Co-Polyesters of Hydroxy-Fatty Acids Extracted from Tomato Peel Agro-Wastes and Glycerol with Tunable 16 Mechanical, Thermal and Barrier Properties

By mimicking the cutin natural polyester networks of plant cuticles, we produced hydrophobic elastomers by a sustainable process, i.e., using a catalyst- and solvent-free polycondensation of glycerol and hydroxy fatty acids, two by-products of the agro-food industry. The hydroxy-fatty acid fraction was obtained by alkaline hydrolysis in ethanol of peels from industrial tomato pomaces. This industrial-like fatty acid fraction contained more than 90% wt. of 9(10)-16 dihydroxyhexadecanoic acid (diOHC16). The co46 polyesters were designed by increasing the ratio of esterified glycerol/diOHC16 in a range observed in plant cutins (up to 6% wt.). Their structure and functional properties (thermal, mechanical, gas permeability, interaction with bacterial cells) were characterized. Increasing the glycerol contents induced a significant decrease in the reticulation degree of the polyesters and the formation of crystalline domains with an hexagonal organization. These structural modifications were related to a marked increase of elastomeric extensibility (up to 217%). While water vapor permeability was not impacted, the increase of glycerol content induced a significant decrease of oxygen permeability. None of the polyesters displayed biocide activity, but an increase of glycerol content significantly reduced the adhesion of bacterial cells, potentially giving rise to antifouling applications. Finally, the increasing content of free hydroxyl groups of the co-polyesters offer opportunities of grafting and covalent substitution for tailored functionalization