Preparation And Properties Of Layer-by-Layer Assembled Graphene-Based Composites

In the exploration and development of advanced materials,researchers have been trying to keep improving mechanical properties of the materials.However,enhancement of the strength is usually companied by reduction of the toughness.In the nature,some biomaterials possess both excellent strength and toughness owing to their unique layered structures,from which we can acquire a lot of inspiration in design,and thus fabricate composites with outstanding comprehensive mechanical properties.In this article,we used graphene oxide(GO)and two kinds of styrenic resin(SEBS and MA-SEBS)to fabricate layered composite films,via layerby-layer assembly.We studied the mechanical properties,structure as well as the interlayer interactions of the two composite films,and drew some conclusions.In the GO/SEBS composite film,structure of “interlocks” tended to form between GO sheets and SEBS resin,and the physical “interlocking effect” could make full use of the excellent mechanical properties of GO sheets.As a result,both of failure strength and elongation at break of the GO/SEBS composite film were enhanced by 50% and 25%,respectively.Different structure was found in the GO/MA-SEBS composite film,where the GO sheets stacked onto the resin closely because of the chemical interaction between them and thus no “interlocks” formed whin the interface.When the GO sheets were highly oxidized,the chemical interface interaction was strong enough to prevent the slide of GO sheets under tension,so that mechanical properties of the GO/MA-SEBS composite film could also be enhanced.From the results above,we can see that in the research of layer-by-layer assembled composite,both of the physical and chemical interface interactions should be fully considered if we want the best improvement for the mechanical properties of materials.Inspired by the multi-layered structure of fish scales of Polypterus Senegalus,we also fabricated three-layered puncture-resistant composite,including the rigid layer,the elastic layer and the fiber layer,from top to bottom.The rigid layer was GO film fabricated via vacuum-assisted selfassembly and complexation-driven assembly,where the GO sheets formed “brick-mortar” structure with organic ingredient,and the film was aimed to enhance the stiffness of the outer layer.The elastic layer was hybrid films fabricated via layer-by-layer assembly,using styrenic resin and polyurethane incorporated with graphene-based nano-sheets.The high elasticity could improve the energy dissipation and absorption of the composite when punctured.The fiber layer was uni-directional fabric composed of UHMWPE fiber and aramid fiber.Static puncture tests were conducted and the results indicated that multi-layered composite with good resistance of puncture could be fabricated via layer-by-layer assembly.