PolyHIPEs

PolyHIPEs are polymer foams produced by polymerizing the continuous phase of high internal phase emulsions (HIPEs) and then removing the internal phase. The HIPE typically contains a very high volume fraction of internal phase (often 74% or more), yielding materials with high porosity (often 70-95%) and interconnected macropores.

The external phase contains monomers or oligomers, a crosslinker, surfactant to stabilize droplets, and an initiator. After emulsification, polymerization fixes the structure around the internal droplets; removal of the internal phase leaves voids that become pores in the solid. Emulsions are typically water-in-oil, though oil-in-water HIPEs are used for certain systems.

Pore sizes are tunable from sub-micrometer to tens or hundreds of micrometers by adjusting emulsification, surfactant type, phase ratios, and polymerization conditions; the pores are typically open-cell and highly interconnected.

PolyHIPEs offer high porosity and surface area, low density, and tunable mechanical properties. Chemical functionality can be introduced by selecting monomers or performing post-polymerization modification.

Applications include tissue engineering scaffolds, adsorption and separation media, catalyst supports, drug delivery, sensors, and energy storage. The materials are often customized by changing monomer chemistry, porogen removal method, and post-synthesis surface treatment.