Biomimetic preparation and multi-scale microstructures of nano-silica/polyurethane elastomeric fibers

Bioinspired by the spinning of spider silks, the biomimetic preparation of nano-silica/polyurethane (nano-SiO2/TPU) elastomeric fibers with distinctive multi-scale microstructures was successfully implemented. The formation mechanism of the nano-SiO2/TPU fibers was considered as the integrated mechanism of diffusion, coagulation, self-assembly, and microphase separation, same as that of the native spider silks. The mass ratio of nano-SiO2 to TPU greatly influenced the external and inner microstructures of the nano-SiO2/TPU fibers. The formation process of the nano-SiO2/TPU fibers was simply described as three main stages, and the second stage, such as the adding of the ethanol solvents and nano-SiO2 in different diameters, was thought to be very crucial for the final external and inner microstructures of the prepared fibers. For example, the adding of the ethanol and the nano-SiO2 spheres in diameter of 10 nm resulted in the existence of many TPU-self-assembled microspheres mostly spaced apart by the nano-SiO2 aggregates in the nano-SiO2/TPU fibers, while the adding of the ethanol and the nano-SiO2 spheres in diameter of 100 nm resulted in the existence of the nano-SiO2 spheres, instead of the TPU-self-assembled microspheres, distributed in the nano-SiO2/TPU fibers.