We use dynamic light scattering and computer simulations to study equilibrium dynamics heterogeneity in concentrated suspensions of colloidal hard spheres. Our covers an unprecedented density range spans seven decades structural relaxation time, tau(alpha0, including measurements above phi(c), the location glass transition deduced from fitting our data mode-coupling theory. Instead falling out equilibrium, system remains ergodic phi(c) enters a new dynamical regime where tau(alpha) increases...

Steady and oscillatory rheology was utilized to study the mechanical response of colloidal glasses gels with particular emphasis in their yielding behaviour. We used a suspension hard sphere particles short-range depletion attractions induced by addition non-adsorbing linear polymer. While high volume fraction exhibit single yield point due cage breaking, attraction dominated show two-step reflecting bond respectively. Here we investigated behaviour frustrated colloid–polymer systems equal...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation K. N. Pham, G. Petekidis, D. Vlassopoulos, S. U. Egelhaaf, W. C. Poon, P. Pusey; Yielding behavior of repulsion- attraction-dominated colloidal glasses. Journal Rheology 1 March 2008; 52 (2): 649–676. https://doi.org/10.1122/1.2838255 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends...

We report experiments on hard-sphere colloidal glasses that show a type of shear banding hitherto unobserved in soft glasses. present scenario relates this to an instability due shear-concentration coupling, mechanism previously thought unimportant these materials. Below characteristic rate ${\stackrel{\ifmmode \dot{}\else \textperiodcentered \fi{}}{\ensuremath{\gamma}}}_{c}$ we observe increasingly nonlinear and localized velocity profiles. attribute very slight concentration gradients the...

The effects of particle softness and the role outer shell mechanics on linear viscoelasticity yielding behaviour colloidal glasses are critically assessed using three different model particles: (i) sterically stabilized PMMA particles with hard sphere interactions, (ii) core–shell microgels a deformable PNIPAM (iii) ultra-soft star-like micelles inter-penetrable multi-arms. volume fraction dependence elastic modulus yield stress reflects effective inter-particle potential. strain exhibits...

We studied yielding in two kinds of colloidal glasses: hard spheres at high concentrations without and with a short-range interparticle attraction induced by adding non-adsorbing polymer. Our oscillatory shear step strain measurements reveal single two-step these glasses, respectively. This finding is interpreted terms simple picture: the breaking local topological constraints (cages) nearest-neighbour bonds.

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation M. Laurati, S. U. Egelhaaf, G. Petekidis; Nonlinear rheology of colloidal gels with intermediate volume fraction. Journal Rheology 1 May 2011; 55 (3): 673–706. https://doi.org/10.1122/1.3571554 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex...

We investigate the structural, dynamical, and viscoelastic properties of colloid-polymer mixtures at intermediate colloid volume fraction varying polymer concentrations, thereby tuning attractive interactions. Within examined range samples varied from fluids to gels. In liquid phase, an increasing correlation length density fluctuations when approaching gelation boundary was observed by static light scattering microscopy, indicating clustering formation space-spanning networks....

Concentrated hard-sphere suspensions and glasses are investigated with rheometry, confocal microscopy, Brownian dynamics simulations during start-up shear, providing a link between microstructure, dynamics, rheology. The microstructural anisotropy is manifested in the extension axis where maximum of pair-distribution function exhibits minimum at stress overshoot. interplay relaxation shear advection as well available free volume determine structural magnitude Shear-induced cage deformation...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Vincent Carrier, George Petekidis; Nonlinear rheology of colloidal glasses soft thermosensitive microgel particles. J. Rheol. 1 March 2009; 53 (2): 245–273. https://doi.org/10.1122/1.3045803 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar...

Using a powerful combination of experiments and simulations we demonstrate how the microstructure its time evolution are linked with mechanical properties in frustrated, out-of-equilibrium, particle gel under shear. An intermediate volume fraction colloid-polymer is used as model system, allowing quantification interplay between interparticle attractions shear forces. Rheometry, confocal microscopy Brownian dynamics reveal that high rates, fully breaking structure, lead after cessation to...

The history dependence of glasses formed from flow-melted steady states by a sudden cessation the shear rate γ[over ˙] is studied in colloidal suspensions, molecular dynamics simulations and mode-coupling theory. In an ideal glass, stresses relax only partially, leaving behind finite persistent residual stress. For intermediate times, relaxation curves scale as function ˙]t, even though no flow present. macroscopic stress evolution connected to length liquefaction displayed microscopic...

We examine the microstructural and mechanical changes which occur during oscillatory shear flow reformation after cessation of an intermediate volume fraction colloidal gel using rheometry Brownian Dynamics (BD) simulations. A model depletion colloid–polymer mixture is used, comprising a hard sphere suspension with addition non-adsorbing linear polymer chains. The results reveal three distinct regimes depending on strain amplitude shear. Large amplitudes fully break structure in more...

We investigate particle rearrangements in colloidal glasses subjected to oscillatory shear strain by the technique of light scattering (LS) echo. LS echo directly follows motion particles through peaks (echoes) intensity autocorrelation function; height peak measures reversible sample. Polydisperse hard-sphere poly-methylmethacrylate were used avoid crystallization under shear. The yielding behavior is monitored irreversible at several volume fractions glass phase region. At high are found...

We have studied some of the rheological properties suspensions hard-sphere colloids with particular reference to behaviour near concentration glass transition. First we monitored strain on samples during and after a transient step stress. find that, at all values applied stress, colloidal glasses show rapid, apparently elastic, recovery stress is removed. This found even in which flowed significantly stressing. attribute this 'cage elasticity', stress-induced distorted environment any...

We study the flow of concentrated hard-sphere colloidal suspensions along smooth, nonstick walls using cone-plate rheometry and simultaneous confocal microscopy. In glass regime, global shows a transition from Herschel-Bulkley behavior at large shear rate to characteristic Bingham slip response small rates, absent for ergodic fluids. Imaging reveals both "solid" microstructure during full local nature "slip shear" transition. Both are described by phenomenological model, associated...

The rheological properties of highly concentrated suspensions hard sphere particles are studied with particular reference to the response shear induced crystals. Using practically monodisperse spheres, we prepare crystals under oscillatory and examine their linear non-linear mechanical responses in comparison glassy counterparts at same volume fraction. It is evident, that crystallization causes a significant drop elastic viscous moduli due structural rearrangements ease flow. For reason...

We use multi-arm star polymers as model soft colloids with tuneable interactions and explore their behaviour in the glassy state. In particular, we perform a systematic rheological study well-defined protocol address aspects of ageing shear melting glasses. Ageing proceeds two distinct steps: fast step O (10 3 s) slow 4 s). focus on creep recovery tests, which reveal rich, albeit complex response. Although waiting time, time between pre-shear (rejuvenation) sample measurement, affects...

The yielding behavior of hard sphere glasses under large-amplitude oscillatory shear has been studied by probing the interplay Brownian motion and shear-induced diffusion at varying oscillation frequencies. Stress, structure dynamics are followed experimental rheology Browian simulations. Brownian-motion-assisted cage escape dominates low frequencies while through collisions high ones, both related with a peak in G''. At intermediate novel, for glasses, double G'' is revealed reflecting...

Thixotropy is a phenomenon related to time dependent change in viscosity the presence or absence of flow. The yield stress, on other hand, represents minimum value stress above which steady flow can be sustained. In addition, material may also as function time. Both these characteristic features strongly influence state curve same. This study aims understand interrelation between thixotropy, and their relation with curve. this regard, we five thixotropic materials that show stress....

We investigate the yielding and flow of hard-sphere colloidal glasses by combining rheological measurements with technique light scattering echo. The polymethylmethacrylate particles used are sufficiently polydisperse that crystallization is suppressed. Creep recovery show can tolerate surprisingly large strains, up to at least 15%, before irreversibly. attribute this behaviour 'cage elasticity', ability a particle its cage neighbours retain their identity under quite distortion. Results...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Frédéric Renou, Jörg Stellbrink, George Petekidis; Yielding processes in a colloidal glass of soft star-like micelles under large amplitude oscillatory shear (LAOS). J. Rheol. 1 November 2010; 54 (6): 1219–1242. https://doi.org/10.1122/1.3483610 Download citation file: Ris (Zotero) Reference Manager EasyBib...