Stress-activated constraints in dense suspension rheology

Singh, Abhinendra; Jackson, Grayson L.; Naald, Michael van der; Pablo, Juan; Jaeger, Heinrich M.

doi:10.1103/physrevfluids.7.054302

Cited by 16 publications

(18 citation statements)

References 57 publications

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“… 11 While great strides have been made in understanding the constraint-based physics of dense suspensions, an emerging challenge is to connect microscopic constraints to specific chemical interactions. 22 …”

Section: Introductionmentioning

confidence: 99%

“…When the viscosity does evolve with time at a constant shear rate as in thixotropy (or antithixotropy), this signals the release (or formation) of constraints . While great strides have been made in understanding the constraint-based physics of dense suspensions, an emerging challenge is to connect microscopic constraints to specific chemical interactions …”

Section: Introductionmentioning

confidence: 99%

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Designing Stress-Adaptive Dense Suspensions Using Dynamic Covalent Chemistry

et al. 2022

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The non-Newtonian behaviors of dense suspensions are central to their use in technological and industrial applications and arise from a network of particle–particle contacts that dynamically adapt to imposed shear. Reported herein are studies aimed at exploring how dynamic covalent chemistry between particles and the polymeric solvent can be used to tailor such stress-adaptive contact networks, leading to their unusual rheological behaviors. Specifically, a room temperature dynamic thia-Michael bond is employed to rationally tune the equilibrium constant ( K eq ) of the polymeric solvent to the particle interface. It is demonstrated that low K eq leads to shear thinning, while high K eq produces antithixotropy, a rare phenomenon where the viscosity increases with shearing time. It is proposed that an increase in K eq increases the polymer graft density at the particle surface and that antithixotropy primarily arises from partial debonding of the polymeric graft/solvent from the particle surface and the formation of polymer bridges between particles. Thus, the implementation of dynamic covalent chemistry provides a new molecular handle with which to tailor the macroscopic rheology of suspensions by introducing programmable time dependence. These studies open the door to energy-absorbing materials that not only sense mechanical inputs and adjust their dissipation as a function of time or shear rate but also can switch between these two modalities on demand.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Designing Stress-Adaptive Dense Suspensions Using Dynamic Covalent Chemistry

et al. 2022

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“…An offset Δ T may arise from two effects: (1) Polymer glass transition is a kinetic event where the dynamics can start to slow down at temperatures as much as 50 °C higher than T g and the characteristic dissipation length scale has a measurable increase at more than 15 °C higher than T g . (2) Polymer interfaces under confinement and, in particular, with different deformation rates can exhibit dynamics different from the bulk. , This result motivates further research to quantify how polymer stress relaxation at the interface can influence the constraints on particle relative motions . For the three materials considered here, the fact that the maximum observed β strongly tracks with T g offers a general yet simple approach to controlling the shear thickening characteristics of dense suspensions by simply tuning the T g of the cross-linked particles.…”

Section: Results and Discussionmentioning

confidence: 90%

“…34,35 This result motivates further research to quantify how polymer stress relaxation at the interface can influence the constraints on particle relative motions. 67 For the three materials considered here, the fact that the maximum observed β strongly tracks with T g offers a general yet simple approach to controlling the shear thickening characteristics of dense suspensions by simply tuning the T g of the cross-linked particles.…”

Section: ■ Results and Discussionmentioning

confidence: 93%

“…While the three types of particles have different sizes (ranging from ca. 1 to 3.5 μm), the effect of particle size is well understood and has been shown to mainly affect the onset shear stress of thickening but not the trend in β. ,, For these higher T g suspensions, the nonmonotonic behavior in β is found to be similar for all particle compositions. The peak, however, is shifted to higher temperatures, consistent with the changes in T g (Figure B–D, see Figure S9 for the flow curves).…”

Section: Results and Discussionmentioning

confidence: 93%

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Leveraging the Polymer Glass Transition to Access Thermally Switchable Shear Jamming Suspensions

et al. 2023

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Suspensions of polymeric nano- and microparticles are fascinating stress-responsive material systems that, depending on their composition, can display a diverse range of flow properties under shear, such as drastic thinning, thickening, and even jamming (reversible solidification driven by shear). However, investigations to date have almost exclusively focused on nonresponsive particles, which do not allow in situ tuning of the flow properties. Polymeric materials possess rich phase transitions that can be directly tuned by their chemical structures, which has enabled researchers to engineer versatile adaptive materials that can respond to targeted external stimuli. Reported herein are suspensions of (readily prepared) micrometer-sized polymeric particles with accessible glass transition temperatures (T g) designed to thermally control their non-Newtonian rheology. The underlying mechanical stiffness and interparticle friction between particles change dramatically near T g. Capitalizing on these properties, it is shown that, in contrast to conventional systems, a dramatic and nonmonotonic change in shear thickening occurs as the suspensions transition through the particles’ T g. This straightforward strategy enables the in situ turning on (or off) of the system’s ability to shear jam by varying the temperature relative to T g and lays the groundwork for other types of stimuli-responsive jamming systems through polymer chemistry.

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