Water plasticization accelerates the underwater self-healing of hydrophobic polyurethanes

With the development of self-healing materials and the increasing demands from complicated application environment, underwater self-healing is attracting more and more attention. However, until now, the effects of different dynamic chain extender and water molecular on the self-healing of polyurethanes have not been investigated yet. In this work, we synthesized two types of polyurethanes with 2,4-pentanedione dioxime (DMG) and bis(4-hydroxyphenyl) disulfide (HPS) as the chain extenders, respectively. Furthermore, PDMS was adopt as the soft segment and isophorone diisocyanate (IPDI) was used the hard segment. It is found that they all have good flexibility, probably due to the low Tg of PDMS soft segment. Interestingly, the five samples own a similar Tg at ∼ -112 °C, which belongs to PDMS. Due to the hydrophilicity of the majority component of PDMS, the five polyurethanes have water contact angle larger than 90°. Nevertheless, the water absorption experiment clearly show that they can absorb water until saturation. The self-healing experiments were carried out in both air and water, which proved that the underwater self-healing speed of DMG polyurethanes was increased significantly. It is deduced that the water could plasticize these hydrophobic polymers and accelerate the self-healing speed underwater.