Recently, a series of new monomers and polymerization mechanisms has been applied to the templating of high internal phase emulsions (HIPEs) providing a route to hierarchically porous materials with a range of functionalities and applications. The high degree of control over the pore size is another attractive feature of these materials. Usually, the continuous phase contains monomers, the droplet phase is used to template the large, primary pores, which are interconnected by secondary pores. The addition of nonpolymerizable components to the continuous phase can result in phase separation during polymerization and tertiary pores. Applications include polymer supports for catalysis and synthesis, separation and filtration, cell culture media, enzyme supports, and structural and isolation applications.
Summary: An oil‐in‐water high internal phase emulsion consisting of acrylic acid, water, and a crosslinker (N,N′‐methylene bisacrylamide) as the water phase, and toluene as the oil phase was successfully stabilised to sustain thermal initiation of radical polymerisation resulting in porous open‐cellular monolithic material. The type of initiator used influenced the average pore size ranging from approx. 708 nm to approx. 1 087 nm, as determined by mercury porosimetry.Schematic of the preparation of an oil‐in‐water‐type polyHIPE (high internal phase emulsion).imageSchematic of the preparation of an oil‐in‐water‐type polyHIPE (high internal phase emulsion).
Monolithic polymer supports and scavengers were prepared via nucleophilic displacement of chlorine in poly(4-vinylbenzyl chloride-codivinylbenzene) PolyHIPE materials. Reactions of monolithic PolyHIPE with tris(2-aminoethyl)amine, 4-aminobutanol, tris(hydroxymethyl)aminomethane, morpholine, and hexamethylenetetramine led to functionalized polymers with amino and hydroxy functionalities with high degrees of conversion. 4-Chlorobenzoyl chloride was efficiently and rapidly scavenged from solution by the tris(2-aminoethyl)amine derivative of monolithic poly(4-vinylbenzyl chloride-co-divinylbenzene) PolyHIPE at ambient temperature.
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