Construction Of Three-dimensional Graphene-based Architectures And The Impact On The Performance Of Flexible Piezoresistive Materials

Three-dimensional graphene architectures(3D-GA)exhibit great potentials in flexible piezoresistive materials,owing to the combination of the 3D porous structures and the excellent intrinsic properties of graphene.However,the irreversible agglomeration or restacking of graphene sheets,because of the strong van der Waals interactions and high inter-sheet junction contact resistance between isolated graphene sheets,severely suppress the intrinsically high conductivity and mechanical strength of individual graphene sheets and diminish its accessible surface area.This study is focus on the relationships among the structures and properties of 3D-GA.In the view of the poor elasticity,unsatisfactory mechanical properties and low linearity of 3D-GA,we constructed 3D-rGO/PAA composite materials with disordered and three-dimensional microstructures through breaking and reassembling.There were abundant contact points between different graphene sheets,the contact area between different graphene sheets changed after applied with external loadings and resulting the sensing properties of 3D-rGO/PAA.And the 3D-rGO/PAA shows excellent linearity,flexibility(> 7000 streching cycles),sensitivity(40-100),fast response(<112 ms)and relaxation time(15 ms),making the 3D-rGO/PAA may be meet the needs in numerous applications for human motion detection.Sodium alginate(SA)was used to modifying graphene oxide(GO)through hydrogen bonding interaction between SA and GO sheets.And 3D-rGO/SA composites with an ordered three-dimensional microstructures are constructed.SA chains can coated and tightly wrapp on the graphene sheets through hydrogen bonding,and act as supporting frameworks and steric hindrance to prevent reunion of GO sheets.And SA chains can tie them up,limiting the sliding of graphene sheets and enhancing the stiffness of the pore walls.The resulting 3D-rGO/SA exhibit outstanding durability(>7000 loading–unloading cycles),excellent sensitivity to compression(gauge factor is 1.01)and bending(bending sensitivity is0.172 rad-1),and the maximum stress was promoted to 4013.1Pa from 1055.2Pa.3D-rGO/SA also exhibit good adsorption capacity,the maximum adsorbing capacity can reach 120.2g·g-1(dichloromethane).We introduced waterborne polyurethane(WPU)to modify GO sheets to fabricate 3D-rGO/WPU composites.The mechanical properties of 3D-rGO/WPU was studied and the results shown the maximum stress is 17892.4kPa,which incsrased obviously.GO/WPU solutions can formed foams under fast stirring,and 3D-rGO/WPU with highly ordered microstructures were synthesized using foams of bubbles as templates.The pH of GO solutions,the stirring rate,the surface tension and the concentration of WPU solutions were studied to adjust and control the microstructure of 3D-rGO/WPU.The resulting 3D-rGO/WPU shows good sensing property and structural stability.