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.
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.
more » « less- NSF-PAR ID:
- 10033785
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 29
- Issue:
- 18
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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