Biobased Unsaturated Polyester Adhesives from Muconic Acid via Radical Cross-Linking for Excellent Multisolvent Resistance

Fossil-derived adhesive systems currently dominate the market; however, their inadequate solvent resistance significantly restricts their application in harsh environments. Developing biobased adhesives with enhanced solvent durability is therefore of great importance. In this study, cis,cis-muconic acid, an unsaturated dicarboxylic acid obtained from the depolymerization of lignocellulosic biomass, was copolymerized with renewable diols and diacids to synthesize muconic acid-based unsaturated polyesters. The successful incorporation of conjugated double bonds and polyester backbone formation was confirmed via FT-IR, XPS, and other structural characterizations. A solvent-resistant adhesive system was subsequently fabricated through dicumyl peroxide-initiated radical cross-linking. The effects of catalyst type, muconic acid content, and comonomer structure on the molecular weight, thermal stability, and adhesive performance were systematically evaluated. Among the resulting materials, the hot-pressed PBMS-20% exhibited outstanding solvent resistance, maintaining a bonding strength of 4.31 MPa after 24 h immersion in various organic solvents and 1.09 MPa after 3 h in 60 °C water. This work offers a viable strategy for the direct utilization of muconic acid in adhesive applications and provides a new pathway toward solving interfacial failure under solvent-rich or extreme service conditions.