Spatial and temporal dynamical heterogeneities approaching the binary colloidal glass transition

Narumi, Takayuki; Franklin, Scott; Desmond, Kenneth W.; Tokuyama, Michio; Weeks, Eric R.

doi:10.1039/c0sm00756k

Cited by 50 publications

(73 citation statements)

References 84 publications

(256 reference statements)

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“…The largest displacements in Fig. 5C are on the order of 2 μm, roughly the diameter of a single particle, which is significant within a crowded environment of bidisperse particles (46). Non-Gaussian distributions are frequently seen for displacements in supercooled liquid samples (2,12,22,26) and have also been seen for rotational displacements in simulation (9,10).…”

Section: Resultsmentioning

confidence: 87%

Decoupling of rotational and translational diffusion in supercooled colloidal fluids

Edmond

Elsesser

Hunter

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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128

117

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We use confocal microscopy to directly observe 3D translational and rotational diffusion of tetrahedral clusters, which serve as tracers in colloidal supercooled fluids. We find that as the colloidal glass transition is approached, translational and rotational diffusion decouple from each other: Rotational diffusion remains inversely proportional to the growing viscosity whereas translational diffusion does not, decreasing by a much lesser extent. We quantify the rotational motion with two distinct methods, finding agreement between these methods, in contrast with recent simulation results. The decoupling coincides with the emergence of non-Gaussian displacement distributions for translation whereas rotational displacement distributions remain Gaussian. Ultimately, our work demonstrates that as the glass transition is approached, the sample can no longer be approximated as a continuum fluid when considering diffusion. R apidly cooling a glass-forming liquid fundamentally changes the nature of fluid transport at a molecular scale (1-7). For a tracer in a continuum fluid, the translational and rotational diffusion coefficients D T and D R , respectively, depend on temperature T and viscosity η as D ∝ T/η. Therefore, the ratio D T /D R is a constant that is independent of both T and η. However, this relationship breaks down in the deeply supercooled regime near the glass transition, according to experiments with molecular glass formers and also molecular dynamics simulations (1)(2)(3)(8)(9)(10)(11)(12)(13)(14).Experiments with glass-forming materials find that rotational diffusion remains strongly coupled with viscosity, where D R ∝ η −1 , whereas translational diffusion decouples, developing a fractional dependence on η where D T ∝ η −ξ with ξ < 1 (2, 8, 15). Near the glass transition, D T can be enhanced by two orders of magnitude over what would be calculated from the material's viscosity. The rotational diffusion coefficients from these experiments are inferred from measurements related to molecular rotations, and are evaluated using the "Debye model" due to an inability to directly observe molecular rearrangements in a material's bulk (3, 8-10, 16, 17). This experimental limitation has inspired computational studies where diffusion can be calculated using the Debye model and also a complementary method, the "Einstein formulation," which is more directly related to the trajectories of the diffusing objects. These simulations studied pure systems of water (9), ortho-terphenyl (10), and hard dumbbell particles (11). Intriguingly, the simulations found that decoupling depends qualitatively on the analysis method: They find rotational motion is enhanced over translational motion when quantified with the Einstein formulation, with the opposite being true in the Debye formulation. The results from these simulations raise the need for a critical reexamination of our current understanding of the relationship between translational and rotational diffusion, and only through direct observation can these differences be add...

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Section: Resultsmentioning

confidence: 87%

Decoupling of rotational and translational diffusion in supercooled colloidal fluids

Edmond

Elsesser

Hunter

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

128

117

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“…Within each confocal image, the small and large particles are easy to tell apart [see Fig. 1(bottom)] and so we can distinguish between them in our data [48].…”

Section: Experimental Methodsmentioning

confidence: 99%

Slow dynamics in cylindrically confined colloidal suspensions

Saklayen

Hunter

Edmond

et al. 2013

AIP Conference Proceedings

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Abstract. We study bidisperse colloidal suspensions confined within glass microcapillary tubes to model the glass transition in confined cylindrical geometries. We use high speed three-dimensional confocal microscopy to observe particle motions for a wide range of volume fractions and tube radii. Holding volume fraction constant, we find that particles move slower in thinner tubes. The tube walls induce a gradient in particle mobility: particles move substantially slower near the walls. This suggests that the confinement-induced glassiness may be due to an interfacial effect.

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“…Fig. 13 shows data for χ 4 from confocal microscopy experiments on dense binary suspensions of PMMA colloids [175]. It is quite instructive to analyse the dependence of ∆t max and ∆L max on the volume fraction φ.…”

Section: Dynamical Heterogeneitymentioning

confidence: 99%

“…While no evidence for a growing dynamical correlation length was found in [173], subsequent research has uncovered indisputable evidence for ξ 4 that increases on approaching the glass transition. Colloid experiments have played a vital role in garnering this evidence, through DLS measurements [174] as well as video microscopy [175]. In light scattering experiments, χ 4 (t) can be quantified approximately from fluctuations in the autocorrelation of the scattered intensity [174,[176][177][178][179][180][181][182].…”

Section: Dynamical Heterogeneitymentioning

confidence: 99%

Deconstructing the glass transition through critical experiments on colloids

Gokhale

Sood

Ganapathy

2016

Advances in Physics

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The glass transition is the most enduring grand-challenge problem in contemporary condensed matter physics. Here, we review the contribution of colloid experiments to our understanding of this problem. First, we briefly outline the success of colloidal systems in yielding microscopic insights into a wide range of condensed matter phenomena. In the context of the glass transition, we demonstrate their utility in revealing the nature of spatial and temporal dynamical heterogeneity.We then discuss the evidence from colloid experiments in favor of various theories of glass formation that has accumulated over the last two decades. In the next section, we expound on the recent paradigm shift in colloid experiments from an exploratory approach to a critical one aimed at distinguishing between predictions of competing frameworks. We demonstrate how this critical approach is aided by the discovery of novel dynamical crossovers within the range accessible to colloid experiments. We also highlight the impact of alternate routes to glass formation such as random pinning, trajectory space phase transitions and replica coupling on current and future research on the glass transition. We conclude our review by listing some key open challenges in glass physics such as the comparison of growing static lengthscales and the preparation of ultrastable glasses, that can be addressed using colloid experiments.

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Spatial and temporal dynamical heterogeneities approaching the binary colloidal glass transition

Cited by 50 publications

References 84 publications

Decoupling of rotational and translational diffusion in supercooled colloidal fluids

Decoupling of rotational and translational diffusion in supercooled colloidal fluids

Slow dynamics in cylindrically confined colloidal suspensions

Deconstructing the glass transition through critical experiments on colloids

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