Multiple H-bonding chain extender-based polyurethane: Ultrastiffness, hot-melt adhesion, and 3D printing finger orthosis

Mallet finger is a common athletic injury, and the current treatment involves fixing the injured finger by a splint or orthosis. 3D printing technology offers an innovative way to customize patient-specific finger orthosis that fits the individual anthropometrics. However, the existing printed materials cannot combine the high stiffness and toughness to construct an ideal finger orthosis. Herein, we report a new chain extender carrying one amide and one urea group in the side chain, and utilize it to extend polyurethane prepolymer to fabricate a highly stiff and tough thermoplastic polyurethane (TPU). Strong and mobile H-bonds in the side chain promote the formation of multiphase-separated structure in the TPU network, thus endowing this TPU with high Young’s modulus (213.0 ± 3.7 MPa) and high toughness (47.8 ± 1.9 MJ m−3). Due to the dynamic H-bonds in the polymer network, this TPU exhibits an excellent 3D printing ability, and can be used to print finger orthosis by fused deposition modeling technology at an elevated temperature. The printed finger orthosis can be attached with a wireless pulse oximeter by virtue of TPU adhesiveness, thus monitoring vital physiological signals on the injured index finger that can be well fixed by the stiff orthosis.