Chemistry

Reacting to the HIPE

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Science  28 Nov 2008:
Vol. 322, Issue 5906, pp. 1304-1305
DOI: 10.1126/science.322.5906.1304c

Emulsions, such as salad dressing, consist of two immiscible liquids that are blended together to form droplets of one liquid suspended in the other. Emulsifiers and stabilizers can be added to prevent the droplets from coalescing, and when the dispersed phase occupies more than 74% of the volume, the mixture is known as a high internal phase emulsion (HIPE). Gitli and Silverstein prepared HIPEs with styrene or 2-ethylhexyl acrylate monomer in the oil phase and acrylamide monomer in the aqueous phase. The monomers were polymerized and cross-linked to form an interpenetrating porous network, with a structure similar to an open-cell foam. The presence of the acrylamide was found to alter the molecular structure of the hydrophobic polymer. Initiation of the polymerization reactions could be triggered in either the oil or water phases, or at the interphase region, and had a direct impact on the structure and properties of the polymers. For all compositions, it was possible to reversibly swell and dry the polyacrylamide component, and the authors envision that these polymers could be used in biomedical and separation applications. — MSL

Soft Matter 4, 2475 (2008).

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