Bio-based poly(ethylene brassylate) as a sustainable high-performance thermoplastic: Insights into its crystalline morphology, mechanical properties and rheology

High-molecular-weight poly(ethylene brassylate) (PEB), a biobased and biodegradable polyester, was synthesized via ring-opening polymerization of ethylene brassylate using a highly active sodium phenoxide catalyst. Reaction conditions were optimized to achieve full monomer conversion and molecular weights up to 600 kDa. A comprehensive characterization has been performed that evidence the strong influence of the molecular weight in the thermal, mechanical, and rheological properties. Differential scanning calorimetry and WAXS confirmed a semicrystalline structure with multiple melting peaks and decreasing crystallinity as molecular weight increased. Mechanical testing revealed a transition from polyethylene-like behavior to a highly ductile, high-strain response in high-M w samples, characterized by exceptional extensibility profile. Rheological analysis provided evidence of long-chain branching in polymers prepared without coinitiator, significantly affecting the viscoelastic response and extensional flow. These findings highlight PEB as a promising sustainable alternative to conventional polyolefins, combining favorable thermal stability, tunable mechanical properties, and processability for advanced applications such as packaging, 3D printing, and shape-memory materials. • Ultra–high-molecular-weight PEB synthesized using a sodium phenoxide catalyst. • Molecular weight drives PEB thermal behavior and semicrystalline structure. • Mechanical behavior shifts from rigid to elastomeric with increasing Mw. • Rheology reveals long-chain branching for PEB prepared without coinitiator. • Processable, sustainable PEB shows strong potential for advanced applications.