Synthesis of porous emulsion-templated polymers using high internal phase CO2-in-water emulsions

Highly porous emulsion-templated materials were synthesized by polymerization of concentrated CO2-in-water (C/W) emulsions. The method does not use any organic solvents, in either the synthesis or purification steps, and no solvent residues are left in the materials. It was found that the emulsion stability is strongly affected both by the nature of the surfactant and by the viscosity of the aqueous continuous phase. By optimizing these parameters, it was possible to generate a highly porous, low-density polyacrylamide material with a pore volume of 5.22 cm(3)/g, an average pore diameter of 9.72 mum, and a bulk density of 0.14 g/cm(3). We have broadened the scope of this approach significantly by identifying inexpensive hydrocarbon surfactants to stabilize the C/W emulsions (e.g., Tween 40) and by developing redox initiation routes that allow the synthesis to be carried out at modest temperatures and pressures (20 degreesC, 65 bar). We have also extended the method to the polymerization of monomers such as hydroxyethyl acrylate, which suggests that it is possible to prepare a range of solvent-free biomaterials by this route.