Regulated Silica Deposition for Porosity Control and Mechanical Enhancement of Bijels

Bicontinuous particle-stabilized emulsions (bijels) are unique soft materials in which two immiscible liquids form an interwoven structure stabilized by colloidal particles at the interface. Their bicontinuous morphology increases the interfacial area between immiscible liquid phases, making them attractive for applications such as catalysis and energy storage. However, their mechanical fragility limits practical use. In this chapter, we enhance bijel robustness by depositing silica to fuse interfacial particles. We investigate a series of tetraalkoxysilanes with varying alkyl groups (methyl, ethyl, 1-propyl or 1-butyl), exhibiting decreasing reactivity. Using shorter alkyl-chain silanes and higher concentrations, we shorten the reinforcement reaction from one day to 1.5 hours. High-resolution scanning electron microscopy and small angle X-ray scattering reveal that silica deposits directionally into the aqueous domains of the bijel. Moreover, the extent of silica growth can be tailored from selectively coating interfacial particles to complete filling the aqueous channels. These findings demonstrate how the extent of silica deposition in bijels can be controlled, offering a versatile route to fabricate robust bicontinuous materials for future applications.