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Graphene’s Insolubility Drives Materials Synthesis

Method exploits pristine graphene’s knack for stabilizing interface between immiscible liquids

by Mitch Jacoby
February 2, 2015 | A version of this story appeared in Volume 93, Issue 5

Pristine graphene’s insolubility in both water and common organic solvents limits its use in applications. Researchers often bypass that problem by using oxidized and other chemically altered forms of graphene. But altering graphene generally degrades its properties. So rather than working around the insolubility, University of Connecticut polymer chemists Steven J. Woltornist and Douglas H. Adamson and coworkers exploited it to devise a simple, low-cost method for making new kinds of materials. The team used graphene as a surfactant to stabilize water-in-oil emulsions, capitalizing on its attraction to the interface between water and organic phases. They used the emulsions as templates for synthesizing graphene/polymer foams (Macromolecules 2015, DOI: 10.1021/ma5024236). The composites are lightweight, strong, and electrically conductive, making them candidates for use as construction materials, supercapacitor electrodes, and catalyst supports. The team explains that when graphene is added to a mixture of immiscible liquids such as water and styrene or other monomers, graphene sheets become trapped and spread along the interface, lowering the interfacial surface energy. The sheets stabilize water-monomer emulsions by forming a thin skin around the water droplets. Gentle heating polymerizes the monomer and removes the water, forming rigid foams.

Three sizes of charcoal-grey foam cylinders (left) and a micrograph of the material’s structure.
Credit: Macromolecules
Graphene stabilizes the water-in-monomer emulsions used for making the polymer foams shown here (left, with U.S. quarter shown for scale; right, a magnified cross section).


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