Colorless, Transparent, Robust, and Fast Scratch‐Self‐Healing Elastomers via a Phase‐Locked Dynamic Bonds Design

Abstract

Robust self-healing thermoplastic elastomers are expected to have repeated healing capability, remarkable mechanical properties, transparency, and superior toughness. The phase-locked design in this work provides excellent tensile mechanical properties and efficient healability at a moderate temperature due to the dynamic disulfide bonds embedded in the hard segments and mainly being locked in the viscoelastic hard microphase region. The self-healing elastomers exhibit a maximum tensile stress of 25 MPa and a fracture strain of over 1600%, which are quite prominent compared to previous reports. The nanoscale domains of the elastomer are smaller than the wavelength of visible light by microphase separation control resulting in colorless, nearly 100% transparency, and are as good as quartz glasses. The high dynamics of the phase-locked disulfide bonds renders a high healing efficiency of scratches on the surface within 60 s at 70 °C. The rapid scratch healing and complete transparency recovery of the elastomers provide new avenues in the highly transparent surface or protective films which finds potential applications for precision optical lenses, flexible display screens, and automobile or aircraft lighting finishes.

Dynamic Covalent Bonds in Polymeric Materials

“…Disulfide exchange is one of the most extensively used chemistry for self‐healing materials . Due to relatively rapid disulfide exchange in the network, self‐healing properties can be achieved at ambient conditions or moderately low temperatures.…”

A Robust and High Self‐Healing Efficiency Poly(Urea‐Urethane) Based on Disulfide Bonds with Cost‐Effective Strategy

“…The main breakage of chemical bonds mainly comes from disulfide bonds owing to the low bond energy of disulfide bond in SPU during fracture or scratch test. In the process of self‐healing by heating, the dynamic disulfide bond can regenerate quickly based on radical mechanism when the healing temperature is above the hard segment T g of SPU, while the number of hydrogen bonds does not change (see Figure ), SPU samples possess high mechanical properties after rapid self‐healing . The critical temperature of SPU for hydrogen bonds breaking and regeneration is about 120 °C.…”

Flourishing Self‐Healing Surface Materials: Recent Progresses and Challenges

“…f) The excellent transparency of healed PUDS after routine scratches. d–f) Reproduced with permission . Copyright 2018, Wiley‐VCH Verlag GmbH & Co. KGaA.…”

“…Very recently, the structural design of phase‐locked dynamic bonds to heal surface scratches has been reported. The polyurethane with disulfide bonds (PUDS) elastomers exhibited fast scratch self‐healing ability at adequate temperature, meanwhile, owing to the special molecular structure (Figure 2d), the self‐healing elastomers also possessed a maximum tensile stress of 25 MPa and a fracture strain of over 1600%. The scratches on the PUDS film were observed to become increasingly shallow and finally faded away within the 60 s upon heating at 70 °C as shown in Figure 2e.…”