Super-strong hydrogel reinforced by an interconnected hollow microfiber network via regulating the water-cellulose-copolymer interplay

The discontinuous fiber reinforced hydrogels are easy to fail due to the fracture of the fiber matrix during load-bearing. Here, we propose a novel strategy based on the synergistic reinforcement of interconnected natural fiber networks at multiple scales to fabricate hydrogels with extraordinary mechanical properties. Specifically, the P(AA-AM)/Cel (P(AA-AM), Poly (acrylic acid-acrylamide); Cel, cellulose) hydrogel is synthesized by copolymerizing AA and AM on a substrate of paper with an interconnected hollow cellulose microfiber network. This innovative design achieves a collaborative improvement of mechanical properties, including a 253-times increase in strength (27.8 vs. 0.11 MPa), 137-times increase in work of fracture (3.59 vs. 0.026 MJ m −3 ), and 235-times increase in fracture energy (16.48 vs. 0.07 kJ m −2 ). These outstanding mechanical properties benefit from the P(AA-AM) network formed by the copolymerization, which fills both the inside and outside of the hollow cellulose fibers, thus establishing abundant strong hydrogen bonds with the fibers and welding the fiber junctions. Consequently, the hydrogel exhibits enhanced resistance to the slippage and fracture of fibers. This strategy demonstrates the mechanical strengthening effectiveness of a variety of hydrogels by regulating the water-cellulose-copolymer interplay, representing a practical and universal route for designing super-strong hydrogels.