Divanillin as a Building Block for Sustainable Polymer Synthesis by Metal-Free Aldol Polycondensation

There is growing demand for biosourced functional polymers, particularly in organic electronics, which continue to rely heavily on petroleum-derived materials. In this regard, platform chemicals obtained from biomass offer sustainable alternatives. However, the development of biosourced polymers prepared by metal-free methods remains limited. In this context, lignin-derived divanillin is an attractive renewable unit that can be incorporated into polymer backbones. This work discusses the synthesis and characterization of a new family of biosourced divanillin-based polymers prepared through metal-free aldol polycondensation. Divanillin was obtained from biosourced vanillin and converted into two dialdehyde monomers bearing either methyl or decyl substituents. These monomers were polymerized via aldol polycondensation, affording the following polymers: PDVMeCP, PDVMeCH, PDVMeIND, and PDVC10IND. The influence of the cyclic ketone unit and side-chain structure on their thermal and optical properties was investigated. The polymers were soluble in common organic solvents and also showed solubility in greener solvents such as ethyl L-lactate and p-cymene. Optical and electrochemical analyses showed absorption maxima between 357 and 391 nm and electronic bandgaps from 1.84 to 2.14 eV. Overall, the results demonstrate that divanillin is a promising renewable building block for the metal-free synthesis of sustainable polymers.