Fig. 1: Formation and structure of bridged emulsion gels.
a The recruitment of negatively charged SiO2 NPs to the interfaces by PDMS-NH2 occurs on different time scales and depends on the relative concentration of each. These processes can be observed by monitoring the interfacial tension as a function of time for a pendant water drop suspended in a bath of toluene for systems configured with either nothing (gray squares), SiO2 NPs (red rhombuses), PDMS-NH2 (green triangles), or SiO2 NPs + PDMS-NH2 (blue triangles). The concentration of SiO2 NPs in water is 0.5% w/w and the concentration of PDMS-NH2 in toluene is 0.05% w/w. b Schematic showing the formation of bridged emulsion gels by employing the polymers to regulate the NP assembly at the water/oil interfaces. The polymers (PDMS-NH2), and the NPs (negatively charged SiO2 NPs), are dissolved in oil and dispersed in water, respectively. When emulsifying the oil and water phase, a few polymer chains attach to the NPs at the interfaces, gaining the three-phase contact angle of ~45° (with respect to the aqueous phase) of the NPs. These NPs with 45° bridge across droplets’ interfaces and ultimately form an interconnected macroscopic network. c Low-magnification (i) and high-magnification (ii) confocal microscopy images of bridged emulsion gels showing adhesive oil droplets in the continuous aqueous phase as the oil phase is stained with Nile red. [SiO2 NPs] = 4% w/w, [PDMS-NH2] = 3% w/w, water/oil ratio is 5:5 (v/v). d Low-magnification (i) and high-magnification (ii) confocal microscopy images of bridged emulsion gels showing a monolayer of particles bridging numbers of faceted droplets as the particles are tagged with rhodamine B isothiocyanate (RITC). [SiO2 NPs] = 8% w/w, [PDMS-NH2] = 3% w/w, water/oil ratio is 5:5 (v/v). The yellow hexagonal dotted box showing approximate hexagonal packing of the NPs.
