Spatial and temporal heterogeneity in supercooled glycerol: Evidence from wide field single molecule imaging

Mackowiak, Stephan A.; Herman, Tobias; Kaufman, Laura J.

doi:10.1063/1.3277141

Cited by 53 publications

(98 citation statements)

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“…Similarly, it is shown that the median τ c is underestimated for short trajectories. These results are consistent with earlier studies on the effects of time-limited trajectories on homogeneous dynamics6,13. For heterogeneous systems with FWHM input of < 0.6, the measured FWHM of the shortest trajectory measurements is overestimated, as in the homogeneous case.…”

supporting

confidence: 92%

“…Fluorescence from probe molecules is used to construct SM linear dichroism (LD) trajectories and the ACF of each LD trajectory is fit to either single or stretched exponential decays. While the magnitude of the deviation of β from 1.0 of an ACF measured in an ensemble experiment is generally interpreted as correlating with the degree of heterogeneity in the system, for SM LD ACFs this is not generally assumed1,6,13. This is because typical SM trajectories are 10-200 τ c , short enough such that trajectories associated with homogeneous dynamics may be best fit by stretched exponential decays with β values significantly different than 1.013.…”

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confidence: 99%

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When the Heterogeneous Appears Homogeneous: Discrepant Measures of Heterogeneity in Single-Molecule Observables

Mackowiak

Kaufman

2011

J. Phys. Chem. Lett.

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Supercooled liquids demonstrate stretched exponential relaxations consistent with the presence of spatially heterogeneous dynamics. Many experimental results are consistent with this picture, but differences in experimental approach may lead to different conclusions about the degree of heterogeneity in a given system. Here, we investigate whether observables accessible with single molecule (SM) approaches are consistent with each other and with ensemble measurements. In particular, the distribution of rotational relaxation times, τ c , obtained from SM measurements is compared with the stretching exponent determined from a quasi-ensemble treatment of the same data. It is shown that the time-limited trajectories typical of SM experiments can lead to a stretching exponent that suggests homogeneous dynamics even in the presence of heterogeneous dynamics. After correction for the time-limited trajectories, additional discrepancy remains between stretching exponents measured via SM experiments and ensemble techniques. The remaining difference is attributed to the limited dynamic range of the SM experiments.Keywords supercooled liquids; single molecule; simulations; glass transition; rotational relaxation Supercooled liquids and glasses have provoked substantial interest, in large measure due to the interesting dynamics these systems display. Based on experiments, simulations, and theoretical work, a picture of the supercooled liquid as a mosaic of local and interchanging dynamic environments has emerged 1 . Such heterogeneous dynamics are not limited to molecular supercooled liquids but indeed are found in a variety of crowded systems [2][3][4] . One * Corresponding Author: kaufman@chem.columbia.edu. In such experiments, the deviation of β from 1 is typically associated with the degree of heterogeneity in the system 1 . The stretched exponential relaxations in supercooled liquids are most commonly attributed to spatial and/or temporal averaging over a distribution of single exponential relaxations. NIH Public AccessThe existence of heterogeneous dynamics in supercooled liquids encourages the application of sub-ensemble approaches to their study. In particular, in recent years single molecule (SM) fluorescence microscopy following the rotational relaxation of fluorescent probes in supercooled liquids has been used to establish the presence of dynamic heterogeneity in these systems as well as to investigate the length scales over which regions of particular dynamics exist and the timescales over which they persist [5][6][7][8][9][10][11] . While SM approaches yield information concealed in ensemble experiments, when sufficient data on sufficient single molecules are collected, these experiments are also expected to return results obtained in bulk experiments. However, for a variety of reasons, this is not always found to be the case [12][13][14] . Discrepancies may emerge due to the fact that SM fluorescence microscopy generally yields much shorter trajectories relative to the timescales of interest as a result...

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confidence: 92%

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confidence: 99%

When the Heterogeneous Appears Homogeneous: Discrepant Measures of Heterogeneity in Single-Molecule Observables

Mackowiak

Kaufman

2011

J. Phys. Chem. Lett.

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“…This point was first addressed in pioneering works with four-dimensional NMR [9] and direct probing of fluctuations at the nanoscopic scale using atomic force microscopy techniques in polymeric glasses [10]. Direct visualizations of molecular trajectories are not yet possible, but recent, very elegant experimental approaches using single-molecule spectroscopy are getting close to it [11,12]. Direct visualization is possible for different types of glasses, such as colloidal [13] and granular [14,15] assemblies.…”

Section: What Is Dynamic Heterogeneity?mentioning

confidence: 99%

Dynamic Heterogeneity in Amorphous Materials

Berthier¹

2011

Physics

223

237

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Dynamical heterogeneity, spatiotemporal fluctuations in local dynamical behavior, may explain the statistical mechanics of amorphous solids that are mechanically rigid but have a disordered structure similar to that of a dense liquid. Subject Areas: Statistical Mechanics, Soft MatterFrom the point of view of statistical physics, glasses are mysterious materials. Glassy materials possess a mechanical rigidity, which is similar to that of a crystalline material. In a crystal, rigidity is a direct consequence of long-range periodic order: It is not possible to move a single particle in a perfect crystal (while preserving the crystalline order) without also moving an extensive set of neighbors [ Fig. 1(a)]. While mechanically rigid-glasses do not seem to be characterized by any type of longrange order, see Fig. 1(b)-they resemble ordinary dense liquids. The comparison between crystals and glasses suggests that perhaps a more subtle symmetry breaking takes place during the formation of a glass, one that is not obvious to the naked eye. This conundrum has been a long-standing issue in condensed-matter physics [1, 2].Experimentally, one faces the difficulty that liquids approaching the glass transition (with decreasing temperature, for example) become too viscous to flow on experimental timescales, and fall out of thermal equilibrium without any reproducible thermodynamic phase transition. It is tempting to interpret this dramatic dynamic slowing down as originating from an underlying phase transition or critical point. Near an ordinary critical point, large-scale spatial fluctuations develop, such as the density fluctuations in the example shown in Fig. 1(c), Fig. 1(b)]. Therefore, finding evidence of a phase transition underlying the physics of amorphous materials would represent important progress.In the last decade, these questions have also come up in the field of soft condensed matter, in which disordered structures known as "jammed" materials [4] (foams, emulsions, colloidal gels, sandpiles) stop flowing when their density becomes large, without possessing long-range crystalline order, just like molecular glasses. J. D. Bernal [5] in the 1960s was one of the first physicists to suggest that disordered atomic fluids and granular packings could be investigated using similar tools and perhaps understood using similar theoretical concepts-an idea that has since remained highly popular [6].Two decades of research on dynamic heterogeneity (described in the next section) in amorphous materials have established that the formation of rigid amorphous structures is indeed accompanied by nontrivial spatiotemporal fluctuations, which become stronger nearer the glassy phase and are characterized by growing dynamic correlation length scales [7]. In this article we revisit the mounting evidence-using mostly the example of supercooled liquids, where dynamic heterogeneity has been most widely analyzed-that the formation of amorphous materials is a complex collective phenomenon, which shares more similarities with ordinary critic...

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“…Fluorescence microscopy of single molecules confirms the presence of large variations in the local viscosities. [7][8][9][10][11] Zondervan et al observed that these variations can be surprisingly long-lived, even at temperatures well above the glass transition temperature (T g ). 9 This may indicate the existence of a nearly static solid-like network at temperatures above T g , which was also revealed by rheological measurements.…”

Section: Introductionmentioning

confidence: 99%

Communication: Crystallite nucleation in supercooled glycerol near the glass transition

Yuan

Xia

Plazanet

et al. 2012

The Journal of Chemical Physics

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Heterogeneity and solid-like structures found near the glass transition provide a key to a better understanding of supercooled liquids and of the glass transition. However, the formation of solid-like structures and its effect on spatial heterogeneity in supercooled liquids is neither well documented nor well understood. In this work, we reveal the crystalline nature of the solid-like structures in supercooled glycerol by means of neutron scattering. The results indicate that inhomogeneous nucleation happens at temperatures near T g . Nevertheless, the thermal history of the sample is essential for crystallization. This implies such structures in supercooled liquids strongly depend on thermal history. Our work suggests that different thermal histories may lead to different structures and therefore to different length and time scales of heterogeneity near the glass transition.

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Spatial and temporal heterogeneity in supercooled glycerol: Evidence from wide field single molecule imaging

Cited by 53 publications

References 50 publications

When the Heterogeneous Appears Homogeneous: Discrepant Measures of Heterogeneity in Single-Molecule Observables

When the Heterogeneous Appears Homogeneous: Discrepant Measures of Heterogeneity in Single-Molecule Observables

Dynamic Heterogeneity in Amorphous Materials

Communication: Crystallite nucleation in supercooled glycerol near the glass transition

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