Flame-Retardant, UV-Blocking, Antioxidant, and Antibacterial Bio-Based Epoxy Vitrimers from Epigallocatechin Gallate via Thiol-Epoxy Click Chemistry for CFRP Composites

Epoxy vitrimers combining recyclability with advanced functional properties represent a key direction for sustainable high-performance polymers. Herein, we report the design and synthesis of biobased epoxy vitrimers derived from biobased epigallocatechin gallate (EGCG), a major green tea polyphenol. An EGCG-based epoxy monomer (EGCG-EP) was synthesized and subsequently cross-linked with a bifunctional thiol-containing cross-linker via epoxy-thiol “click” chemistry, producing a series of epoxy vitrimers (EGB- x ). The abundant aromatic structure of EGCG imparts exceptional multifunctional properties, including intrinsic flame retardancy (UL-94 V-0 rating, LOI up to 28.5%), broad-spectrum UV-blocking (full shielding in the 200∼400 nm range), strong antioxidant activity (radical scavenging efficiency >95% within 10 min), and effective antibacterial activity against both Staphylococcus aureus and Escherichia coli . Meanwhile, the dynamic boronic ester bonds enable rapid stress relaxation, efficient self-healing (95% efficiency), and complete reprocessability under mild conditions without compromising mechanical performance. The EGB- x also exhibits excellent thermal stability, solvent resistance, and chemical recyclability, allowing for nondestructive recovery of carbon fibers from its composites.