Sat, 26 Jul 2008 04:29:55 BST CiteULike: Tag colloids http://www.citeulike.org/tag/colloids CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/weeks/article/1676566 <i>Physical Review Letters, Vol. 96, No. 18. (2006)</i><br /><br />We directly probe the microscopic structure, connectivity, and elasticity of colloidal gels using confocal microscopy. We show that the gel is a random network of one-dimensional chains of particles. By measuring thermal fluctuations, we determine the effective spring constant between pairs of particles as a function of separation; this is in agreement with the theory for fractal chains. Long-range attractions between particles lead to freely rotating bonds, and the gel is stabilized by multiple connections among the chains. By contrast, short-range attractions lead to bonds that resist bending, with dramatically suppressed formation of loops of particles. Microscopic Structure and Elasticity of Weakly Aggregated Colloidal Gels AD Dinsmore V Prasad IY Wong DA Weitz doi:10.1103/PhysRevLett.96.185502 Physical Review Letters, Vol. 96, No. 18. (2006) 2007-09-19T16:41:52-00:00 2006 Physical Review Letters 96 18 APS colloidal-gel colloids confocal depletion elasticity journal-club pmma http://www.citeulike.org/user/weeks/article/2030059 <i>Science, Vol. 304, No. 5673. (14 May 2004), pp. 987-990.</i><br /><br />We report on a microfluidic particle-separation device that makes use of the asymmetric bifurcation of laminar flow around obstacles. A particle chooses its path deterministically on the basis of its size. All particles of a given size follow equivalent migration paths, leading to high resolution. The microspheres of 0.8, 0.9, and 1.0 micrometers that were used to characterize the device were sorted in 40seconds with a resolution of [~]10nanometers, which was better than the time and resolution of conventional flow techniques. Bacterial artificial chromosomes could be separated in 10 minutes with a resolution of [~]12%. 10.1126/science.1094567 Continuous Particle Separation Through Deterministic Lateral Displacement Lotien Huang Edward Cox Robert Austin James Sturm doi:10.1126/science.1094567 Science, Vol. 304, No. 5673. (14 May 2004), pp. 987-990. 2007-11-30T17:48:27-00:00 2004 Science 304 5673 987 990 colloids microfluidics http://www.citeulike.org/user/weeks/article/1304927 <i>Physical Review E, Vol. 58, No. 5. (November 1998), 6073.</i><br /><br />Dynamic light-scattering measurements are reported for suspensions at concentrations in the vicinity of the glass transition. In a mixture of identically sized but optically different particles having hard-sphere-like interactions; we project out the incoherent (or self-) intermediate scattering functions by adjusting the refractive index of the suspending liquid until scattering from the structure is suppressed. Due to polydispersity; crystallization is sufficiently slow so that good estimates of ensemble-averaged quantities can be measured for the metastable fluid states. Crystallization of the suspensions is still exploited; however; to set the volume fraction scale in terms of effective hard spheres and to eliminate (coherent) scattering from the structure. The glass-transition volume fraction is identified by the value where large-scale particle motion ceases. The nonequilibrium nature of the glass state is evidenced by the dependence on the waiting time of the long time decay of the relaxation functions. The self-intermediate scattering functions show negligible deviation from Gaussian behavior up to the onset of large-scale diffusion in the fluid or the onset of waiting time effects in the glass. Measurement of the self-intermediate scattering function of suspensions of hard spherical particles near the glass transition W van Megen TC Mortensen SR Williams J Müller doi:10.1103/PhysRevE.58.6073 Physical Review E, Vol. 58, No. 5. (November 1998), 6073. 2007-05-18T07:35:41-00:00 1998 Physical Review E 58 5 6073 American Physical Society aging colloids dls glass hard-sphere http://www.citeulike.org/user/weeks/article/1304894 <i>Physical Review E, Vol. 49, No. 5. (May 1994), pp. 4206-4220.</i><br /><br />Suspensions of identical particles with hard-sphere-like interactions are studied at concentrations for which the equilibrium state is crystalline. Dynamic light scattering measurements on these suspensions; in their metastable amorphous states prior to crystallization; identify the kinetic glass transition (GT) by the arrest of particle concentration fluctuations on the experimental time scale. This kinetic glass transition coincides with a spectacular change in the mechanism of crystallization from the formation of small crystals; which appear homogeneously nucleated throughout the sample at concentrations below the transition; to the growth; above the transition; of larger and highly asymmetric crystals whose shape and orientation depend on the shear history of the suspension. The intermediate scattering functions are measured over a time window spanning up to eight decades and for several wave vectors near the position of the main structure factor peak. From an analysis of the data in terms of the idealized version of mode-coupling theory; we conclude that both α and β processes are necessary to describe the slow structural relaxation in the fluid near the GT. The superposition principle of the α process; for the colloidal fluid; and the factorization property of the β process; for the colloidal fluid and glass; are verified. Glass transition in colloidal hard spheres: Measurement and mode-coupling-theory analysis of the coherent intermediate scattering function W van Megen SM Underwood doi:10.1103/PhysRevE.49.4206 Physical Review E, Vol. 49, No. 5. (May 1994), pp. 4206-4220. 2007-05-18T07:16:01-00:00 1994 Physical Review E 49 5 4206 4220 American Physical Society colloids dls glass mct http://www.citeulike.org/user/weeks/article/1706964 <i>Physical Review E, Vol. 47, No. 1. (January 1993), pp. 248-261.</i><br /><br />Dynamic light scattering is applied to the glass phase of nonaqueous suspensions of sterically stabilized colloidal spheres. The short-ranged steric repulsion ensures that the particle interactions are close to hard sphere. This is supported by the observation that the equilibrium phase behavior of these suspensions agrees with that predicted for the hard-sphere atomic system. We verify a model for a nonergodic medium; which assumes that the particles are localized during an experiment and which allows the intermediate scattering function to be calculated from a single measurement of the time-averaged intensity autocorrelation function. Intermediate scattering functions are obtained for several concentrations over a range of wave vectors around the main diffraction peak. The measured nonergodicity parameters are in good agreement with the predictions of mode-coupling theory for the hard-sphere glass. The comparison involves no adjustable parameters. At long times the intermediate scattering functions can be scaled to a single curve for over 2.5 decades in time. This; combined with the results that the nonergodicity parameters and critical amplitudes required for the scaling are in quantitative agreement with mode-coupling theory; provides a convincing verification of the predicted factorization property of the β process in the glass phase. Dynamic-light-scattering study of glasses of hard colloidal spheres W van Megen SM Underwood doi:10.1103/PhysRevE.47.248 Physical Review E, Vol. 47, No. 1. (January 1993), pp. 248-261. 2007-09-29T02:11:30-00:00 1993 Physical Review E 47 1 248 261 American Physical Society colloids dls hard-sphere mct http://www.citeulike.org/user/weeks/article/1706953 <i>Physical Review A, Vol. 43, No. 10. (15 May 1991), pp. 5442-5448.</i><br /><br />The glass transition studied for suspensions of colloidal particles through dynamical light-scattering experiments is analyzed within the mode-coupling theory for the supercooled liquid dynamics. These suspensions are treated as simple atomic systems with a hard-sphere interaction. The scaling properties predicted by the theory are verified. The shape of the master function for the β-relaxation region agrees well with the experimental data. Beta relaxation at the glass transition of hard-spherical colloids W Götze L Sjögren doi:10.1103/PhysRevA.43.5442 Physical Review A, Vol. 43, No. 10. (15 May 1991), pp. 5442-5448. 2007-09-29T02:07:38-00:00 1991 Physical Review A 43 10 5442 5448 American Physical Society colloids glass mct theory http://www.citeulike.org/user/weeks/article/1706951 <i>Physical Review A, Vol. 43, No. 10. (15 May 1991), pp. 5429-5441.</i><br /><br />This paper describes a light-scattering study of the glass transition in nonaqueous suspensions of sterically stabilized colloidal spheres. The observed phase behavior; fluid; crystal; and glass; is consistent with an essentially hard-sphere interaction between the particles. Metastable fluid states were obtained upon shear melting the crystalline phases by tumbling the samples. Their intermediate scattering functions; measured by dynamic light scattering; showed the emergence of a nondecaying component; implying structural arrest; at essentially the same concentration as that at which homogeneously nucleated crystallization was no longer observed. The overall forms of the intermediate scattering functions are consistent with the predictions of mode-coupling theories for the glass transition. Supplementary studies of the static structure factors indicated only short-ranged spatial order for particle concentrations ranging from the equilibrium fluid through the metastable fluid to the glass. Dynamic light-scattering study of the glass transition in a colloidal suspension W van Megen PN Pusey doi:10.1103/PhysRevA.43.5429 Physical Review A, Vol. 43, No. 10. (15 May 1991), pp. 5429-5441. 2007-09-29T02:06:40-00:00 1991 Physical Review A 43 10 5429 5441 American Physical Society colloids dls glass mct http://www.citeulike.org/user/weeks/article/1685995 <i>Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 74, No. 6. (2006)</i><br /><br />We investigate clogging of microchannels at the single-pore level using microfluidic devices as model porous media. The process of clogging is studied at low volume fractions and high flow rates, a technologically important regime. We show that clogging is independent of particle flow rate and volume fraction, indicating that collective effects do not play an important role. Instead, the average number of particles that can pass through a pore before it clogs scales with the ratio of pore to particle size. We present a simple model that accounts for the data. Mechanism for clogging of microchannels Hans Wyss Daniel Blair Jeffrey Morris Howard Stone David Weitz doi:10.1103/PhysRevE.74.061402 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 74, No. 6. (2006) 2007-09-22T19:57:03-00:00 2006 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 74 6 APS colloids journal-club microfluidics http://www.citeulike.org/user/weeks/article/2147206 <i>The European Physical Journal E - Soft Matter, Vol. 18, No. 3. (4 November 2005), pp. 287-293.</i><br /><br />We have studied binary two-dimensional (2D) mixtures of superparamagnetic colloidal particles interacting through magnetic dipole moments, which were induced by an external magnetic field B. By tuning B the effective system temperature could be widely adjusted. Time-dependent particle coordinates measured by video-microscopy provide radial pair-distribution functions, mean-square displacements as well as evidence for heterogeneous dynamics. Characteristic features of 3D glass formers are observed experimentally in 2D for the first time. Experimental realization of a model glass former in 2D H König R Hund K Zahn G Maret doi:10.1140/epje/e2005-00034-9 The European Physical Journal E - Soft Matter, Vol. 18, No. 3. (4 November 2005), pp. 287-293. 2007-12-19T15:56:52-00:00 2005 The European Physical Journal E - Soft Matter 18 3 287 293 2d colloids glass http://www.citeulike.org/user/weeks/article/1685994 <i>Physical Review Letters, Vol. 92, No. 18. (2004), pp. 185506-185506.</i><br /><br />We study the flow of model hard-sphere colloidal suspensions at high volume fraction driven through a constriction by a pressure gradient. Above a particle-size dependent limit 0, direct microscopic observations demonstrate jamming and unjamming—conversion of fluid to solid and vice versa—during flow. We show that such a jamming flow produces a reduction in colloid concentration x downstream of the constriction. We propose that this "self-filtration" effect is due to a combination of jamming of the particulate part of the system and continuing flow of the liquid part, i.e., the solvent, through the pores of the jammed solid. Thus we link jamming in colloidal and granular media with a "two-fluid-like" picture of the flow of concentrated suspensions. Results are also discussed in the light of the original experiments of Reynolds on dilation in granular materials. Jamming, Two-Fluid Behavior, and “Self-Filtration” in Concentrated Particulate Suspensions MD Haw doi:10.1103/PhysRevLett.92.185506 Physical Review Letters, Vol. 92, No. 18. (2004), pp. 185506-185506. 2007-09-22T19:54:19-00:00 2004 Physical Review Letters 92 18 185506 185506 APS colloids jamming journal-club microfluidics pmma http://www.citeulike.org/user/weeks/article/733339 <i>J. Phys. Chem. B, Vol. 109, No. 45. (17 November 2005), pp. 21235-21240.</i><br /><br />We perform experiments on two different dense colloidal suspensions with confocal microscopy to probe the relationship between local structure and dynamics near the glass transition. We calculate the Voronoi volume for our particles and show that this quantity is not a universal probe of glassy structure for all colloidal suspensions. We correlate the Voronoi volume to displacement and find that these quantities are only weakly correlated. We observe qualitatively similar results in a simulation of a polymer melt. These results suggest that the Voronoi volume does not predict dynamical behavior in experimental colloidal suspensions; a purely structural approach based on local single particle volume likely cannot describe the colloidal glass transition. Weak Correlations between Local Density and Dynamics near the Glass Transition JC Conrad FW Starr DA Weitz doi:10.1021/jp0514168 J. Phys. Chem. B, Vol. 109, No. 45. (17 November 2005), pp. 21235-21240. 2006-07-03T19:08:55-00:00 2005 J. Phys. Chem. B 109 45 21235 21240 colloids confocal glass pmma structure http://www.citeulike.org/user/weeks/article/1304873 <i>Langmuir, Vol. 14, No. 18. (1 September 1998), pp. 5004-5010.</i><br /><br />Abstract: Optical video microscopy and digital image processing have been used to study the self-diffusion of colloidal particles with a hard-sphere potential. The colloid particles consist of cross-linked polymers and are dispersed in a good solvent to avoid aggregation. To investigate single particle motion in highly concentrated dispersions, a host-tracer system, consisting of two different kinds of polymer particles, has been designed: the host particles are made of poly-t-butylacrylate (with ethanedioldiacrylate as cross-linker) and have the same refractive index as the employed solvent, 4-fluorotoluene. The tracer particles have a core-shell structure with a polystyrene core (cross-linked with m-diisopropenylbenzene) and a shell consisting of cross-linked poly-t-butylacrylate to match surface properties and interaction potential to those of the "invisible" particles. The motion of the strongly scattering core-shell particles ("tracer" particles) was observed by dark-field light microscopy. From the obtained particle trajectories, mean squared displacements, van Hove autocorrelation functions, and vector-vector correlation functions were calculated, yielding a direct real-space image of the "cage effect" at = 0.52 and of the transition to a glassy state between = 0.56 and = 0.60, as expected for a hard sphere system. The extracted long-time self-diffusion coefficients Dself,long are fully consistent with a recent theoretical prediction using full many-body hydrodynamics at 0.56 and a colloid glass transition at g = 0.583. However, even at = 0.60, Dself,long seems to be still finite, possibly indicating the existence of long-time motion of colloidal particles even in the glassy state. Self-Diffusion in Concentrated Colloid Suspensions Studied by Digital Video Microscopy of Core-Shell Tracer Particles A Kasper E Bartsch H Sillescu doi:10.1021/la971089y Langmuir, Vol. 14, No. 18. (1 September 1998), pp. 5004-5010. 2007-05-18T06:56:19-00:00 1998 Langmuir 14 18 5004 5010 cages colloids dyn-het particle-tracking http://www.citeulike.org/user/weeks/article/2147170 <i>Physical Review Letters, Vol. 99, No. 5. (2007)</i><br /><br />We report a numerical study of the rate of crystal nucleation in a binary suspension of oppositely charged colloids. Two different crystal structures compete in the thermodynamic conditions under study. We find that the crystal phase that nucleates is metastable and, more surprisingly, its nucleation free-energy barrier is not the lowest one. This implies that, during nucleation, there is insufficient time for subcritical nuclei to relax to their lowest free-energy structure. Such behavior is in direct contradiction with the common assumption that the phase that crystallizes most readily is the one with the lowest free-energy barrier for nucleation. The phenomenon that we describe should be relevant for crystallization experiments where competing solid structures are not connected by an easy transformation. Evidence for Out-of-Equilibrium Crystal Nucleation in Suspensions of Oppositely Charged Colloids Eduardo Sanz Chantal Valeriani Daan Frenkel Marjolein Dijkstra doi:10.1103/PhysRevLett.99.055501 Physical Review Letters, Vol. 99, No. 5. (2007) 2007-12-19T15:45:09-00:00 2007 Physical Review Letters 99 5 APS charged colloids crystals http://www.citeulike.org/user/weeks/article/1410887 <i>Physical Review Letters, Vol. 82, No. 21. (24 May 1999), 4352.</i><br /><br />The long-range entropic forces that arise between two micrometer-sized colloidal spheres in a fluid of much smaller colloidal spheres were directly measured using a line-scanned optical tweezer. This new technique allowed us to measure the functional form of the potential with sub- k B T energy and 15 nm spatial resolution. At the lowest small sphere concentrations; the potential was monotonically attractive; while at higher concentrations an oscillatory potential was observed; due to the liquid structure of the small spheres. Surprisingly; the large spheres came together only rarely at the higher concentrations; suggesting a new means for stabilizing suspensions using entropy alone. Entropic Attraction and Repulsion in Binary Colloids Probed with a Line Optical Tweezer JC Crocker JA Matteo AD Dinsmore AG Yodh doi:10.1103/PhysRevLett.82.4352 Physical Review Letters, Vol. 82, No. 21. (24 May 1999), 4352. 2007-06-25T15:00:08-00:00 1999 Physical Review Letters 82 21 4352 American Physical Society colloids depletion journal-club laser-tweezer http://www.citeulike.org/user/weeks/article/1203416 <i>Physical Review Letters, Vol. 89, No. 9. (2002), pp. 095704-095704.</i><br /><br />We use confocal microscopy to study particle motion in colloidal systems. Near the glass transition; motion is inhibited; as particles spend time trapped in transient “cages” formed by neighboring particles. We measure the cage sizes and lifetimes; which; respectively; shrink and grow as the glass transition approaches. Cage rearrangements are more prevalent in regions with lower concentrations and higher disorder. Neighboring rearranging particles typically move in parallel directions; although a nontrivial fraction moves in antiparallel directions; usually from particle pairs with initial separations corresponding to local maxima and minima of the pair correlation function g ( r ); respectively. Properties of Cage Rearrangements Observed near the Colloidal Glass Transition Eric Weeks DA Weitz doi:10.1103/PhysRevLett.89.095704 Physical Review Letters, Vol. 89, No. 9. (2002), pp. 095704-095704. 2007-04-02T22:33:06-00:00 2002 Physical Review Letters 89 9 095704 095704 American Physical Society cages colloids confocal diffusion glass msd pmma http://www.citeulike.org/user/weeks/article/1567407 <i>Physical Review Letters, Vol. 97, No. 26. (2006)</i><br /><br />We use confocal microscopy to visualize individual particles near the colloidal glass transition. We identify the most slowly-relaxing particles and show that they form spatially correlated clusters that percolate across the sample. In supercooled fluids, the largest cluster spans the system on short time scales but breaks up on longer time scales. In contrast, in glasses, a percolating cluster exists on all accessible time scales. Using molecular dynamics simulation, we show that these clusters make the dominant contribution to the bulk elasticity of the sample. Contribution of Slow Clusters to the Bulk Elasticity Near the Colloidal Glass Transition Jacinta Conrad Param Dhillon Eric Weeks David Reichman David Weitz doi:10.1103/PhysRevLett.97.265701 Physical Review Letters, Vol. 97, No. 26. (2006) 2007-08-15T16:26:46-00:00 2006 Physical Review Letters 97 26 APS colloids confocal elasticity glass pmma slow-particles http://www.citeulike.org/user/weeks/article/1605887 <i>Journal of Physics: Condensed Matter, Vol. 19, No. 20. (2007), pp. 205131-205131.</i><br /><br />We use a confocal microscope to examine the motion of individual particles in a dense colloidal suspension. Close to the glass transition, particle motion is strongly spatially correlated. The correlations decay exponentially with particle separation, yielding a dynamic length scale of O(2-3s) (in terms of particle diameter s). This length scale grows modestly as the glass transition is approached. Further, the correlated motion exhibits a strong spatial dependence on the pair correlation function g(r). Motion within glassy samples is weakly correlated, but with a larger spatial scale for this correlation. Short- and long-range correlated motion observed in colloidal glasses and liquids Eric Weeks John Crocker DA Weitz doi:10.1088/0953-8984/19/20/205131 Journal of Physics: Condensed Matter, Vol. 19, No. 20. (2007), pp. 205131-205131. 2007-08-29T17:41:41-00:00 2007 Journal of Physics: Condensed Matter 19 20 205131 205131 colloids confocal glass pmma two-point http://www.citeulike.org/user/weeks/article/1449898 <i>Physical Review E, Vol. 65, No. 4. (April 2002), pp. 041405-041405.</i><br /><br />Measurements of the low-shear viscosity η o with a Zimm-Crothers viscometer for dispersions of colloidal hard spheres are reported as a function of volume fraction φ up to 0.56. Nonequilibrium theories based on solutions to the two-particle Smoluchoski equation or ideal mode coupling approximations do not capture the divergence. However; the nonhydrodynamic contribution to the relative viscosity Δη o is correlated over a wide range of volume fractions by the Doolittle and Adam-Gibbs equations; indicating an exponential divergence at φ m =0.625±0.015. The data extend the previously proposed master curve; providing a test for improved theories for the many-body thermodynamic and hydrodynamic interactions that determine the viscosity of hard-sphere dispersions. Nature of the divergence in low shear viscosity of colloidal hard-sphere dispersions Zhengdong Cheng Jixiang Zhu Paul Chaikin See-Eng Phan William Russel doi:10.1103/PhysRevE.65.041405 Physical Review E, Vol. 65, No. 4. (April 2002), pp. 041405-041405. 2007-07-11T20:42:14-00:00 2002 Physical Review E 65 4 041405 041405 American Physical Society colloids jamming journal-club pmma viscosity http://www.citeulike.org/user/weeks/article/2909079 <i>Physical Review Letters, Vol. 95, No. 7. (2005)</i><br /><br />A theoretical approach is developed to derive a hierarchy of mode-coupling equations for the dynamics of concentrated colloidal suspensions, which improves the prediction of the colloidal glass transition. Our derivation is based on a matrix formalism for stochastic dynamics and the resulting recursive expressions for irreducible memory functions. The 1st order truncation of the generalized mode-coupling closure recovers mode-coupling theory, whereas its 2nd and 3rd order truncations provide corrections. The predictions of the transition volume fraction and Debye-Waller parameter for the hard-sphere colloidal system improve with the increasing mode-coupling order and compare favorably with experimental measurements. High-Order Mode-Coupling Theory for the Colloidal Glass Transition Jianlan Wu Jianshu Cao doi:10.1103/PhysRevLett.95.078301 Physical Review Letters, Vol. 95, No. 7. (2005) 2008-06-19T23:08:11-00:00 2005 Physical Review Letters 95 7 APS colloids glass mct http://www.citeulike.org/user/weeks/article/1835891 <i>Physica A, Vol. 216, No. 1-2. (1 June 1995), pp. 85-119.</i><br /><br />A systematic theory for the dynamics of hard-sphere suspensions of interacting Brownian particles with both hydrodynamic and direct interactions is presented. A generalized diffusion equation is derived for concentrated suspensions. The volume fraction ([phi]) dependence of the short- and long-time self-diffusion coefficients are thus explored from a unifying point of view. The long-range hydrodynamic interactions due to the Oseen tensor are shown to play a crucial role in both coefficients, while the short-range hydrodynamic interactions just lead to corrections. The importance of the correlation effects between particles due to the long-range hydrodynamic interactions is also stressed. The nonlocal correlation effect is an important factor, leading to the behavior of the long-time self-diffusion coefficient (DSL) as DSL ~ (1 - [phi]/[phi]0)2 near the volume fraction of [phi]0 = 0.5718. The direct interactions are also found to be drastically reduced by the short-range hydrodynamic interactions. On the theory of concentrated hard-sphere suspensions Michio Tokuyama Irwin Oppenheim doi:10.1016/0378-4371(94)00280-7 Physica A, Vol. 216, No. 1-2. (1 June 1995), pp. 85-119. 2007-10-29T15:17:13-00:00 1995 Physica A 216 1-2 85 119 colloids diffusion glass theory http://www.citeulike.org/user/weeks/article/1835880 <i>Physica A, Vol. 378, No. 2. (15 May 2007), pp. 157-166.</i><br /><br />The experimental and the simulation results for the mean-square displacements in eight different systems (four suspensions of colloids and four molecular systems) are analyzed near their glass transitions by the mean-field theory recently proposed. The dependence of various physical quantities such as the relaxation times and the mean-free path on the long-time self-diffusion coefficient is fully investigated. Each physical quantity is shown to be a unique function of it. It is then suggested that the dynamics of apparently very different glass-forming systems is described by a master function if a value of that coefficient is the same. The universal features near the glass transitions are thus discussed from a unified point of view. Similarities in diversely different glass-forming systems Michio Tokuyama doi:10.1016/j.physa.2006.12.047 Physica A, Vol. 378, No. 2. (15 May 2007), pp. 157-166. 2007-10-29T15:09:29-00:00 2007 Physica A 378 2 157 166 colloids msd theory http://www.citeulike.org/user/weeks/article/1702049 <i>Physica A: Statistical and Theoretical Physics, Vol. 233, No. 1-2. (15 November 1996), pp. 102-116.</i><br /><br />Phase behaviour, crystallisation kinetics and particle dynamics are compared for two colloidal suspensions of hard spherical particles with different particle size distributions; one is narrow and roughly symmetrical and the other is broader and skewed towards smaller particles. Both suspensions exhibit the equilibrium phase behaviour expected for a system of identical hard spheres and they show a glass transition, indicated by the cessation of homogeneous nucleation and the partial arrest of concentration fluctuations, at approximately the same volume fraction, [Phi]g [approximate] 0.58. Interestingly, compared to the suspension with the narrower size distribution, crystallisation rates are significantly slower in the more polydisperse suspension. In its colloidal glass state no crystal growth occurs on secondary nuclei, such as the shear-aligned crystals that can be induced in both suspensions by regular rocking. Effect of particle size distribution on crystallisation and the glass transition of hard sphere colloids SI Henderson TC Mortensen SM Underwood W van Megen doi:10.1016/S0378-4371(96)00153-7 Physica A: Statistical and Theoretical Physics, Vol. 233, No. 1-2. (15 November 1996), pp. 102-116. 2007-09-27T16:45:30-00:00 1996 Physica A: Statistical and Theoretical Physics 233 1-2 102 116 colloids crystals dls glass polydisperse http://www.citeulike.org/user/weeks/article/1454769 <i>Physical Review Letters, Vol. 99, No. 2. (2007), pp. 025702-025702.</i><br /><br />We study a colloidal suspension confined between two quasiparallel walls as a model system for glass transitions in confined geometries. The suspension is a mixture of two particle sizes to prevent wall-induced crystallization. We use confocal microscopy to directly observe the motion of colloidal particles. This motion is slower in confinement, thus producing glassy behavior in a sample which is a liquid in an unconfined geometry. For higher volume fraction samples (closer to the glass transition), the onset of confinement effects occurs at larger length scales. Colloidal Glass Transition Observed in Confinement Carolyn Nugent Kazem Edmond Hetal Patel Eric Weeks doi:10.1103/PhysRevLett.99.025702 Physical Review Letters, Vol. 99, No. 2. (2007), pp. 025702-025702. 2007-07-13T19:38:05-00:00 2007 Physical Review Letters 99 2 025702 025702 APS binary colloids confinement confocal glass goldman msd pmma http://www.citeulike.org/user/weeks/article/1699104 <i>Nature, Vol. 387, No. 6636. (26 June 1997), pp. 883-885.</i> Crystallization of hard-sphere colloids in microgravity Jixiang Zhu Min Li R Rogers W Meyer RH Ottewill Sts-73 WB Russel PM Chaikin Nature, Vol. 387, No. 6636. (26 June 1997), pp. 883-885. 2007-09-27T03:17:26-00:00 1997 Nature 387 6636 883 885 colloids crystals glass gravity journal-club pmma http://www.citeulike.org/user/weeks/article/1702297 <i>Journal of Physics: Condensed Matter, Vol. 17, No. 31. (2005), pp. S2779-S2786.</i><br /><br />We studied the structures formed in aqueous dispersions of charged colloidal spheres under a constant low salt concentration of c = 6 × 10[?]6 mol l[?]1. Particles of diameter 2a = 1000 nm were confined to a low angle wedge geometry with plate separation 0<S<50 µm and observed with video microscopy. Irrespective of the initial particle density n we reproducibly observe the particles to migrate to the narrow wedge side on the timescale of a few days. Thereby an interface between a crystalline structure and a near particle free region is formed, which propagates slowly until the dilute region is exhausted of particles. While the origin of this separation is still unclear, the final extension of the crystalline region is stable on the timescale of months. Within the crystal phase we observe a characteristic sequence of structures with increasing plate separation similar to that seen in previous experiments on hard sphere-like systems but here with non-touching particles. Moreover, we find that mechanical equilibrium is a necessary prerequisite for observing the full richness of different phases. A detailed comparison to recent theoretical calculations for bilayers was performed and semi-quantitative agreement with the predictions observed. A comparative study on the phase behaviour of highly charged colloidal spheres in a confining wedge geometry Ana Fontecha Hans Schöpe Hans König Thomas Palberg René Messina Hartmut Löwen doi:10.1088/0953-8984/17/31/002 Journal of Physics: Condensed Matter, Vol. 17, No. 31. (2005), pp. S2779-S2786. 2007-09-27T16:53:09-00:00 2005 Journal of Physics: Condensed Matter 17 31 S2779 S2786 colloids confinement microscopy http://www.citeulike.org/user/weeks/article/1835839 <i>Philosophical Magazine B, Vol. 77, No. 2. (February 1998), pp. 621-631.</i><br /><br />Recent dynamic light scattering measurement on concentrated suspensions of 'hard-sphere' colloidal particles by Segre and Pusey (1996, Phys. Rev. Lett ., 77, 771) are compared with the theoretical results calculated by the coupling model. The calculated normalized intermediate scattering function decays exponentially at both short and long times, f (Q, short t) proportional exp[-DS(Q)Q2t] and f(Q, long t) proportional exp[-DL(Q)Q2t] respectively, with DL(Q) and DS(Q) having the same Q dependence. The ratio DL(Q)/DS(Q) decreases rapidly with volume fraction phi. At intermediate times, the decay of f(Q, t) is slower and nonexponential, becomes increasing slower and extends to longer times as phi increases. There is good agreement between theory and experiment. It is also pointed out that the diffusional dynamics found in concentrated colloidal suspensions are general and shared by other densely packed interacting systems. A coupling model analysis of dynamics of concentrated colloidal suspensions KL Ngai RW Rendell Philosophical Magazine B, Vol. 77, No. 2. (February 1998), pp. 621-631. 2007-10-29T14:52:12-00:00 1998 Philosophical Magazine B 77 2 621 631 colloids diffusion glass theory http://www.citeulike.org/user/weeks/article/1987776 <i>Physical Review Letters, Vol. 75, No. 14. (2 October 1995), pp. 2770-2773.</i><br /><br />The frequency-dependent viscoelastic shear modulus of concentrated suspensions of colloidal hard spheres is shown to be strongly modified as the volume fraction approaches the glass transition. The elastic or storage component; G ′ ; becomes larger than the viscous or loss component; G ′′ . The frequency dependence of G ′ develops a plateau while that of G ′′ develops a minimum. We propose a physical model to account for these data; using a description of the glasslike behavior based on mode-coupling theory; and a description of the high-frequency behavior based on hydrodynamic flow calculations. Linear Viscoelasticity of Colloidal Hard Sphere Suspensions near the Glass Transition TG Mason DA Weitz doi:10.1103/PhysRevLett.75.2770 Physical Review Letters, Vol. 75, No. 14. (2 October 1995), pp. 2770-2773. 2007-11-26T18:16:34-00:00 1995 Physical Review Letters 75 14 2770 2773 American Physical Society colloids glass hard-sphere mct rheology http://www.citeulike.org/user/weeks/article/1678149 <i>Current Opinion in Colloid & Interface Science, Vol. 7, No. 3-4. (August 2002), pp. 196-203.</i><br /><br />Colloidal suspensions are simple model systems for the study of phase transitions. Video microscopy is capable of directly imaging the structure and dynamics of colloidal suspensions in different phases. Recent results related to crystallization, glasses, and 2D systems complement and extend previous theoretical and experimental studies. Moreover, new techniques allow the details of interactions between individual colloidal particles to be carefully measured. Understanding these details will be crucial for designing novel colloidal phases and new materials, and for manipulating colloidal suspensions for industrial uses. Video microscopy of colloidal suspensions and colloidal crystals Piotr Habdas Eric Weeks doi:10.1016/S1359-0294(02)00049-3 Current Opinion in Colloid & Interface Science, Vol. 7, No. 3-4. (August 2002), pp. 196-203. 2007-09-20T04:33:58-00:00 2002 Current Opinion in Colloid & Interface Science 7 3-4 196 203 colloids crystals microscopy particle-tracking review http://www.citeulike.org/user/weeks/article/1337783 <i>Advanced Materials, Vol. 16, No. 14. (2004), pp. 1204-1208.</i><br /><br />No abstract. Colloidal Clusters of Silica or Polymer Microspheres G-R Yi VN Manoharan E Michel MT Elsesser S-M Yang DJ Pine doi:10.1002/adma.200306638 Advanced Materials, Vol. 16, No. 14. (2004), pp. 1204-1208. 2007-05-27T21:16:49-00:00 2004 Advanced Materials 16 14 1204 1208 colloids synthesis http://www.citeulike.org/user/weeks/article/1678143 <i>Chemical Physics, Vol. 284, No. 1-2. (1 November 2002), pp. 361-367.</i> Subdiffusion and the cage effect studied near the colloidal glass transition Eric Weeks DA Weitz doi:10.1016/S0301-0104(02)00667-5 Chemical Physics, Vol. 284, No. 1-2. (1 November 2002), pp. 361-367. 2007-09-20T04:31:56-00:00 2002 Chemical Physics 284 1-2 361 367 anomalous-diffusion cages colloids confocal glass msd pmma http://www.citeulike.org/user/weeks/article/1337781 <i>Colloid & Polymer Science, Vol. 282, No. 1. (1 December 2003), pp. 7-13.</i><br /><br />We discuss a dispersion polymerization procedure for preparing monodisperse and micron-sized poly(methyl methacrylate) (PMMA) particles in hexanes with methacryloxypropyl-terminated polydimethylsiloxane stabilizers. We investigate the effects of the stabilizer molecular weight, stabilizer concentration, and monomer concentration on the particle size and polydispersity. We find that a minimum molecular weight of 10 000 g/mol is necessary to synthesize colloidally stable PMMA dispersions. The particle polydispersity is minimal (=5%) for stabilizer to monomer weight ratios of 0.02 to 0.1, while PMMA particles prepared under conditions outside this range are polydisperse. The particle diameter can be varied from 0.4 to 1.5 µm by appropriate choices of stabilizer and monomer concentrations. Stable PMMA suspensions can be prepared at up to 26.3% solids. The dispersions are stable in most liquid aliphatics, and are monodisperse enough to form ordered domains at high concentration. This single-stage synthesis, requiring only commercially available materials, may be of interest to those seeking a simple way to prepare highly monodisperse non-aqueous dispersions in the micron size range. Preparation of monodisperse PMMA microspheres in nonpolar solvents by dispersion polymerization with a macromonomeric stabilizer Sascha Klein Vinothan Manoharan David Pine Fred Lange doi:10.1007/s00396-003-0915-0 Colloid & Polymer Science, Vol. 282, No. 1. (1 December 2003), pp. 7-13. 2007-05-27T21:14:34-00:00 2003 Colloid & Polymer Science 282 1 7 13 colloids hard-sphere synthesis http://www.citeulike.org/user/weeks/article/1678133 <i>Science, Vol. 292, No. 5515. (13 April 2001), pp. 258-262.</i><br /><br />Crystallization of concentrated colloidal suspensions was studied in real space using laser scanning confocal microscopy. Direct imaging in three dimensions allowed identification and observation of nucleation and growth of crystalline regions, providing the first experimental measure of properties of the nucleating crystallites. By following their evolution, critical nuclei were identified, nucleation rates were determined, and the average surface tension of the crystal-liquid interface was measured. The structure of the nuclei was the same as the bulk solid phase, random-hexagonal-close-packed (rhcp), and their average shape was rather aspherical, with rough rather than faceted surfaces. Real-Space Imaging of Nucleation and Growth in Colloidal Crystallization U Gasser Eric Weeks Andrew Schofield PN Pusey DA Weitz doi:10.1126/science.1058457 Science, Vol. 292, No. 5515. (13 April 2001), pp. 258-262. 2007-09-20T04:28:54-00:00 2001 Science 292 5515 258 262 colloids confocal crystals nucleation structure http://www.citeulike.org/user/weeks/article/1706440 <i>Journal of Non-Crystalline Solids, Vol. 192-193 (2 December 1995), pp. 384-392.</i><br /><br />Scattering experiments studying the dynamics of glass-forming systems have become of special importance for understanding glass transition phenomena. They monitor the density autocorrelation function which has become a key observable since it is calculated within a new concept of the glass transition, the mode coupling theory (MCT). After a short reference to the main predictions and examples of scattering experiments where these phenomena have been observed, results for two model systems will be analyzed with MCT: a recently reported analysis of neutron scattering data for orthoterphenyl in the [beta]-regime is improved and photon correlation spectroscopy data on colloidal spheres are described by simultaneously analyzing the [beta]- and [alpha]-relaxation dynamics using the MCT scaling laws. Scattering experiments for the microscopic understanding of the glass transition E Bartsch doi:10.1016/0022-3093(95)00379-7 Journal of Non-Crystalline Solids, Vol. 192-193 (2 December 1995), pp. 384-392. 2007-09-28T21:17:33-00:00 1995 Journal of Non-Crystalline Solids 192-193 384 392 colloids dls glass mct soft-sphere http://www.citeulike.org/user/weeks/article/1304890 <i>Physica A, Vol. 201, No. 1-3. (1 December 1993), pp. 363-371.</i><br /><br />The collective and single particle dynamics of highly concentrated polystyrene micronetwork spheres of 200 nm diameter as measured by photon correlation spectroscopy (PCS) and forced Rayleigh scattering (FRS), respectively, show the same qualitative features as known for molecular liquids or colloidal suspensions close to the glass transition. A two step decay of the density fluctuations is observed with PCS, which can be quantitatively interpreted by mode coupling theory with a critical volume fraction [phi]c of 0.64. At the same volume fraction a glass transition is indicated independent of any theory through specific changes in the intensity fluctuation pattern. The long time self-diffusion coefficient, as determined by FRS, decreases over about three orders of magnitude in a small volume fraction interval between 0.55 and 0.68. However, traces of ergodicity restoring structure relaxation processes are found even beyond [phi]c = [phi]g. Colloidal polystyrene micronetwork spheres -- a new mesoscopic model of the glass transition in simple liquids E Bartsch V Frenz S Moller H Sillescu doi:10.1016/0378-4371(93)90433-5 Physica A, Vol. 201, No. 1-3. (1 December 1993), pp. 363-371. 2007-05-18T07:14:49-00:00 1993 Physica A 201 1-3 363 371 colloids dls glass soft-sphere http://www.citeulike.org/user/weeks/article/1706425 <i>Science, Vol. 263, No. 5143. (7 January 1994), pp. 66-68.</i><br /><br />The time evolution of void structures in highly purified polymer latex dispersions was studied with a confocal laser scanning microscope. In such dispersions, which were initially homogeneous, the voids grew with time when the dispersions were kept standing and formed more quickly in the internal material than in material close to the glass-dispersion interface. Void formation is thus not an artifact arising from the presence of the interface. A similar structural inhomogeneity, in apparently homogeneous systems, is discussed for simple ionic solutions, ionic polymer solutions, and Langmuir-Blodgett films. 10.1126/science.263.5143.66 Void Structure in Colloidal Dispersions Kensaku Ito Hiroshi Yoshida Norio Ise doi:10.1126/science.263.5143.66 Science, Vol. 263, No. 5143. (7 January 1994), pp. 66-68. 2007-09-28T21:09:17-00:00 1994 Science 263 5143 66 68 colloids confocal structure http://www.citeulike.org/user/weeks/article/1706419 <i>Physical Review B, Vol. 44, No. 1. (1 July 1991), pp. 435-438.</i><br /><br />By using a confocal laser scanning microscope and a digital image analyzer; the influence of a glass-suspension interface on colloidal crystals was studied. Particular attention was paid to the interparticle distance (2 D expt ) in the ordered structure and the crystallization process. The 2 D expt was insensitive to the distance from the interface up to about 40 μm. The crystallization process of the ordered structure was characterized by a strong anisotropy originating at the glass-suspension interface. Localized ordered structure in polymer latex suspensions as studied by a confocal laser scanning microscope Hiroshi Yoshida Kensaku Ito Norio Ise doi:10.1103/PhysRevB.44.435 Physical Review B, Vol. 44, No. 1. (1 July 1991), pp. 435-438. 2007-09-28T21:06:12-00:00 1991 Physical Review B 44 1 435 438 American Physical Society colloids confocal crystals structure http://www.citeulike.org/user/weeks/article/1706390 <i>Physical Review Letters, Vol. 68, No. 24. (15 June 1992), pp. 3646-3649.</i><br /><br />We used diffusing wave spectroscopy to determine the phase diagrams of binary mixtures of charge-stabilized colloidal particles of different dimensions in the low-screening limit. As the ratio of radii r = r 1 / r 2 was increased progressively towards 1; the structure of the diagrams evolved from eutecticlike to azeotropiclike and finally to a diagram where complete solubility was found; much like in atomic systems. We present for the first time evidence for liquid-galss transitions in these strongly interacting systems as the relative composition of both species is varied. Glass transition and phase diagrams of strongly interacting binary colloidal mixtures Amit Meller Joel Stavans doi:10.1103/PhysRevLett.68.3646 Physical Review Letters, Vol. 68, No. 24. (15 June 1992), pp. 3646-3649. 2007-09-28T20:49:28-00:00 1992 Physical Review Letters 68 24 3646 3649 American Physical Society binary colloids dws glass phase-diagram http://www.citeulike.org/user/weeks/article/1706378 <i>Physical Review Letters, Vol. 80, No. 4. (26 January 1998), pp. 877-880.</i><br /><br />Structural relaxation of metastable fluids and the kinetics of subsequent crystallization are measured by dynamic light scattering and by the growth of the main interlayer reflection in binary mixtures of colloidal polymer particles with hard-sphere-like interactions. The size ratios of the particles lie in the range for which eutectic phase behavior is expected. We find that at a constant volume fraction; close to the melting value of the one-component hard-sphere solid; the addition of up to about 10% by volume of the second component has negligible effect on the particle dynamics in the metastable fluid but significantly retards crystal nucleation and growth. Metastability and Crystallization in Suspensions of Mixtures of Hard Spheres SI Henderson W van Megen doi:10.1103/PhysRevLett.80.877 Physical Review Letters, Vol. 80, No. 4. (26 January 1998), pp. 877-880. 2007-09-28T20:43:05-00:00 1998 Physical Review Letters 80 4 877 880 American Physical Society colloids crystals dls hard-sphere nucleation polydisperse http://www.citeulike.org/user/weeks/article/688326 <i>Journal of Physics: Conference Series, Vol. 40, No. 1. (2006), pp. 124-132.</i><br /><br />Interesting flow properties are observed when a concentrated suspension of colloidal particles flows into a geometrical constriction. We present here a description of two different experimental techniques used to study the pressure driven flow of dense suspensions of micron-sized hard spheres into glass capillaries. The first one involves the analysis of the driving pressure during the flow, the other one is based on fast confocal microscopy. Technical details are given, together with a selection of preliminary results. Experimental studies of the flow of concentrated hard sphere suspensions into a constriction L Isa R Besseling ER Weeks WCK Poon doi:10.1088/1742-6596/40/1/016 Journal of Physics: Conference Series, Vol. 40, No. 1. (2006), pp. 124-132. 2006-06-07T11:46:33-00:00 2006 Journal of Physics: Conference Series 1742-6596 40 1 124 132 Institute of Physics Publishing colloids confocal jamming microfluidics pmma http://www.citeulike.org/user/weeks/article/1409983 <i>The Journal of Chemical Physics, Vol. 125, No. 7. (2006), pp. 074716-074716.</i><br /><br />Coherent anti-Stokes Raman scattering microscopy is performed on glassy systems of poly(methylmethacrylate) colloidal particles in density- and refractive-index-matched solvents. Samples are prepared with varying amounts of linear polystyrene, which induces a depletion driven attraction between the nearly hard-sphere particles. Images collected over several hours confirm the existence of a reentrant glass transition. The images also reveal that the dynamics of repulsive and attractive glasses are qualitatively different. Colloidal particles in repulsive glasses exhibit cage rattling and escape, while those in attractive glasses are nearly static while caged but exhibit large displacements upon (infrequent) cage escape. ©2006 American Institute of Physics Direct imaging of repulsive and attractive colloidal glasses Laura Kaufman David Weitz doi:10.1063/1.2227386 The Journal of Chemical Physics, Vol. 125, No. 7. (2006), pp. 074716-074716. 2007-06-25T01:35:08-00:00 2006 The Journal of Chemical Physics 125 7 074716 074716 AIP colloids depletion glass microscopy http://www.citeulike.org/user/weeks/article/3015834 <i>Physical Review E, Vol. 55, No. 3. (1 March 1997), pp. 3054-3067.</i><br /><br />The crystallization of suspensions of sterically stabilized polymer particles, with hard-sphere-like interactions, is studied by laser light scattering. Over the range of volume fractions examined, from just below melting to the glass transition, crystallization occurs by homogeneous nucleation. After the suspensions are shear melted, the intensity, position, and width of the main interlayer Bragg reflection are measured as functions of time. From these the amount of crystal, the average linear crystal dimension, the number of crystals, and the volume fraction of the crystal phase are obtained. No assumptions are made concerning the functional time dependence of nucleation or growth processes. Below the melting concentration the observed crystallization process is compatible with the classical picture of sequential nucleation and growth of isolated crystals. However, when the melting concentration is exceeded, nucleation events are correlated, nucleation is accelerated, and high nucleation rate densities suppress crystal growth. Above the melting concentration we infer, with the aid of the equations of state for the hard-sphere fluid and solid, that the first identifiable crystals are in mechanical equilibrium with the embedding fluid and, consequently, strongly compressed by it. Ensuing nucleation lags expansion of the crystal lattice. Crystallization kinetics of suspensions of hard colloidal spheres JL Harland W van Megen doi:10.1103/PhysRevE.55.3054 Physical Review E, Vol. 55, No. 3. (1 March 1997), pp. 3054-3067. 2008-07-17T21:42:04-00:00 1997 Physical Review E 55 3 3054 3067 American Physical Society colloids crystals hard-sphere nucleation http://www.citeulike.org/user/weeks/article/1303139 <i>Science, Vol. 270 (November 1995), pp. 1177-1179.</i><br /><br />The real-space structure of hard-sphere glasses quenched from colloidal liquids in thermodynamic equilibrium has been determined. Particle coordinates were obtained by combining the optical sectioning capability of confocal fluorescence microscopy with the structure of specially prepared fluorescent silica colloids. Both the average structure and the local structure of glasses, with volume fractions ranging from 0.60 to 0.64, were in good agreement with glasses and random close packings generated by computer simulations. No evidence of a divergent correlation length was found. The method used to obtain the three-dimensional particle coordinates is directly applicable to other colloidal structures, such as crystals, gels, and flocs.<p> Real-Space Structure of Colloidal Hard-Sphere Glasses A van Blaaderen P Wiltzius Science, Vol. 270 (November 1995), pp. 1177-1179. 2007-05-17T16:29:59-00:00 1995 Science 270 1177 1179 classic colloids confocal glass structure http://www.citeulike.org/user/weeks/article/3015341 <i>Physical Review Letters, Vol. 97, No. 22. (2006)</i><br /><br />We investigate the structure and dynamics of the crystal-fluid interface of colloidal hard spheres in real space by confocal microscopy. Tuning the buoyancy of the particles allows us to study the interface close to and away from equilibrium. We find that the interface broadens from 8–9 particle diameters close to equilibrium to 15 particle diameters away from equilibrium. Furthermore, the interfacial velocity, i.e., the velocity by which the interface moves upwards, increases significantly. The increasing gravitational drive leads to supersaturation of the fluid above the crystal surface. This dramatically affects crystal nucleation and growth, resulting in the observed dynamic broadening of the crystal-fluid interface. Dynamic Broadening of the Crystal-Fluid Interface of Colloidal Hard Spheres Roel Dullens Dirk Aarts Willem Kegel doi:10.1103/PhysRevLett.97.228301 Physical Review Letters, Vol. 97, No. 22. (2006) 2008-07-17T18:53:31-00:00 2006 Physical Review Letters 97 22 APS colloids confocal crystals nucleation http://www.citeulike.org/user/weeks/article/1706356 <i>Physical Review A, Vol. 43, No. 12. (15 June 1991), pp. 6900-6907.</i><br /><br />Static structure factors S ( q ) were measured by laser light scattering for very concentrated systems of spherical; near-monosized; sterically stabilized particles dispersed in nonpolar liquids. A range of systems with particle concentrations beyond that corresponding to the disorder to order transition configurations were found to have amorphous structures. As the particles were stabilized by means of very short chain polymers; these systems were thought to closely approximate the fundamentally important amorphous; hard-sphere system. Subsequent analysis of S ( q ) carried out by means of data generated by the molecular-dynamics method for very concentrated; amorphous states of the hard-sphere system confirmed this interpretation. Thus we were able; by a combination of experiment and simulation; to give an extensive analysis and description of the structure of the amorphous state of a system of hard spheres. This study complements past work on the thermodynamic and transport properties of metastable; amorphous states of a system of hard spheres. Structure of colloidal glasses calculated by the molecular-dynamics method and measured by light scattering I Snook W van Megen P Pusey doi:10.1103/PhysRevA.43.6900 Physical Review A, Vol. 43, No. 12. (15 June 1991), pp. 6900-6907. 2007-09-28T20:36:00-00:00 1991 Physical Review A 43 12 6900 6907 American Physical Society colloids dls glass hard-sphere simulation structure http://www.citeulike.org/user/weeks/article/301921 <i>Nature, Vol. 320, No. 6060. (27 March 1986), pp. 340-342.</i><br /><br />Suspensions of spherical colloidal particles in a liquid show a fascinating variety of phase behaviour which can mimic that of simple atomic liquids and solids. 'Colloidal fluids', in which there are significant short-range correlations between the positions of neighbouring particles, and 'colloidal crystals', which have long-range spatial order, have been investigated extensively. We report here a detailed study of the phase diagram of suspensions of colloidal spheres which interact through a steep repulsive potential. With increasing particle concentration we observed a progression from colloidal fluid, to fluid and crystal phases in coexistence, to fully crystallized samples. At the highest concentrations we obtained very viscous samples in which full crystallization had not occurred after several months an in which the particles appeared to be arranged as an amorphous 'colloidal glass'. The empirical phase diagram can be repoduced reasonably well by an effective hard-sphere model. The observation of the colloidal glass phase is interesting both in itself and because of possible relevance to the manufacture of high-strength ceramics. Phase behaviour of concentrated suspensions of nearly hard colloidal spheres PN Pusey W van Megen doi:10.1038/320340a0 Nature, Vol. 320, No. 6060. (27 March 1986), pp. 340-342. 2005-08-23T18:57:37-00:00 1986 Nature 320 6060 340 342 classic colloids glass phase-diagram pmma http://www.citeulike.org/user/weeks/article/2945540 <i>Journal of Physics: Condensed Matter, Vol. 17, No. 45. (2005), pp. S3543-S3549.</i><br /><br />We study the dynamic behaviour of concentrated colloidal hard spheres using time resolved correlation, a light scattering technique that can detect the slow evolution of the dynamics in out-of-equilibrium systems. Surprisingly, equilibrium is reached a very long time after sample initialization, the non-stationary regime lasting up to three orders of magnitude more than the relaxation time of the system. Before reaching equilibrium, the system displays unusual ageing behaviour. The intermediate scattering function decays faster than exponentially and its relaxation time evolves non-monotonically with sample age. Ageing and ultra-slow equilibration in concentrated colloidal hard spheres El Masri M Pierno L Berthier L Cipelletti doi:10.1088/0953-8984/17/45/046 Journal of Physics: Condensed Matter, Vol. 17, No. 45. (2005), pp. S3543-S3549. 2008-06-30T17:17:03-00:00 2005 Journal of Physics: Condensed Matter 17 45 S3543 S3549 aging colloids trc http://www.citeulike.org/user/weeks/article/1678103 <i>Langmuir, Vol. 21, No. 24. (22 November 2005), pp. 11040-11047.</i><br /><br />Abstract: We investigate the phase behavior and 3D structure of strongly attractive mixtures of silica microspheres and polystyrene nanoparticles. These binary mixtures are electrostatically tuned to promote a repulsion between like-charged (microsphere-microsphere and nanoparticle-nanoparticle) species and a strong attraction between oppositely charged (microsphere-nanoparticle) species. Using confocal fluorescence scanning microscopy, we directly observe the 3D structure of colloidal phases assembled from these mixtures as a function of varying composition. In the absence of nanoparticle additions, the charged-stabilized microspheres assemble into a polycrystalline array upon sedimentation. With increasing nanoparticle volume fraction, nanoparticle bridges form between microspheres, inducing their flocculation. At even higher nanoparticle volume fractions, the microspheres become well coated with nanoparticles, leading to their charge reversal and subsequent restabilization. We demonstrate how this fluid-gel-fluid transition can be utilized to control the morphology of the colloidal phases formed under gravity-driven sedimentation. Phase Behavior and 3D Structure of Strongly Attractive Microsphere-Nanoparticle Mixtures JF Gilchrist AT Chan ER Weeks JA Lewis doi:10.1021/la051998k Langmuir, Vol. 21, No. 24. (22 November 2005), pp. 11040-11047. 2007-09-20T04:13:37-00:00 2005 Langmuir 21 24 11040 11047 colloidal-gel colloids confocal structure http://www.citeulike.org/user/weeks/article/1678101 <i>Langmuir, Vol. 21, No. 22. (25 October 2005), pp. 9978-9989.</i><br /><br />Abstract: We investigate the interparticle interactions, phase behavior, and structure of microsphere-nanoparticle mixtures that possess high size and charge asymmetry.1 We employ a novel Monte Carlo simulation scheme2 to calculate the effective microsphere interactions in suspension, yielding new insight into the origin of the experimentally observed behavior.3 The initial settling velocity, final sediment density, and three-dimensional structure of colloidal phases assembled from these binary mixtures via gravitational settling of silica microspheres in water and index-matched solutions exhibit a strong compositional dependence. Confocal laser scanning microscopy is used to directly image and quantify their structural evolution during assembly. Below a lower critical nanoparticle volume fraction (nano < L,C), the intrinsic van der Waals attraction between microspheres leads to the formation of colloidal gels. These gels exhibit enhanced consolidation as nano approaches L,C. When nano exceeds L,C, an effective repulsion arises between microspheres due to the formation of a dynamic nanoparticle halo around the colloids. From this stable fluid phase, the microspheres settle into a crystalline array. Finally, above an upper critical nanoparticle volume fraction (nano > U,C), colloidal gels form whose structure becomes more open with increasing nanoparticle concentration due to the emergence of an effective microsphere attraction,3 whose magnitude exhibits a superlinear dependence on nano. Interparticle Interactions and Direct Imaging of Colloidal Phases Assembled from Microsphere-Nanoparticle Mixtures CJ Martinez J Liu SK Rhodes E Luijten ER Weeks JA Lewis doi:10.1021/la050382s Langmuir, Vol. 21, No. 22. (25 October 2005), pp. 9978-9989. 2007-09-20T04:12:36-00:00 2005 Langmuir 21 22 9978 9989 colloidal-gel colloids confocal depletion structure http://www.citeulike.org/user/weeks/article/2949709 <i>Annual Review of Fluid Mechanics, Vol. 37, No. 1. (2005), pp. 129-149.</i><br /><br />Abstract We review the fluid mechanics and rheology of dense suspensions, emphasizing investigations of microstructure and total stress. Dense or highly concentrated suspensions are those in which the average particle separation distance is less than the particle radius. For these suspensions, multiple-body interactions as well as two-body lubrication play a significant role and the rheology is non-Newtonian. We include investigations of multimodal suspensions, but not those of suspensions with dominant nonhydrodynamic interactions. We consider results from both physical experiments and computer simulations and explore scaling theories and the development of constitutive equations. FLUID MECHANICS AND RHEOLOGY OF DENSE SUSPENSIONS Jonathan Stickel Robert Powell doi:10.1146/annurev.fluid.36.050802.122132 Annual Review of Fluid Mechanics, Vol. 37, No. 1. (2005), pp. 129-149. 2008-07-02T01:54:13-00:00 2005 Annual Review of Fluid Mechanics 37 1 129 149 colloids review rheology viscosity http://www.citeulike.org/user/weeks/article/1304903 <i>Colloids and Surfaces, Vol. 17, No. 1. (January 1986), pp. 67-78.</i><br /><br />A single-stage method is described for preparing monodisperse poly(methyl methacrylate) latices stabilised by poly(12-hydroxy-stearic acid) in hydrocarbon media. By variation of solvency conditions, it was possible to obtain a variation in particle size. At high monomer concentrations, a range of particle diameters between 178 nm and 2.6 [mu]m was obtained with a small coefficient of variation on the number average size. At low monomer concentrations, stable latices were obtained with diameters of ~ 80 nm. Some suggestions are made for the mechanism of particle formation and growth in non-aqueous latices. The preparation of poly(methyl methacrylate) latices in non-aqueous media L Antl JW Goodwin RD Hill RH Ottewill SM Owens S Papworth JA Waters doi:10.1016/0166-6622(86)80187-1 Colloids and Surfaces, Vol. 17, No. 1. (January 1986), pp. 67-78. 2007-05-18T07:18:28-00:00 1986 Colloids and Surfaces 17 1 67 78 colloids methods pmma synthesis