PolyHIPEs — Porous Polymers from High Internal Phase Emulsions

Abstract

A large variety of porous polymers, generally known as polyHIPEs, have been synthesized using high internal phase emulsions (HIPEs) as templates for the porous structure. HIPEs are formed by mixing two immiscible liquids in the presence of an emulsifier, usually a surfactant, such that the internal phase content is more than 74 %. PolyHIPE are synthesized through the polymerization of monomers in the external phase. The internal phase can be evacuated through holes that develop in the polymer walls, yielding a porous polymer. Hydrophobic polymers can be synthesized within water‐in‐oil emulsions and hydrophilic polymers can be synthesized within oil‐in‐water emulsions. The types of materials synthesized include copolymers, interpenetrating polymer networks, biodegradable materials, organic‐inorganic hybrids that can be pyrolyzed to porous inorganics, nanocomposites, and hydrophobic‐hydrophilic bicontinuous polymers. The large number of methods available to functionalize polyHIPEs have enhanced their utility for such applications as chemical synthesis, chromatography, ion exchange, separation, sensing, tissue engineering, and controlled drug delivery, to name but a few. This article describes HIPE formation and stability, polyHIPE synthesis and functionalization, polyHIPE morphology, polyHIPE properties, a variety of different polyHIPE‐based materials, and polyHIPE applications.

Water swellable rubber composites: An update review from preparation to properties

“…A schematic mechanism of interpenetrating polymer networks. 38 [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] REVIEW WILEYONLINELIBRARY.COM/APP particles with sizes of approximately 50-60 nm of into polyimide matrices shown by SEM.…”

Macroporous hydrogel formed by high internal phase emulsion-templating and their applications in tissue engineering

“…With sufficient surfactant and polymerization in the continuous phase, the high porosity and high degree of pore interconnectivity of the poly(merized)HIPEs is hence caused by this high internal phase close packing feature. Myriad of different polyHIPEs were created [12][13][14][15][16]. The most widely studied monomer systems used for the synthesis of polyHIPEs since the advent of polyHIPEs are styrene (St) and divinylbenzene (DVB) used in or as the continuous oil phase [12,194], but have since diversified to include many other monomers and/or prepolymers.…”

“…To overcome these challenges, the method of high internal phase emulsion (HIPE) templating is identified as an effective and facile way to create tailormade very high porosity, interconnected macroporous polymer foam [12][13][14][15][16].…”

“…High internal phase emulsion (HIPE) templating is a relatively facile method of fabricating porous polymers by exploiting the immiscibility of hydrophobic and hydrophilic liquids in the formation of an emulsion [14,16,182]. Porous polymers can be formed from emulsion templates by subsequently polymerizing or solidifying the continuous but minority emulsion phase followed by the removal of the liquid templating phase.…”

“…However, most of the methods to date involve polymerization to solidify the continuous phase and large amount of surfactant(s) for the stabilization of the HIPE [13][14]244]. In tissue engineering applications, the use of surfactants poses a challenge because it is difficult to be completely removed and can potentially contaminate the foams produced.…”