Confocal microscopy and rheology studies of two bijel systems are presented to elucidate relationships between the physicochemical properties of bijels and their ability to be utilized as soft matter templates for materials synthesis. For the first time, the origins of viscoelasticity in these systems are investigated using conventional rheometry and a direct correspondence between the elastic storage modulus, particle loading, and the departure from criticality is observed. Further, the rheological transitions that accompany fluid re‐mixing in bijels are characterized, providing key insights into the synergistic role of interfacial tension and interparticle interactions in mediating their mechanical robustness. Bijels that are predominantly stabilized by interfacial tension are also highly sensitive to gradients in chemical composition and more easily prone to mechanical failure during processing. Despite this increased sensitivity, a modified strategy for processing these more delicate systems is developed and its efficacy is demonstrated by synthesizing a bicontinuous macroporous hydrogel scaffold.

Bijels are non-equilibrium solid-stabilized emulsions with bicontinuous arrangement of the constituent fluid phases. These multiphase materials spontaneously form through arrested spinodal decomposition in mixtures of partially miscible liquids and neutrally wetting colloids. Here, we present a new solidstabilized emulsion with an overall bicontinuous morphology similar to a bijel, but with one continuous phase containing a network of colloid-bridged droplets. This dual morphology is the result of combined spinodal decomposition and nucleation and growth in a binary liquid mixture containing colloidal particles with off-neutral wetting properties and partial affinity for one liquid phase. The rheology of these systems, which we call bridged bijels, is nearly identical to their simple bijel counterparts, with a unique exponential dependence of the zero-shear elastic modulus on the colloid volume fraction. However, partitioning of the colloids between the spinodal surface and the fluid domains delays the onset of structural arrest, providing access to domain sizes much larger than available in simple bijels without loss of mechanical stability. This ability greatly expands the potential technological applications of these unique materials. In addition, our findings reveal new strategies for tuning the rheology of bijels and outline new directions for future fundamental research on this unique class of soft materials.

Bijel processing provides a unique route to energy materials with co-continuous microstructure and tunable electrochemical properties for simultaneous delivery of large power and energy densities.