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Sustainable bisphenol A (BPA) substitutes should be safe and renewable to abolish the environmental burden of BPA’s endocrine disruption and petrochemical origin. Suitable alternatives preferably also retain the rigid and stiff methylenediphenol (MDP) scaffold to emulate the hallmark performance of BPA-based polymers. Here, we report a holistic solution to sustainable BPA substitutes made from abundant lignin-derivable o-methoxyphenols that display low-to-undetectable xeno-estrogenic activity while preserving the MDP scaffold. More specifically, we propose an innovative zeolite-catalyzed synthesis towards the similar albeit safer methylenediguaiacol (MDG) scaffold via Brønsted acid-catalyzed alkylation of guaiacol with different p-alkenylguaiacols yielding various so-called bisguaiacols. Zeolite catalysis favors regioselectivity and prompts higher rate and chemoselectivity for entropic reasons thanks to active site pocket confinement. Exploiting the intrinsic handles present in o-methoxyphenols not only simplifies and ameliorates classic bisphenol chemistry, but also enables to design out xeno-estrogenic activity. Successful direct reaction of a crude lignin oil extract, as produced by reductive catalytic fractionation, highlights the feasibility and robustness of this route as a downstream process for future wood biorefineries. Last but not least, pure p,p’-bisguaiacols are polymerized into high-molecular weight thermoplastic and thermosetting polymers with promising thermo-physical properties. Overall, this work elucidates that renewability should not merely serve as a goal (renewable carbon), but also as a means (safer chemicals), thereby transcending the scope of renewability.

Over the last few decades extensive research gave unambiguous evidence for the endocrine disrupting nature of bisphenol A (BPA), which has been an indispensable precursor in polymer chemistry since 1946. Unfortunately, current alternatives (e.g., bisphenol F and bisphenol S), are as endocrine active as BPA, emphasizing the need for a more multidisciplinary approach to design BPA alternatives, including a preliminary toxicity screening of the endocrine disrupting character in addition to performance screening. Moreover, the current topical transition towards a circular- and bio-economy stresses to adopt renewable resources to produce future chemicals and materials. To enable, inspire and stimulate the design of safer, functional and renewable BPA alternatives, this review gathered all research concerning bio-based bisphenol structures, their performance and in vitro oestrogenic activity. As a key structural feature providing high-performance polymer properties, only bio-based bisphenols with a diphenylmethane core scaffold, published in peer-reviewed papers, were included in this study. This focus revealed valuable structure–property and structure–toxicity relationships, providing the fundament for rational design of safe bisphenols.

Lignin valorization will be pivotal for the success of future lignocellulose biorefineries. This chapter focuses on the emerging reductive catalytic fractionation (RCF) technology. In Section 1, the structure of native lignin is briefly discussed and the RCF biorefinery concept is presented. The importance of proper characterization of the resulting lignin fraction as well as their relation to the native lignin structure is highlighted herein. In Section 2, a selection of novel phenolic monomer valorization strategies is discussed including: dimerization toward renewable and safer bisphenols, amination strategies to obtain lignin-derived amines, and several production routes to phenol. In a final part, the importance of a techno-economic and life cycle assessment integrated with a thorough process design for the development of future RCF biorefineries is exemplified by a lignocellulose-to-phenol case study.

Bisguaiacol F (BGF), a potentially safer and renewable bisphenol A (BPA) replacement made from lignin-derivable vanillyl alcohol (p-VA), is a promising building block for future aromatic biopolymers. Unfortunately, like BPA synthesis, this electrophilic condensation reaction is also prone to regioselectivity issues, giving rise to m,p′- and o,p′-BGF byproducts. In this work, the hitherto unconsidered influence of m,p′-BGF, viz. the main isomeric byproduct of p,p′-BGF synthesis, on the physicochemical properties of poly(BGF carbonate) (BGF-PC) was systematically investigated by random copolymerisation with different fractions of pure m,p′-BGF (25, 50 and 75 wt%). To do so, the elusive m,p′-isomer was made in unparalleled regioselectivity (72%) by alkylation condensation of isovanillyl alcohol (m-VA) with guaiacol. Surprisingly, no isomeric scrambling due to acid-catalysed isomerisation was encountered for pure BGF isomers, which strongly facilitates their synthesis in contrast to petrochemical bisphenol F (BPF). Furthermore, to ensure safer chemical design, an in vitro human oestrogen receptor α (hERα) transactivation assay was performed. Both pure m,p′- and p,p′-BGF displayed a significantly reduced oestrogenic potency (∼426–457 times lower affinity than BPA) and oestrogenic efficacy (∼39–50% of BPA's maximum induction). Interestingly, mutual comparison between p,p′-BPF and p,p′-BGF reveals and proves for the first time the direct link between ortho-methoxy substitution and reduced in vitro oestrogenic activity (for transactivation of hERα). In contrast to o,p′-BPA, viz. the main byproduct of p,p′-BPA synthesis, m,p′-BGF was proven suitable for utilization in thermoplastics, thereby avoiding time-consuming and labour-intensive (re)crystallizations to obtain regioisomerically pure p,p′-BGF.