Bifunctional graphene oxide nanosheets for interfacially robust polymer actuators with instant solvent-induced self-folding

Polymers are ideal for deformation-induced actuating in soft robotics due to their great physical flexibility. However, creating polymer films with tunable deformation and a sufficient binding strength between layers is a big challenge. In this work, graphene oxide nanosheets with tunable radical contents are prepared for in-situ polymerization and grafting of polymers to achieve chemically crosslinked composites. The radical density and loading of nanosheets control the crosslinking density of a polymer film, which tunes its solvent-absorbing (swelling) capacity. A solvent-responsive polymer actuator that folds and grips an object can be fabricated by assembling two films with different degrees of swelling. Thermal annealing of two polymer strips at 100 degrees C significantly improves the fracture strength from 60 KPa to 380 KPa and the fracture strain from 70% to 170%. The results of this work demonstrate that radical-engineered graphene oxide nanosheets can be used to fabricate smart polymers with tunable bending performance and super interfacial binding strength for applications such as soft robotics.