Environmentally Friendly Synthesis of Cardanol-Based Polyesters and Their Application as Poly(lactic acid) Additives

Byproducts derived from the food industry are an interesting biomass to valorize as they are cheap to source, their generation does not compete with food and feed production, and their utilization solves the waste disposal issue. In this work, we focused on the production of a series of polyesters using a cardanol-derived diol produced from the inedible shell of cashew nuts. The synthesized polymers are 100% biobased since the diacid components of the structure (adipic acid and succinic acid) can also be bio-derived monomers. Moreover, the overall process is a paradigm for a green circular economy as the synthesis was conducted via mild enzymatic catalysis (T < 90 °C) in a solventless system. The final workup procedure to recover the materials was conducted using the biomass-derived solvent methyl-tetrahydrofuran, therefore presenting a methodology that does not include any petroleum-based component. This work led to the biocatalyzed synthesis of linear cardanol-based polyesters having mean average molecular weights between 1800 and 4100 g mol–1 and low dispersity values (2 < D̵), which were used to plasticize poly(lactic acid), leading to an increase in the elongation at break of the resulting blends.