Chemically modified graphene films with tunable negative Poisson’s ratios

Abstract

Graphene-derived macroscopic assemblies feature hierarchical nano- and microstructures that provide numerous routes for surface and interfacial functionalization achieving unconventional material properties. We report that the microstructural hierarchy of pristine chemically modified graphene films, featuring wrinkles, delamination of close-packed laminates, their ordered and disordered stacks, renders remarkable negative Poisson’s ratios ranging from −0.25 to −0.55. The mechanism proposed is validated by the experimental characterization and theoretical analysis. Based on the understanding of microstructural origins, pre-strech is applied to endow chemically modified graphene films with controlled negative Poisson’s ratios. Modulating the wavy textures of the inter-connected network of close-packed laminates in the chemically modified graphene films also yields finely-tuned negative Poisson’s ratios. These findings offer the key insights into rational design of films constructed from two-dimensional materials with negative Poisson’s ratios and mechanomutable performance.

Continuous crystalline graphene papers with gigapascal strength by intercalation modulated plasticization

“…In the other perpendicular direction, f increases slightly from 0.85 to 0.87 at an SR of 2% and keeps steady within 2−8% of SR. The beginning increase is caused by the negative Poisson ratio of wrinkles, which was observed in GOP recently 36 . After 2% SR, the Poisson ratio becomes normal positive and type II wrinkles become compressed in the perpendicular direction of stretching ( Supplementary Fig.…”

“…GPs were revealed to have a hierarchical structure: graphene sheets stack to form a basic plate with nanometers thickness and these plates pile up to become papers with micrometers thickness ( Supplementary Fig. 9) 36 . The anisotropic pores between basic plates can be detected by SAXS and their alignments equally reflect the ordering of plates.…”

3D printing-directed auxetic Kevlar aerogel architectures with multiple functionalization options

“…On the other hand, auxetic architectures with a negative Poisson's ratio describe the degree of transverse deformation of a given material when it is axially stretched or compressed. [8][9][10] This unusual mechanical behaviour has been shown to occur in carbon allotropes, 11 foams, 12 microporous polymers, 13,14 laminates 15,16 and other crystalline materials with hinged crystal structures. 17 Such designable auxetic architectures possess intriguing mechanical properties including superior shear resistance, indentation resistance, fracture toughness and damping performance, [18][19][20] promising a diverse range of applications, particularly under stringent conditions such as in aerospace, defence and smart systems as well as biomedical devices.…”

Bio-inspired self-folding strategy to break the trade-off between strength and ductility in carbon-nanoarchitected materials

“…1. It is remarked here that the graphene-based materials fabricated in experiments possess multi-level structures and considerable defects resulting from the fabrication process, 52 which are difficult to directly compare with defect-free SFGMs. For example, a regular self-folded structure is considered in the previous discussion and the effects of defects in the building blocks and nonuniform functional groups have not been considered, which, however, are common microstructural structures of graphene-based materials and are responsible for the weakening of building blocks and load transfer.…”