Mechanically Strong Shape-Memory and Solvent-Resistant Double-Network Polyurethane/Nanoporous Cellulose Gel Nanocomposites

We report the design and fabrication of double-network polyurethane (PU)/nanoporous cellulose gel (NCG) nanocomposites with excellent mechanical properties, multistimuli-responsive shape-memory effects, and solvent resistance using NCG as a 3D reinforcement nanofiller for the PU network. The interconnected nanofibrillar cellulose networks of the NCG are finely distributed and preserved well in the PU network after polymerization. The modified percolation model agrees well with the mechanical properties of the PU/NCG nanocomposites. The remarkable reinforcement effect on the PU network is most probably due to the incorporation of the permanent, rigid, three-dimensional percolating network of the NCG that successfully transfers mechanical stresses through the covalent cross-linking, hydrogen bonds, and chain entanglements between the NCG and PU networks. The PU/NCG nanocomposites have excellent shape-memory properties with good thermal- and water-stimuli responsiveness, good dimensional stability, excellent solvent resistance, and outstanding mechanical properties in organic solvents, and they have considerable potential applications in switchable devices, sensors, biomaterials, and many other fields.