Polymer/Pristine Graphene Based Composites: From Emulsions to Strong, Electrically Conducting Foams

Abstract

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 overlapping graphene sheets playing the role of surfactant by covering the droplet surface and stabilizing the interfaces with a thin graphitic skin. These emulsions are used as templates for the synthesis of open cell foams with densities below 0.35 g/cm3 that exhibit remarkable mechanical and electrical properties including compressive moduli up to ∼100 MPa, compressive strengths of over 8.3 MPa (1200 psi), and bulk conductivities approaching 7 S/m.

Boron Nitride Surface Activity as Route to Composite Dielectric Films

“…This free energy change is lower than the corresponding 2.2 mN/m change of the free energy obtained for graphene displacement from an interface using similar calculations. 23,24 Using this value, we estimate the work required to displace BN sheets with 100 × 100 nm lateral dimensions from the water/ heptane interface into the heptane phase to be 4420 k B T. This energy is sufficiently strong to localize the BN sheet at the water/heptane interface.…”

“…This behavior is analogous to that observed for graphite in previous studies. 23,24 Because the BN sheets spread at the water wet hydrophilic glass surfaces of a vial that are in contact with an oil phase, they also climb the surface of glass slides placed in a vial. Figure 2A shows such a glass slide covered with a BN film.…”

Atomistic modeling of graphene/hexagonal boron nitride polymer nanocomposites: a review

“…Due to accuracy and less intensive mathematical formulations, MD-based simulations are emerging as potential technique for investigating the nanomaterial's for the purpose of water desalination, enhancing impact strength of nanocomposites for armor grade materials, study involving the effect of radiation on nanomaterials, hydrogen storage, defect engineering, and developing biomaterials; yet challenges due to the lack of solubility of PG/BN in water and common organic solvents have somewhat limited its practical utilization. 216 The prime mechanism for the bonding to accomplish is largely due to the high surface-to-volume ratio of graphene and BN derivatives that tends to stretch the polymer chains and pack them along the graphene/BN nanofiller surface leading to a higher densification in vicinity of filler relative to the bulk. Studies have further revealed that the graphene/BN and their derivatives can form various noncovalent bindings to biomolecules and such interactions can lead to the secondary structural changes in the biomolecules and some innovative outcomes; forming the basis for nanobiocomposite materials.…”

A feasible strategy to constructing hybrid conductive networks in PLA‐based composites modified by CNT‐d‐RGO particles and PEG for mechanical and electrical properties

“…Interestingly, in the recent decade, graphene has attracted considerable attention due to its distinguished electrical and magnetic behavior and excellent thermal and mechanical properties . Graphene nanoplate materials are typical 2D plate‐like materials with a high aspect ratio, good modulus, and heat conductivity; thus, it is used as reinforcement and conductive filler for polymer composites . Commonly, scholars have given a direct improvement strategy, that is, the functionalization of graphene nanoplates, to enhance compatibility between graphene materials and a variety of polymers .…”

“…18,19 Graphene nanoplate materials are typical 2D plate-like materials with a high aspect ratio, good modulus, and heat conductivity; thus, it is used as reinforcement and conductive filler for polymer composites. [20][21][22] Commonly, scholars have given a direct improvement strategy, that is, the functionalization of graphene nanoplates, to enhance compatibility between graphene materials and a variety of polymers. [23][24][25] Schvezov et al 26 blended PLA, thermoplastic cassava starch (TPCS), and functionalized graphene (GRH) by the reactive extruding process to obtain ternary PLA-g-TPCS-GRH composite, which exhibited better toughness compared with neat PLA.…”