Deciphering the enzymatic grafting of vanillin onto lignosulfonate for the production of versatile aldehydes-bearing biomaterials.

Modification of lignin plays a crucial role in extending its applications. While chemical functionalization has been extensively applied, exploring the enzyme-catalyzed approach for grafting phenolic molecules presents a promising avenue. Herein, we investigate the controlled laccase-mediated grafting of vanillin onto lignosulfonates (LS) as a sustainable approach to introduce aldehydes into LS, paving the way for further (bio)chemical functionalizations (e.g., reductive amination and Knoevenagel-Doebner condensations). The resulting vanillin-grafted LS is comprehensively characterized (HPLC, SEC, Pyrolysis-GC/MS, FTIR). The study reveals four key steps in the grafting process: (i) vanillin acts as a mediator, generating the phenoxyl radical that initiates LS oxidation, (ii) the oxidation leads to depolymerization of LS, resulting in a decrease in molecular weight, (iii) rearrangement in the vanillin-grafted LS, evidenced by the replacement of labile bonds by stronger 5-5 bonds that resist to pyrolysis, and (iv) if the reaction is prolonged after complete consumption of vanillin, condensation of the vanillin-grafted LS occurs, leading to a significant increase in molecular weight. This study provides valuable insights on the behavior of vanillin and LS throughout the process and allows to identify the optimal reaction conditions, thereby enhancing the production of vanillin-grafted LS for its subsequent functionalization.

Biobased Amines: From Synthesis to Polymers; Present and Future.

Amines are key intermediates in the chemical industry due to their nucleophilic characteristic which confers a high reactivity to them. Thus, they are key monomers for the synthesis of polyamides, polyureas, polyepoxydes, which are all of growing interest in automotive, aerospace, building, or health applications. Despite a growing interest for biobased monomers and polymers, and particularly polyamides, it should be noticed that very few natural amines are available. Actually, there is only chitosan and poly(lysine). In this review we present both fundamental and applied research on the synthesis of biobased primary and secondary amines with current available biobased resources. Their use is described as a building block for material chemistry. Hence, we first recall some background on the synthesis of amines, including the reactivity of amines. Second we focus on the synthesis of biobased amines from all sorts of biomass, from carbohydrate, terpenes, or oleochemical sources. Third, because they need optimization and technological developments, we discuss some examples of their use for the creation of biobased polymers. We conclude with the future of the synthesis of biobased amines and their use in different applications.