Bijel reinforcement by droplet bridging: a route to bicontinuous materials with large domains

Abstract

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.

Microstructural tunability of co-continuous bijel-derived electrodes to provide high energy and power densities

“…2 for denition), is directly related to the internal surface area per unit volume, S v , and can be tuned through the colloid volume fraction and wetting properties. 17 Through post-processing techniques recently pioneered in our laboratory, these so materials can be converted into macroporous and hierarchically porous metals, ceramics, and polymers with tunable pore size distributions. [18][19][20][21] Building on these developments, here we demonstrate the use of bijels as so matter templates for the synthesis of three-dimensional, co-continuous composite electrodes for electrochemical energy storage and conversion.…”

Particle-size effects in the formation of bicontinuous Pickering emulsions

“…the formation of new droplets during spinodal decomposition, was not observed in the above-mentioned simulations [5,28,30], presumably because the quench was instantaneous [27]. Secondary nucleation during bijel formation has previously been observed in experiments and attributed to the finite rate of temperature change [6,27].…”

“…Note that we have also observed droplet formation via secondary phase separation (Appendix B), but this does not seem to be a pivotal effect, i.e. it can both happen and fail to happen irrespective of bijel formation failing or succeeding [6,19,26,27]. This suggests that MPs fail to produce bijels via slow heating, because depercolation via pinch- off events occurs before the interfacial particles jam and lock-in the bicontinuous structure.…”

“…. Note that droplets have appeared, presumably due to secondary nucleation, which has previously been observed during slow quenches [6,27]. Scale bars: 100 µm.…”

“…(D20) can explain several observations. First, the larger L f , the longer the jamming time, which may help explain the empirical upper limit to bijel channel width [27]. Secondly, the larger the coarsening speed v L , the shorter the jamming time.…”