(239d) Dynamics and Rheology Characterization of Solvent Segregation Driven Gel (SeedGel)

Arresting bicontinuous structures has been an important research topic in the fields of both soft matter physics and materials science. Recently, a new type of colloidal gel, solvent segregation driven gel (SeedGel), was observed to effectively stabilize spinodal decomposition and form interconnected bicontinuous channels. In SeedGel systems, small colloidal particles dispersed in a binary solvent can form thermoreversible gels by jamming particles in one domain that is rich with one component of the binary solvent. As the applications of the SeedGel depends on its mechanical property, it was investigated along with the dynamics in a model SeedGel system by rheology and X-ray photon correlation spectroscopy (XPCS). For a SeedGel system, temperature serves as a key knob to effectively change the dynamics, static structure, and rheology of the sample. The storage moduli are found to be highly reversible and exhibit strong temperature dependence. A maximum value of the storage modulus is observed at around 30 ËšC in this model system. Above or below this temperature, the storage modulus decreases. The results of our XPCS experiments clearly indicate that the formation of the SeedGel is driven by the glass transition in the particle domains. The nonergodicity parameter, relaxation time, and stretch exponent are extrapolated from the experimental data at different temperatures, which provides more quantitative description of the dynamics at different length scales. The relaxation time shows a q^-1 dependence, which is attributed to internal stress within a heterogeneous colloidal gel. XPCS measurements also reveal a transition from sub-diffusion to hyper-diffusion when SeedGel is heated up.