Healability Demonstrates Enhanced Shape-Recovery of Graphene-Oxide-Reinforced Shape-Memory Polymeric Films.

The fabrication of shape-memory polymers or films that can simultaneously heal the mechanical damage and the fatigued shape-memory function remains challenging. In this study, mechanically robust healable shape-memory polymeric films that can heal the mechanical damage and the fatigued shape-memory function in the presence of water are fabricated by layer-by-layer assembly of branched poly(ethylenimine) (bPEI)-graphene oxide (GO) complexes with poly(acrylic acid) (PAA), followed by the release of the (PAA/bPEI-GO)*n films from the underlying substrates. The free-standing (PAA/bPEI-GO)*35 films made of bPEI-GO complexes with a mass ratio of 0.02 between GO nanosheets and bPEI are mechanically robust with a Young's modulus of 19.8 ± 2.1 GPa and a hardness of 0.92 ± 0.15 GPa and exhibit excellent humidity-induced healing and shape-memory functions. Benefiting from the highly efficient healing function, the (PAA/bPEI-GO)*35 films can heal cuts penetrating thorough the entire film and achieve an ∼100% shape-recovery ratio for a long-term shape-memory application. Meanwhile, the shape-memory function of the mechanically damaged (PAA/bPEI-GO)*35 films can be finely restored after being healed in water. The shape-memory functions of the (PAA/bPEI-GO)*35 films and their healing capacity originate from the reversibility of electrostatic and hydrogen-bonding interactions induced by water between PAA and bPEI-GO complexes.