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Viterbi Research Opens Doors for New Harmful Gas Capture Technology

Robust plastic shells for hard-to-handle ionic liquids show promise for environmental and energy applications
Eric Mankin
September 20, 2012 —

Ionic liquids (ILs) are salts that are liquids at room temperature. The global scientific community is very interested in ILs as environmentally-friendly alternatives to organic solvents because ILs are non-volatile, non-flammable and recyclable. ILs have uses in a wide range of applications such as biofuels, energy storage and carbon dioxide absorption. For example, ILs have been shown to absorb harmful gases such as carbon dioxide and sulfur dioxide. Malancha Gupta’s laboratory at the USC Viterbi School of Engineering is currently addressing a variety of environmental and energy concerns by developing methods to encapsulate ILs within robust composites and polymer shells.

Malancha Gupta:
A recent paper published by Professor Gupta and Laura Bradley in Langmuir  demonstrates a method for encapsulating dozens of millimeter-sized IL droplets at once within robust polymer shells. Small IL droplets are rolled around in a Petri dish containing micron-sized hydrophobic particles in order to form structures called liquid marbles. The next step is to deposit a polymer shell onto the outer surface of the marbles using a vacuum processing technique called initiated chemical vapor deposition (iCVD). Several polymer compositions were tested. A highly connected polymer network containing fluorine moieties proved superior, creating a shell strong enough to survive being dropped onto a water bath and stacked into pyramids. Future work involves creating still smaller mini-marbles, which would increase the surface area available for absorption applications.

This work builds on two earlier papers [paper 1] [paper 2] published in Macromolecules. The iCVD process is traditionally used to modify solid surfaces such as membranes and fibers with polymer coatings. Liquids are generally difficult to place into vacuum systems because they evaporate too fast. Because ILs have extremely low vapor pressures, the Gupta lab is able to introduce these liquids into the iCVD system. The findings are quite exciting; nanoparticles, films, and core-shell particles can be made by tuning reaction conditions and the surface tension of the ILs. The resulting polymeric materials exhibit a wide range of functional properties such as hydrophobicity, hydrophilicity, conductivity, and responsiveness to heat, pH, and light.

Another promising direction of Professor Gupta’s research is creating polymer/IL composite substances that can be used as more efficient battery and fuel cell components. Gupta, an assistant professor in the Viterbi School's Mork Family Department of Chemical Engineering and Materials Science, recently received an American Chemical Society Petroleum Research Fund Doctoral New Investigator award to make such composites which combine the high ion conductivity of ionic liquids and the mechanical properties of polymers.