Other hydrogen bond assisted tough hydrogels combined hydrophilic polyurethanes (PU) with lignin, tannic acid, or used gellan gum and gelatin as hydrogen bond donors. Overall, the majority of samples with elastic moduli exceeding several MPa are in line with reduced water contents in the range of 40% to 55%. Additionally, it was shown that clever design of hydrogen bonding networks could substantially push the boundaries of both elastic moduli and fracture energies. Analogous to ionicallydriven tough hydrogels, the multiplication of hydrogen bonds within the gel is key to increase stiffness and fracture tough-ness, which is in turn tied to higher polymer fractions and reduced water contents. Nonetheless, the gels with the most remarkable (fracture) mechanical properties in this category are single networks.