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Agarwal M, Kaushal M, Joshi YM. Signatures of Overaging in an Aqueous Dispersion of Carbopol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:14849-14863. [PMID: 33241688 DOI: 10.1021/acs.langmuir.0c02887] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this work, we study the effect of the deformation field on the physical aging behavior of an aqueous Carbopol dispersion. It is composed of soft swollen particles of gel that get deformed and acquire a polygonal shape, with flat interfaces rendering the dispersion a soft solid-like consistency as filled volume fraction approaches unity. It has been proposed that owing to release of stored elastic energy in the deformed particles, Carbopol dispersion undergoes microstructural evolution that is reminiscent of physical aging in soft glassy materials. We observe that application of moderate magnitude of oscillatory strain to Carbopol dispersion slows down its relaxation dynamics, thereby showing characteristics of overaging. On the other hand, the sufficiently high magnitude of strain makes the relaxation dynamics faster, causing rejuvenation. We also solve the soft glassy rheology model, which, when subjected to the same flow field, corroborates with experimental observations on the Carbopol dispersion. This behavior, therefore, suggests that in a system of jammed soft particles of Carbopol, the particles occupying shallow energy wells upon application of moderate strain field adjust themselves in such a manner that they predominantly occupy the deeper energy wells leading to observe the overaging dynamics.
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Affiliation(s)
- Mayank Agarwal
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Manish Kaushal
- Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Yogesh M Joshi
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
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Suman K, Mittal M, Joshi YM. Effect of sodium pyrophosphate and understanding microstructure of aqueous LAPONITE ® dispersion using dissolution study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:224002. [PMID: 32015220 DOI: 10.1088/1361-648x/ab724d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In this work, we investigate the physical origin of ergodicity breaking in an aqueous colloidal dispersion of synthetic hectorite clay, LAPONITE®, by performing dissolution and rheological experiments with monovalent salt and tetrasodium pyrophosphate solution. We also study the effect of pH and nature of interface, nitrogen and paraffin oil on the same. Dissolution experiments carried out for dispersions with both the interfaces show similar results. However, for samples with a nitrogen interface, all the effects are observed to get expedited in time compared to a paraffin oil interface. When kept in contact with water, 1.5 wt.% and 2.8 wt.% colloidal dispersion at pH 10 swells at small ages, while it does not swell at large ages. The solution of tetrasodium pyrophosphate, interestingly, dissolves the entire colloidal dispersion sample with pH 10 irrespective of the concentration of clay. Experiments carried out on colloidal dispersions prepared in water having pH 13 demonstrate no effect of water as well as sodium pyrophosphate solution on the same suggesting a possibility of the presence of negative charge on edge at that pH. We believe that all the behaviors observed for samples at pH 10 can be explained by an attractive gel microstructure formed by edge-to-face contact. Furthermore, the absence of swelling in old colloidal dispersion at pH 10 and dissolution of the same by sodium pyrophosphate solution cannot be explained by merely repulsive interactions. This behavior suggests that attractive interactions originating from edge-to-face contact play an important role in causing ergodicity breaking in the colloidal dispersions at pH 10 at all the ages irrespective of the clay concentration. We further substantiate the presence of a fractal network structure formed by interparticle edge-face association using rheological tools and cryo-TEM imaging. We also conduct a comprehensive study of the effect of tetrasodium pyrophosphate on the sol-gel transition of LAPONITE® dispersion.
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Affiliation(s)
- Khushboo Suman
- Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016, India
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Suman K, Joshi YM. Microstructure and Soft Glassy Dynamics of an Aqueous Laponite Dispersion. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:13079-13103. [PMID: 30180583 DOI: 10.1021/acs.langmuir.8b01830] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Synthetic hectorite clay Laponite RD/XLG is composed of disk-shaped nanoparticles that acquire dissimilar charges when suspended in an aqueous medium. Owing to their property to spontaneously self-assemble, Laponite is used as a rheology modifier in a variety of commercial water-based products. In particular, an aqueous dispersion of Laponite undergoes a liquid-to-solid transition at about 1 vol % concentration. The evolution of the physical properties as the dispersion transforms to the solid state is reminiscent of physical aging in molecular as well as colloidal glasses. The corresponding soft glassy dynamics of an aqueous Laponite dispersion, including the rheological behavior, has been extensively studied in the literature. In this feature article, we take an overview of recent advances in understanding soft glassy dynamics and various efforts taken to understand the peculiar rheological behavior. Furthermore, the continuously developing microstructure that is responsible for the eventual formation of a soft solid state that supports its own weight against gravity has also been a topic of intense debate and discussion. In particularly, extensive experimental and theoretical studies lead to two types of microstructures for this system: an attractive gel-like or a repulsive glass-like structure. We carefully examine and critically analyze the literature and propose a state (phase) diagram that suggests an aqueous Laponite dispersion to be present in an attractive gel state.
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Affiliation(s)
- Khushboo Suman
- Department of Chemical Engineering , Indian Institute of Technology Kanpur , India
| | - Yogesh M Joshi
- Department of Chemical Engineering , Indian Institute of Technology Kanpur , India
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Shukla A, Arnipally S, Dagaonkar M, Joshi YM. Yielding in Surfactant Suspension Pastes: Effect of Surfactant Type. J SURFACTANTS DETERG 2016. [DOI: 10.1007/s11743-016-1844-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Joshi YM. A model for aging under deformation field, residual stresses and strains in soft glassy materials. SOFT MATTER 2015; 11:3198-3214. [PMID: 25760675 DOI: 10.1039/c5sm00217f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A model is proposed that considers aging and rejuvenation in a soft glassy material as, respectively, a decrease and an increase in free energy. The aging term is weighted by an inverse of characteristic relaxation time suggesting that greater mobility of the constituents induces faster aging in a material. A dependence of relaxation time on free energy is proposed, which under quiescent conditions leads to a power law dependence of relaxation time on waiting time as observed experimentally. The model considers two cases, namely, a constant modulus when aging is entropy controlled and a time dependent modulus. In the former and the latter cases the model has, respectively, two and three experimentally measurable parameters that are physically meaningful. Overall, the model predicts how the material undergoes aging and approaches a rejuvenated state under the application of a deformation field. In particular, the model proposes distinctions between various kinds of rheological effects for different combinations of parameters. Interestingly, when the relaxation time evolution is stronger than linear, the model predicts various features observed in soft glassy materials such as thixotropic and constant yield stress, thixotropic shear banding, and the presence of residual stress and strain.
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Affiliation(s)
- Yogesh M Joshi
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India.
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Abstract
Many household and industrially important soft colloidal materials, such as pastes, concentrated suspensions and emulsions, foams, slurries, inks, and paints, are very viscous and do not flow over practical timescales until sufficient stress is applied. This behavior originates from restricted mobility of the constituents arrested in disordered structures of varying length scales, termed colloidal glasses and gels. Usually these materials are thermodynamically out of equilibrium, which induces a time-dependent evolution of the structure and the properties. This review presents an overview of the rheological behavior of this class of materials. We discuss the experimental observations and theoretical developments regarding the microstructure of these materials, emphasizing the complex coupling between the deformation field and nonequilibrium structures in colloidal glasses and gels, which leads to a rich array of rheological behaviors with profound implications for various industrial processes and products.
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Affiliation(s)
- Yogesh M Joshi
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India;
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Shahin A, Joshi YM. Physicochemical effects in aging aqueous Laponite suspensions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:15674-15686. [PMID: 23057660 DOI: 10.1021/la302544y] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We study aging behavior of an aqueous suspension of Laponite as a function of concentration of Laponite, concentration of salt, time elapsed since preparation of suspension (idle time), and temperature by carrying extensive rheological and conductivity experiments. We observe that temporal evolution of elastic moduli, which describes structural build-up and aging, shifts to low times for experiments carried out for higher concentration of Laponite, higher concentration of salt, greater temperature, and longer idle time while preserving the curvature of evolution in the solid regime (elastic modulus greater than viscous modulus). Consequently appropriate shifting of evolution of elastic modulus in the solid regime leads to aging time-idle time-salt concentration-Laponite concentration-temperature superposition. The existence of such a superposition suggests the generic nature of microstructure buildup irrespective of mentioned variables in the explored range. The behavior of shift factors needed to obtain the superposition indicate that the energy barrier associated with structural buildup decreases with an increase in idle time and temperature and decreases linearly with an increase in concentration of Laponite and that of salt. The conductivity experiments show that ionic conductivity of the suspension increases with increasing Laponite concentration, salt concentration, temperature, and very importantly the idle time. We also analyze the interparticle interactions using DLVO theory that suggests an increase in idle time, temperature, and salt concentration increases the height of the repulsive energy barrier while it decreases the width of the same when particles approach each other in a parallel fashion. However when particles approach each other in a perpendicular fashion, owing to dissimilar charges on edge and face, the energy barrier for the attractive interaction is expected to decrease with an increase in idle time, temperature, and salt concentration. Analysis of rheological and conductivity experiments suggests a strong influence of attractive interactions on the low energy structures in an aqueous suspension of Laponite.
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Affiliation(s)
- A Shahin
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, India
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Sun W, Yang Y, Wang T, Huang H, Liu X, Tong Z. Effect of adsorbed poly(ethylene glycol) on the gelation evolution of Laponite suspensions: Aging time-polymer concentration superposition. J Colloid Interface Sci 2012; 376:76-82. [DOI: 10.1016/j.jcis.2012.01.064] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 12/06/2011] [Accepted: 01/10/2012] [Indexed: 11/26/2022]
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Joshi YM, Shahin A, Cates ME. Delayed solidification of soft glasses: new experiments, and a theoretical challenge. Faraday Discuss 2012; 158:313-24; discussion 351-70. [DOI: 10.1039/c2fd20005h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Morariu S, Bercea M. Effect of Temperature and Aging Time on the Rheological Behavior of Aqueous Poly(ethylene glycol)/Laponite RD Dispersions. J Phys Chem B 2011; 116:48-54. [DOI: 10.1021/jp208136g] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Simona Morariu
- Petru Poni Institute of Macromolecular Chemistry, 41-A Grigore Ghica Vodǎ Alley, 700487 Iasi, Romania
| | - Maria Bercea
- Petru Poni Institute of Macromolecular Chemistry, 41-A Grigore Ghica Vodǎ Alley, 700487 Iasi, Romania
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Shahin A, Joshi YM. Irreversible aging dynamics and generic phase behavior of aqueous suspensions of Laponite. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:4219-4225. [PMID: 20099829 DOI: 10.1021/la9032749] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We study the aging behavior of aqueous suspension of Laponite having 2.8 wt % concentration using rheological tools. At various salt concentration all the samples demonstrate orientational order when observed using crossed polarizers. In rheological experiments we observe inherent irreversibility in the aging dynamics which forces the system not to rejuvenate to the same state in the shear melting experiment carried out at a later date since preparation. The extensive rheological experiments carried out as a function of time elapsed since preparation demonstrate the self-similar trend in the aging behavior irrespective of the concentration of salt. We observe that the exploration of the low-energy states as a function of aging time is only kinetically affected by the presence of salt. We estimate that the energy barrier to attain the low-energy states decreases linearly with increase in the concentration of salt. The observed superposition of all the elapsed time and the salt-concentration-dependent data suggests that the aging that occurs in low salt concentration systems over a very long period is qualitatively similar to the aging behavior observed in systems with high salt concentration over a shorter period.
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Affiliation(s)
- A Shahin
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
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Wang X, Sun P, Xue G, Winter HH. Late-State Ripening Dynamics of a Polymer/Clay Nanocomposite. Macromolecules 2010. [DOI: 10.1021/ma901665m] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xiaoliang Wang
- Department of Polymer Science and Engineering, Nanjing University, Nanjing 210093, China
| | - Pingchuan Sun
- Key Laboratory of Functional Polymer Materials, Ministry of Education, College of Chemistry, Nankai University, Tianjin 300071, China
| | - Gi Xue
- Department of Polymer Science and Engineering, Nanjing University, Nanjing 210093, China
| | - H. Henning Winter
- Department of Chemical Engineering and Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003
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