Dynamical mechanical properties of gelling colloidal disks

Cocard, Stéphane; Tassin, Jean-François; Nicolai, Taco

doi:10.1122/1.551107

Cited by 88 publications

(106 citation statements)

References 25 publications

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“…The ageing dynamics shown in figure 3 essentially capture this, where an increase in the salt concentration changes the evolution of complex viscosity (elastic modulus) with age. Cocard et al (2000) reported that the rate of gelation increases with ionic strength. However, if the increase in complex viscosity with age is considered as a signature of ageing (or gelation at higher ionic strength), we observe that after sufficient age, the rate of gelation decreases with the increase in ionic strength.…”

Section: Resultsmentioning

confidence: 99%

“…Lately, the focus of various studies is dominated by understanding the microstructural description through rheological measurements. Cocard et al (2000) studied the frequency dependence of the time evolution of the elastic modulus for an ageing laponite suspension that is in a gel state at various salt concentrations. They also observed that frequency dependence of the elastic and viscous moduli, which is similar to that of a viscous liquid at a small age, weakens with age (or gelation time).…”

Section: Introductionmentioning

confidence: 99%

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Rheological behaviour of aqueous suspensions of laponite: new insights into the ageing phenomena

et al. 2007

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In this paper, the ageing behaviour of suspensions of laponite with varying salt concentration is investigated using rheological tools. It is observed that ageing is accompanied by an increase in the complex viscosity. The creep experiments performed at various ages show damped oscillations in the strain. The characteristic time scale of the damped oscillations, the retardation time, shows a prominent decrease with increasing age of the system. However, this dependence weakens with an increase in the salt concentration, which is known to change the microstructure of the system from glass like to gel like. We postulate that a decrease in the retardation time can be represented as a decrease in the viscosity (friction) of the dissipative environment surrounding the arrested entities that oppose elastic deformation of the system. We believe that ageing in colloidal glass leads to a greater ordering that enhances relative spacing between the constituents, thereby reducing the frictional resistance. However, since a gel state is inherently different in structure (fractal network) to that of a glass state (disordered), ageing in the gel does not induce ordering. Consequently, we observe an inverse dependence of retardation time on age, which becomes weaker with an increase in the salt concentration. We analyse these results from the perspective of ageing dynamics of both glass and gel states of laponite suspensions.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rheological behaviour of aqueous suspensions of laponite: new insights into the ageing phenomena

et al. 2007

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“…Such expectation is based on the observation that similar master curves, through rescaling, represent the time-dependent rheology of such diverse materials as cross-linking epoxies, 10 aging of colloidal suspensions with weakly attractive particles, 12 Laponite clay suspensions, [13][14][15][16][17][18] and surface aggregation. This suggests that, when applying such scaling methods to our model material, a general framework of ripening dynamics might become apparent through the experimental findings with a model material.…”

Section: Introductionmentioning

confidence: 99%

Late-State Ripening Dynamics of a Polymer/Clay Nanocomposite

et al. 2010

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A remarkably simple viscoelastic relaxation pattern was found for a physical gel that, beyond its gel point, slowly ripens toward a stable structural state. The material is a nanocomposite that consists of two components, an organoclay and an end-functionalized polymer, which get mixed at prescribed ratio. When freshly combined, the polymer intercalates into the clay galleries and eventually exfoliates the clay. The exfoliation occurs without applying flow. The nanocomposite quickly passes through the gel point and, with increasing ripening time, t r , its characteristic modulus G c (t r ) and relaxation time λ c (t r ) grow and decay by orders of magnitude, respectively. Surprisingly, their product, G c (t r )λ c (t r ), is found to remain constant during the two vastly different structuring processes of intercalation and exfoliation. For the rheological experiments, G c (t r )λ c (t r ) = constant means that dynamic mechanical data can be merged into each other by log/log shifting under 45°.

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“…[19][20][21] For instance, for the widely studied case of hardsphere colloids, the glassy phase (repulsion-dominated) is formed for volume fractions f > 0.5 as a result of excluded volume interactions and strong dynamic cooperativity in the absence of a macroscopic phase separation; 1,2,22 in the same systems, gelation (attraction dominated) takes place at low volume fractions (f $ 0.2) but only under the influence of osmotic force of added depletants. 9,12,22,23 In contrast, in clay suspensions (which are typical anisotropic systems), like laponite consisting of charged colloidal discs, dynamic frustration occurs at relatively low f ( 0.5, implying a large effective pervaded volume without necessarily the involvement of a phase separation; 18,19,[23][24][25][26][27] this is analogous to the differences between polymeric flexible coils and rods. 28 Note that gelation is much more common in these anisotropic systems than glass transition (at high volume fractions orientational order and/or phase separation may well take place).…”

Section: -18mentioning

confidence: 99%

Solvent-mediated pathways to gelation and phase separation in suspensions of grafted nanoparticles

et al. 2009

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We explore the role of the solvent medium on the interplay between gelation and phase separation in suspensions of organosilicate planar hybrids grafted with hydrocarbon chains. We establish their phase diagram by means of dynamic light scattering, rheology and visual observations, and different routes to gelation, depending on the solvent used. In agreement with earlier works, the solvent quality for the grafted chains at a given temperature controls the balance between attractions and repulsions, and hence the phase diagram of the nanoparticles and their tendency to gel. Here we show how to tune the suspension state and hence its rheology. For decane, a good solvent for the hydrocarbon chains, gelation occurs at rather low volume fractions in the presence of phase separation. This is due to the interdigitation of solvent molecules with the grafted chains, resulting in their crystalline packing that promotes the attraction between particles. For toluene, a solvent of reduced quality for the hydrocarbon chains, no interdigitation takes place, and hence gelation is triggered by clustering at higher volume fractions before phase separation. Our results support the generic picture of complex kinetic arrest/phase separation interplay in soft matter, where phase separation can proceed, be interrupted or be completely inhibited. A number of interesting possibilities for tailoring the rheology of grafted colloidal systems emerge.

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Dynamical mechanical properties of gelling colloidal disks

Cited by 88 publications

References 25 publications

Rheological behaviour of aqueous suspensions of laponite: new insights into the ageing phenomena

Rheological behaviour of aqueous suspensions of laponite: new insights into the ageing phenomena

Late-State Ripening Dynamics of a Polymer/Clay Nanocomposite

Solvent-mediated pathways to gelation and phase separation in suspensions of grafted nanoparticles

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