Reproducible, self-healable polyurethane composite networks with high toughness, florescence and water-insensitivity

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For self-healing polymers, the poor elastic properties and low self-healing efficiency have limited their applications, smart polymer systems adaptable to complex environment have became a hot topic. To address this issue, in this study, a series of polyurethane composite networks were developed, using poly(ɛ-caprolactone) (PCL) and polytetramethylene ether glycol (PTMG) as the soft segment, isophorone diisocyanate (IPDI) as the hard segment, with the incorporation of florescent SrAl2O4: Eu2+, Dy3+ phosphors. The chemically crosslinked networks were investigated by differential scanning calorimetry (DSC), X-ray scattering (XRD), and dynamic mechanical analysis (DMA) on their crystalline properties. Atomic force microscopy (AFM) confirmed the micro-phase separation structures, where soft segments facilitated self-healing and the hard segments enhanced rigidity. Scanning electron microscopy (SEM) and optical microscopy presented highly efficient and rapid healing could be achieved. The materials emitted an intense green light in UV without significant fluorescent intensity reduction in water emersion. Additionally, the synergistic effect of transesterification provided the composite networks reproducibility for recycling use.