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Graphene is attractive as a functional 2D surfactant for polymerized high internal phase emulsions (polyHIPEs) due to its remarkable mechanical and electrical properties. We have developed polyHIPEs stabilized by pristine, unoxidized graphene via the spontaneous exfoliation of graphite at high-energy aqueous/organic interfaces. The exfoliated graphene self-assembles into a percolating network and incorporates into the polyHIPE cell walls as verified by TEM. The resulting composites showed compressive strengths of 7.0 MPa at densities of 0.22 g/cm3 and conductivities up to 0.36 S/m. Systematically reducing the concentration of monomer in the oil phase by dilution with a porogenic-acting solvent increased the porosity and lowered the density of the polyHIPEs. Characterization of these composites indicated that graphene’s high compressive strength and modulus was transferred to the polyHIPEs and provided mechanical reinforcement even at low polymer content. SEM showed that the morphology of the polymer changed with decreasing monomer content while the graphene lined cells retained their shape. Moreover, we show that the polyHIPEs contain a continuous graphene percolating network resulting in electrically conductive materials at low graphene loading.

Highly conductive, metal-like poly(ethylene terephthalate) (PET) nonwoven fabric was prepared by coating poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) containing dimethyl sulfoxide (DMSO) onto PET nonwoven fabric previously coated with graphene/graphite. The sheet resistance of the original nonwoven fabric decreases from80 MΩ□

Inexpensive, strong, and electrically conductive pristine graphene composites are synthesized from graphene-stabilized emulsions. These materials do not utilize oxidized graphite (GO) or reduced oxidized graphite (rGO), instead taking advantage of the recently demonstrated surfactant qualities of pristine graphene sheets. Using monomer as the oil phase, water-in-oil emulsions stabilized by graphene are polymerized to form porous composites with a continuous network of hollow graphene lined spheres. The effects of graphite flake size, emulsion settling, graphite concentration, and solvent ratio on composite properties such as electrical conductivity, strength, and density are investigated. We relate changes in the composite morphology to the observed property changes, and discuss the cause and effect of larger sphere sizes in the composite materials. Controlling and understanding properties such as conductivity and strength is a critical requirement for envisioned applications such as batteries, capacitors...

The conversion of graphite to graphite oxide (GO) is an effective and widely used method for solubilizing and exfoliating graphite. The oxidation is not uniform however, and wide variations in the degree of oxidation exist between and within batches of GO. In this article we introduce an approach to both quantify the global degree of oxidation in GO and to separate GO into fractions with more uniform extents of oxidation. Using the formation of GO stabilized oil-in-water emulsions, GO is separated into an emulsion fraction and a water fraction. We find GO sheets that stabilize the emulsion droplets are less oxidized than sheets suspended in water as shown by XRD, Raman spectroscopy, FTIR, elemental analysis and electrical conductance. The use of successive fractionation allows not only for the preparation of GO fractions with more narrowly defined properties, but also provides a method for characterizing GO batches. This promises to provide the field with a critical missing piece: a straightforward and standard method for the global characterization and comparison of GO made by different procedures and by different investigators.

The unique electrical, thermal, and mechanical properties of graphene make it a perfect candidate for applications in graphene/graphite based polymer composites, yet challenges due to the lack of solubility of pristine graphene/graphite in water and common organic solvents have limited its practical utilization. Here we report a scalable and environmentally friendly technique to form water-in-oil type emulsions stabilized by overlapping pristine graphene sheets, enabling the synthesis of open cell foams containing a continuous graphitic network. Our approach utilizes the insolubility of graphene/graphite in both water and organic solvents and so does not require oxidation, reduction, surfactants, high boiling solvents, chemical functionalization, or the input of large amounts of mechanical energy or heat. At the heart of our technique is the strong attraction of graphene to high-energy oil and water interfaces. This allows for the creation of stable water-in-oil emulsions with controlled droplet size and ...

Conductive fabrics are central to smart textiles, a concept that has been gaining attention for applications such as wearable electronics or biosensors. However, current approaches for creating electrically conductive fabrics struggle with issues ranging from low conductivity to skin irritation. The use of graphitic carbon has been investigated as a possible way to impart conductivity to fabrics, yet low loadings, required post-infusion reductions, or the need to remove additives, has limited the application of these materials. In this paper, we introduce an approach that infuses fabric with pristine few layer graphene (FLG)/graphite from natural bulk graphite using an interfacial trapping method. No additives or chemical modification of the graphite is required, and electrical conductivities an order of magnitude higher than previous approaches are achieved.

Driven by the surface activity of graphene, electrically conductive elastomeric foams have been synthesized by the controlled reassembly of graphene sheets; from their initial stacked morphology, as found in graphite, to a percolating network of exfoliated sheets, defining hollow spheres. This network creates a template for the formation of composite foams, whose swelling behavior is sensitive to the composition of the solvent, and whose electrical resistance is sensitive to physical deformation. The self-assembly of graphene sheets is driven thermodynamically, as graphite is found to act as a 2D surfactant and is spread at high-energy interfaces. This spreading, or exfoliation, of graphite at an oil/water interface stabilizes water-in-oil emulsions, without the need for added surfactants or chemical modification of the graphene. Using a monomer such as butyl acrylate for the emulsion's oil phase, elastomeric foams are created by polymerizing the continuous oil phase. Removal of the aqueous phase then results in robust, conductive, porous, and inexpensive composites, with potential applications in energy storage, filtration, and sensing.

Graphite’s insolubility in conventional solvents is a major obstacle to its utilization. This challenge is typically addressed by chemical modification such as oxidation, followed by reduction. However, pristine graphene possesses superior properties as oxidation and reduction lead to degradation of the graphene. Here we demonstrate the use of an interfacial trapping technique to assemble laterally macroscopic films of pristine graphene that are up to 95% transparent. This is accomplished by modest sonication of natural flake graphite in a water/heptane mixture to form continuous films at the interface between two immiscible liquids. Furthermore, the graphene sheets readily climb hydrophilic solid substrates, forming a homogeneous thin film one to four layers thick. These films are composed of a network of overlapping graphene sheets and shown to have long-range structure with conductivities on the order of 400 S/cm.

Thermodynamically-driven exfoliation and self-assembly of pristine graphene sheets is shown to provide thermally and electrically functional polymer composites. The spreading of graphene sheets at a high energy liquid/liquid interface is driven by lowering the overall energy of the system, and provides for the formation of water-in-oil emulsions stabilized by overlapping graphene sheets. Polymerization of the oil phase, followed by removal of the dispersed water phase, produces inexpensive and porous composite foams. Contact between the graphene-stabilized water droplets provides a pathway for electrical and thermal transport through the composite. Unlike other graphene foams, the graphite used to synthesize these composites is natural flake material, with no oxidation, reduction, sonication, high temperature thermal treatment, addition of surfactants, or high shear mixing required. The result is an inexpensive, low-density material that exhibits Joule heating and displays increasing electrical conductivity with decreasing thermal conductivity.