Viscoelasticity and rheology of depletion flocculated gels and fluids

Shah, S. A.; Chen, Yeng-Long; Schweizer, Kenneth S.; Zukoski, Charles F.

doi:10.1063/1.1598192

Cited by 117 publications

(128 citation statements)

References 57 publications

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“…Mixtures of hard sphere colloids and nonadsorbing polymers have been used extensively as interesting model systems to induce gelation via the depletion mechanism and their properties extensively studied [Asakura and Oosawa (1958); Vrij (1976); Vincent et al (1986); Tuinier et al (2000); Poon (2002); Shah et al (2003); Lekkerkerker and Tuinier (2011)]. However, the seminal work of Pham et al (2002) demonstrated that with this system, one can span the whole colloidal morphology diagram simply via entropic interactions.…”

Section: Introductionmentioning

confidence: 99%

Depletion gels from dense soft colloids: Rheology and thermoreversible melting

Truzzolillo¹,

Vlassopoulos²,

Munam³

et al. 2014

Journal of Rheology

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SynopsisUpon addition of small nonadsorbing linear polymers, colloidal glasses composed of large hard spheres melt and eventually revitrify into the so-called attractive glass regime. We show that, when replacing the hard spheres by star polymers representing model soft particles, a reentrant gel is formed. This is the result of compression and depletion of the stars due to the action of the osmotic pressure from the linear homopolymers. The viscoelastic properties of the soft dense gel were studied with emphasis on the shear-induced yielding process, which involved localized breaking of elements with a size of the order of the correlation length. Based on these results, a phenomenological attempt was made at describing the universal rheological features of colloid/nonadsorbing polymer mixtures of varying softness. The star gel was found to undergo thermoreversible melting, despite the fact that conventional hard-sphere depletion gels are invariant to heating. This phenomenon is attributed to the hybrid internal microstructure of the stars, akin to a dry-to-wet brush transition, and is characterized by slow kinetics, on the time scale of the osmotic gel formation process. These results may be useful in finding generic features in colloidal gelation, as well as in the molecular design of new soft composite materials. V C 2014 The Society of Rheology. [http://dx

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Section: Introductionmentioning

confidence: 99%

Depletion gels from dense soft colloids: Rheology and thermoreversible melting

Truzzolillo¹,

Vlassopoulos²,

Munam³

et al. 2014

Journal of Rheology

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“…For glass forming systems, the so-called re-entry phenomenon has been predicted theoretically [Fabbian et al (1999a); Fabbian et al (1999b); Dawson et al (2001)] and confirmed experimentally for various model systems. Diffusive motion of particles is accelerated and fluid states are observed even at particle loadings beyond the colloidal glass transition (U g ¼ 0.58) due to the weak attraction among particles [Pham et al (2002); Pham et al (2004); Shah et al (2003a); Shah et al (2003b); Eckert and Bartsch (2004); Eckert and Bartsch (2002); Eckert and Bartsch (2003)]. Beyond that, even the macroscopic flow behavior changes and the low shear viscosity drops drastically [Willenbacher et al (2011)].…”

Section: Introductionmentioning

confidence: 99%

Effect of weak attractive interactions on flow behavior of highly concentrated crystalline suspensions

Weis¹,

Natalia²,

Willenbacher³

2014

Journal of Rheology

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SynopsisWeak attractive interactions lead to a substantial broadening of the fluid-crystalline coexistence region of crystalline, colloidal hard-sphere dispersions. Here, we demonstrate that a weak depletion attraction introduced by nonadsorbing polymer added to the continuous phase results in a strong decrease of the low shear viscosity even at particle concentrations up to U ¼ 0.65 analogous to the re-entry phenomenon in highly concentrated glassy systems. This promotes flow in macroscopic channels but the scenario changes in confined, microfluidic geometries. Pure crystalline suspensions exhibit flow induced melting in the region of highest shear rates close to the wall, and this promotes flow through microchannels (<100 lm). In contrast, weak attractive interactions fortify preferential crystallization at the channel walls finally resulting in channel clogging and cessation of flow. This wall crystallization phenomenon particularly impairs viscosity determination from classical parallel plate rotational rheometry if the gap width is set too low. These findings may find application in the important biotechnological field of protein preparation and crystallization.

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“…In addition to thermodynamic phases, kinetically arrested states start intervening with thermodynamic equilibrium at highly concentrated or strongly attractive systems. 3,4 Therefore while at high particle volume fractions particles are trapped entropically in cages formed by their neighbors creating an amorphous glassy system, 3 in the presence of strong interparticle attractions free floating clusters, fractal percolating particle networks, or more concentrated cluster dominated gels [5][6][7][8] and attractive glasses 4 are formed as the particle volume fraction is increased. In both cases the system exhibits a transition from an ergodic liquid to non-ergodic solid, either by increasing the volume fraction or the attraction strength.…”

Section: Introductionmentioning

confidence: 99%

Colloidal gels tuned by oscillatory shear

et al. 2017

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We examine microstructural and mechanical changes which occur during oscillatory shear flow and reformation after flow cessation of an intermediate volume fraction colloidal gel using rheometry and Brownian Dynamics (BD) simulations. A model depletion colloid-polymer mixture is used, comprising of a hard sphere colloidal suspension with the addition of non-adsorbing linear polymer chains. Results reveal three distinct regimes depending on the strain amplitude of oscillatory shear. Large shear strain amplitudes fully break the structure which results into a more homogenous and stronger gel after flow cessation. Intermediate strain amplitudes densify the clusters and lead to highly heterogeneous and weak gels. Shearing the gel to even lower strain amplitudes creates a less heterogonous stronger solid. These three regimes of shearing are connected to the microscopic shear-induced structural heterogeneity. A comparison with steady shear flow reveals that the latter does not produce structural heterogeneities as large as oscillatory shear. Therefore oscillatory shear is a much more efficient way of tuning the mechanical properties of colloidal gels. Moreover, colloidal gels presheared at large strain amplitudes exhibit a distinct nonlinear response characterized largely by a single yielding process while in those presheared at lower rates a two step yield process is promoted due to the creation of highly heterogeneous structures.2

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Viscoelasticity and rheology of depletion flocculated gels and fluids

Cited by 117 publications

References 57 publications

Depletion gels from dense soft colloids: Rheology and thermoreversible melting

Depletion gels from dense soft colloids: Rheology and thermoreversible melting

Effect of weak attractive interactions on flow behavior of highly concentrated crystalline suspensions

Colloidal gels tuned by oscillatory shear

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