Shear stresses of colloidal dispersions at the glass transition in equilibrium and in flow

Crassous, Jérôme J.; Siebenbürger, Miriam; Ballauff, Matthias; Drechsler, Markus; Hajnal, David; Henrich, Oliver; Fuchs, Matthias

doi:10.1063/1.2921801

Cited by 86 publications

(180 citation statements)

References 66 publications

(155 reference statements)

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“…i.e., the integrated normalized shear modulus [10,[18][19][20][21], to exist. We assume that this integral can be regularized for hard spheres, as outlined in Appendix A.…”

Section: B Approximations For Correlation Functionsmentioning

confidence: 99%

From equilibrium to steady-state dynamics after switch-on of shear

2010

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A relation between equilibrium, steady-state, and waiting-time dependent dynamical two-time correlation functions in dense glass-forming liquids subject to homogeneous steady shear flow is discussed. The systems under study show pronounced shear thinning, i.e., a significant speedup in their steady-state slow relaxation as compared to equilibrium. An approximate relation that recovers the exact limit for small waiting times is derived following the integration through transients (ITT) approach for the nonequilibrium Smoluchowski dynamics, and is exemplified within a schematic model in the framework of the mode-coupling theory of the glass transition (MCT).Computer simulation results for the tagged-particle density correlation functions corresponding to wave vectors in the shear-gradient directions from both event-driven stochastic dynamics of a twodimensional hard-disk system and from previously published Newtonian-dynamics simulations of a three-dimensional soft-sphere mixture are analyzed and compared with the predictions of the ITTbased approximation. Good qualitative and semi-quantitative agreement is found. Furthermore, for short waiting times, the theoretical description of the waiting time dependence shows excellent quantitative agreement to the simulations. This confirms the accuracy of the central approximation used earlier to derive fluctuation dissipation ratios (Phys. Rev. Lett. 102, 135701). For intermediate waiting times, the correlation functions decay faster at long times than the stationary ones. This behavior is predicted by our theory and observed in simulations.

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“…i.e., the integrated normalized shear modulus [10,[18][19][20][21], to exist. We assume that this integral can be regularized for hard spheres, as outlined in Appendix A.…”

Section: B Approximations For Correlation Functionsmentioning

confidence: 99%

From equilibrium to steady-state dynamics after switch-on of shear

2010

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“…For 0.2 < φ < 0.5, the situation is complicated: arrested states can only occur thanks to pronounced structural heterogeneities, typically on length scales larger than R 0 . Therefore, they are more related to gelation [4], rather than to the caging typical of crowded random media [5]. However, such arrested states are also hardly classifiable as classic network gels in view of the different morphology and stress-bearing mechanisms.…”

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confidence: 99%

Elasticity of Arrested Short-Ranged Attractive Colloids: Homogeneous and Heterogeneous Glasses

2009

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We evaluate the elasticity of arrested short-ranged attractive colloids by combining an analytically solvable elastic model with a hierarchical arrest scheme into a new approach, which allows to discriminate the microscopic (primary particle-level) from the mesoscopic (cluster-level) contribution to the macroscopic shear modulus. The results quantitatively predict experimental data in a wide range of volume fractions and indicate in which cases the relevant contribution is due to mesoscopic structures. On this basis we propose that different arrested states of short-ranged attractive colloids can be meaningfully distinguished as homogeneous or heterogeneous colloidal glasses in terms of the length-scale which controls their elastic behavior.PACS numbers: 82.70.Dd,81.40.Jj Solutions of short-ranged attractive colloidal particles are the object of intense study due to their technological applications (proteins, paints etc.), as the constituent blocks of nanomaterials, as well as model systems to investigate phase behavior and dynamical arrest of condensed matter [1]. A landscape of phases has been observed upon varying the volume fraction φ or the interaction parameters [2], and, as a matter of fact, extended regions of the phase diagram are still poorly understood. In very dense suspensions (φ > 0.5) the arrested states are spatially homogeneous (i.e. the typical linear size of structural heterogeneity is smaller than the particle diameter R 0 ). Particles are immobilized within the range of attraction, giving rise to bonds that are persistent under strain in the linear regime, and the high density leads to (attractive) glassy states [3]. For 0.2 < φ < 0.5, the situation is complicated: arrested states can only occur thanks to pronounced structural heterogeneities, typically on length scales larger than R 0 . Therefore, they are more related to gelation [4], rather than to the caging typical of crowded random media [5]. However, such arrested states are also hardly classifiable as classic network gels in view of the different morphology and stress-bearing mechanisms. For them, different microscopic phenomena should be considered and a new theoretical framework, able to account for the strong spatial heterogeneities and currently still missing, would be desirable. A crucial point, mostly neglected in recent studies, is that arrested states occurring at different volume fractions and attraction strengths do display dramatically diverse mechanical and rheological properties [6]. That is why, their characterization is of true interest in technological applications and material design.In this Letter we propose a new, more down to earth, approach to characterize arrested short-ranged attractive colloids, based on their mechanical response. Being the problem extremely hard to tackle, we rely on a simplified picture: We combine an analytically solvable elastic model with a hierarchical arrest scheme and provide a first attempt to discriminate the microscopic (primary particle-level) from the mesoscopic (cluster-level)...

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“…To this end, linear frequency dependent shear moduli and nonlinear shear rate dependent flow curves were measured and analysed in parallel [6]. Here, we summarize some of the observations on the steady state flow curves and provide some new insights into the flow curves close to the glass transition.…”

Section: Introductionmentioning

confidence: 99%

“…A colloidal model system of hard spheres was developed [5], and experiments at high densities were performed [6] to test the connection between glassy dynamics and nonlinear rheology, which is at the heart of the theoretical approach. To this end, linear frequency dependent shear moduli and nonlinear shear rate dependent flow curves were measured and analysed in parallel [6].…”

Section: Introductionmentioning

confidence: 99%

Theory of Thermodynamic Stresses in Colloidal Dispersions at the Glass Transition

Hajnal

Henrich

Crassous

et al. 2008

AIP Conference Proceedings

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Abstract. We discuss the nonlinear rheology of dense colloidal dispersions at the glass transition. A first principles approach starting with interacting Brownian particles in given arbitrary homogeneous (incompressible) flow neglecting hydrodynamic interactions is sketched. It e.g. explains steady state flow curves for finite shear rates measured in dense suspensions of thermosensitive core-shell particles consisting of a polystyrene core and a crosslinked poly(N-isopropylacrylamide)(PNIPAM) shell. The exponents of simple and generalized Herschel Bulkley laws are computed for hard spheres.

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Shear stresses of colloidal dispersions at the glass transition in equilibrium and in flow

Cited by 86 publications

References 66 publications

From equilibrium to steady-state dynamics after switch-on of shear

From equilibrium to steady-state dynamics after switch-on of shear

Elasticity of Arrested Short-Ranged Attractive Colloids: Homogeneous and Heterogeneous Glasses

Theory of Thermodynamic Stresses in Colloidal Dispersions at the Glass Transition

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