Length scale dependence of dynamical heterogeneity in a colloidal fractal gel

Duri, Agnès; Cipelletti, Luca

doi:10.1209/epl/i2006-10357-4

Cited by 169 publications

(295 citation statements)

References 27 publications

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“…At low wave vector the relaxation time deduced from the incoherent scattering function scales as q −2 , suggesting that the large-scale single-particle dynamics are diffusive. On the contrary, the relaxation time extracted from the coherent scattering function has a ballistic scaling (τ q ∼ q −1 ), in accordance with experimental results on gels and other soft materials [14,15].…”

Section: Particle Localization In the Gel Networksupporting

confidence: 87%

“…A q-dependent dynamical heterogeneity in colloidal gels has indeed been reported in recent light scattering experiments [15,60]. It is worth mentioning that the experiments do not show a peak in χ 4 associated to thermally induced fluctuations of the gel branches (i.e.…”

Section: Casesupporting

confidence: 63%

“…The authors of Ref. 15 propose that the slow relaxation dynamics of a colloidal gel and the associated dynamical fluctuations result from a series of discrete, instantaneous rearrangement events taking place inside the gel volume as a consequence of the progressive relaxation of internal stresses. The average degree of correlation F (q, t) and the related dynamical susceptibility χ(q, t) can therefore be quantitatively connected with the number of such events taking place in a time interval t. If in our model gel we identify the elementary rearrangement event with the breaking of a single bond, then an elementary event can have quite different effects depending on the local environment of the broken bond [30].…”

Section: Discussionmentioning

confidence: 99%

“…low wave vector) the incoherent scattering function decays exponentially (β ≈ 1) as one would expect for simple particle diffusion. However, with increasing q within the range where the plateau is observed the decay of correlations becomes more and more stretched (β < they report a two-step decay of dynamical correlators, a length scale dependence of the slow relaxation dynamics, and a β exponent decreasing with increasing wave vector [14,15,56]. However, while we find that the decay of time correlations is exponential at low wave vector and becomes progressively stretched with increasing q, in the experiments a compressed decay (β 1.5) is consistently reported.…”

Section: Particle Localization In the Gel Networkmentioning

confidence: 99%

“…First, we characterize the cooperative dynamics of the gels by means of the dynamical susceptibility χ 4 . This quantity has been extensively analyzed in numerical simulations of dense glassy systems [31], but it has been relatively less studied in gels [14,15,[32][33][34][35], in spite of the fact that experimental measures of χ 4 in colloidal gels have already been performed [15,32]. We compute χ 4 and its dependence on the scattering wave vector q in networks with varying density, discussing possible connections with experimental observations.…”

Section: Introductionmentioning

confidence: 99%

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Self-assembly and cooperative dynamics of a model colloidal gel network

Colombo

Gado

2014

Soft Matter

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We study the assembly into a gel network of colloidal particles, via effective interactions that yield local rigidity and make dilute network structures mechanically stable. The self-assembly process can be described by a Flory-Huggins theory, until a network of chains forms, whose mesh size is on the order of, or smaller than, the persistence length of the chains. The localization of the particles in the network, akin to some extent to caging in dense glasses, is determined by the network topology, and the network restructuring, which takes place via bond breaking and recombination, is characterized by highly cooperative dynamics. We use N V E and N V T Molecular Dynamics as well as Langevin Dynamics and find a qualitatively similar time dependence of time correlations and of the dynamical susceptibility of the restructuring gel. This confirms that the cooperative dynamics emerge from the mesoscale organization of the network.

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Section: Particle Localization In the Gel Networksupporting

confidence: 87%

Section: Casesupporting

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Section: Particle Localization In the Gel Networkmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Self-assembly and cooperative dynamics of a model colloidal gel network

Colombo

Gado

2014

Soft Matter

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Applications of Biopolymer Microgels

Pashkovski

2011

Microgel Suspensions

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IntroductionAs a result of their structural versatility, rich dynamic behavior, biocompatibility, and sustainability, biopolymer microgels are employed in a wide range of industrial applications. Most biopolymers are linear or branched macromolecules forming microgel particles due to intermolecular binding. As was discussed in previous chapters, an essential property of microgel particles is their ability to swell, thus occupying a large volume in solution at very low-weight fractions of polymer. In the case of synthetic microgels, swelling is due to osmotic effects and the equilibrium swelling ratio is given by a balance between the entropic elasticity of the macromolecules, the polymer-solvent interactions [1-3], and, for flexible polyelectrolytes, the ionic strength and/or solution pH. By contrast, microgels of biological origin are composed of relatively rigid macromolecules; it is this intrinsic rigidity that largely determines the swelling of these biopolymer microgels.Above a critical overlap, concentrated suspensions of microgel particles behave as jammed materials [4,5], or more precisely, as soft glassy materials [6], which possess both a high elastic modulus and a yield stress. In the linear viscoelastic regime, the stress relaxation is very slow because the stress relaxes via collective rearrangements of the microgel particles. This makes microgels ideal for applications in consumer and food industries, where they are used to stabilize emulsions and suspensions and to control the rheological characteristics of the products. Microgel particles formed by biopolymers are preferred in pharmaceutical, food, and oral care industries due to their natural origin and biocompatibility [7][8][9]. In addition, microgels of biological origin have found applications in oil recovery because of their high solubility in water, low sensitivity to temperature, and high thickening potential. Biogels also find applications in drug delivery, particularly for oral [10] and ocular [11] delivery.There are other important reasons for using microgels of biological origin. First, high prices of petrochemicals make synthetic microgels, such as polyacrylates or Microgel Suspensions: Fundamentals and Applications Edited

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X‐ray Photon Correlation Spectroscopy Studies of Surfaces and Thin Films

2014

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The technique of X-ray Photon Correlation Spectroscopy (XPCS) is reviewed as a method for studying the relatively slow dynamics of materials on time scales ranging from microseconds to thousands of seconds and length scales ranging from microns down to nanometers. We focus on the application of this technique to study dynamical fluctuations of surfaces, interfaces and thin films. We first discuss instrumental issues such as the effects of partial coherence (or alternatively finite instrumental resolution) and optimization of signal-to-noise ratios in the experiments. We then review what has been learned from recent XPCS studies of capillary wave fluctuations on liquid surfaces and polymer films, of nanoparticles used as probes to study the interior dynamics of polymer films, of liquid crystals and multilamellar surfactant films, and of metal surfaces, and magnetic domain wall fluctuations in antiferromagnets. We then discuss studies of non-equilibrium dynamics described by 2-time correlation functions. Finally, we briefly speculate on possible future XPCS experiments at new synchrotron sources currently under development including studies of dynamics on time scales down to femtoseconds.

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Length scale dependence of dynamical heterogeneity in a colloidal fractal gel

Cited by 169 publications

References 27 publications

Self-assembly and cooperative dynamics of a model colloidal gel network

Self-assembly and cooperative dynamics of a model colloidal gel network

Applications of Biopolymer Microgels

X‐ray Photon Correlation Spectroscopy Studies of Surfaces and Thin Films

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