Solvent Segregation Driven Gel (SeedGel) Formation via Self-assembly of Nanoparticles in Binary Solvents*

Due to the high specific surface area and interconnected channels, bicontinuous structures have found a broad range of applications in energy storage, membrane science, and biomaterials. Here, we report a new type of colloidal gel, solvent segregation driven gel (SeedGel), that successfully stabilizes such bicontinuous channels. SeedGel consists of alternating particle and solvent domains, which is driven by the solvent phase separation using temperature. A model system of nanoparticles in a binary solvent mixture of water/ 2,6-lutidine is used to demonstrate the formation of the SeedGel. Interestingly, the binary solvent also leads to bicontinuous structures with water (particles favor) enriched in the particle domain. Excellent thermo-reversibility and structure reproducibility over multi-length scales are confirmed by the studies using ultra-small angle neutron scattering (USANS) and small-angle neutron scattering (SANS). Ramping rate is shown to accurately control the channel width of the bicontinuous domains. Different binary solvents can be used to adjust the gelation temperature of SeedGel, making it adaptable for various applications over a wide temperature range. And the refractive index of these domains can also be manipulated by controlling the partition of the solvents in different domains to gain interesting optical properties.