Polymerized high internal phase emulsions containing a porogen: Specific surface area and sorption

Highly porous, open-cell polymers [poly(HIPE)] were prepared by polymerizing the monomers in the continuous phase (∼ 10%) of high internal phase emulsions (HIPE). This paper discusses using poly(HIPE) to remove bromoform from an aqueous solution through sorption, a combination of adsorption and absorption. The crosslinked polystyrene (xPS) and crosslinked poly(ethylhexyl acrylate) (xPEHA) had cell diameters from 1.5 to 15 μm, intercellular pore diameters from 0.3 to 1.5 μm, and densities of about 0.10 g/cc. The specific surface area of the glassy xPS increased from 7.9 to 28.8 m²/g on extraction in methanol, most likely due to crazing. The use of a toluene porogen in the xPS (xPS-T) reduced the density to 0.05 g/cc and yielded a rough surface with nanoscale porosity and a specific surface area of 132 m²/g. xPS and xPEHA, with very different molecular structures but with similar specific surface areas, exhibited similar sorption behavior. Extraction produced increases in the xPS and xPS-T sorption plateaus and sorption capacities. For larger specific surface areas, the sorption at low concentrations was relatively independent of concentration, indicating a case of adsorption with the sites occupied. For all the other cases, absorption seems to dominate and sorption is more strongly dependent upon concentration. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2233–2239, 2004