Spirocyclic Bio-Based Epoxy Resins from Lignin-Derived Guaiacol: Molecular Design for Enhanced Thermal, Mechanical, and Hygrothermal Stability

Abstract Growing global demand for sustainable materials has driven the development of high-performance biobased epoxy resins. However, conventional strategies are plagued by reliance on fossil resources and subpar performance across key metrics (e.g., glass transition temperature, tensile modulus, and hygrothermal stability), making it difficult to simultaneously balance sustainability and high performance. Herein, an innovative biobased epoxy resin featuring a spirocyclic molecular architecture was synthesized from guaiacol (2-methoxyphenol), a lignin-derived platform monomer. Compared with diglycidyl ether of bisphenol A (DGEBA) thermosets, the cured networks exhibited a significantly higher glass transition temperature (Tg) and enhanced tensile modulus. Furthermore, the networks exhibited exceptional hygrothermal stability, retaining 94.2% of their initial tensile strength and 93.7% of their initial tensile modulus after aging for 15 days under 60 °C and 90% relative humidity. This paper introduces a macromolecular architecture design strategy centered on spirocyclic topology and establishes a deoxygenation-free route to transform lignin-derived monomers into high-performance epoxy thermosets.