Mechanistic Study over the Cross-Linking between Vanillic Acid-Based Epoxy and Sulfur

Sustainable epoxy thermosets with reprocessability and degradability are critical for advancing circular materials design. Herein, we report a zinc diethyldithiocarbamate (ZDC)-catalyzed curing system involving elemental sulfur and a vanillic acid-derived diepoxy (VDE), achieving full cross-linking within 4 h at 180 °C─significantly faster than existing sulfur-epoxy systems. Mechanistic studies reveal a dual-pathway process involving sulfur-radical-mediated hydrogen abstraction and Zn2+-catalyzed thiol-epoxy ring-opening. A ternary formulation incorporating VDE, hexanediol diglycidyl ether (HDE), and sulfur yields reprocessable networks that exhibit strong adhesion to steel and selective degradability in n-octylamine. This work demonstrates a sustainable strategy to engineer recyclable thermosets using biobased epoxies and elemental sulfur.