Rapid photothermal self-healing bio-based waterborne polyurethane enabled by oxime-urethane and quadruple hydrogen bonds with h-BN

A high bio-based content (86.3 wt%) waterborne polyurethane was designed using renewable PLA, HCO, and PDI. • Oxime groups and UPy quadruple hydrogen bonds synergistically enhance mechanical properties and self-healing capability. • h-BN doping increases thermal conductivity by 112% and enables photothermal healing. To address the inherent conflict between the environmental sustainability and material durability of bio-based waterborne polyurethane (BWPU), this research proposes a synergistic strategy that integrates bio-based materials, functional nanofillers, and dual dynamic bonding networks. These networks consist of quadruple hydrogen-bonding arrays from 2-amino-6-methylpyrimidin-4(3H)-one (UPy) units and dynamic covalent oxime bonds. Firstly, a series of oxime-containing BWPUs was synthesized from bio-based polylactic acid polyol (PLA), hydrogenated castor oil (HCO), and 1,5-pentamethylene diisocyanate (PDI), with dimethylglyoxime (DMG) or 1,4-benzoquinone dioxime (BQDO) as chain extenders instead of conventional small-molecule diols, i.e., 1,4-Butanediol (BDO). Subsequently, a dual dynamic crosslinked network was established via end-capping modification with UPy. Finally, the hexagonal boron nitride (h-BN) was incorporated to enhance thermal conductivity of composite material. The experimental results showed that, compared with the single oxime-based system, the dual dynamic network constructed based on the oxime-urethane and UPy quadruple hydrogen bonds (BWPU-Q-U10) significantly enhances the comprehensive mechanical properties. The toughness of the BWPU-Q-U10 film increases from 1660.3 MJ/m 3 to 2907.4 MJ/m 3 . Furthermore, this material achieves a self-healing efficiency of 97.2% within 24 h at room temperature (25 °C), demonstrating an optimal synergy between mechanical properties and self-healing efficiency. On this basis, the introduction of 10 wt% h-BN, identified as the optimal loading, increases the thermal conductivity of the composite by 112%. Meanwhile, leveraging the photothermal effect of BQDO, this composite achieves a healing efficiency of 86.3% within 5 min under 365 nm UV irradiation. This research presents a durable, bio-based waterborne polyurethane for smart coatings that achieves rapid self-healing while maintaining environmental sustainability. Download: Download high-res image (168KB) Download: Download full-size image