Correlations of structure and dynamics in an aging colloidal glass (original) (raw)
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Invariance of Structure in an Aging Colloidal Glass
AIP Conference Proceedings, 2006
We study concentrated colloidal suspensions, a model system which has a glass transition. The non-equilibrium nature of the glassy state is most clearly highlighted by aging-the dependence of the system's properties on the time elapsed since vitrification. Fast laser scanning confocal microscopy allows us to image a colloidal glass and track the particles in three dimensions. We analyze the static structure in terms of tetrahedral packing. We find that while the aging of the suspension clearly affects its dynamics, none of the geometrical quantities associated with tetrahedra change with age.
Weeks: Invariance of Structure in an Aging Colloidal Glass
2020
Abstract. We study concentrated colloidal suspensions, a model system which has a glass transition. The non-equilibrium nature of the glassy state is most clearly highlighted by aging -the dependence of the system's properties on the time elapsed since vitrification. Fast laser scanning confocal microscopy allows us to image a colloidal glass and track the particles in three dimensions. We analyze the static structure in terms of tetrahedral packing. We find that while the aging of the suspension clearly affects its dynamics, none of the geometrical quantities associated with tetrahedra change with age.
Dynamics and structure of an aging binary colloidal glass
2008
We study aging in a colloidal suspension consisting of micron-sized particles in a liquid. This system is made glassy by increasing the particle concentration. We observe samples composed of particles of two sizes, with a size ratio of 1 : 2.1 and a volume fraction ratio 1 : 6, using fast laser scanning confocal microscopy. This technique yields real-time, three-dimensional movies deep inside the colloidal glass. Specifically, we look at how the size, motion and structural organization of the particles relate to the overall aging of the glass. Particles move in spatially heterogeneous cooperative groups. These mobile regions tend to be richer in small particles, and these small particles facilitate the motion of nearby particles of both sizes.
Aging dynamics in a colloidal glass
Physical Review E, 2001
The aging dynamics of colloidal suspensions of Laponite, a synthetic clay, is investigated using dynamic light stattering (DLS) and viscometry after a quench into the glassy phase. DLS allows to follow the diffusion of Laponite particles and reveals that there are two modes of relaxation. The fast mode corresponds to a rapid diffusion of particles within "cages" formed by the neighboring particles. The slow mode corresponds to escape from the cages: its average relaxation time increases exponentially fast with the age of the glass. In addition, the slow mode has a broad distribution of relaxation times, its distribution becoming larger as the system ages. Measuring the concomitant increase of viscosity as the system ages, we can relate the slowing down of the particle dynamics to the viscosity.
Direct visualization of ageing in colloidal glasses
2003
We use confocal microscopy to directly visualize the dynamics of ageing colloidal glasses. We prepare a colloidal suspension at high density, a simple model system that shares many properties with other glasses, and initiate experiments by stirring the sample. We follow the motion of several thousand colloidal particles after the stirring and observe that their motion significantly slows as the sample ages. The ageing is both spatially and temporally heterogeneous. Furthermore, while the characteristic relaxation timescale grows with the age of the sample, nontrivial particle motions continue to occur on all timescales.
Aging behavior of the localization length in a colloidal glass
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
The localization length r loc associated with a fast secondary relaxation in glassy Laponite is determined by X-ray photon correlation spectroscopy (XPCS) through a Debye-Waller fit of the non-ergodicity parameter. Quantitative differences are observed between the time dependence (aging) of r loc in spontaneously aged and rejuvenated samples. This behavior is also reflected in the calculated shear modulus which matches well with data obtained by rheological measurements. (R. Angelini).
Physical review. E, 2016
Three important kinetic phenomena have been cataloged by Kovacs in the investigation of molecular glasses during structural recovery or physical aging. These are responses to temperature-jump histories referred to as intrinsic isotherms, asymmetry of approach, and memory effect. Here we use a thermosensitive polystyrene-poly (N-isopropylacrylamide)-poly (acrylic acid) core-shell particle-based dispersion as a colloidal model and by working at a constant number concentration of particles we use temperature changes to create volume-fraction changes. This imposes conditions similar to those defined by Kovacs on the colloidal system. We use creep experiments to probe the physical aging and structural recovery behavior of colloidal glasses in the Kovacs-type histories and compare the results with those seen in molecular glasses. We find that there are similarities in aging dynamics between molecular glasses and colloidal glasses, but differences also persist. For the intrinsic isotherms,...
Structural and microscopic relaxations in a colloidal glass
Soft Matter, 2015
The aging dynamics of a colloidal glass has been studied by multiangle dynamic light scattering, neutron spin echo, X-ray photon correlation spectroscopy and molecular dynamics simulations. The two relaxation processes, microscopic (fast) and structural (slow), have been investigated in an unprecedentedly wide range of time and length scales covering both ergodic and nonergodic regimes. The microscopic relaxation time remains diffusive at all length scales across the glass transition scaling with wavevector Q as Q À2. The length-scale dependence of structural relaxation time changes from diffusive, characterized by a Q À2-dependence in the early stages of aging, to a Q À1-dependence in the full aging regime which marks a discontinuous hopping dynamics. Both regimes are associated with a stretched behaviour of the correlation functions. We expect these findings to provide a general description of both relaxations across the glass transition.
The physics of the colloidal glass transition
2012
As one increases the concentration of a colloidal suspension, the system exhibits a dramatic increase in viscosity. Beyond a certain concentration, the system is said to be a colloidal glass; structurally, the system resembles a liquid, yet motions within the suspension are slow enough that it can be considered essentially frozen. For several decades, colloids have served as a valuable model system for understanding the glass transition in molecular systems. The spatial and temporal scales involved allow these systems to be studied by a wide variety of experimental techniques. The focus of this review is the current state of understanding of the colloidal glass transition, with an emphasis on experimental observations. A brief introduction is given to important experimental techniques used to study the glass transition in colloids. We describe features of colloidal systems near and in glassy states, including increases in viscosity and relaxation times, dynamical heterogeneity and ageing, among others. We also compare and contrast the glass transition in colloids to that in molecular liquids. Other glassy systems are briefly discussed, as well as recently developed synthesis techniques that will keep these systems rich with interesting physics for years to come. 18 4.3. Shear of colloidal glasses 20 5. Other soft glassy materials 21 5.1. Soft colloids, sticky particles, emulsions and foams 21 5.2. Future directions: anisotropic colloidal particles 22 6. Conclusion 23 Acknowledgments 24 References 24