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Vialetto J, Ramakrishna SN, Isa L, Laurati M. Effect of particle stiffness and surface properties on the non-linear viscoelasticity of dense microgel suspensions. J Colloid Interface Sci 2024; 672:814-823. [PMID: 38878623 DOI: 10.1016/j.jcis.2024.05.214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Revised: 05/24/2024] [Accepted: 05/28/2024] [Indexed: 07/07/2024]
Abstract
HYPOTHESIS Particle surface chemistry and internal softness are two fundamental parameters in governing the mechanical properties of dense colloidal suspensions, dictating structure and flow, therefore of interest from materials fabrication to processing. EXPERIMENTS Here, we modulate softness by tuning the crosslinker content of poly(N-isopropylacrylamide) microgels, and we adjust their surface properties by co-polymerization with polyethylene glycol chains, controlling adhesion, friction and fuzziness. We investigate the distinct effects of these parameters on the entire mechanical response from restructuring to complete fluidization of jammed samples at varying packing fractions under large-amplitude oscillatory shear experiments, and we complement rheological data with colloidal-probe atomic force microscopy to unravel variations in the particles' surface properties. FINDINGS Our results indicate that surface properties play a fundamental role at smaller packings; decreasing adhesion and friction at contact causes the samples to yield and fluidify in a lower deformation range. Instead, increasing softness or fuzziness has a similar effect at ultra-high densities, making suspensions able to better adapt to the applied shear and reach complete fluidization over a larger deformation range. These findings shed new light on the single-particle parameters governing the mechanical response of dense suspensions subjected to deformation, offering synthetic approaches to design materials with tailored mechanical properties.
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Affiliation(s)
- Jacopo Vialetto
- Department of Chemistry "Ugo Schiff", University of Florence, via della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy; Laboratory for Soft Materials and Interfaces, Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 5, 8093 Zürich, Switzerland; Consorzio interuniversitario per lo sviluppo dei Sistemi a Grande Interfase (CSGI), via della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy.
| | - Shivaprakash N Ramakrishna
- Laboratory for Soft Materials and Interfaces, Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 5, 8093 Zürich, Switzerland
| | - Lucio Isa
- Laboratory for Soft Materials and Interfaces, Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 5, 8093 Zürich, Switzerland
| | - Marco Laurati
- Department of Chemistry "Ugo Schiff", University of Florence, via della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy; Consorzio interuniversitario per lo sviluppo dei Sistemi a Grande Interfase (CSGI), via della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy.
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2
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Höfken T, Gasser U, Schneider S, Petrunin AV, Scotti A. Real and In Silico Microgels Show Comparable Bulk Moduli Below and Above the Volume Phase Transition. Macromol Rapid Commun 2024; 45:e2400043. [PMID: 38613338 DOI: 10.1002/marc.202400043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 04/02/2024] [Indexed: 04/14/2024]
Abstract
The compressibility of soft colloids influences their phase behavior and flow properties, especially in concentrated suspensions. Particle compressibility, which is proportional to the reciprocal of the bulk modulus K, is a key parameter for soft polymer-based particles that can be compressed in crowded environments. Here, microgels with different degrees of cross-linking, i.e., softness, are investigated below and above their volume phase transition temperature (VPTT). By combining molecular dynamics simulations with small-angle neutron scattering with contrast variation, a change in the particle bulk moduli of two orders of magnitude is observed. The degree of cross-linking has a significant impact on the bulk modulus of the swollen microgel, while above the VPTT the values of K are almost independent of the cross-linking density. The excellent agreement between experimental results and simulations also highlight that the model microgels from computer simulations possess both the internal architecture and the elastic properties of real polymeric networks. This paves the way to a systematic use of simulations to investigate the behavior of dense microgel suspensions below and above their VPTT.
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Affiliation(s)
- Tom Höfken
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
| | - Urs Gasser
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Villigen, 5232, Switzerland
| | - Stefanie Schneider
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
| | - Alexander V Petrunin
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
| | - Andrea Scotti
- Department of Biomedical Science, Faculty of Health and Society, Malmö University, Malmö, SE-205 06, Sweden
- Biofilms-Research Center for Biointerfaces, Malmö University, Malmö, SE-205 06, Sweden
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3
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Yamamoto A, Inui T, Suzuki D, Urayama K. Stress-independent delay time in yielding of dilute colloidal gels. SOFT MATTER 2023; 19:9082-9091. [PMID: 37987474 DOI: 10.1039/d3sm01238g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
We investigate the yielding under shear for dilute poly(N-isopropyl acrylamide-co-fumaric acid) (PNIPAM-FAc) colloidal gels obtained above the volume phase transition temperature. In this temperature range, the microgel suspensions form colloidal gels due to hydrophobic interparticle interactions under appropriate pH and ionic strength conditions. Step-strain tests revealed that yielding occurs when the applied strain exceeds a specific threshold, requiring a finite, stress-independent delay time (tD). This is distinct from previous findings on delayed yielding in other colloidal gels, where tD decreases with increasing stress. In the start-up shear tests, yield strain (γy) at a higher strain rate () increases with escalating , while γy at lower remains constant. This characteristic γy- relationship is successfully explained by a simple model using the stress-independent tD value without an adjustable fitting parameter. The distinctive yielding behavior, underscored by a stress-independent tD, is expected to originate from strain-induced macroscopic phase separation into a dense colloidal gel and water, observable separately from rheological measurements.
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Affiliation(s)
- Atsushi Yamamoto
- Department of Macromolecular Science and Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan
| | - Takumi Inui
- Graduate School of Textile Science & Technology, Shinshu University, Ueda 386-8567, Japan.
| | - Daisuke Suzuki
- Graduate School of Textile Science & Technology, Shinshu University, Ueda 386-8567, Japan.
- Research Initiative for Supra-Materials, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, Ueda 386-8567, Japan
| | - Kenji Urayama
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
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Akgonullu DZ, Murray BS, Connell SD, Fang Y, Linter B, Sarkar A. Synthetic and biopolymeric microgels: Review of similarities and difference in behaviour in bulk phases and at interfaces. Adv Colloid Interface Sci 2023; 320:102983. [PMID: 37690329 DOI: 10.1016/j.cis.2023.102983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 08/12/2023] [Accepted: 08/14/2023] [Indexed: 09/12/2023]
Abstract
This review discusses the current knowledge of interfacial and bulk interactions of biopolymeric microgels in relation to the well-established properties of synthetic microgels for applications as viscosity modifiers and Pickering stabilisers. We present a timeline showing the key milestones in designing microgels and their bulk/ interfacial performance. Poly(N-isopropylacrylamide) (pNIPAM) microgels have remained as the protagonist in the synthetic microgel domain whilst proteins or polysaccharides have been primarily used to fabricate biopolymeric microgels. Bulk properties of microgel dispersions are dominated by the volume fraction (ϕ) of the microgel particles, but ϕ is difficult to pinpoint, as addressed by many theoretical models. By evaluating recent experimental studies over the last five years, we find an increasing focus on the analysis of microgel elasticity as a key parameter in modulating their packing at the interfaces, within the provinces of both synthetic and biopolymeric systems. Production methods and physiochemical factors shown to influence microgel swelling in the aqueous phase can have a significant impact on their bulk as well as interfacial performance. Compared to synthetic microgels, biopolymer microgels show a greater tendency for polydispersity and aggregation and do not appear to have a core-corona structure. Comprehensive studies of biopolymeric microgels are still lacking, for example, to accurately determine their inter- and intra- particle interactions, whilst a wider variety of techniques need to be applied in order to allow comparisons to real systems of practical usage.
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Affiliation(s)
- Daisy Z Akgonullu
- Food Colloids and Bioprocessing Group, School of Food Science and Nutrition, University of Leeds, UK
| | - Brent S Murray
- Food Colloids and Bioprocessing Group, School of Food Science and Nutrition, University of Leeds, UK
| | - Simon D Connell
- Molecular and Nanoscale Physics Group, School of Physics and Astronomy, University of Leeds, UK
| | - Yuan Fang
- PepsiCo, Valhalla, New York, NY, USA
| | | | - Anwesha Sarkar
- Food Colloids and Bioprocessing Group, School of Food Science and Nutrition, University of Leeds, UK.
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5
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Negro G, Carenza LN, Gonnella G, Mackay F, Morozov A, Marenduzzo D. Yield-stress transition in suspensions of deformable droplets. SCIENCE ADVANCES 2023; 9:eadf8106. [PMID: 37256946 PMCID: PMC10413676 DOI: 10.1126/sciadv.adf8106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 04/27/2023] [Indexed: 06/02/2023]
Abstract
Yield-stress materials, which require a sufficiently large forcing to flow, are currently ill-understood theoretically. To gain insight into their yielding transition, we study numerically the rheology of a suspension of deformable droplets in 2D. We show that the suspension displays yield-stress behavior, with droplets remaining motionless below a critical body-force. In this phase, droplets jam to form an amorphous structure, whereas they order in the flowing phase. Yielding is linked to a percolation transition in the contacts of droplet-droplet overlaps and requires strict conservation of the droplet area to exist. Close to the transition, we find strong oscillations in the droplet motion that resemble those found experimentally in confined colloidal glasses. We show that even when droplets are static, the underlying solvent moves by permeation so that the viscosity of the composite system is never truly infinite, and its value ceases to be a bulk material property of the system.
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Affiliation(s)
- Giuseppe Negro
- Dipartimento di Fisica, Universitá degli Studi di Bari and INFN, Sezione di Bari, via Amendola 173, Bari I-70126, Italy
- School of Physics and Astronomy (SUPA), University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK
| | - Livio Nicola Carenza
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
| | - Giuseppe Gonnella
- Dipartimento di Fisica, Universitá degli Studi di Bari and INFN, Sezione di Bari, via Amendola 173, Bari I-70126, Italy
| | - Fraser Mackay
- School of Physics and Astronomy (SUPA), University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK
| | - Alexander Morozov
- School of Physics and Astronomy (SUPA), University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK
| | - Davide Marenduzzo
- School of Physics and Astronomy (SUPA), University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK
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Elancheliyan R, Del Monte G, Chauveau E, Sennato S, Zaccarelli E, Truzzolillo D. Role of Charge Content in the Two-Step Deswelling of Poly( N-isopropylacrylamide)-Based Microgels. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c00995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rajam Elancheliyan
- Laboratoire Charles Coulomb, UMR 5221, CNRS−Université de Montpellier, F-34095 Montpellier, France
| | - Giovanni Del Monte
- National Research Council−Institute for Complex Systems (CNR-ISC), Sapienza University of Rome, 00185 Rome, Italy
- Department of Physics, Sapienza University of Rome, 00185 Rome, Italy
| | - Edouard Chauveau
- Laboratoire Charles Coulomb, UMR 5221, CNRS−Université de Montpellier, F-34095 Montpellier, France
| | - Simona Sennato
- National Research Council−Institute for Complex Systems (CNR-ISC), Sapienza University of Rome, 00185 Rome, Italy
- Department of Physics, Sapienza University of Rome, 00185 Rome, Italy
| | - Emanuela Zaccarelli
- National Research Council−Institute for Complex Systems (CNR-ISC), Sapienza University of Rome, 00185 Rome, Italy
- Department of Physics, Sapienza University of Rome, 00185 Rome, Italy
| | - Domenico Truzzolillo
- Laboratoire Charles Coulomb, UMR 5221, CNRS−Université de Montpellier, F-34095 Montpellier, France
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Bennett C, Hayes PJ, Thrasher CJ, Chakma P, Wanasinghe SV, Zhang B, Petit LM, Varshney V, Nepal D, Sarvestani A, Picu CR, Sparks JL, Zanjani MB, Konkolewicz D. Modeling Approach to Capture Hyperelasticity and Temporary Bonds in Soft Polymer Networks. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c02319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Camaryn Bennett
- Department of Chemistry and Biochemistry, Miami University, 651 East High Street, Oxford, Ohio 45056, United States
| | - Peter J. Hayes
- Department of Mechanical and Manufacturing Engineering, Miami University, 650 East High Street, Oxford, Ohio 45056, United States
| | - Carl J. Thrasher
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, Ohio 45433, United States
- UES Inc., Dayton, Ohio 45432, United States
| | - Progyateg Chakma
- Department of Chemistry and Biochemistry, Miami University, 651 East High Street, Oxford, Ohio 45056, United States
| | - Shiwanka V. Wanasinghe
- Department of Chemistry and Biochemistry, Miami University, 651 East High Street, Oxford, Ohio 45056, United States
| | - Borui Zhang
- Department of Chemistry and Biochemistry, Miami University, 651 East High Street, Oxford, Ohio 45056, United States
| | - Leilah M. Petit
- Department of Chemistry and Biochemistry, Miami University, 651 East High Street, Oxford, Ohio 45056, United States
| | - Vikas Varshney
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, Ohio 45433, United States
| | - Dhriti Nepal
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, Ohio 45433, United States
| | - Alireza Sarvestani
- Department of Mechanical Engineering, Mercer University, Macon, Georgia 31207, United States
| | - Catalin R. Picu
- Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Jessica L. Sparks
- Department of Chemical, Paper, and Biomedical Engineering, Miami University, 650 East High Street, Oxford, Ohio 45056, United States
| | - Mehdi B. Zanjani
- Department of Mechanical and Manufacturing Engineering, Miami University, 650 East High Street, Oxford, Ohio 45056, United States
| | - Dominik Konkolewicz
- Department of Chemistry and Biochemistry, Miami University, 651 East High Street, Oxford, Ohio 45056, United States
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Rudyak VY, Sergeev AV, Kozhunova EY, Molchanov VS, Philippova OE, Chertovich AV. Viscosity of macromolecules with complex architecture. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.124622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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9
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Dang S, Brady J, Rel R, Surineni S, O'Shaughnessy C, McGorty R. Core-shell droplets and microcapsules formed through liquid-liquid phase separation of a colloid-polymer mixture. SOFT MATTER 2021; 17:8300-8307. [PMID: 34550150 DOI: 10.1039/d1sm01091c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Microcapsules allow for the controlled containment, transport, and release of cargoes ranging from pharmaceuticals to fragrances. Given the interest from a variety of industries in microcapsules and other core-shell structures, a multitude of fabrication strategies exist. Here, we report on a method relying on a mixture of temperature-responsive microgel particles, poly(N-isopropylacrylamide) (pNIPAM), and a polymer which undergo fluid-fluid phase separation. At room temperature this mixture separates into colloid-rich (liquid) and colloid-poor (gas) fluids. By heating the sample above a critical temperature where the microgel particles shrink dramatically and develop a more deeply attractive interparticle potential, the droplets of the colloid-rich phase become gel-like. As the temperature is lowered back to room temperature, these droplets of gelled colloidal particles reliquefy and phase separation within the droplet occurs. This phase separation leads to colloid-poor droplets within the colloid-rich droplets surrounded by a continuous colloid-poor phase. The gas/liquid/gas all-aqueous double emulsion lasts only a few minutes before a majority of the inner droplets escape. However, the colloid-rich shell of the core-shell droplets can solidify with the addition of salt. That this method creates core-shell structures with a shell composed of stimuli-sensitive microgel colloidal particles using only aqueous components makes it attractive for encapsulating biological materials and making capsules that respond to changes in, for example, temperature, salt concentration, or pH.
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Affiliation(s)
- Steven Dang
- Department of Physics and Biophysics, University of San Diego, San Diego, CA, 92110, USA.
| | - John Brady
- Department of Physics and Biophysics, University of San Diego, San Diego, CA, 92110, USA.
| | - Ryle Rel
- Department of Physics and Biophysics, University of San Diego, San Diego, CA, 92110, USA.
| | - Sreenidhi Surineni
- Department of Physics and Biophysics, University of San Diego, San Diego, CA, 92110, USA.
| | - Conor O'Shaughnessy
- Department of Physics and Biophysics, University of San Diego, San Diego, CA, 92110, USA.
| | - Ryan McGorty
- Department of Physics and Biophysics, University of San Diego, San Diego, CA, 92110, USA.
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Two-step deswelling in the Volume Phase Transition of thermoresponsive microgels. Proc Natl Acad Sci U S A 2021; 118:2109560118. [PMID: 34508008 PMCID: PMC8449345 DOI: 10.1073/pnas.2109560118] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2021] [Indexed: 11/18/2022] Open
Abstract
Microgels, colloidal-scale polymer networks, are the prototype soft colloids. When the constituent polymers are thermoresponsive, they undergo a volume phase transition (VPT) from a swollen to a collapsed state at a characteristic temperature, close to ambient one, of great appeal for several applications. To describe this phenomenon, microgels are usually treated as neutral, but here we show that electrostatics needs to be taken into account. In particular, deswelling occurs via a two-step, rather than a homogeneous, particle collapse, mainly driven by peripheral charges located on the microgel corona, for which we also establish a unifying framework encompassing all studied microgels. Our work thus provides a change of perspective to describe these fascinating systems. Thermoresponsive microgels are one of the most investigated types of soft colloids, thanks to their ability to undergo a Volume Phase Transition (VPT) close to ambient temperature. However, this fundamental phenomenon still lacks a detailed microscopic understanding, particularly regarding the presence and the role of charges in the deswelling process. This is particularly important for the widely used poly(N-isopropylacrylamide)–based microgels, where the constituent monomers are neutral but charged groups arise due to the initiator molecules used in the synthesis. Here, we address this point combining experiments with state-of-the-art simulations to show that the microgel collapse does not happen in a homogeneous fashion, but through a two-step mechanism, entirely attributable to electrostatic effects. The signature of this phenomenon is the emergence of a minimum in the ratio between gyration and hydrodynamic radii at the VPT. Thanks to simulations of microgels with different cross-linker concentrations, charge contents, and charge distributions, we provide evidence that peripheral charges arising from the synthesis are responsible for this behavior and we further build a universal master curve able to predict the two-step deswelling. Our results have direct relevance on fundamental soft condensed matter science and on applications where microgels are involved, ranging from materials to biomedical technologies.
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