Tandem Catalysis as a Platform for the Mild Synthesis of Renewable Aliphatic Polyanhydrides

The development of one‐pot catalytic strategies that transform renewable feedstocks into functional polymers remains an important challenge in sustainable polymer chemistry. Here, we report a tandem‐catalyzed strategy for the mild step‐growth polymerization of a fatty acid‐derived monomer into high‐molar‐mass aliphatic polyanhydrides. Selective ruthenium‐catalyzed self‐metathesis of 10‐undecenoic acid affords eicos‐10‐enedioic acid with high conversion and minimal olefin positional isomerization within the substrate. The resulting diacid is subsequently converted into a polyanhydride through magnesium‐catalyzed dehydrative polycondensation using dimethyl dicarbonate as a stoichiometric dehydrating reagent. The two catalytic transformations are operationally compatible and can be performed as a sequential one‐pot process without isolation of the diacid intermediate. The orthogonal Ru/Mg sequence affords polyanhydrides with weight‐average molar masses above 30 kg/mol, while the independently optimized magnesium‐catalyzed polymerization reaches weight‐average molar masses above 80 kg/mol. A ruthenium species derived from the metathesis catalyst can also promote the dehydrative coupling step, providing an auto‐tandem pathway, although with lower molar‐mass control. The resulting polyanhydride films exhibit water contact angles of 95°–100°, within the range reported for polyethylene and polypropylene surfaces. This work establishes a mild and step‐efficient route from a renewable unsaturated fatty acid to hydrophobic aliphatic polyanhydrides.