Emulsion templated bicontinuous hydrophobic-hydrophilic polymers: Loading and release

Water absorption is often poor in hydrophobic polyHIPEs, porous polymers synthesized within high internal phase emulsions (HIPEs). This paper describes bicontinuous polyHIPEs, the simultaneous polymerization of hydrophobic monomers (external phase) and hydrophilic monomers (internal phase). Integrating hydrogels within polyHIPEs extended the release of water-soluble dye from 10 h to more than 10 days. PolyHIPE capillary action promoted the rapid distribution of water throughout the hydrogel. The diffusion pathway in this bicontinuous system was similar to diffusion through an assembly of polydisperse spheres. The copolymerization of the hydrophilic monomers with the monomers in the external phase enhanced the hydrophilicity of the scaffold, reduced the modulus of the hydrated polyHIPE, and reduced the tortuosity of the diffusion path. Pre-polymerization of the external phase reduced the extent of copolymerization, enhanced the modulus, sealed the interconnecting holes, reduced the capillary action, increased the tortuosity, and extended the release time to 3 weeks.