Architectural Tuning of Bio‐Based PDI ‐Trimer Polyurethane Networks via Furan Precursor Design for Optimized Self‐Healing Performance

ABSTRACT Sustainable self‐healing polyurethane Diels–Alder (PU‐DA) networks were synthesized from bio‐based pentamethylene diisocyanate (PDI) trimer, polyethylene glycol, 1,4‐butanediol, and bismaleimide using furfuryl alcohol (FA) or furfurylamine (FAm) as furan precursors. This study investigates how the chemistry of the furan precursor regulates network architecture and the resulting thermal, thermomechanical, and self‐healing properties. The density, swelling, and gel content measurements indicated that the precursor‐dependent urethane or urea linkages influenced the network cohesion and solvent resistance. Thermal and dynamic mechanical analyses further revealed formulation‐dependent changes in thermal stability and storage modulus, demonstrating that thermal healing effects were not uniform across the PU‐DA networks. FAm generally enhanced the thermal stability and stiffness of PEG and mixed PEG/BDO‐based architectures, whereas the response depended on the surrounding segmental structure. Scratch‐healing experiments and tensile recovery measurements demonstrated that higher network cohesion did not necessarily result in superior mechanical recovery. Instead, the healing response was influenced by the combined effects of network connectivity, intermolecular interactions, reversible DA/rDA reactions, and segmental mobility. The FA‐based mixed PEG/BDO network exhibited the highest tensile recovery, indicating that moderate network cohesion and sufficient chain mobility promote effective network reconstruction. These findings establish furan precursor chemistry as an effective molecular design parameter for tailoring the structure–property–healing relationship in bio‐based PDI‐trimer PU‐DA networks.