Renewable Epoxy Resins with Dual Dynamic Covalent Network for Tunable Properties and Closed-Loop Recycling

Traditional thermosetting epoxy resins are highly reliant on petroleum-derived feedstocks and confront an inherent, irreconcilable trade-off between environmental sustainability and high material performance. To address these critical challenges, this work presents a synthetic strategy for constructing dual dynamic covalent networks exclusively from renewable biomass resources. With modified castor oil (EMCO) as the polymer backbone, and fully biobased itaconic acid (IA) and thioctic acid (TA) as binary curing agents, high-performance vitrimer materials (EMCO-IAx-TAy) were successfully fabricated. This system realizes balanced modulation of strength and toughness via a dual curing mechanism integrating epoxy ring-opening esterification and free radical polymerization─its tensile strength can be continuously tailored within the range of 2.2–34.2 MPa, with corresponding elongation at break spanning 43.5%–12%. Concurrently, the materials exhibit exceptional thermal stability (5% weight loss temperature Td5% > 280 °C) and chemical stability (no macroscopic damage observed after 30 days of solvent immersion). Leveraging the synergistic dual dynamic covalent network formed by disulfide bonds and ester bonds, the materials demonstrate remarkable dynamic responsiveness (stress relaxation time τ = 43 s at 150 °C) and enable closed-loop recycling via either complete degradation in ethanol or hot-press reshaping. The EMCO-IAx-TAy vitrimers developed in this study not only overcome the performance bottlenecks of existing biobased resins but also feature fully biobased synthetic route and excellent dynamic reversible characteristics perfectly align with the principles of circular economy and green development, offering a feasible method for the design and development of high-performance, eco-friendly epoxy resins.