Enhanced mechanical properties, water stability and repeatable shape recovery behavior of Ca2+ crosslinking graphene oxide-based nacre-mimicking hybrid film

Artificial nacre-like inorganic-organic hybrid films are fabricated by a facile evaporation-induced self-assembly method using graphene oxide (GO) nanosheets as rigid bricks and a natural polysaccharide of sodium alginate (SA) as soft mortar. To further improve tensile mechanical properties of the GO/SA films, Ca2+ is utilized as a substitute for the most widely used glutaraldehyde to crosslink the films. Owing to the high chelation affinity for metal ions, the Ca2+ modified (Ca-GO/SA) films show higher tensile mechanical properties than those of the original samples. Water uptake in the Ca-GO/SA film is greatly decreased and water stability is improved by the introduction of Ca2+. The Ca-GO/SA films exhibit water-triggered shape recovery behavior. The films show two-way shape memory effect and possess two original shapes, which can be reversibly transformed by immersion in water and removal of the absorbed moisture. This advanced hybrid film will broaden the applications for biomimetic materials and shows potential for applications in the fields of water-sensitive actuators and sensors. (C) 2016 Elsevier Ltd. All rights reserved.