Synthesis of Hierarchically Porous Materials From Bicontinuous Interfacially Jammed Emulsion Gels (Bijels)

Materials possessing hierarchical porosity across the nanometer and micrometer scales are of value in several emerging technologies such as catalysis, separations, tissue engineering, and electrochemical systems, to name a few. In an effort to further both the breadth of applications and the performance of these types of materials, robust methods for their synthesis with tunable chemistry and pore sizes are needed. The ability to prescribe the size separation between large and small pore networks may provide an additional avenue for optimization. In this work, a novel family of macroporous and hierarchically porous materials are synthesized from bicontinuous interfacially jammed emulsion gels (bijels), which are a recent class of soft materials formed by arrested spinodal decomposition of partially miscible fluids by neutrally wetting colloids. Through selective polymerization of one fluid phase, a fluid-fluid bijel is transformed into a crosslinked polymer template, which provides a versatile platform for synthesis of several types of porous materials, including ceramics and metals. All the materials share a 3D bicontinuous, spinodal-like morphology, inherent to their bijel parent. Processing of materials through nanocasting is of particular utility here, and allows for tuning of hierarchical pores over several orders of magnitude, from tens of nanometers to over a hundred microns. Application of these novel microstructures in several emerging fields, including tissue engineering and electrochemical systems, will be discussed.