P. J. McCauley, Christine Huang, L. Porcar, Satish Kumar, M. Calabrese
The formation and evolution of a heterogeneous flow and flow reversal are examined in highly elastic, gel-like wormlike micelles (WLMs) formed from an amphiphilic triblock poloxamer P234 in 2M NaCl. A combination of linear viscoelastic, steady shear, and creep rheology demonstrate that these WLMs have a yield stress and exhibit viscoelastic aging, similar to some soft glassy materials. Nonlinear shear rheology and rheoparticle tracking velocimetry reveal that these poloxamer WLMs undergo a period of strong elastic recoil and flow reversal after the onset of shear startup. As flow reversal subsides, a fluidized high shear rate region and a nearly immobile low shear rate region of fluid form, accompanied by wall slip and elastic instabilities. The features of this flow heterogeneity are reminiscent of those for aging yield stress fluids, where the heterogeneous flow forms during the initial stress overshoot and is sensitive to the inherent stress gradient of the flow geometry. Additionally, macroscopic bands that form transiently above a critical shear rate become “trapped” due to viscoelastic aging in the nearly immobile region. This early onset of the heterogeneous flow during the rapidly decreasing portion of the stress overshoot differs from that typically observed in shear banding WLMs and is proposed to be necessary for observing significant flow reversal. Exploring the early-time, transient behavior of this WLM gel with rheology similar to both WLM solutions and soft glassy materials provides new insights into spatially heterogeneous flows in both of these complex fluids.
{"title":"Evolution of flow reversal and flow heterogeneities in high elasticity wormlike micelles (WLMs) with a yield stress","authors":"P. J. McCauley, Christine Huang, L. Porcar, Satish Kumar, M. Calabrese","doi":"10.1122/8.0000535","DOIUrl":"https://doi.org/10.1122/8.0000535","url":null,"abstract":"The formation and evolution of a heterogeneous flow and flow reversal are examined in highly elastic, gel-like wormlike micelles (WLMs) formed from an amphiphilic triblock poloxamer P234 in 2M NaCl. A combination of linear viscoelastic, steady shear, and creep rheology demonstrate that these WLMs have a yield stress and exhibit viscoelastic aging, similar to some soft glassy materials. Nonlinear shear rheology and rheoparticle tracking velocimetry reveal that these poloxamer WLMs undergo a period of strong elastic recoil and flow reversal after the onset of shear startup. As flow reversal subsides, a fluidized high shear rate region and a nearly immobile low shear rate region of fluid form, accompanied by wall slip and elastic instabilities. The features of this flow heterogeneity are reminiscent of those for aging yield stress fluids, where the heterogeneous flow forms during the initial stress overshoot and is sensitive to the inherent stress gradient of the flow geometry. Additionally, macroscopic bands that form transiently above a critical shear rate become “trapped” due to viscoelastic aging in the nearly immobile region. This early onset of the heterogeneous flow during the rapidly decreasing portion of the stress overshoot differs from that typically observed in shear banding WLMs and is proposed to be necessary for observing significant flow reversal. Exploring the early-time, transient behavior of this WLM gel with rheology similar to both WLM solutions and soft glassy materials provides new insights into spatially heterogeneous flows in both of these complex fluids.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44139077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lithium-ion battery cathode slurries have a microstructure that depends sensitively on how they are processed due to carbon black's (CB) evolving structure when subjected coating flows. While polyvinylidene difluoride (PVDF), one of the main components of the cathode slurry, plays an important role in modifying the structure and rheology of CB, a quantitative understanding is lacking. In this work, we explore the role of PVDF in determining the structural evolution of Super C65 CB in N-methyl-2-pyrrolidinone (NMP) with rheo-electric measurements. We find that PVDF enhances the viscosity of NMP resulting in a more extensive structural erosion of CB agglomerates with increasing polymer concentration and molecular weight. We also show that the relative viscosity of all suspensions can be collapsed by the fluid Mason number [Formula: see text], which compares the hydrodynamic forces imposed by the medium to cohesive forces holding CB agglomerates together. Using simultaneous rheo-electric measurements, we find at high [Formula: see text], the dielectric strength [Formula: see text] scales with [Formula: see text], and the power-law scaling can be quantitatively predicted by considering the self-similar break up of CB agglomerates. The collapse of the relative viscosity and scaling of [Formula: see text] both suggest that PVDF increases the hydrodynamic force of the suspending medium without directly changing the CB agglomerate structure. These findings are valuable for optimizing the rheology of lithium ion battery cathode slurries. We also anticipate that these findings can be extended to understand the microstructure of similar systems under flow.
{"title":"Rheo-electric measurements of carbon black suspensions containing polyvinylidene difluoride in N-methyl-2-pyrrolidone","authors":"Qingsong Liu, J. J. Richards","doi":"10.1122/8.0000615","DOIUrl":"https://doi.org/10.1122/8.0000615","url":null,"abstract":"Lithium-ion battery cathode slurries have a microstructure that depends sensitively on how they are processed due to carbon black's (CB) evolving structure when subjected coating flows. While polyvinylidene difluoride (PVDF), one of the main components of the cathode slurry, plays an important role in modifying the structure and rheology of CB, a quantitative understanding is lacking. In this work, we explore the role of PVDF in determining the structural evolution of Super C65 CB in N-methyl-2-pyrrolidinone (NMP) with rheo-electric measurements. We find that PVDF enhances the viscosity of NMP resulting in a more extensive structural erosion of CB agglomerates with increasing polymer concentration and molecular weight. We also show that the relative viscosity of all suspensions can be collapsed by the fluid Mason number [Formula: see text], which compares the hydrodynamic forces imposed by the medium to cohesive forces holding CB agglomerates together. Using simultaneous rheo-electric measurements, we find at high [Formula: see text], the dielectric strength [Formula: see text] scales with [Formula: see text], and the power-law scaling can be quantitatively predicted by considering the self-similar break up of CB agglomerates. The collapse of the relative viscosity and scaling of [Formula: see text] both suggest that PVDF increases the hydrodynamic force of the suspending medium without directly changing the CB agglomerate structure. These findings are valuable for optimizing the rheology of lithium ion battery cathode slurries. We also anticipate that these findings can be extended to understand the microstructure of similar systems under flow.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49062181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present an algorithm to predict the linear relaxation spectra for linear polymers of fully general and arbitrary polydispersity. As is common in the tube theory descriptions of linear polymers, we assume that the stress relaxation is affected by both the constraint release and tube escape modes, but unlike most existing descriptions we consider how these two modes of relaxation affect each other. We argue that the proper description for relaxation in an arbitrary blend of linear polymers requires consideration of multiple embedded tubes affecting the different relaxation pathways; we propose a novel but minimal description involving five embedded tubes. Building on prior work for binary blends, we derive the scaling level descriptions of the relaxation pathways. We use a large number of existing experimental results on the stress and dielectric relaxations to validate our model, ensuring we explore a very broad range of parameter space.
{"title":"A tube model for predicting the stress and dielectric relaxations of polydisperse linear polymers","authors":"Chinmay Das, D. Read","doi":"10.1122/8.0000605","DOIUrl":"https://doi.org/10.1122/8.0000605","url":null,"abstract":"We present an algorithm to predict the linear relaxation spectra for linear polymers of fully general and arbitrary polydispersity. As is common in the tube theory descriptions of linear polymers, we assume that the stress relaxation is affected by both the constraint release and tube escape modes, but unlike most existing descriptions we consider how these two modes of relaxation affect each other. We argue that the proper description for relaxation in an arbitrary blend of linear polymers requires consideration of multiple embedded tubes affecting the different relaxation pathways; we propose a novel but minimal description involving five embedded tubes. Building on prior work for binary blends, we derive the scaling level descriptions of the relaxation pathways. We use a large number of existing experimental results on the stress and dielectric relaxations to validate our model, ensuring we explore a very broad range of parameter space.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45203471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
From a mechanical perspective, blood is a complex fluid with a rate- and time-dependent response to an applied deformation. At small deformation rates, cell aggregations owing to the bridging of fibrinogen proteins result in the formation of rouleaux structures manifesting in a large increase in the overall viscosity of the blood viscosity and the emergence of measurable yield stress. At elevated deformation rates, these internal aggregated mesostructures are broken down in a dynamical fashion, giving rise to a thermokinematic memory and thixotropic behavior of the blood. These rich and complex rheological features of blood are primarily governed by the interactions between different cells as well as the fraction of red blood cells (RBCs). Here, using a series of detailed computational tools and benchmarking experimental measurements, we present a constitutive model that accurately describes the rate- and time-dependent rheology of blood based on two physiological metrics of the blood: the hematocrit and fibrinogen concentration. We show that the model is capable of accurately predicting blood flow, not only under simple steady flows but also under different flow protocols relevant to a real circulatory system.
{"title":"A fully physiologically-informed time- and rate-dependent hemorheological constitutive model","authors":"E. Javadi, M. Armstrong, S. Jamali","doi":"10.1122/8.0000552","DOIUrl":"https://doi.org/10.1122/8.0000552","url":null,"abstract":"From a mechanical perspective, blood is a complex fluid with a rate- and time-dependent response to an applied deformation. At small deformation rates, cell aggregations owing to the bridging of fibrinogen proteins result in the formation of rouleaux structures manifesting in a large increase in the overall viscosity of the blood viscosity and the emergence of measurable yield stress. At elevated deformation rates, these internal aggregated mesostructures are broken down in a dynamical fashion, giving rise to a thermokinematic memory and thixotropic behavior of the blood. These rich and complex rheological features of blood are primarily governed by the interactions between different cells as well as the fraction of red blood cells (RBCs). Here, using a series of detailed computational tools and benchmarking experimental measurements, we present a constitutive model that accurately describes the rate- and time-dependent rheology of blood based on two physiological metrics of the blood: the hematocrit and fibrinogen concentration. We show that the model is capable of accurately predicting blood flow, not only under simple steady flows but also under different flow protocols relevant to a real circulatory system.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48501240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We study the effect of varying polymer concentration, measured by the dimensionless polymer viscosity partition function [Formula: see text], on the steady shear rheology of rigid particle suspensions using direct numerical simulation of the Oldroyd-B model. We compare the bulk rheology using immersed boundary simulations at [Formula: see text] and [Formula: see text] to body-fitted single-particle simulations and find that the per-particle viscosity and first normal stress difference coefficient are always shear-thickening at all values of [Formula: see text] considered. However, as [Formula: see text] decreases, the polymer stress transforms the flow field near each particle from closed concentric streamlines to helical streamlines that advect stretched polymers away from the particle surface. At low [Formula: see text], the polymer stress is diffuse, where the distribution of the particle induced fluid stress (PIFS) caused by the stretched polymers is spread out in the simulation domain rather than concentrated near the particle surface. Therefore in multiparticle simulations, the polymer stress can be significantly affected by particle-particle interactions. The stress generated by a given particle is disrupted by the presence of particles in its vicinity, leading to a significantly lower PIFS than that of the single-particle simulation. In addition, at increased volume fractions and low values of [Formula: see text], the polymer stress distribution on the particle surface shifts so as to increase the magnitude of the polymer stress moments, resulting in a shear-thickening stresslet contribution to the viscosity that is not seen in single particle or high [Formula: see text] simulations. This result indicates that for suspensions in highly viscoelastic suspending fluids that are characterized by a low [Formula: see text] parameter, hydrodynamic interactions are significant even at modest particle concentrations and fully resolved multiparticle simulations are necessary to understand the rheological behavior.
{"title":"Rheology of non-Brownian particle suspensions in viscoelastic solutions. Part 1: Effect of the polymer concentration","authors":"Anni Zhang, E. Shaqfeh","doi":"10.1122/8.0000540","DOIUrl":"https://doi.org/10.1122/8.0000540","url":null,"abstract":"We study the effect of varying polymer concentration, measured by the dimensionless polymer viscosity partition function [Formula: see text], on the steady shear rheology of rigid particle suspensions using direct numerical simulation of the Oldroyd-B model. We compare the bulk rheology using immersed boundary simulations at [Formula: see text] and [Formula: see text] to body-fitted single-particle simulations and find that the per-particle viscosity and first normal stress difference coefficient are always shear-thickening at all values of [Formula: see text] considered. However, as [Formula: see text] decreases, the polymer stress transforms the flow field near each particle from closed concentric streamlines to helical streamlines that advect stretched polymers away from the particle surface. At low [Formula: see text], the polymer stress is diffuse, where the distribution of the particle induced fluid stress (PIFS) caused by the stretched polymers is spread out in the simulation domain rather than concentrated near the particle surface. Therefore in multiparticle simulations, the polymer stress can be significantly affected by particle-particle interactions. The stress generated by a given particle is disrupted by the presence of particles in its vicinity, leading to a significantly lower PIFS than that of the single-particle simulation. In addition, at increased volume fractions and low values of [Formula: see text], the polymer stress distribution on the particle surface shifts so as to increase the magnitude of the polymer stress moments, resulting in a shear-thickening stresslet contribution to the viscosity that is not seen in single particle or high [Formula: see text] simulations. This result indicates that for suspensions in highly viscoelastic suspending fluids that are characterized by a low [Formula: see text] parameter, hydrodynamic interactions are significant even at modest particle concentrations and fully resolved multiparticle simulations are necessary to understand the rheological behavior.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43216451","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ahmad Awdi, C. Chateau, F. Chevoir, J. Roux, A. Fall
The present work investigates nonlinear behavior in large amplitude oscillatory shear (LAOS) of unsaturated wet granular materials using pressure-imposed rheometric measurements that enable to explore how the material properties characterizing the flow response depend on both strain amplitude and frequency of deformation. Away from the quasistatic limit, we show that the energy dissipated per unit volume in a single LAOS cycle, which can be visualized by the area enclosed by the Lissajous curve of stress versus strain, is an increasing function of the viscosity of the wetting liquid and is also influenced by the reduced pressure (comparing the cohesive to confining forces) and the frequency. Introducing the inertial number [Formula: see text] and the viscous number [Formula: see text] as previously done, it is shown that the influence of surface tension, viscosity, and driving frequency can be captured by plotting the dissipated energy per unit volume versus the viscous number: a good collapse is obtained. It is shown that an increase in liquid content shifts the whole curve of the dissipated energy upwards, indicating that the overall dissipation mechanism does not change with liquid content, only the energy dissipation related to the internal structure and its breakdown changes.
{"title":"Viscous dissipation in large amplitude oscillatory shear of unsaturated wet granular matter","authors":"Ahmad Awdi, C. Chateau, F. Chevoir, J. Roux, A. Fall","doi":"10.1122/8.0000507","DOIUrl":"https://doi.org/10.1122/8.0000507","url":null,"abstract":"The present work investigates nonlinear behavior in large amplitude oscillatory shear (LAOS) of unsaturated wet granular materials using pressure-imposed rheometric measurements that enable to explore how the material properties characterizing the flow response depend on both strain amplitude and frequency of deformation. Away from the quasistatic limit, we show that the energy dissipated per unit volume in a single LAOS cycle, which can be visualized by the area enclosed by the Lissajous curve of stress versus strain, is an increasing function of the viscosity of the wetting liquid and is also influenced by the reduced pressure (comparing the cohesive to confining forces) and the frequency. Introducing the inertial number [Formula: see text] and the viscous number [Formula: see text] as previously done, it is shown that the influence of surface tension, viscosity, and driving frequency can be captured by plotting the dissipated energy per unit volume versus the viscous number: a good collapse is obtained. It is shown that an increase in liquid content shifts the whole curve of the dissipated energy upwards, indicating that the overall dissipation mechanism does not change with liquid content, only the energy dissipation related to the internal structure and its breakdown changes.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43308165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. A. Ruíz-López, S. S. Prasanna Kumar, A. Vázquez-Quesada, J. D. de Vicente, M. Ellero
The rheology of concentrated suspensions of particles is complex and typically exhibits a shear-thickening behavior in the case of repulsive interactions. Despite the recent interest arisen, the causes of the shear-thickening remain unclear. Frictional contacts have been able to explain the discontinuous shear thickening in simulations. However, the interparticle friction coefficient is considered to be constant in most simulations and theoretical works reported to date despite the fact that tribological experiments demonstrate that the friction coefficient can not only be constant (boundary regime) but also decrease (mixed regime) or even increase (full-film lubrication regime), depending on the normal force and the relative velocity between the particles and the interstitial liquid between them. Interestingly, the transition between the boundary regime and the full-lubrication regime is governed by the particle average roughness. Particle-level simulations of suspensions of hard spheres were carried out using short-range lubrication and roughness-dependent frictional forces describing the full Stribeck curve. Suspensions with different particle’s roughness were simulated to show that the particle roughness is a key factor in the shear-thickening behavior; for sufficiently rough particles, the suspension exhibits a remarkable shear-thickening, while for sufficiently smooth particles, the discontinuous shear-thickening disappears.
{"title":"Tribological variable-friction coefficient models for the simulation of dense suspensions of rough polydisperse particles","authors":"J. A. Ruíz-López, S. S. Prasanna Kumar, A. Vázquez-Quesada, J. D. de Vicente, M. Ellero","doi":"10.1122/8.0000514","DOIUrl":"https://doi.org/10.1122/8.0000514","url":null,"abstract":"The rheology of concentrated suspensions of particles is complex and typically exhibits a shear-thickening behavior in the case of repulsive interactions. Despite the recent interest arisen, the causes of the shear-thickening remain unclear. Frictional contacts have been able to explain the discontinuous shear thickening in simulations. However, the interparticle friction coefficient is considered to be constant in most simulations and theoretical works reported to date despite the fact that tribological experiments demonstrate that the friction coefficient can not only be constant (boundary regime) but also decrease (mixed regime) or even increase (full-film lubrication regime), depending on the normal force and the relative velocity between the particles and the interstitial liquid between them. Interestingly, the transition between the boundary regime and the full-lubrication regime is governed by the particle average roughness. Particle-level simulations of suspensions of hard spheres were carried out using short-range lubrication and roughness-dependent frictional forces describing the full Stribeck curve. Suspensions with different particle’s roughness were simulated to show that the particle roughness is a key factor in the shear-thickening behavior; for sufficiently rough particles, the suspension exhibits a remarkable shear-thickening, while for sufficiently smooth particles, the discontinuous shear-thickening disappears.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47692169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Margaret Braunreuther, M. Liegeois, J. Fahy, G. Fuller
Programmable hydrogels, such as thiolated hydrogels, are frequently used for tissue engineering and drug delivery applications, because they offer the ability to control gelation, degradation, and adhesion. Understanding how the mechanical properties of these materials change during these processes is essential as they directly impact cell fate and delivery efficacy. The rheology of hydrogels has been quantified primarily via bulk rheological methods. While such methods are effective, they require large sample volumes and result in the destruction of the sample; therefore, responses to multiple stimuli must be recorded across many different samples. We have developed a magnetic microwire rheometer that can characterize the rheology of small sample volumes while maintaining the integrity of the sample, such that the material response to a range of stimuli can be recorded for a single sample. This capability enables insights into time-dependent rheological changes, such as gelation and degradation, and can be applied to characterize dynamic in situ systems that are the basis for tissue scaffolding, drug delivery vehicles, and other important biological applications.
{"title":"Nondestructive rheological measurements of biomaterials with a magnetic microwire rheometer","authors":"Margaret Braunreuther, M. Liegeois, J. Fahy, G. Fuller","doi":"10.1122/8.0000606","DOIUrl":"https://doi.org/10.1122/8.0000606","url":null,"abstract":"Programmable hydrogels, such as thiolated hydrogels, are frequently used for tissue engineering and drug delivery applications, because they offer the ability to control gelation, degradation, and adhesion. Understanding how the mechanical properties of these materials change during these processes is essential as they directly impact cell fate and delivery efficacy. The rheology of hydrogels has been quantified primarily via bulk rheological methods. While such methods are effective, they require large sample volumes and result in the destruction of the sample; therefore, responses to multiple stimuli must be recorded across many different samples. We have developed a magnetic microwire rheometer that can characterize the rheology of small sample volumes while maintaining the integrity of the sample, such that the material response to a range of stimuli can be recorded for a single sample. This capability enables insights into time-dependent rheological changes, such as gelation and degradation, and can be applied to characterize dynamic in situ systems that are the basis for tissue scaffolding, drug delivery vehicles, and other important biological applications.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49257818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Pasquino, Pietro Renato Avallone, S. Costanzo, Ionita Inbal, D. Danino, Vincenzo Ianniello, G. Ianniruberto, G. Marrucci, N. Grizzuti
We report on shear startup data for two wormlike micellar solutions, differing only in concentration and type of two binding aromatic sodium salts. The surfactant molecule is cetylpiridinium chloride at a fixed concentration (100 mM). Sodium salicylate (NaSal) and diclofenac sodium (Diclo) are used as binding salts at concentrations 68 mM NaSal and 52 mM Diclo such that both systems are fully entangled and their linear viscoelastic response is essentially identical. Both systems show the linear response typical of a wormlike micellar solution, with terminal behavior at low frequencies, a well-defined moduli crossover, and a plateau modulus. In the nonlinear regime, however, the behavior of the two systems is totally different, suggesting that the molecular structure difference of the salts and their binding activity to the surfactant molecule are both crucial to determine the fast flow behavior. The NaSal solution shows a very complex rheological response, with strain hardening and very sharp stress peaks, whereas the solution containing Diclo behaves much like ordinary linear polymers, exhibiting pronounced overshoots as well as moderate undershoots in the transient shear viscosity, before approaching the steady state. This polymerlike behavior has also been proved by successfully comparing data with predictions of a constitutive equation recently adopted for both entangled polymers and linear wormlike micelles. As far as NaSal is concerned, a phenomenological model based on rubber network theory is developed, which describes the flow singularities. A physical interpretation of the different behavior in the nonlinear regime is also suggested.
我们报道了两种类似蠕虫的胶束溶液的剪切启动数据，这两种溶液的不同之处仅在于两种结合芳香族钠盐的浓度和类型。表面活性剂分子是固定浓度（100 mM）。水杨酸钠（NaSal）和双氯芬酸钠（Diclo）用作浓度为68的结合盐 mM NaSal和52 mM-Diclo，使得两个系统完全纠缠并且它们的线性粘弹性响应基本上相同。这两个系统都显示出蠕虫状胶束溶液的典型线性响应，在低频下具有末端行为，具有明确的模量交叉和平台模量。然而，在非线性状态下，两个系统的行为完全不同，这表明盐的分子结构差异及其与表面活性剂分子的结合活性对决定快速流动行为都至关重要。NaSal溶液表现出非常复杂的流变响应，具有应变硬化和非常尖锐的应力峰值，而含有Diclo的溶液表现得非常像普通线性聚合物，在接近稳态之前，在瞬态剪切粘度中表现出明显的过冲和适度的下冲。通过将数据与最近采用的纠缠聚合物和线性蠕虫状胶束的本构方程的预测进行成功比较，也证明了这种类似聚合物的行为。就NaSal而言，基于橡胶网络理论建立了一个描述流动奇点的现象学模型。还提出了对非线性状态下不同行为的物理解释。
{"title":"On the startup behavior of wormlike micellar networks: The effect of different salts bound to the same surfactant molecule","authors":"R. Pasquino, Pietro Renato Avallone, S. Costanzo, Ionita Inbal, D. Danino, Vincenzo Ianniello, G. Ianniruberto, G. Marrucci, N. Grizzuti","doi":"10.1122/8.0000537","DOIUrl":"https://doi.org/10.1122/8.0000537","url":null,"abstract":"We report on shear startup data for two wormlike micellar solutions, differing only in concentration and type of two binding aromatic sodium salts. The surfactant molecule is cetylpiridinium chloride at a fixed concentration (100 mM). Sodium salicylate (NaSal) and diclofenac sodium (Diclo) are used as binding salts at concentrations 68 mM NaSal and 52 mM Diclo such that both systems are fully entangled and their linear viscoelastic response is essentially identical. Both systems show the linear response typical of a wormlike micellar solution, with terminal behavior at low frequencies, a well-defined moduli crossover, and a plateau modulus. In the nonlinear regime, however, the behavior of the two systems is totally different, suggesting that the molecular structure difference of the salts and their binding activity to the surfactant molecule are both crucial to determine the fast flow behavior. The NaSal solution shows a very complex rheological response, with strain hardening and very sharp stress peaks, whereas the solution containing Diclo behaves much like ordinary linear polymers, exhibiting pronounced overshoots as well as moderate undershoots in the transient shear viscosity, before approaching the steady state. This polymerlike behavior has also been proved by successfully comparing data with predictions of a constitutive equation recently adopted for both entangled polymers and linear wormlike micelles. As far as NaSal is concerned, a phenomenological model based on rubber network theory is developed, which describes the flow singularities. A physical interpretation of the different behavior in the nonlinear regime is also suggested.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49372731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The design of flow processes to build a macroscopic bulk material from rod-shaped colloidal particles has drawn considerable attention from researchers and engineers. Here, we systematically explore and show that the characteristic strain rate of the flow universally determines the orientational ordering of colloidal rods. We employed the fluctuating lattice Boltzmann method by simulating hydrodynamically interacting Brownian rods in a Newtonian liquid moving under various flow types. By modeling a rigid rod as a chain of nonoverlapping solid spheres with constraint forces and torque, we elucidate rigid rod dynamics with an aspect ratio ([Formula: see text]) either 4.1 or 8.1 under various rotational Péclet number ([Formula: see text]) conditions. The dynamics of colloidal rods in dilute ([Formula: see text]) and semidilute suspensions ([Formula: see text]) were simulated for a wide range of [Formula: see text] ([Formula: see text]) under shear flows including Couette and Poiseuille flows in a planar channel geometry, and an extensional and mixed-kinematics flow in a periodic four-roll mill geometry, where [Formula: see text] is the number density, and [Formula: see text] and [Formula: see text] are the diameter and length of the rod, respectively. By evaluating the degree of orientational alignment of rods along the flows, we observed that there is no significant difference between flow types, and the flow-induced ordering of rods depends on the variation of [Formula: see text] up to moderate [Formula: see text] ([Formula: see text]). At a high [Formula: see text] ([Formula: see text]), the degree of orientational ordering is prone to diversify depending on the flow type. The spatial inhomogeneity of the strain-rate distribution leads to a substantial decrease in the orientational alignment at high [Formula: see text].
{"title":"Universal flow-induced orientational ordering of colloidal rods in planar shear and extensional flows: Dilute and semidilute concentrations","authors":"Byoungjin Chun, H. Jung","doi":"10.1122/8.0000550","DOIUrl":"https://doi.org/10.1122/8.0000550","url":null,"abstract":"The design of flow processes to build a macroscopic bulk material from rod-shaped colloidal particles has drawn considerable attention from researchers and engineers. Here, we systematically explore and show that the characteristic strain rate of the flow universally determines the orientational ordering of colloidal rods. We employed the fluctuating lattice Boltzmann method by simulating hydrodynamically interacting Brownian rods in a Newtonian liquid moving under various flow types. By modeling a rigid rod as a chain of nonoverlapping solid spheres with constraint forces and torque, we elucidate rigid rod dynamics with an aspect ratio ([Formula: see text]) either 4.1 or 8.1 under various rotational Péclet number ([Formula: see text]) conditions. The dynamics of colloidal rods in dilute ([Formula: see text]) and semidilute suspensions ([Formula: see text]) were simulated for a wide range of [Formula: see text] ([Formula: see text]) under shear flows including Couette and Poiseuille flows in a planar channel geometry, and an extensional and mixed-kinematics flow in a periodic four-roll mill geometry, where [Formula: see text] is the number density, and [Formula: see text] and [Formula: see text] are the diameter and length of the rod, respectively. By evaluating the degree of orientational alignment of rods along the flows, we observed that there is no significant difference between flow types, and the flow-induced ordering of rods depends on the variation of [Formula: see text] up to moderate [Formula: see text] ([Formula: see text]). At a high [Formula: see text] ([Formula: see text]), the degree of orientational ordering is prone to diversify depending on the flow type. The spatial inhomogeneity of the strain-rate distribution leads to a substantial decrease in the orientational alignment at high [Formula: see text].","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46988668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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