Rapid production of bicontinuous macroporous materials using intrinsically polymerizable bijels

Abstract

The discovery of bicontinuous interfacially jammed emulsion gels (bijels) in 2007 motivated the development of processing techniques to harness their unique morphological attributes in applications such as electrochemical energy storage and conversion, catalysis, and regenerative biomaterials. These techniques are primarily based on selective polymerization of one phase, and subsequent chemical processing of the resultant scaffold into porous, micro-architectured materials. A significant limitation of these protocols is the need to transport polymer precursors into one of the fluid phases after bijel formation, a time-consuming step that can also impose disruptive gravitational and interfacial stresses, sometimes causing a complete breakdown of the bijel backbone. Here, we introduce a class of intrinsically polymerizable bijels (IPBs) comprising partially miscible mixtures of solvent and poly(ethylene glycol) precursor, which can be directly transformed into bijel-templated materials (BTMs), completely bypassing the precursor transport step and relaxing the associated limitations of previous protocols. To achieve selective polymerization, we incorporated into the mixture a common fluorescent dye, sodium fluorescein, which had strong affinity for the monomer-poor phase. Spectrophotometry experiments demonstrated a local photon quenching effect due to the fluorescent dye, which in turn curtailed activation of the photoinitiator and thus prevented polymerization in the monomer-poor phase. We establish the generality of our approach by using different monomers and monomer blends, and demonstrate how this modularity enables tuning of the mechanical properties of BTMs, measured by flexural testing. Our protocol establishes a scalable and efficient platform for producing BTMs, paving the way for their protential applications in emerging technologies.