UC Irvine

Bicontinuous interfacially jammed emulsion gels, or bijels, is a class of soft material uniquely characterized by its co-continuous and interpenetrating fluid domains. These novel materials are formed by jamming nano-scale colloidal particles at the interface between two fluids undergoing spinodal decomposition. As such, the internal microstructure of the resulting bijel bears a striking resemblance to the morphology of spinodal decomposition. This unique morphology exhibits attractive transport potentials that are desired in the development of functional porous materials such as bio-implants, electrochemical devices, catalytic devices, separation membranes, and structural supports. However, there is a lack of understanding of the mechanisms that impart stability in bijels, which significantly limits the large-scale production of bijels and their derivatives. To this end, I have performed extensive rheological characterizations to examine the roles of particles and the interface within bijels to elucidate the origin of mechanical stability. First, by testing bijels at different temperatures and particle volume fractions, it was revealed that interfacial jamming alone is sufficient to impart stability in bijels. Second, bijels were deformed near their yield limits to explore the connection between particle jamming and the continuous interface which percolates the sample. In the transition to yielding, bijels uniquely exhibit a self-rejuvenating quality where shear-induced stretching of the interface is reversible by interfacial compaction. Incorporating approximate particle dynamics under dilute conditions into a simple rheological model produces stress responses that closely mimic the nonlinear rheological response measured from bijels. Lastly, I have developed a bijel templating method that bypasses a significant limiting factor of existing protocols, specifically the addition of monomer to bijels which disrupts the stability of the particle-laden interface. Bijel templating was simplified by forming bijels using partially miscible mixtures of solvent and monomer and directly polymerizing them into porous polymeric scaffolds for further processing. My results provide insights into the fundamental physics of bijels and pave ways for mass production of bijel-derivatives.