Rapid soil degradation of a cross-linked, semicrystalline polyethylene-like polyester produced by Colletes bees

Polyethylene (PE)-like polyesters have long been investigated as biodegradable alternatives to conventional polyolefins but degrade poorly despite possessing hydrolyzable esters due to high crystallinity and hydrophobicity. Bees of the genus Colletes line their nests with a PE-like polyester that shows no environmental accumulation despite decades of nesting in dense aggregations, suggesting rapid biodegradability. This work provides a comprehensive characterization of Colletes inaequalis polyester and demonstrates its rapid degradation under ambient environmental conditions. Colletes polyester is completely insoluble in trichlorobenzene or toluene at elevated temperatures, indicating cross-linking despite originating from macrocyclic lactones that lack obvious cross-linkable functionality. Small molecules extracted from the network match the Dufour’s gland secretion but lack macrolactone, indicating complete monomer conversion. Although its repeat unit resembles amorphous, network-like plant cutin, Colletes polyester is highly crystalline ( X c = 60%), with PE-like orthorhombic packing and T m = 75 °C, indicating a much lower cross-link density. Composition analysis of nest linings collected 0 to 11 mo after construction reveals significant degradation, with polyester content falling from 73 to 40 wt% within 4 mo in ambient soil. Esterase activity against the model substrate p-nitrophenylbutyrate is observed in both newly constructed and 4-mo aged linings, which may accelerate environmental degradation. Crystallites also lack higher-order spherulitic or lamellar structure, possibly due to cross-linking, which may promote degradation by leaving more esters exposed to cleavage. This PE-like polyester is shown to degrade rapidly in the environment, offering a template for next-generation biodegradable PE-like polymers.