.