Atom-Economic Synthesis and Morphology-Dependent Marine Biodegradation Behavior of 2-Pyrone-4,6-Dicarboxylic Acid–Based Polyesteramide

2-Pyrone-4,6-dicarboxylic acid (PDC) is a lignin-derived biometabolic intermediate that serves as a versatile monomer for the development of sustainable polymers. In the present study, a bio-based polyesteramide, P(PDC-BiOx), was successfully synthesized via the atom-economical ring-opening polyaddition of PDC and 2,2′-bis(2-oxazoline). The thermal, crystalline, and mechanical properties of the resulting polymer were fully characterized, revealing a completely amorphous backbone with a fracture stress of 10.34 MPa. The marine biodegradability behavior was investigated under both surface and deep seawater conditions, demonstrating a clear correlation between material morphology and biodegradation rate. The experimental results demonstrated that, in surface seawater, the electrosprayed microparticles degraded more rapidly than the hot-pressed film, although both eventually reached a comparable extent of degradation. In comparison, in deep seawater, the electrosprayed microparticles achieved approximately 30% biodegradation within 45 days, which was higher than that of the hot-pressed film. Overall, PDC polyesteramides are promising biomass-derived polymers with straightforward accessibility and potential marine biodegradability.