Optimal conditions for pre-shearing thixotropic or aging soft materials

Choi, Jiho; Rogers, Simon A.

doi:10.1007/s00397-020-01250-4

Cited by 24 publications

(12 citation statements)

References 46 publications

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“…These features confer foams the properties of systems that are near the jamming transition, where mechanical noise effectively leads to local structural relaxation. However, while the properties of jammed materials sensitively depend on shear history, 38,39 the coarsening process in foam naturally erases shear history in time by constantly re-injecting mechanical noise into the system. This makes foams ideal systems to study the mechanics of almost jammed systems in the linear range.…”

Section: Discussionmentioning

confidence: 99%

Delayed elastic contributions to the viscoelastic response of foams

Lavergne

Sollich

Trappe

2022

The Journal of Chemical Physics

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We show that the slow viscoelastic response of a foam is that of a power-law fluid with a terminal relaxation. Investigations of the foam mechanics in creep and recovery tests reveal that the power-law contribution is fully reversible, indicative of a delayed elastic response. We demonstrate how this contribution fully accounts for the non-Maxwellian features observed in all tests, probing the linear mechanical response function. The associated power-law spectrum is consistent with soft glassy rheology of systems with mechanical noise temperatures just above the glass transition [Fielding et al., J. Rheol. 44, 323 (2000)] and originates from a combination of superdiffusive bubble dynamics and stress diffusion, as recently evidenced in simulations of coarsening foam [Hwang et al., Nat. Mater. 15, 1031 (2016)].

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Section: Discussionmentioning

confidence: 99%

Delayed elastic contributions to the viscoelastic response of foams

Lavergne

Sollich

Trappe

2022

The Journal of Chemical Physics

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“…Preshear imparts a directional memory inside the suspension which remembers the last direction it has been sheared, for a long period of time [40,41]. This memory effect can make the transient behavior of the suspensions dependent on the preshearing direction [55,56]. Here we use it as a way to track the influence of the preshear on the subsequent startup flow experiments.…”

Section: Reversibility Of the Startup Flow Responsementioning

confidence: 99%

“…Here we use it as a way to track the influence of the preshear on the subsequent startup flow experiments. We consider that the directional disturbance introduced by the preshear is negligible when the response is reversible upon flow reversal [56]. When the preshear direction is reversed (𝛾̇0 < 0, 𝛾̇> 0), the stress variations are affected, particularly at short waiting times, the stress overshoot being smaller and slightly shifted to lower strain values.…”

Section: Reversibility Of the Startup Flow Responsementioning

confidence: 99%

Transient dynamics of soft particle glasses in startup shear flow. Part II: Memory and aging

Dio

Khabaz

Bonnecaze

et al. 2022

Journal of Rheology

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We explore the rheology during a startup flow of well-characterized polyelectrolyte microgel suspensions, which form soft glasses above the jamming concentration. We present and discuss results measured using different mechanical histories focusing on the variations of the static yield stress and yield strain. The behavior of the shear stress growth function is affected by long-lived residual stresses and strains that imprint a slowly decaying mechanical memory inside the materials. The startup flow response is not reversible upon flow reversal and the amplitude of the static yield stress increases with the time elapsed after rejuvenation. We propose an experimental protocol that minimizes the directional memory and we analyze the effect of aging. The static yield strain γp and the reduced static yield stress σp/ σy, where σy is the dynamic yield stress measured from steady flow measurements, are in good agreement with our previous simulations [Khabaz et al., “Transient dynamics of soft particle glasses in startup shear flow. Part I: Microstructure and time scales,” J. Rheol. 65, 241 (2021)]. Our results demonstrate the need to consider memory and aging effects in transient measurements on soft particle glasses.

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“…60,61 The stress overshoot during shear was measured after various wait times while compensating for a measured recoverable strain after yielding between each step (Figure 6a and Figure S13). 59 McKinley and co-workers reported that the growth of this overshoot is representative of a characteristic recovery or restructuring time scale (Figure 6c−e). 62 We find that an analogous time scale (τ S ) can be found by fitting the stress overshoot growth data according to…”

Section: ■ Results and Discussionmentioning

confidence: 87%

“…To examine the time scale associated with recovery, or thixotropy, we performed stress-overshoot experiments on all formulations at shear rates in the flow regime . Stress overshoot behavior, while not fully understood, has been found to be characteristic of yield stress fluid behavior. , The stress overshoot during shear was measured after various wait times while compensating for a measured recoverable strain after yielding between each step (Figure a and Figure S13).…”

Section: Resultsmentioning

confidence: 99%

Extreme Extensibility in Physically Cross-Linked Nanocomposite Hydrogels Leveraging Dynamic Polymer–Nanoparticle Interactions

et al. 2022

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Designing yield stress fluids to exhibit desired functional properties is an integral challenge in many applications such as 3D printing, drilling, food formulation, fiber spinning, adhesives, and injectable biomaterials. Extensibility in particular has been found to be a highly beneficial characteristic for materials in these applications; however, few highly extensible, high water content materials have been reported to date. Herein we engineer a class of high water content nanocomposite hydrogel materials leveraging multivalent, noncovalent, polymer–nanoparticle (PNP) interactions between modified cellulose polymers and biodegradable nanoparticles. We show that modulation of the chemical composition of the PNP hydrogels controls the dynamic cross-linking interactions within the polymer network and directly impacts yielding and viscoelastic responses. These materials can be engineered to stretch up to 2000% strain and occupy an unprecedented property regime for extensible yield stress fluids. Moreover, a dimensional analysis of the relationships between extensibility and the relaxation and recovery time scales of these nanocomposite hydrogels uncovers generalizable design criteria that will be critical for future development of extensible materials.

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Optimal conditions for pre-shearing thixotropic or aging soft materials

Cited by 24 publications

References 46 publications

Delayed elastic contributions to the viscoelastic response of foams

Delayed elastic contributions to the viscoelastic response of foams

Transient dynamics of soft particle glasses in startup shear flow. Part II: Memory and aging

Extreme Extensibility in Physically Cross-Linked Nanocomposite Hydrogels Leveraging Dynamic Polymer–Nanoparticle Interactions

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