Anisotropic and heterogeneous dynamics in an aging colloidal gel

Abstract

We investigate the out-of-equilibrium dynamics of a colloidal gel obtained by quenching a suspension of soft polymer-coated gold nanoparticles close to and below its gelation point using X-ray Photon Correlation Spectroscopy (XPCS).

Microscopic Dynamics of Liquid-Liquid Phase Separation and Domain Coarsening in a Protein Solution Revealed by X-Ray Photon Correlation Spectroscopy

“…Our results clearly show that the coarsening dynamics of the protein droplets at this length scale are not governed by Brownian dynamics but instead by a ballistic and partially cooperative motion of the protein droplets driven by the spinodal decomposition. Similar super diffusive ballistic types of dynamics have been observed frequently in soft matter systems, e.g., in the late stage of colloidal gelation processes [52][53][54], during spinodal decomposition of colloidal systems [27], and in the framework of MD simulations of metallic glasses [55] with strongly interconnected clusters moving together. Phenomenological models of single microcollapse events PHYSICAL REVIEW LETTERS 126, 138004 (2021)…”

From Femtoseconds to Hours—Measuring Dynamics over 18 Orders of Magnitude with Coherent X-rays

“…As introduced above, the use of higher-order correlation functions reveals non-equilibrium processes by accessing the age-dependence of the relaxation time in real-time experiments. Dynamical heterogeneities are particularly present in gels [47,104,105], elastomers [106], in glasses and close to the glass transition [29,[107][108][109][110], as well as reported recently during liquid-liquid separations in dense protein dispersions [39]. Here, we want to highlight few recent examples.…”

“…Recently, thanks to the increased detector performance and coherent flux, direction-dependent structural heterogeneities could be accessed for different samples, calculated from fractions of pixels. Jain et al studied the aging of a colloidal gel after quenching it close to and below the gelation point [105]. Stress-induced microcollapses were found to couple with cooperative rearrangements on larger scales, as indicated by dynamical heterogeneities at small q.…”

“…Many studies on dynamics in gels and during gelation revealed a reduction of the experimental speckle contrast [105,122,123]. This indicates that a faster dynamic process appears during gelation that falls outside the accessible time scale of the detector.…”

20 µs-resolved high-throughput X-ray photon correlation spectroscopy on a 500k pixel detector enabled by data-management workflow

“…Area detectors allow multiple intensity-time series to be measured simultaneously, improving the equilibrium g 2 SNR by (N p ) 1/2 , while also providing concurrent measurements of the Q dependence of g 2 , thereby improving the efficiency of measurements. In the case of two-time measurements where the dynamics evolve over time (Fluerasu et al, 2005;Madsen et al, 2010;Das et al, 2019;Mokhtarzadeh et al, 2019;Hoshino et al, 2020;Jain et al, 2020), the SNR does not improve by increasing N f since the correlation is calculated between two frames, making the large N p provided by an area detector the only way to maintain the SNR of the correlation without sacrificing the time resolution indicated by t e .…”