Non-linear rheology of a face-centred cubic phase in a diblock copolymer gel

Daniel, Christophe; Hamley, Ian W.; Wilhelm, Manfred; Mingvanish, Withawat

doi:10.1007/s003970000124

Cited by 63 publications

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“…Though we did not find cross over between G′ and G′′ within measured frequency range, judging from the trends, it could be assumed that G′ and G′′ intersect each other below this frequency, i.e., the system shows viscoelastic behavior. The value of G′ slightly increases with frequency and monotonically increases with squalane concentration in the I 1 phase and reaches a value ( 10 5 Pa), which is consistent with a hard gel cubic structure 23) . Simultaneously, the cross over between G′ and G′′ is expected to shift lower frequency although not detected in measured range, indicating an increase in the relaxation time.…”

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confidence: 56%

Phase Behavior, Formation, and Rheology of Cubic Phase and Related Gel Emulsion in Tween80/Water/Oil Systems

2009

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We investigated the phase behavior, formation, and rheology of the cubic phase (I 1 ) and related O/I 1 gel emulsion in water/Tween 80/oil systems using squalane, liquid paraffin (LP), and decane as oil components. In the phase behavior study, the phase sequences were similar for squalane and LP systems, while a lamellar liquid crystal (L a ) was observed for decane system. In all the systems the addition of oil to W m or H 1 phase induced the I 1 phase, which can solubilize some amounts of oil followed by the appearance of I 1 +O phase. The formation of the O/I 1 gel emulsion has been studied at a fixed w/s (50/50) and we found that 30 wt% decane, 70 wt% squalane, and 60 wt% LP can form the gel emulsion. The water/Tween 80/squalane system has been taken as a model system to study viscoelastic properties of the I 1 phase and O/I 1 gel emulsion. The I 1 phase shows a typical hard gel cubic structure under the frequency and the values of the complex viscosity, |h*| and the elastic modulus, G¢ increase with the addition of squalane, which could be due to the neighboring micellar interaction. On the other hand, the decreasing values of the viscoelastic parameters in the O/I 1 gel emulsion simply relate to the volume fraction of the I 1 phase in the system.

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confidence: 56%

Phase Behavior, Formation, and Rheology of Cubic Phase and Related Gel Emulsion in Tween80/Water/Oil Systems

2009

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“…The I 1 phase is normally formed between the micellar and the hexagonal phase as a function of surfactant concentration. Several authors studied the rheological behavior of the I 1 phase [31,32] and O/I 1 gel emulsion [22,24].…”

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Effect of molecular weight of triglycerides on the formation and rheological behavior of cubic and hexagonal phase based gel emulsions

Alam

Aramaki

2009

Journal of Colloid and Interface Science

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“…The pronounced peak in the loss modulus is a remarkably robust feature of soft glassy materials [1,3,5,6,7]. The ubiquitousness and similarity of the rheological response, both linear and nonlinear, of so many soft materials suggests that the response is governed by a common underlying mechanism.…”

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“…We show that SRFS can isolate the response due to structural relaxation, even when it occurs at frequencies too low to be accessible with standard techniques. Concentrated suspensions [1], pastes [2], emulsions [3], foams [4], or associative polymer systems [5,6] represent commonly encountered examples of soft solids. Their structures are often metastable, with dynamics strongly reminescent of that of glasses.…”

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Strain-Rate Frequency Superposition: A Rheological Probe of Structural Relaxation in Soft Materials

et al. 2007

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The rheological properties of soft materials often exhibit surprisingly universal linear and non-linear features. Here we show that these properties can be unified by considering the effect of the strainrate amplitude on the structural relaxation of the material. We present a new form of oscillatory rheology, Strain-Rate Frequency Superposition (SRFS), where the strain-rate amplitude is fixed as the frequency is varied. We show that SRFS can isolate the response due to structural relaxation, even when it occurs at frequencies too low to be accessible with standard techniques. , is remarkably similar. The storage modulus G ′ is only very weakly dependent on frequency. The loss modulus G ′′ also shows a very weak frequency dependence and is much larger than the response due to the continuous phase fluid. It often exhibits a shallow minimum near the lowest experimentally accessible frequencies. At even lower frequencies, there should be a crossover from solid-like to liquid-like behavior which is signaled by a pronounced peak in G ′′ (ω), reflecting the structural relaxation. Unfortunately, the relaxation frequencies are often much too low to be accessed by standard linear rheological measurements. A typical example of this linear viscoelastic behavior is shown in Fig. 1(a) for soft hydrogel spheres. Remarkably, the similarities in the rheological response of these materials extend even to nonlinear measurements, characterized by straindependent viscoelastic measurements performed at constant ω, varying the strain amplitude. Above a critical yield strain, the storage modulus exhibits a power-law decay. By contrast, the loss modulus exhibits a well-defined peak, before falling as a power-law; typically with ν ′′ ≈ ν ′ /2. The pronounced peak in the loss modulus is a remarkably robust feature of soft glassy materials [1,3,5,6,7]. The ubiquitousness and similarity of the rheological response, both linear and nonlinear, of so many soft materials suggests that the response is governed by a common underlying mechanism. A possible clue to the origin of this behavior comes from a proposed explanation for the response of a supercooled fluid [9]. Within this picture, the peak in G ′′ (γ 0 ) observed in nonlinear measurements is directly related to a decrease of the structural relaxation time with increasing shear rate [8,10,11,12,13]; the applied strain drives the relaxation and forces it to a higher frequency, where it is directly probed. While this picture provides an excellent description of a colloidal supercooled liquid, the underlying physical concept should be much more generally applicable. If this link is verified, the relaxation could be probed using the nonlinear response, even when the relaxation frequency is experimentally inaccessible. This would provide a new probe of the dynamics and rheology of soft materials. However, there have been no attempts to exploit this behavior and explore its general applicability to a variety of different materials.In this Letter, we show that the typical linear and nonlinear vis...

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Non-linear rheology of a face-centred cubic phase in a diblock copolymer gel

Cited by 63 publications

References 0 publications

Phase Behavior, Formation, and Rheology of Cubic Phase and Related Gel Emulsion in Tween80/Water/Oil Systems

Phase Behavior, Formation, and Rheology of Cubic Phase and Related Gel Emulsion in Tween80/Water/Oil Systems

Effect of molecular weight of triglycerides on the formation and rheological behavior of cubic and hexagonal phase based gel emulsions

Strain-Rate Frequency Superposition: A Rheological Probe of Structural Relaxation in Soft Materials

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