Mechanically strong hydrogels achieved by designing homogeneous network structure

Abstract Mechanically strong poly(acrylamide) nanocomposite hydrogels (NC gels), reinforced by calcium hydroxide nano-spherulites (CNS) with diameter N , N ′‑methylenebisacrylamide (BIS), are fabricated via free radical polymerization. In traditional hydrogels using BIS as cross-linker, the existence of non-cross-linked polymer chain tails leads to brittleness of hydrogels due to structural defects between adjacent clusters. However, CNS released by the tricalcium silicate can interconnect bare polymer chain tails at boundary of adjacent separated clusters and then connect vicinal clusters to form well-cross-linked network by reconstructing structural integrity of the cross-linked network in gels. Thus, our gels exhibit excellent mechanical behaviors, even considering low CNS content (200 ppm) in the presence of BIS clusters. Such NC gels can sustain high compressive stress (220 MPa) at 97% strain and revert to its original size in 1 s after loading is released. The gels can also maintain similar mechanical strength after 10 cyclic compression tests, indicating the achievement of desirable self-recoverability. Furthermore, such gels could be stretched to 2200% strain with tensile stress of 920 kPa. The improved mechanical performance is ascribed to the homogeneous network structure in our NC gels reinforced by the synergistic effects of CNS and BIS clusters.