Organic-Inorganic Linear Segmented Polyurethanes Simultaneously Having Shape Recovery and Self-Healing Properties

Double-decker silsesquioxane (DDSOJ and hindered urea bonds were simultaneously introduced into the main chains of linear segmented polyurethane (PU) to synthesize organic-inorganic linear segmented poly(urea urethanes) (PUUs). The organic-inorganic PUUs were microphase-separated, and the POSS cages were aggregated into the microdomains with the size of 10-20 nm. The organic-inorganic PUUs had the improved thermomechanical properties in comparison to those of the control PU. Notably, the strong physical cross-linking was formed in the organic-inorganic PUUs, and thus the materials could display the properties of thermoset elastomers. The physical cross-linking was attributable to the formation of POSS microdomains, which acted as the nano-cross-linking sites. Owing to the formation of physical cross-linking, the shape memory properties have been imparted to the organic-inorganic nanocomposites; the fixing of temporary shapes and the recovery of original shapes were significantly improved. The inclusion of hindered urea bonds provided the organic-inorganic PUUs with the solid-state plasticity at room temperature (i.e., self-healing properties) via the dynamic exchange of hindered urea bonds. It was found that the nanoreinforcement of POSS microdomains did not significantly decrease the self-healing properties of the organic-inorganic PUUs. This work reports an approach simultaneously to optimize the shape memory and self-healing properties of polyurethanes.