Porous Polymer Monoliths by Emulsion Templating

Abstract

Porous polymer monoliths (PPM) are an increasingly important and popular class of materials finding applications in fields such as separation, purification, cell and tissue culturing, storage of liquids and gases, energy storage, structural applications, supports for catalysts and reagents, etc. In contrast to particulate polymer material, monoliths are defined as intractable articles with a homogeneous microstructure. While the method of preparation and the chemical composition largely govern the resulting porous structure, the porous monoliths can be characterized by their pore size profile (micro‐, meso‐, macroporous material), morphology (interconnected or isolated pores, shape of pores), total porosity (pore volume), surface area, and special features, for example, hierarchical porous structure. Meso‐ and micropores mainly contribute to the total surface area of the monolith, whereas macropores, if interconnected, enable the convective mass transfer through the monolith and reduce the overall density of the material. Obtaining PPM with a multimodal pore size distribution is possible via a combination of methods or by a postpolymerization treatment. This is a useful feature allowing the production of materials with tailored porous structure for specific applications where macro‐ and micropores are needed. Generally, the methods for PPM preparation can be divided between templating (two phases are present during the preparation, of which one templates the porosity) and nontemplating (one phase system, eg, phase separation induces pores). This paper introduces the various methods and focuses on the emulsion templating approach. Recently introduced chemistries and combinations of methods as well as new examples of applications are highlighted.

Fundamentals and Design‐Led Synthesis of Emulsion‐Templated Porous Materials for Environmental Applications

“…The reactions in emulsion templating generally take place within the external phase, whereas the reactions normally begins with monomers solubilized within surfactant micelles and polymerization continues within the monomer‐swollen polymer NPs in the case of emulsion polymerization and at the oil–water interface in the microencapsulation systems. [ 29 , 81 ]…”

Surface Modification of Hypercrosslinked Vinylbenzyl Chloride PolyHIPEs by Grafting via RAFT

“…Macroporous polyHIPE (poly high internal phase emulsions) materials are prepared by the polymerization of monomer containing continuous phase of the emulsion with volume fraction of droplet phase more than 74 vol% and can reach up to 99 vol% still having acceptable mechanical properties. [ 16,17 ] PolyHIPEs have interconnected cellular open porous structure, and are thus useful for a wide variety of applications such as columns in separation systems, [ 18–20 ] solid phase synthesis supports, [ 21–24 ] as scaffold in tissue engineering. [ 25–28 ] In order to induce meso‐ and micropores into a polyHIPE material, post polymerization process of hypercrosslinking can be used.…”

Influence of Functional Group Concentration on Hypercrosslinking of Poly(vinylbenzyl chloride) PolyHIPEs: Upgrading Macroporosity with Nanoporosity

“…On the other hand, macroporous polymers in monolithic form can be obtained by the polymerisation of a continuous phase of high internal phase emulsion (polyHIPE) [ 25 , 26 , 27 , 28 ]. The internal (or droplet) phase is dispersed in the continuous phase of the emulsion and represents at least 74.05% of the total volume of the emulsion in the uniform packing of monodispersed droplets, or 64% in the case of random packing [ 29 ].…”