Polymerization of N-acryloylsemicarbazide: a facile and versatile strategy to tailor-make highly stiff and tough hydrogels

Constructing highly stiff and tough supramolecular polymer hydrogels situated in an aqueous environment is a great challenge due to intrinsically weak and unstable physical interaction strength. Here, we propose the concept of a mechanical enhancer, that is, starting from an unprecedented feature monomer, N-acryloylsemicarbazide (NASC), with one amide and one urea group on the side chain. The strong H-bonding crosslinks from the NASC side chain result in a marvelous supramolecular poly(N-acryloylsemicarbazide) (PNASC) hydrogel with tensile strengths of 1.7–4.7 MPa, compressive strengths of 6.5–23.4 MPa at 80% compressive strain, Young's moduli of 48.4–100.3 MPa, a fracture energy up to 11.4 kJ m−2, and excellent toughness of 5.66–20.35 MJ m−3 in the swelling equilibrium state, which are superior to those of the reported supramolecular polymer hydrogels, including the PNAGA hydrogel previously reported, due to much denser H-bonding interactions of amide and urea. Importantly, this NASC can be copolymerized with a variety of other monomers to customize diverse supramolecular polymer hydrogels with a specific function, such as antiprotein fouling properties and anticoagulation activity. Furthermore, a casting-made stiff poly(N-acryloylsemicarbazide-co-heparin methacrylamide) hydrogel microtube can rapidly anastomose rabbit's broken arteria carotis, prolonging coagulation time compared to the PNASC hydrogel tube, suggesting great potential as an artificial blood vessel for temporary intravascular shunt utilization.