Molecularly Structured Castor Oil-Derived Epoxy Vitrimers Crosslinked with Acidic Disulfide-Bearing Curing Agents: Efficient Dynamic Response, Degradability, And Recyclability

Abstract

Conventional thermosets combine strength with irreversibility, but their lack of recyclability drives the urgent search for dynamic, bio-based alternatives. Here, a molecularly engineered polyglycidyl ether resin was deliberately designed and synthesized from castor oil via epoxidation, ring-opening transamidation, and glycidylation, yielding a highly functional and reactive epoxy precursor. This resin was subsequently crosslinked with aromatic 2,2′-dithiobenzoic acid (DBA) and aliphatic 3,3′-dithiopropionic acid (DPA) to generate dynamic epoxy vitrimer networks. Comprehensive structural, thermal, mechanical, and rheological analyses demonstrated that the curing agent chemistry decisively governed vitrimer properties. The DBA-cured vitrimer exhibited high tensile strength and superior gel content, albeit with brittle behavior. In contrast, the DPA-cured vitrimer displayed remarkable ductility and rapid stress relaxation due to its flexible aliphatic crosslinks, though at the expense of lower strength. Both vitrimers showed high mechanical recyclability via hot-pressing, partial chemical degradability under reductive conditions, and effective reprocessability with retention of mechanical integrity after multiple cycles. These findings establish castor oil-derived epoxy vitrimers as promising candidates for reprocessable, degradable, and high-performance thermosets, with tunable properties tailored by molecular design and curing agent structure.

Graphical Abstract