Synthesis and characterization of thermosetting epoxy resins from lignin-inspired phenolics

The need for renewable polymers able to replace their petrochemical counterparts continues to grow as sustainability concerns constantly rise. Bisguaiacol, a bio-based alternative to bisphenol-A, has been synthesized using vanillyl alcohol and guaiacol via an electrophilic aromatic condensation. Purification provides both bisguaiacol and an oligomeric coproduct with a consistent number average molecular weight and dispersity of about 650 Da and 1.00, respectively, across multiple reaction volume scales. This coproduct has been well characterized as a low molecular weight novolac averaging 5 hydroxyls per molecule and was transformed into an epoxy resin suitable for use in thermosetting resin development. By utilizing the coproduct strategically, the overall production of bisguaiacol has the potential to become more economically feasible. The thermosetting polymers produced in this work, consisting of the epoxidized coproduct and an amine curing agent, exhibited Tg values over 100°C and glassy storage moduli values of 2-3 GPa at 25°C. When compared to a commercial BPA-based resin, the epoxidized coproduct resin shows comparable thermomechanical properties. The epoxy resin produced in this work demonstrates potential use in formulations for military applications such as composites, adhesives, and coatings