High-performance waterborne polyurethane tailored with long-chain hydrophobic chain extenders and application in leather finishing

In this study, a novel long-chain hydrophobic chain extender (DOD) was synthesized via a thiol-olefin click reaction. The molecular structure of DOD integrated the rigid benzene ring derived from bisphenol and the flexible alkyl chain from octadecyl thiol. Waterborne polyurethane (DWPU) emulsions were synthesized as a series via stepwise polymerization, with isophorone diisocyanate (IPDI) and polytetrahydrofuran ether diol (PTMG) serving as the essential monomers. System characterization demonstrated that the material's optimal comprehensive performance was obtained at a DOD content of 3 wt%. At this content, the tensile strength reached 28.00 MPa, the elongation at break increases to 1161.36 %, and thermal stability was improved, with T max2 rising to 423.1 °C. Concurrently, hydrophobicity was enhanced, as evidenced by a water contact angle of 88.3° and a reduced water absorption rate of 7.01 %. This enhancement stems from the incorporation of alkyl long-chain structures and benzene rings. When applied to leather finishing, the DWPU-3 coating exhibited enhanced glossiness (69.7 GU), an increased water contact angle of 86.6°, and improved wear resistance, with a gloss loss rate of 38.12 %, which was significantly superior to that of the unmodified system. This research established a new paradigm for creating high-efficiency, ecologically compatible leather finishing systems.