This work details the synthesis and characterization of potentially lignin-derived bisguaiacols as alternatives to petroleum-derived bisphenol A (BPA) in diamine-cured epoxy resins. The variations in the number of methoxy groups of lignin facilitate the systematic chemical and thermomechanical manipulation of bisguaiacol-based thermosets to achieve desirable properties. Herein, ten bisguaiacols (including structural isomers), differing in the number of methoxy groups and regioisomer content, were synthesized from substituted bioderivable hydroxybenzyl alcohols and phenols by acidcatalyzed electrophilic aromatic substitution approaches and then functionalized with oxirane groups. These bisguaiacol diglycidyl ethers were subsequently cured with a model diamine. All cured bioderivable resins had glass transition temperatures (T g 's) above 100 °C, 5 wt % loss temperatures above 300 °C, and room-temperature glassy storage moduli above 2.0 GPa, values that were comparable to bisphenol A diglycidyl ether (BADGE/DGEBA) cured resins. Furthermore, final cured resin T g 's (111−151 °C) and high-temperature rubbery moduli (15−46 MPa) were easily tuned by manipulating the relative number of methoxy moieties and the regioisomer content, demonstrating the versatility and robustness of these bioinspired materials.

Alternatives to bisphenol A (BPA), such as lignin-inspired bisguaiacol F (BGF), are of interest for food contact materials due to increasing evidence of estrogenic activity (EA) and exposure-correlated harmful effects of BPA and its analogues. BGF has similar thermal and mechanical properties to BPA, but contains additional methoxy substituents that may significantly reduce its endocrine disruption potential. In this study, the EA of four BGF samples with different regioisomer ratios was quantified relative to 17β-estradiol at ten concentrations by using two in vitro assays: MCF-7 cell proliferation and VM7Luc4E2 transactivation (TA). The results suggest BGF mixtures with higher molar ratios of p,p′-BGF and o,p′-BGF regioisomers exhibited lower EA than BPA, while BGF samples containing higher molar ratios of m,p′-BGF had no detectable EA over a wide range of test concentrations. These findings suggest the potential of BGF as a viable alternative to BPA for use in more environmentally friendly materials.

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