Salt-induced fast aggregation of polystyrene latex

Carpineti, Marina; Ferri, F.; Giglio, M.; Paganini, E.; Perini, U.

doi:10.1103/physreva.42.7347

Cited by 173 publications

(129 citation statements)

References 16 publications

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“…The aggregation process results in a relatively monodisperse size distribution of clusters, which is reflected by a peak in the static scattering intensity Iq; this peak shifts to a lower wave vector q and increases in intensity as clusters grow [13]. Fractal clusters are formed, as evidenced by the power law decay of Iq; we show in Fig.…”

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confidence: 87%

Time-Dependent Strength of Colloidal Gels

et al. 2005

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Colloidal silica gels are shown to stiffen with time, as demonstrated by both dynamic light scattering and bulk rheological measurements. Their elastic moduli increase as a power law with time, independent of particle volume fraction; however, static light scattering indicates that there are no large-scale structural changes. We propose that increases in local elasticity arising from bonding between neighboring colloidal particles can account for the strengthening of the network, while preserving network structure. DOI: 10.1103/PhysRevLett.95.048302 PACS numbers: 82.70.Gg, 61.43.Hv, 62.20.Dc, 82.70.Dd Gels are dilute connected networks which are capable of supporting applied stresses; they are commonly used to control the rheological properties of complex materials. Such networks can be formed by the aggregation of colloidal particles, which occurs when an attractive interaction is induced between them. Network elasticity is highly sensitive to the connectivity and arrangement of particles in the constituent aggregates. Colloidal gels are out-ofequilibrium systems; as a result, these networks frequently display time-dependent properties, due to network restructuring. This kind of aging is modeled for generic nonequilibrium systems as an evolution toward lower energy states, as the system explores a complex energy landscape [1,2]. However, network elasticity is also dependent on the interactions between particles; therefore, time-dependent interactions may also lead to changes in network properties. For colloidal gels, it is generally assumed that interparticle attractions, such as those described by Derujaguin-LandauVerwey-Overbeek [3,4] or Asakura-Oosawa potentials [5], determine local bond elasticity, thus, in principle, limiting their strength [6,7]. In the absence of a steric stabilization layer, particle interactions can also arise from physical bonds, as a result of covalent bonding or polymer entanglements. Within this framework, time evolution of network properties can be linked to the interparticle potential, for example, through the transport of particles from secondary to primary minima [8]. Aging can also be a consequence of time-dependent physical bonding; for example, the sintering of aggregated polystyrene particles is thought to drive local shrinkage that deforms the network [9]. The strength of the local interparticle bonds will have a direct impact on the network elasticity; however, these critical effects have never been explored.In this Letter, we present measurements of the elasticity of colloidal silica gels. Surprisingly, we find that, upon gelation, their storage moduli G 0 increase as a power law in time, G 0 t 0:4 , independent of initial volume fraction . Moreover, the time evolution of the network persists long after gelation occurs, for the duration of the measurement. As a consequence, their elasticity maintains the same volume fraction dependence, G 0 3:6 , independent of time. We postulate that the stiffening of the network is a result of chemical reactions at the junctions be...

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confidence: 87%

Time-Dependent Strength of Colloidal Gels

et al. 2005

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“…Furthermore, they did not yield ceramic bodies with a monomodal pore-size distribution, even when crystallization occurred during consolidation. 2,30 Despite these limitations, monodisperse colloidal systems (e.g., those based on silica spheres) 11 have served as excellent model systems for the study of aggregation, [31][32][33][34][35] rheological, 36 -40 sedimentation, 40 -42 and drying phenomena 3,43 Lange and co-workers 44,45 proposed a new paradigm for powder processing in the early 1990s. Their approach embodied many principles that guided earlier efforts, including use of powders with controlled size, morphology, and purity; no added binder; and dispersion control.…”

Section: Historical Perspectivementioning

confidence: 99%

Colloidal Processing of Ceramics

Lewis

2000

Journal of the American Ceramic Society

1,205

640

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Colloidal processing of ceramics is reviewed with an emphasis on interparticle forces, suspension rheology, consolidation techniques, and drying behavior. Particular attention is given to the scientific concepts that underpin the fabrication of particulate-derived ceramic components. The complex interplay between suspension stability and its structural evolution during colloidal processing is highlighted.

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“…The instrument has been briefly described elsewhere (Carpineti et al 1990). Again the sample is a horizontal liquid slab, 4.5 mm thick and confined between two thick sapphire plates.…”

Section: The Earlier Measurements On a Quasi-critical Mixturementioning

confidence: 99%

Giant fluctuations in diffusion processes

Brogioli

Vailati

Giglio

2000

J. Phys.: Condens. Matter

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Abstract. Concentration fluctuations in a homogeneous mixture are in general small and confined to the molecular lengthscale. It has been recently predicted that stressed fluids should exhibit anomalously large fluctuations. We will show here that anomalously large fluctuations also occur when macroscopic concentration gradients relax to the uniform state via diffusion. The measurements have been taken by low angle static light scattering and shadowgraphs. We find that at larger wavevectors the amplitude of the fluctuations diverges as q −4 . It is also found that gravity stabilizes at a constant value the fluctuations below a critical wavevector. We will present data on a mixture close to a consolution critical point. Recent results will also be presented on ordinary liquid mixtures, a polymer and a protein solution. These new results have been obtained by means of a quantitative shadowgraph technique. They confirm that giant fluctuations are always associated with mass flow due to diffusion across a macroscopic gradient.

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Salt-induced fast aggregation of polystyrene latex

Cited by 173 publications

References 16 publications

Time-Dependent Strength of Colloidal Gels

Time-Dependent Strength of Colloidal Gels

Colloidal Processing of Ceramics

Giant fluctuations in diffusion processes

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