Temperature-Dependent Gelation Process in Colloidal Dispersions by Diffusing Wave Spectroscopy

Abstract

Temperature-dependent microrheology of a concentrated charge-stabilized poly(methyl methacrylate) colloidal dispersion with different salt concentrations was investigated by diffusing wave spectroscopy in backscattering mode. The critical temperature where the system undergoes aggregation and gelation depends upon the particle volume fraction or salt concentration. The viscoelastic properties of the systems have been discussed using Maxwell and Kelvin-Voigt models. Temperature-dependent crossover (G' = G″) frequency has been used to calculate activation energies representing a critical energy of interaction of gel formation.

Introducing Diffusing Wave Spectroscopy as a Process Analytical Tool for Pharmaceutical Emulsion Manufacturing

“…Therefore, the use of DWS allowed to identify a second crossover at high frequencies for all emulsions, where G′′ prevailed over G′ . This second crossover has been previously observed and it reflects the short‐time relaxation and dissipation mechanisms in the system …”

“…This second crossover has been previously observed 42,50 and it reflects the short-time relaxation and dissipation mechanisms in the system. 51 The results indicate that the xanthan-containing emulsions were viscoelastic, with a liquid-like behavior at very low frequencies, a gel-like structure at higher frequencies, and again a dissipation dominated behavior at very high frequencies.…”

Phase Behavior of Aqueous Suspension of Laponite: New Insights with Microscopic Evidence

“…For a gelation process, E for variety of chemically gel forming polymeric systems have been reported to be in between 40 to 100 kJ/mol. 58,59,60 Figure 2(b) suggests that, over an explored range, dependences of g t on L C and S C is given by:…”

Crack formation and prevention in colloidal drops

“…To verify the onset of gelation in the suspensions containing PS polymer, light scattering experiments were conducted. Diffusing wave spectroscopy (DWS) experiments were performed to examine the changes of the autocorrelation functions of the interacting particles, given by , where I ( t ) is the light intensity and denotes the ensemble averaging 43 44 . Figure 5 shows the intensity autocorrelation function, g 2 ( τ ) − 1, for varying polymer concentrations.…”