Alexander Bismarck, Imperial College London, UK, and colleagues have developed a closed-cell elastomer polymer that expands to many times its original volume in a vacuum. This polymer could instantly stop leaks in airplane fuel tanks, passenger cabins, or other containers that operate in a reduced-pressure environment.

The researchers started with silicone oil, hardener, surfactant, and an aqueous solution of sodium hydrogen carbonate. They heated the mixture briefly to decrease its viscosity, agitated it to produce an emulsion, and cured it at room temperature for 48 hours. The resulting closed-cell polymer contained pockets of the NaHCO₃ solution.

Heating the polymer decomposed the NaHCO₃ to Na₂CO₃, water vapor, and carbon dioxide. Placing polymer monoliths under vacuum caused them to expand as much as an order of magnitude. The monoliths returned to their original size under ambient pressure.

The team placed a film of this polymer between two aluminum sheets and expanded it to plug a hole in the metal. They note that replacing the aqueous solution in the pores with supercritical CO₂ could produce a polymer emulsion that expands at atmospheric pressure.

• Inflatable Elastomeric Macroporous Polymers Synthesized from Medium Internal Phase Emulsion Templates,
  Michael Tebboth, Qixiang Jiang, Andreas Kogelbauer, Alexander Bismarck,
  ACS Appl. Mater. Interfaces 2015.
  DOI: 10.1021/acsami.5b05123