Vanillin-Based epoxy vitrimers regulated by dual dynamic covalent bonds

Tunable mechanical properties from rigid to soft via monomer selection. • Excellent thermally-induced healing, reprocessing, and partial recovery to vanillin. • High adhesion performance: 9 MPa lap shear strength on steel substrates. • Bio-based vitrimers with multiple dynamic covalent bonds for sustainability. Replacing petrochemical-derived bisphenol A (BPA) in high-performance thermosets remains a critical challenge. Herein, we report the facile synthesis of a vanillin-derived multifunctional intermediate (BA) to construct dynamically cross-linked epoxy vitrimers. By curing BA with 4,4-diaminodiphenylmethane (DDM) alongside distinct epoxy monomers-either diglycidyl ether of bisphenol A (DGEBA) or epoxidized soybean oil (ESO)-we engineered materials with highly tunable properties. Remarkably, tailoring the epoxy monomer enables a transition from rigid to flexible networks; the fully bio-based BA/ESO system can be modulated from soft to hard simply by adjusting the ESO content. The rigid BA/DGEBA network outperforms commercial DGEBA/DDM, exhibiting a 29.4 % enhanced storage modulus (3066 MPa), a 23.0 % increased tensile strength (89.7 MPa), and a 2.85-fold increase in char yield (33.26 %). Furthermore, multiple dynamic covalent bonds endow these vitrimers with exceptional remodeling, thermally-induced healing, and adhesive capabilities (9 MPa lap shear strength on steel). Crucially, the vitrimers are capable of degrading completely within 1 h under alkaline conditions at 80 °C to recover the starting vanillin with a recovery rate up to 43.6 %. This strategy presents a robust, tunable alternative to BPA-based resins, advancing green polymer development. Download: Download high-res image (148KB) Download: Download full-size image