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Schelling MPM, Verouden TWJ, Stevens TCM, Meijer JM. 3D visualization reveals the cooling rate dependent crystallization near a wall in dense microgel systems. SOFT MATTER 2024; 20:6343-6352. [PMID: 38963471 PMCID: PMC11323939 DOI: 10.1039/d4sm00517a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Accepted: 06/19/2024] [Indexed: 07/05/2024]
Abstract
Controlled crystallization, melting and vitrification are important fundamental processes in nature and technology. However, the microscopic details of these fundamental phenomena still lack understanding, in particular how the cooling rate and presence of a wall influence the crystal nucleation and glass formation. Thermoresponsive microgels provide the possibility to study phase transitions at the single-particle level, owing to the ability to tune the particle size with temperature. In this study, we employ composite microgels consisting of a hard core and a crosslinked poly(N-isopropyl acrylamide-co-methacrylic acid) shell to study the crystallization of dense suspensions of soft colloids near a wall using confocal microscopy. We investigate the effect of the cooling rate on the fluid-to-solid transition close to the sample wall. The structures formed during cooling range from glassy in the case of a rapid temperature quench to crystalline when a slow cooling rate is used. Detailed analysis of the final structure reveals that the cooling rate also sets the degree of alignment of the crystal domains with the wall as a result of a balance between homogeneous and heterogeneous crystal nucleation. The results presented here yield valuable insight into the microscopic details of temperature-controlled crystallization near a wall. This understanding will help pave the way towards optimal crystallization conditions for microgel applications.
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Affiliation(s)
- M P M Schelling
- Department of Applied Physics and Science Education, Eindhoven University of Technology, Groene Loper 19, 5612 AP Eindhoven, The Netherlands.
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Groene Loper 19, 5612 AP Eindhoven, The Netherlands
| | - T W J Verouden
- Department of Applied Physics and Science Education, Eindhoven University of Technology, Groene Loper 19, 5612 AP Eindhoven, The Netherlands.
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Groene Loper 19, 5612 AP Eindhoven, The Netherlands
| | - T C M Stevens
- Department of Applied Physics and Science Education, Eindhoven University of Technology, Groene Loper 19, 5612 AP Eindhoven, The Netherlands.
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Groene Loper 19, 5612 AP Eindhoven, The Netherlands
| | - J-M Meijer
- Department of Applied Physics and Science Education, Eindhoven University of Technology, Groene Loper 19, 5612 AP Eindhoven, The Netherlands.
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Groene Loper 19, 5612 AP Eindhoven, The Netherlands
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2
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Pany B, Majumdar AG, Bhat S, Si S, Yamanaka J, Mohanty PS. Polymerized stimuli-responsive microgel hybrids of silver nanoparticles as efficient reusable catalyst for reduction reaction. Heliyon 2024; 10:e26244. [PMID: 38434308 PMCID: PMC10907737 DOI: 10.1016/j.heliyon.2024.e26244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 02/05/2024] [Accepted: 02/08/2024] [Indexed: 03/05/2024] Open
Abstract
We have showcased the potential of polymerized hydrogels (PGMs) with uniform-sized stimuli-responsive microgel particles as promising alternatives to prevent aggregation in solution based nanoparticle systems. In the current work, we implemented the PGM concept by embedding anionic stimuli-responsive microgels (PNIPAM-co-AAc)-silver (Ag) hybrids within a hydrogel matrix. These PGM@AgNP hybrid materials are used as catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of sodium borohydride. UV-VIS spectroscopy is used for studying catalytic activity. In the solution based system, the complete reduction of 4-NP to 4-AP took 30 minutes with pure Ag nanoparticles, 24 minutes with PNIPAM-Ag hybrid (Neutral) microgels and 15 minutes with PNIPAM-co-AAc-Ag (Anionic) hybrid microgels. In contrast PGM containing PNIPAM-co-AAc-Ag hybrids achieved full reduction in just 15 minutes, along with a 3-minute induction period. For pure Ag nanoparticles, the first-order rate constant is found to be 0.25 min-1, for PNIPAM-Ag hybrid (Neutral), it is 0.21 min-1 and for PNIPAM-co-AAc-Ag (Anionic), it is 0.5 min-1 where as for PGM containing anionic microgel hybrids it is found to be 0.8 min-1. Furthermore, the reusability of the PGM-Ag (anionic) materials for catalytic activity remains unaltered even after several washings. In summary, our study highlights the effectiveness of PGM@AgNP materials as efficient catalysts for the reduction of 4-nitrophenol to 4-aminophenol, indicating their versatile potential in various catalytic applications.
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Affiliation(s)
- Biswajit Pany
- School of Chemical Technology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar, 751024, India
- School of Biotechnology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar, 751024, India
| | - Amrito Ghosh Majumdar
- School of Biotechnology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar, 751024, India
| | - Suresh Bhat
- Polymer Science & Engineering Division, CSIR-National Chemical Laboratory, Pune, 411008, India
| | - Satybrata Si
- School of Chemical Technology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar, 751024, India
- School of Biotechnology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar, 751024, India
| | - Junpei Yamanaka
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, 467-8603, Japan
| | - Priti S. Mohanty
- School of Chemical Technology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar, 751024, India
- School of Biotechnology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar, 751024, India
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3
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Alziyadi MO, Denton AR. Osmotic swelling behavior of surface-charged ionic microgels. J Chem Phys 2023; 159:184901. [PMID: 37942869 DOI: 10.1063/5.0161027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 10/19/2023] [Indexed: 11/10/2023] Open
Abstract
In recent years, ionic microgels have garnered much attention due to their unique properties, especially their stimulus-sensitive swelling behavior. The tunable response of these soft, permeable, compressible, charged colloidal particles is increasingly attractive for applications in medicine and biotechnologies, such as controlled drug delivery, tissue engineering, and biosensing. The ability to model and predict variation of the osmotic pressure of a single microgel with respect to changes in particle properties and environmental conditions proves vital to such applications. In this work, we apply both nonlinear Poisson-Boltzmann theory and molecular dynamics simulation to ionic microgels (macroions) in the cell model to compute density profiles of microions (counterions, coions), single-microgel osmotic pressure, and equilibrium swelling ratios of spherical microgels whose fixed charge is confined to the macroion surface. The basis of our approach is an exact theorem that relates the electrostatic component of the osmotic pressure to the microion density profiles. Close agreement between theory and simulation serves as a consistency check to validate our approach. We predict that surface-charged microgels progressively deswell with increasing microgel concentration, starting well below close packing, and with increasing salt concentration, in qualitative agreement with experiments. Comparison with previous results for microgels with fixed charge uniformly distributed over their volume demonstrates that surface-charged microgels deswell more rapidly than volume-charged microgels. We conclude that swelling behavior of ionic microgels in solution is sensitive to the distribution of fixed charge within the polymer-network gel and strongly depends on bulk concentrations of both microgels and salt ions.
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Affiliation(s)
- Mohammed O Alziyadi
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
| | - Alan R Denton
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
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4
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Zhou B, Gasser U, Fernandez-Nieves A. Poly(N-isopropylacrylamide) microgel swelling behavior and suspension structure studied with small-angle neutron scattering. Phys Rev E 2023; 108:054604. [PMID: 38115405 DOI: 10.1103/physreve.108.054604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 09/11/2023] [Indexed: 12/21/2023]
Abstract
Microgels are of high interest for applications and as model systems due to their volume response to external stimuli. We use small-angle neutron scattering to measure the form and structure factors of poly(N-isopropylacrylamide) microgels in dilute and concentrated suspensions and find that microgels keep a constant size up to a concentration, above which they deswell. This happens before random-close packing. We emphasize suspension polydispersity must be considered to obtain accurate form and structure factors. Our results are compatible with microgel deswelling triggered by the osmotic pressure set by counterions associated to charged groups in the microgel periphery, which sharply increases when the counterion clouds surrounding the microgels percolate throughout the suspension volume.
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Affiliation(s)
- B Zhou
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - U Gasser
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - A Fernandez-Nieves
- Department of Condensed Matter Physics, University of Barcelona, 08028 Barcelona, Spain; ICREA-Institucio Catalana de Recerca i Estudis Avancats, 08010 Barcelona, Spain; and Institute for Complex Systems (UBICS), University of Barcelona, 08028 Barcelona, Spain
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5
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Zhou B, Gasser U, Fernandez-Nieves A. Measuring the counterion cloud of soft microgels using SANS with contrast variation. Nat Commun 2023; 14:3827. [PMID: 37419879 DOI: 10.1038/s41467-023-39378-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 06/09/2023] [Indexed: 07/09/2023] Open
Abstract
The behavior of microgels and other soft, compressible colloids depends on particle concentration in ways that are absent in their hard-particulate counterparts. For instance, poly-N-isopropylacrylamide (pNIPAM) microgels can spontaneously deswell and reduce suspension polydispersity when concentrated enough. Despite the pNIPAM network in these microgels is neutral, the key to understanding this distinct behavior relies on the existence of peripheric charged groups, responsible for providing colloidal stability when deswollen, and the associated counterion cloud. When in close proximity, clouds of different particles overlap, effectively freeing the associated counterions, which are then able to exert an osmotic pressure that can potentially cause the microgels to decrease their size. Up to now, however, no direct measurement of such an ionic cloud exists, perhaps even also for hard colloids, where it is referred to as an electric double layer. Here, we use small-angle neutron scattering with contrast variation with different ions to isolate the change in the form factor directly related to the counterion cloud, and obtain its radius and width. Our results highlight that the modeling of microgel suspensions must unavoidably and explicitly consider the presence of this cloud, which exists for nearly all microgels synthesized today.
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Affiliation(s)
- Boyang Zhou
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Forschungsstrasse 111, 5232, Villigen, Switzerland
| | - Urs Gasser
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Forschungsstrasse 111, 5232, Villigen, Switzerland.
| | - Alberto Fernandez-Nieves
- Department of Condensed Matter Physics, University of Barcelona, Carrer de Martí i Franqués 1, Barcelona, 08028, Spain
- ICREA-Institucio Catalana de Recerca i Estudis Avançats, Barcelona, 08028, Spain
- Institute for Complex Systems (UBICS), University of Barcelona, Barcelona, 08028, Spain
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6
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Scotti A, Schulte MF, Lopez CG, Crassous JJ, Bochenek S, Richtering W. How Softness Matters in Soft Nanogels and Nanogel Assemblies. Chem Rev 2022; 122:11675-11700. [PMID: 35671377 DOI: 10.1021/acs.chemrev.2c00035] [Citation(s) in RCA: 36] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Softness plays a key role in determining the macroscopic properties of colloidal systems, from synthetic nanogels to biological macromolecules, from viruses to star polymers. However, we are missing a way to quantify what the term "softness" means in nanoscience. Having quantitative parameters is fundamental to compare different systems and understand what the consequences of softness on the macroscopic properties are. Here, we propose different quantities that can be measured using scattering methods and microscopy experiments. On the basis of these quantities, we review the recent literature on micro- and nanogels, i.e. cross-linked polymer networks swollen in water, a widely used model system for soft colloids. Applying our criteria, we address the question what makes a nanomaterial soft? We discuss and introduce general criteria to quantify the different definitions of softness for an individual compressible colloid. This is done in terms of the energetic cost associated with the deformation and the capability of the colloid to isotropically deswell. Then, concentrated solutions of soft colloids are considered. New definitions of softness and new parameters, which depend on the particle-to-particle interactions, are introduced in terms of faceting and interpenetration. The influence of the different synthetic routes on the softness of nanogels is discussed. Concentrated solutions of nanogels are considered and we review the recent results in the literature concerning the phase behavior and flow properties of nanogels both in three and two dimensions, in the light of the different parameters we defined. The aim of this review is to look at the results on micro- and nanogels in a more quantitative way that allow us to explain the reported properties in terms of differences in colloidal softness. Furthermore, this review can give researchers dealing with soft colloids quantitative methods to define unambiguously which softness matters in their compound.
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Affiliation(s)
- Andrea Scotti
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany, European Union
| | - M Friederike Schulte
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany, European Union
| | - Carlos G Lopez
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany, European Union
| | - Jérôme J Crassous
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany, European Union
| | - Steffen Bochenek
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany, European Union
| | - Walter Richtering
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany, European Union
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7
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Bergman MJ, Nöjd S, Mohanty PS, Boon N, Immink JN, Maris JJE, Stenhammar J, Schurtenberger P. On the role of softness in ionic microgel interactions. SOFT MATTER 2021; 17:10063-10072. [PMID: 34714903 PMCID: PMC8597585 DOI: 10.1039/d1sm01222c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 10/24/2021] [Indexed: 05/17/2023]
Abstract
Thermoresponsive microgels are a popular model system to study phase transitions in soft matter, because temperature directly controls their volume fraction. Ionic microgels are additionally pH-responsive and possess a rich phase diagram. Although effective interaction potentials between microgel particles have been proposed, these have never been fully tested, leading to a gap in our understanding of the link between single-particle and collective properties. To help resolve this gap, four sets of ionic microgels with varying crosslinker density were synthesised and characterised using light scattering techniques and confocal microscopy. The resultant structural and dynamical information was used to investigate how particle softness affects the phase behaviour of ionic microgels and to validate the proposed interaction potential. We find that the architecture of the microgel plays a marked role in its phase behaviour. Rather than the ionic charges, it is the dangling ends which drive phase transitions and interactions at low concentration. Comparison to theory underlines the need for a refined theoretical model which takes into consideration these close-contact interactions.
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Affiliation(s)
- Maxime J Bergman
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Sofi Nöjd
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Priti S Mohanty
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Niels Boon
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Jasper N Immink
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - J J Erik Maris
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Joakim Stenhammar
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Peter Schurtenberger
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
- Lund Institute for advanced Neutron and X-ray Science (LINXS), Lund University, Lund, Sweden
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8
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Scotti A. Characterization of the volume fraction of soft deformable microgels by means of small-angle neutron scattering with contrast variation. SOFT MATTER 2021; 17:5548-5559. [PMID: 33978056 DOI: 10.1039/d1sm00277e] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The volume occupied by colloids in a suspension - namely the volume fraction - is the thermodynamic variable that determines the phase behavior of these systems. While for hard incompressible spheres this quantity is well defined, for soft compressible colloids such as microgels - polymeric crosslinked networks swollen in a good solvent - the determination of the real volume occupied by these particles in solution is particularly challenging. This fact depends on two aspects: first the surface and, therefore, the volume of the microgels is hard to define properly given their external fuzziness; second, microgels can osmotically deswell, deform or interpenetrate their neighbors, i.e. change their shape and size depending on the solution concentration. Here, the form factors of few hydrogenated microgels embedded in a matrix of deuterated but otherwise identical microgels are measured using small-angle neutron scattering with contrast variation. From the analysis of the scattering data, the variation of the volume of the microgels as a function of concentration is obtained and used to calculate the real microgel volume fraction in solution. Soft neutral microgels are shown to facet already at low concentrations while in contrast, harder microgels maintain their shape and change their volume.
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Affiliation(s)
- Andrea Scotti
- Institute of Physical Chemistry, RWTH Aachen University, 52056, Aachen, Germany.
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9
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Shangwei L, Urakawa O, Inoue T. Rheo-Optical Study on the Viscoelastic Relaxation Modes of a Microgel Particle Suspension around the Liquid–Solid Transition Regime. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02205] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Li Shangwei
- Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
| | - Osamu Urakawa
- Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
| | - Tadashi Inoue
- Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
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10
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Bhol P, Mohanty M, Mohanty PS. Polymer-matrix stabilized metal nanoparticles: Synthesis, characterizations and insight into molecular interactions between metal ions, atoms and polymer moieties. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2020.115135] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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11
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Scotti A, Houston JE, Brugnoni M, Schmidt MM, Schulte MF, Bochenek S, Schweins R, Feoktystov A, Radulescu A, Richtering W. Phase behavior of ultrasoft spheres show stable bcc lattices. Phys Rev E 2020; 102:052602. [PMID: 33327194 DOI: 10.1103/physreve.102.052602] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 10/01/2020] [Indexed: 06/12/2023]
Abstract
The phase behavior of supersoft spheres is explored using solutions of ultralow cross-linked poly(N-isopropylacrylamide)-based microgels as a model system. For these microgels, the effects of the electric charges on their surfaces can be neglected and therefore only the role of softness on the phase behavior is investigated. The samples show a liquid-to-crystal transition at higher volume fraction with respect to both hard spheres and stiffer microgels. Furthermore, stable body centered cubic (bcc) crystals are observed in addition to the expected face centered cubic (fcc) crystals. Small-angle x-ray and neutron scattering with contrast variation allow the characterization of both the microgel-to-microgel distance and the architecture of single microgels in crowded solutions. The measurements reveal that the stable bcc crystals depend on the interplay between the collapse and the interpenetration of the external shell of the ultralow cross-linked microgels.
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Affiliation(s)
- A Scotti
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - J E Houston
- European Spallation Source ERIC, Box 176, SE-221 00 Lund, Sweden
| | - M Brugnoni
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - M M Schmidt
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - M F Schulte
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - S Bochenek
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - R Schweins
- Institut Laue-Langevin ILL DS/LSS, 71 Avenue des Martyrs, F-38000 Grenoble, France
| | - A Feoktystov
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science JCNS at Heinz Maier-Leibnitz Zentrum MLZ, 85748 Garching, Germany
| | - A Radulescu
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science JCNS at Heinz Maier-Leibnitz Zentrum MLZ, 85748 Garching, Germany
| | - W Richtering
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
- JARA-SOFT, 52056 Aachen, Germany
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12
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Kawaguchi H. On Going to a New Era of Microgel Exhibiting Volume Phase Transition. Gels 2020; 6:gels6030026. [PMID: 32824458 PMCID: PMC7559898 DOI: 10.3390/gels6030026] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 08/03/2020] [Accepted: 08/10/2020] [Indexed: 12/14/2022] Open
Abstract
The discovery of phenomena of volume phase transition has had a great impact not only on bulk gels but also on the world of microgels. In particular, research on poly(N-isopropylacrylamide) (PNIPAM) microgels, whose transition temperature is close to body temperature, has made remarkable progress in almost 35 years. This review presents some breakthrough findings in microgels that exhibit volume phase transitions and outlines recent works on the synthesis, structural analysis, and research direction of microgels.
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Affiliation(s)
- Haruma Kawaguchi
- Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama 241-0814, Japan
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13
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Hu Y, Li C, Wang J, Jia X, Zhu J, Wang Q, Wang H, Yang Y. Osmosis manipulable morphology and photonic property of microcapsules with colloidal nano-in-micro structure. J Colloid Interface Sci 2020; 574:337-346. [PMID: 32335483 DOI: 10.1016/j.jcis.2020.04.062] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/03/2020] [Accepted: 04/16/2020] [Indexed: 01/01/2023]
Abstract
Full visible spectrum photonic droplets and consequent microcapsules with nano-in-micro structure were prepared through microfluidic technique. Photo-curable resin and suspension of monodispersed soft nanogels were used as shell and core of the microcapsules, respectively. Upon UV irradiation, the droplets can be subsequently transformed into photonic microcapsules with an ultrathin polymeric shell. The shell thickness of the photonic microcapsules was found to be approximately 700 nm. Due to the ultrathin shell and soft core, the photonic microcapsules with nano-in-micro structure display dramatic changes both in shapes and photonic property under the impact of osmosis effect or temperature stimulus. Typically, the shell and core parts of nano-in-micro structure could respectively undergo a size expansion/even rupture and a size decrease/buckling under hypotonic and hypertonic condition. Correspondingly, the peak value of the reflection spectra of the microcapsules showed a redshift and blue shift, respectively. The mechanism to the structure and optical properties variation involves the osmotic pressure induced the volume-fraction change of the nanogel-based photonic dispersion and the shell buckling of the core/shell microcapsules.
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Affiliation(s)
- Yuandu Hu
- Hubei Key Lab of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Chengnian Li
- Hubei Key Lab of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jianying Wang
- Hubei Key Lab of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Xiaolu Jia
- Hubei Key Lab of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jintao Zhu
- Hubei Key Lab of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
| | - Qin Wang
- Hubei Key Lab of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Hong Wang
- Hubei Key Lab of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yajiang Yang
- Hubei Key Lab of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
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14
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Bhol P, Mohanty PS. Smart microgel-metal hybrid particles of PNIPAM-co-PAA@AgAu: synthesis, characterizations and modulated catalytic activity. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:084002. [PMID: 33017813 DOI: 10.1088/1361-648x/abbe79] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Smart pH and thermoresponsive, poly(N-isopropyl acrylamide co acrylic acid) (PNIPAM-co-PAA) microgel particles are used as microreactors to prepare hybrids of gold (Au) and silver (Ag) nanoparticles (PNIPAM-co-PAA@AgAu) using a facile two steps in situ approach. These hybrid particles are characterized using the transmission electron microscope (TEM), UV-VIS spectrometer, and dynamic light scattering (DLS). TEM directly confirms the successful loading of metal nanoparticles onto microgels and the hybrid particles have a narrow size distribution. UV-VIS spectroscopy at different concentration ratios of silver/gold chloride strongly reveals the presence of plasmon peaks of both silver and gold between 10% to 25% of gold chloride concentration. DLS studies demonstrate that these hybrid microgels exhibit both pH and thermoresponsive properties comparatively with a lesser swelling than the pure microgels without loaded nanoparticles. Further, the catalytic activities of PNIPAM-co-PAA@AgAu hybrids are studied through a reduction of 4-nitrophenol (4-NP)-to-4-aminophenol (4-AP) in the presence of sodium borohydride at different pH. Interestingly, these hybrid particles exhibit modulating catalytic activity with variation in pH. The reduction kinetics decreases with increasing pH and the corresponding apparent rate constant exhibits two linear regimes with one at pH below pKa and another at pH above pKa of acrylic acid. This pH-modulated catalytic behavior of PNIPAM-co-PAA@AgAu hybrids is discussed based on pH-induced swelling/deswelling transition, the core-shell nature of microgel particles, and its intrinsic interplay with the diffusion of nitrophenols within the microgel network. Finally, our results are compared and discussed in the context of previously studied catalytic activities in different polymer-metal hybrids.
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Affiliation(s)
- Prachi Bhol
- School of Chemical Technology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar-751024, India
- School of Applied Sciences, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar-751024, India
| | - Priti S Mohanty
- School of Chemical Technology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar-751024, India
- School of Biotechnology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar-751024, India
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15
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Bareigts G, Kiatkirakajorn PC, Li J, Botet R, Sztucki M, Cabane B, Goehring L, Labbez C. Packing Polydisperse Colloids into Crystals: When Charge-Dispersity Matters. PHYSICAL REVIEW LETTERS 2020; 124:058003. [PMID: 32083896 DOI: 10.1103/physrevlett.124.058003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 01/06/2020] [Indexed: 06/10/2023]
Abstract
Monte Carlo simulations, fully constrained by experimental parameters, are found to agree well with a measured phase diagram of aqueous dispersions of nanoparticles with a moderate size polydispersity over a broad range of salt concentrations, c_{s}, and volume fractions, ϕ. Upon increasing ϕ, the colloids freeze first into coexisting compact solids then into a body centered cubic phase (bcc) before they melt into a glass forming liquid. The surprising stability of the bcc solid at high ϕ and c_{s} is explained by the interaction (charge) polydispersity and vibrational entropy.
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Affiliation(s)
- Guillaume Bareigts
- ICB, CNRS UMR 6303, Université Bourgogne Franche-Comté, 21000 Dijon, France
| | | | - Joaquim Li
- LCMD, CNRS UMR 8231, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France
| | - Robert Botet
- Physique des Solides, CNRS UMR 8502, Université Paris-Saclay, F-91405 Orsay, France
| | - Michael Sztucki
- ESRF-The European Synchrotron, CS40220, 38043 Grenoble Cedex 9, France
| | - Bernard Cabane
- LCMD, CNRS UMR 8231, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France
| | - Lucas Goehring
- School of Science and Technology, Nottingham Trent University, Nottingham NG11 8NS, United Kingdom
| | - Christophe Labbez
- ICB, CNRS UMR 6303, Université Bourgogne Franche-Comté, 21000 Dijon, France
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16
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Frenzel L, Lehmkühler F, Lokteva I, Narayanan S, Sprung M, Grübel G. Anomalous Dynamics of Concentrated Silica-PNIPAm Nanogels. J Phys Chem Lett 2019; 10:5231-5236. [PMID: 31433650 DOI: 10.1021/acs.jpclett.9b01690] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We present the structure and dynamics of highly concentrated core-shell nanoparticles composed of a silica core and a poly(N-isoproylacrylamide) (PNIPAm) shell suspended in water. With X-ray photon correlation spectroscopy, we are able to follow dynamical changes over the volume phase transition of PNIPAm at LCST = 32 °C. On raising the temperature beyond LCST, the structural relaxation times continue to decrease. The effect is accompanied by a transition from stretched to compressed exponential shape of the intensity autocorrelation function. Upon further heating, we find a sudden slowing down for the particles in their collapsed state. The q dependence of the relaxation time shows an anomalous change from τc ∝ q-3 to τc ∝ q-1. Small angle X-ray scattering data evidence a temperature-induced transition from repulsive to attractive forces. Our results indicate a temperature-induced phase transition from a colloidal liquid with polymer-driven dynamics toward a colloidal gel.
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Affiliation(s)
- Lara Frenzel
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
- The Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Felix Lehmkühler
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
- The Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Irina Lokteva
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
- The Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Suresh Narayanan
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Michael Sprung
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - Gerhard Grübel
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
- The Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, 22761 Hamburg, Germany
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17
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Sbeih S, Mohanty PS, Morrow MR, Yethiraj A. Structural parameters of soft PNIPAM microgel particles as a function of crosslink density. J Colloid Interface Sci 2019; 552:781-793. [DOI: 10.1016/j.jcis.2019.05.047] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 05/14/2019] [Accepted: 05/15/2019] [Indexed: 10/26/2022]
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18
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Kumar S, Ray D, Abbas S, Saha D, Aswal VK, Kohlbrecher J. Reentrant phase behavior of nanoparticle solutions probed by small-angle scattering. Curr Opin Colloid Interface Sci 2019. [DOI: 10.1016/j.cocis.2019.02.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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19
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Conley GM, Zhang C, Aebischer P, Harden JL, Scheffold F. Relationship between rheology and structure of interpenetrating, deforming and compressing microgels. Nat Commun 2019; 10:2436. [PMID: 31164639 PMCID: PMC6547648 DOI: 10.1038/s41467-019-10181-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Accepted: 04/23/2019] [Indexed: 11/30/2022] Open
Abstract
Thermosensitive microgels are widely studied hybrid systems combining properties of polymers and colloidal particles in a unique way. Due to their complex morphology, their interactions and packing, and consequentially the viscoelasticity of suspensions made from microgels, are still not fully understood, in particular under dense packing conditions. Here we study the frequency-dependent linear viscoelastic properties of dense suspensions of micron sized soft particles in conjunction with an analysis of the local particle structure and morphology based on superresolution microscopy. By identifying the dominating mechanisms that control the elastic and dissipative response, we can explain the rheology of these widely studied soft particle assemblies from the onset of elasticity deep into the overpacked regime. Interestingly, our results suggest that the friction between the microgels is reduced due to lubrification mediated by the polymer brush-like corona before the onset of interpenetration.
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Affiliation(s)
- Gaurasundar M Conley
- Department of Physics, University of Fribourg, Chemin du Musée 3, 1700, Fribourg, Switzerland
| | - Chi Zhang
- Department of Physics, University of Fribourg, Chemin du Musée 3, 1700, Fribourg, Switzerland
| | - Philippe Aebischer
- Department of Physics, University of Fribourg, Chemin du Musée 3, 1700, Fribourg, Switzerland
| | - James L Harden
- Department of Physics, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
| | - Frank Scheffold
- Department of Physics, University of Fribourg, Chemin du Musée 3, 1700, Fribourg, Switzerland.
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20
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Scotti A, Denton AR, Brugnoni M, Houston JE, Schweins R, Potemkin II, Richtering W. Deswelling of Microgels in Crowded Suspensions Depends on Cross-Link Density and Architecture. Macromolecules 2019. [DOI: 10.1021/acs.macromol.9b00729] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Andrea Scotti
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - Alan R. Denton
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050 United States
| | - Monia Brugnoni
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - Judith E. Houston
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748 Garching, Germany
- European Spallation
Source ERIC, Box 176, SE-221 00 Lund, Sweden
| | - Ralf Schweins
- Institut Laue-Langevin
ILL DS/LSS, 71 Avenue des Martyrs, F-38000 Grenoble, France
| | - Igor I. Potemkin
- Physics Department, Lomonosov Moscow State University, 119991 Moscow, Russian Federation
- DWI - Leibniz
Institute
for Interactive Materials, Aachen 52056, Germany
- National Research South
Ural State University, Chelyabinsk 454080, Russian Federation
| | - Walter Richtering
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
- JARA, Jülich Aachen
Research Alliance, 52056 Aachen, Germany
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21
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Jathavedan K, Bhat SK, Mohanty PS. Alternating electric-field-induced assembly of binary mixtures of soft repulsive ionic microgel colloids. J Colloid Interface Sci 2019; 544:88-95. [PMID: 30826533 DOI: 10.1016/j.jcis.2019.02.075] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 02/21/2019] [Accepted: 02/21/2019] [Indexed: 11/17/2022]
Abstract
An external alternating electric field is used to study the assembly of a binary mixture of Poly(N-isopropylacrylamide-co-acrylic acid) microgels in their swollen form at hydrodynamic size ratio 2:1 under deprotonated state. The AC field experiments were carried out at a fixed frequency of 100 kHz in the fluid regime for three number density ratios 1:3, 1:1 and 3:1 of big-to-small microgels using a confocal microscope. Strings with different types of co-assembly structures such as buckled, ring, flame and sandwich have been observed at low and intermediate field strengths at ratio 1:3, 1:1. In buckled and ring type, one or two small particles sit at the contact of two big particles and in the flame type, small particles arrange like a cone at end of the string. In the sandwich structure, several double small particle layers lie in between big particles. At high field strength, aggregation of strings and a phase separation into individual aggregates of strings from both big and small microgels have been observed. At higher ratio 3:1, the string formation is mostly dominated by big particles. Our experimental results are discussed with the recent simulation and experimental works on AC field induced structures in binary hard sphere mixtures.
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Affiliation(s)
- Kiran Jathavedan
- Polymer Science & Engineering Division, CSIR-National Chemical Laboratory, Pune 411008, India
| | - Suresh K Bhat
- Polymer Science & Engineering Division, CSIR-National Chemical Laboratory, Pune 411008, India.
| | - Priti S Mohanty
- School of Chemical Technology and Biotechnology, Kalinga Institute of Industrial Technology (KIIT), Deemed to be University, Bhubaneswar 751024, India.
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22
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Gasser U, Scotti A, Fernandez-Nieves A. Spontaneous deswelling of microgels controlled by counterion clouds. Phys Rev E 2019; 99:042602. [PMID: 31108698 DOI: 10.1103/physreve.99.042602] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Indexed: 06/09/2023]
Abstract
Concentrated poly(N-isopropylacrylamide) (pNIPAM) microgel suspensions at a fixed temperature below the deswelling transition of pNIPAM exhibit spontaneous particle deswelling. The microgels deswell before they are in direct contact and in polydisperse suspensions this deswelling is most pronounced for the largest microgel particles; as a consequence, the polydispersity of the suspension is reduced. Recently, we presented a model for this spontaneous deswelling that is based on the presence of counterions originating from charged groups on the surface of the pNIPAM microgels [A. Scotti et al., Proc. Natl. Acad. Sci. USA 113, 5576 (2016)PNASA60027-842410.1073/pnas.1516011113]. Here we present numerical Poisson-Boltzmann calculations of the electrostatic potential and osmotic pressure inside and outside a pNIPAM microgel that could trigger the observed deswelling at high particle concentrations.
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Affiliation(s)
- U Gasser
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - A Scotti
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - A Fernandez-Nieves
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
- Department of Condensed Matter Physics, University of Barcelona, 08028 Barcelona, Spain
- ICREA - Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
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23
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Responsive hydrogel colloids: Structure, interactions, phase behavior, and equilibrium and nonequilibrium transitions of microgel dispersions. Curr Opin Colloid Interface Sci 2019. [DOI: 10.1016/j.cocis.2019.02.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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24
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Effect of entanglements on temperature response of gel immobilized microgel photonic crystals. Colloids Surf A Physicochem Eng Asp 2018. [DOI: 10.1016/j.colsurfa.2018.09.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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25
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Weyer TJ, Denton AR. Concentration-dependent swelling and structure of ionic microgels: simulation and theory of a coarse-grained model. SOFT MATTER 2018; 14:4530-4540. [PMID: 29796467 DOI: 10.1039/c8sm00799c] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We study swelling and structural properties of ionic microgel suspensions within a comprehensive coarse-grained model that combines the polymeric and colloidal natures of microgels as permeable, compressible, charged spheres governed by effective interparticle interactions. The model synthesizes the Flory-Rehner theory of cross-linked polymer gels, the Hertz continuum theory of effective elastic interactions, and a theory of density-dependent effective electrostatic interactions. Implementing the model using Monte Carlo simulation and thermodynamic perturbation theory, we compute equilibrium particle size distributions, swelling ratios, volume fractions, net valences, radial distribution functions, and static structure factors as functions of concentration. Trial Monte Carlo moves comprising particle displacements and size variations are accepted or rejected based on the total change in elastic and electrostatic energies. The theory combines first-order thermodynamic perturbation and variational free energy approximations. For illustrative system parameters, theory and simulation agree closely at concentrations ranging from dilute to beyond particle overlap. With increasing concentration, as microgels deswell, we predict a decrease in the net valence and an unusual saturation of pair correlations. Comparison with experimental data for deionized, aqueous suspensions of PNIPAM particles demonstrates the capacity of the coarse-grained model to predict and interpret measured swelling behavior.
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Affiliation(s)
- Tyler J Weyer
- Department of Physics, North Dakota State University, Fargo, ND 58108-6050, USA.
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26
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Nöjd S, Holmqvist P, Boon N, Obiols-Rabasa M, Mohanty PS, Schweins R, Schurtenberger P. Deswelling behaviour of ionic microgel particles from low to ultra-high densities. SOFT MATTER 2018; 14:4150-4159. [PMID: 29744516 DOI: 10.1039/c8sm00390d] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The swelling of ionic microgel particles is investigated at a wide range of concentrations using a combination of light, X-ray and neutron scattering techniques. We employ a zero-average contrast approach for small-angle neutron scattering experiments, which enables a direct determination of the form factor at high concentrations. The observed particle size initially decreases strongly with the particle concentration in the dilute regime but approaches a constant value at intermediate concentrations. This is followed by a further deswelling at high concentrations above particle overlap. Theory and experiments point at a pivotal contribution of dangling polymer ends to the strong variation in size of ionic microgels, which presents itself mainly through the hydrodynamics properties of the system.
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Affiliation(s)
- Sofi Nöjd
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Peter Holmqvist
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Niels Boon
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Marc Obiols-Rabasa
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Priti S Mohanty
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden. and School of Chemical Technology, Kalinga Institute of Industrial Technology (KIIT), Bhubaneswar, India
| | - Ralf Schweins
- Large Scale Structures Group, Institut Laue-Langevin, Grenoble, 38042, France
| | - Peter Schurtenberger
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
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27
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Quesada-Pérez M, Maroto-Centeno JA, Martín-Molina A, Moncho-Jordá A. Direct determination of forces between charged nanogels through coarse-grained simulations. Phys Rev E 2018; 97:042608. [PMID: 29758622 DOI: 10.1103/physreve.97.042608] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Indexed: 06/08/2023]
Abstract
In this work, electrostatic forces between charged nanogels are explored through coarse-grained simulations. These simulations allow us to explicitly consider the complex topology of these nanoparticles and provide reliable force values to examine highly charged nanogels of a few tens of nanometers. The results obtained here clearly reveal that the electrostatic interactions between these nanoparticles are not governed by the net charge of the nanogel, which includes not only the charge of the polymer network but also the charge of ions inside. Thus two theoretical procedures for predicting effective charges are also proposed and investigated. Both provide predictions of the same order and capture the behavior found for the effective charge obtained from simulations.
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Affiliation(s)
- Manuel Quesada-Pérez
- Departamento de Física, Escuela Politécnica Superior de Linares, Universidad de Jaén, 23700, Linares, Jaén, Spain
| | - José Alberto Maroto-Centeno
- Departamento de Física, Escuela Politécnica Superior de Linares, Universidad de Jaén, 23700, Linares, Jaén, Spain
| | - Alberto Martín-Molina
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain
- Instituto Carlos I de Física Teórica y Computacional, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain
| | - Arturo Moncho-Jordá
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain
- Instituto Carlos I de Física Teórica y Computacional, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain
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28
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Rauh A, Carl N, Schweins R, Karg M. Role of Absorbing Nanocrystal Cores in Soft Photonic Crystals: A Spectroscopy and SANS Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:854-867. [PMID: 28767251 DOI: 10.1021/acs.langmuir.7b01595] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Periodic superstructures of plasmonic nanoparticles have attracted significant interest because they can support coupled plasmonic modes, making them interesting for plasmonic lasing, metamaterials, and as light-management structures in thin-film optoelectronic devices. We have recently shown that noble metal hydrogel core-shell colloids allow for the fabrication of highly ordered 2-dimensional plasmonic lattices that show surface lattice resonances as the result of plasmonic/diffractive coupling (Volk, K.; Fitzgerald, J. P. S.; Ruckdeschel, P.; Retsch, M.; König, T. A. F.; Karg, M. Reversible Tuning of Visible Wavelength Surface Lattice Resonances in Self-Assembled Hybrid Monolayers. Adv. Optical Mater. 2017, 5, 1600971, DOI: 10.1002/adom.201600971). In the present work, we study the photonic properties and structure of 3-dimensional crystalline superstructures of gold hydrogel core-shell colloids and their pitted counterparts without gold cores. We use far-field extinction spectroscopy to investigate the optical response of these superstructures. Narrow Bragg peaks are measured, independently of the presence or absence of the gold cores. All crystals show a significant reduction in low-wavelength scattering. This leads to a significant enhancement of the plasmonic properties of the samples prepared from gold-nanoparticle-containing core-shell colloids. Plasmonic/diffractive coupling is not evident, which we mostly attribute to the relatively small size of the gold cores limiting the effective coupling strength. Small-angle neutron scattering is applied to study the crystal structure. Bragg peaks of several orders clearly assignable to an fcc arrangement of the particles are observed for all crystalline samples in a broad range of volume fractions. Our results indicate that the nanocrystal cores do not influence the overall crystallization behavior or the crystal structure. These are important prerequisites for future studies on photonic materials built from core-shell particles, in particular, the development of new photonic materials from plasmonic nanocrystals.
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Affiliation(s)
- Astrid Rauh
- Physical Chemistry I, Heinrich-Heine-University , 40225 Düsseldorf, Germany
- Physical Chemistry I, University of Bayreuth , 95440 Bayreuth, Germany
| | - Nico Carl
- Physical Chemistry I, University of Bayreuth , 95440 Bayreuth, Germany
- Department of Chemistry, University of Paderborn , 33098 Paderborn, Germany
- Large Scale Structures Group, Institut Laue-Langevin , 38402 Grenoble, France
| | - Ralf Schweins
- Large Scale Structures Group, Institut Laue-Langevin , 38402 Grenoble, France
| | - Matthias Karg
- Physical Chemistry I, Heinrich-Heine-University , 40225 Düsseldorf, Germany
- Physical Chemistry I, University of Bayreuth , 95440 Bayreuth, Germany
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29
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Scotti A, Gasser U, Herman ES, Han J, Menzel A, Lyon LA, Fernandez-Nieves A. Phase behavior of binary and polydisperse suspensions of compressible microgels controlled by selective particle deswelling. Phys Rev E 2017; 96:032609. [PMID: 29346879 DOI: 10.1103/physreve.96.032609] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Indexed: 06/07/2023]
Abstract
We investigate the phase behavior of suspensions of poly(N-isopropylacrylamide) (pNIPAM) microgels with either bimodal or polydisperse size distribution. We observe a shift of the fluid-crystal transition to higher concentrations depending on the polydispersity or the fraction of large particles in suspension. Crystallization is observed up to polydispersities as high as 18.5%, and up to a number fraction of large particles of 29% in bidisperse suspensions. The crystal structure is random hexagonal close-packed as in monodisperse pNIPAM microgel suspensions. We explain our experimental results by considering the effect of bound counterions. Above a critical particle concentration, these cause deswelling of the largest microgels, which are the softest, changing the size distribution of the suspension and enabling crystal formation in conditions where incompressible particles would not crystallize.
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Affiliation(s)
- A Scotti
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - U Gasser
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - E S Herman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Jun Han
- Laboratory for Macromolecules and Bioimaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - A Menzel
- Laboratory for Macromolecules and Bioimaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - L A Lyon
- Schmid College of Science and Technology, Chapman University, Orange, California 92866, USA
| | - A Fernandez-Nieves
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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30
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Karthickeyan D, Joshi RG, Tata BVR. FCC-HCP coexistence in dense thermo-responsive microgel crystals. J Chem Phys 2017; 146:224503. [PMID: 29166046 DOI: 10.1063/1.4984978] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Analogous to hard-sphere suspensions, monodisperse thermo-responsive poly (N-isopropyl acrylamide) (PNIPAM) microgel particles beyond a volume fraction (ϕ) of 0.5 freeze into face centered cubic (FCC)-hexagonal close packed (HCP) coexistence under as prepared conditions and into an FCC structure upon annealing. We report here FCC-HCP coexistence to be stable in dense PNIPAM microgel crystals (ϕ > 0.74) with particles in their deswollen state (referred to as osmotically compressed microgel crystals) and the FCC structure with particles in their swollen state by performing annealing studies with different cooling rates. The structure of PNIPAM microgel crystals is characterized using static light scattering technique and UV-Visible spectroscopy and dynamics by dynamic light scattering (DLS). DLS studies reveal that the particle motion is diffusive at short times in crystals with ϕ < 0.74 and sub-diffusive at short times in PNIPAM crystals with ϕ > 0.74. The observed sub-diffusive behavior at short times is due to the overlap (interpenetration) of the dangling polymer chains between the shells of neighbouring PNIPAM microgel particles. Overlap is found to disappear upon heating the crystals well above their melting temperature, Tm due to reduction in the particle size. Annealing studies confirm that the overlap of dangling polymer chains between the shells of neighbouring PNIPAM spheres is responsible for the stability of FCC-HCP coexistence observed in osmotically compressed PNIPAM microgel crystals. Results are discussed in the light of recent reports of stabilizing the HCP structure in hard sphere crystals by adding interacting polymer chains.
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Affiliation(s)
- D Karthickeyan
- Condensed Matter Physics Division, Indira Gandhi Centre for Atomic Research, Homi Bhabha National Institute, Kalpakkam 603 102, India
| | - R G Joshi
- Condensed Matter Physics Division, Indira Gandhi Centre for Atomic Research, Homi Bhabha National Institute, Kalpakkam 603 102, India
| | - B V R Tata
- Condensed Matter Physics Division, Indira Gandhi Centre for Atomic Research, Homi Bhabha National Institute, Kalpakkam 603 102, India
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31
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Yang M, Liu C, Lian Y, Zhao K, Zhu D, Zhou J. Relaxations and phase transitions during the collapse of a dense PNIPAM microgel suspension-thorough insight using dielectric spectroscopy. SOFT MATTER 2017; 13:2663-2676. [PMID: 28332691 DOI: 10.1039/c7sm00144d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The dielectric behavior of a thermo-sensitive poly-(N-isopropylacrylamide) (PNIPAM) microgel suspension with a dense concentration was investigated over the frequency range of 40 Hz to 110 MHz in a wide temperature window of 10-60 °C. By successfully removing the electrode polarization effect from the original data, two remarkable and temperature-dependent relaxation processes were observed. Both of the two-phase transition processes, i.e., the colloidal crystal-to-liquid transition, which has not yet been detected by dielectric spectroscopy before, as well as the volume phase transition, were detected by the relaxation parameters. Based on the three physical states of the microgel suspension, the relaxation mechanisms are discussed in detail. The slow relaxation originates from the segmental motion and the counterion motion along the polymer chain over the whole temperature range. It was found that when the system is in the colloidal crystal and liquid state, the segmental motion is cooperative with side chain and hydrogen bonding networks, while in the phase separation state (at temperatures above the lower critical solution temperature (LCST)), the cooperative interaction disappears. The fast relaxation is due to the fluctuation of counterions below the LCST and the interfacial polarization above the LCST. Based on interfacial polarization theory, which describes the dielectric model of a conventional particle dispersion, the temperature dependence of the electrical properties for the constituent phases (the permittivity, conductivity and volume fraction of the microgel (εp, κp, ϕ); the conductivity of the medium water (κa); the water content in the PNIPAM microgel (fw)) were calculated using the Hanai equation. The water content is close to the result obtained using light scattering, indicating that the dielectric model for a conventional particle dispersion is also applicable to a soft atypical colloidal dispersion.
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Affiliation(s)
- Man Yang
- College of Chemistry, Beijing Normal University, Beijing 100875, China.
| | - Chunyan Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, China.
| | - Yiwei Lian
- College of Chemistry, Beijing Normal University, Beijing 100875, China.
| | - Kongshuang Zhao
- College of Chemistry, Beijing Normal University, Beijing 100875, China.
| | - Dan Zhu
- College of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210046, China
| | - Jianfeng Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026, P. R. China
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32
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Mohanty PS, Nöjd S, Bergman MJ, Nägele G, Arrese-Igor S, Alegria A, Roa R, Schurtenberger P, Dhont JKG. Dielectric spectroscopy of ionic microgel suspensions. SOFT MATTER 2016; 12:9705-9727. [PMID: 27808335 DOI: 10.1039/c6sm01683a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The determination of the net charge and size of microgel particles as a function of their concentration, as well as the degree of association of ions to the microgel backbone, has been pursued in earlier studies mainly by scattering and rheology. These methods suffer from contributions due to inter-particle interactions that interfere with the characterization of single-particle properties. Here we introduce dielectric spectroscopy as an alternative experimental method to characterize microgel systems. The advantage of dielectric spectroscopy over other experimental methods is that the polarization due to mobile charges within a microgel particle is only weakly affected by inter-particle interactions. Apart from electrode polarization effects, experimental spectra on PNIPAM-co-AA [poly(N-isopropylacrylamide-co-acrylic acid)] ionic microgel particles suspended in de-ionized water exhibit three well-separated relaxation modes, which are due to the polarization of the mobile charges within the microgel particles, the diffuse double layer around the particles, and the polymer backbone. Expressions for the full frequency dependence of the electrode-polarization contribution to the measured dielectric response are derived, and a theory is proposed for the polarization resulting from the mobile charges within the microgel. Relaxation of the diffuse double layer is modeled within the realm of a cell model. The net charge and the size of the microgel particles are found to be strongly varying with concentration. A very small value of the diffusion coefficient of ions within the microgel is found, due to a large degree of chemical association of protons to the polymer backbone.
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Affiliation(s)
- P S Mohanty
- Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden and School of Applied Sciences, KIIT University, Bhubaneswar 751024, India
| | - S Nöjd
- Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden
| | - M J Bergman
- Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden
| | - G Nägele
- Institute of Complex Systems ICS-3, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. and Heinrich-Heine Universität Düsseldorf, Department of Physics, D-40225 Düsseldorf, Germany and JARA-SOFT, 52425 Jülich, Germany
| | - S Arrese-Igor
- Centro de Física de Materiales (CSIC-UPV/EHU), Materials Physics Center, 20018 San Sebastián, Spain
| | - A Alegria
- Centro de Física de Materiales (CSIC-UPV/EHU), Materials Physics Center, 20018 San Sebastián, Spain and Universidad del País Vasco (UPV/EHU), Departamento de Física de Materiales, 20080 San Sebastián, Spain
| | - R Roa
- Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, 14109 Berlin, Germany
| | - P Schurtenberger
- Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden
| | - J K G Dhont
- Institute of Complex Systems ICS-3, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. and Heinrich-Heine Universität Düsseldorf, Department of Physics, D-40225 Düsseldorf, Germany and JARA-SOFT, 52425 Jülich, Germany
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33
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Lo Verso F, Pomposo JA, Colmenero J, Moreno AJ. Tunable slow dynamics in a new class of soft colloids. SOFT MATTER 2016; 12:9039-9046. [PMID: 27774553 DOI: 10.1039/c6sm02136k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
By means of extensive simulations, we investigate concentrated solutions of globular single-chain nanoparticles (SCNPs), an emergent class of synthetic soft nano-objects. By increasing the concentration, the SCNPs show flattening, and even reentrant behaviour, in the density dependence of their structural and dynamic correlations, as well as a soft caging regime and weak dynamic heterogeneity. The latter is confirmed by validation of the Stokes-Einstein relation up to concentrations far beyond the overlap density. Therefore SCNPs arise as a new class of soft colloids, exhibiting slow dynamics and actualizing in a real system the structural and dynamic anomalies proposed by models of ultrasoft particles. Quantitative differences in the dynamic behaviour depend on the SCNP deformability, which can be tuned through the degree of internal cross-linking.
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Affiliation(s)
- Federica Lo Verso
- Centro de Física de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain.
| | - José A Pomposo
- Centro de Física de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain. and Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU), Apartado 1072, E-20080 San Sebastián, Spain and IKERBASQUE - Basque Foundation for Science, María Díaz de Haro 3, E-48013 Bilbao, Spain
| | - Juan Colmenero
- Centro de Física de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain. and Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU), Apartado 1072, E-20080 San Sebastián, Spain and Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain
| | - Angel J Moreno
- Centro de Física de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain. and Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain
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34
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Urich M, Denton AR. Swelling, structure, and phase stability of compressible microgels. SOFT MATTER 2016; 12:9086-9094. [PMID: 27774556 DOI: 10.1039/c6sm02056a] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Microgels are soft colloidal particles that, when dispersed in a solvent, swell and deswell in response to changes in environmental conditions, such as temperature, concentration, and pH. Using Monte Carlo simulation, we model bulk suspensions of microgels that interact via Hertzian elastic interparticle forces and can expand or contract via trial moves that allow particles to change size in accordance with the Flory-Rehner free energy of cross-linked polymer gels. We monitor the influence of particle compressibility, size fluctuations, and concentration on bulk structural and thermal properties by computing particle swelling ratios, radial distribution functions, static structure factors, osmotic pressures, and freezing densities. For microgels in the nanoscale size range, particle compressibility and associated size fluctuations suppress crystallization, shifting the freezing transition to a higher density than for the hard-sphere fluid. As densities increase beyond close packing, microgels progressively deswell, while their intrinsic size distribution grows increasingly polydisperse.
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Affiliation(s)
- Matthew Urich
- Department of Physics, North Dakota State University, Fargo, ND 58108-6050, USA.
| | - Alan R Denton
- Department of Physics, North Dakota State University, Fargo, ND 58108-6050, USA.
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35
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Affiliation(s)
- Alan R. Denton
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
| | - Qiyun Tang
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
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36
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Temperature-driven volume phase transition of a single stimuli-responsive microgel particle using optical tweezers. Colloid Polym Sci 2016. [DOI: 10.1007/s00396-016-3952-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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37
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Braibanti M, Haro-Pérez C, Quesada-Pérez M, Rojas-Ochoa LF, Trappe V. Impact of volume transition on the net charge of poly-N-isopropyl acrylamide microgels. Phys Rev E 2016; 94:032601. [PMID: 27739781 DOI: 10.1103/physreve.94.032601] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Indexed: 06/06/2023]
Abstract
We explore the electrostatic properties of poly-N-isopropyl acrylamide microgels in dilute, quasi-de-ionized dispersions and show that the apparent net charge of these thermosensitive microgels is an increasing function of their size, the size being conveniently varied by temperature. Our experimental results obtained in a combination of light scattering, conductivity, and mobility experiments are consistent with those obtained in Poisson-Boltzmann cell model calculations, effectively indicating that upon shrinking the number of counterions entrapped within the microgels increases. Remarkably, this behavior shows that the electrostatic energy per particle remains constant upon swelling or deswelling the microgel, resulting in a square root dependence of the net charge on the particle radius.
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Affiliation(s)
- M Braibanti
- Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland
| | - C Haro-Pérez
- Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana-Azcapotzalco, Avenida San Pablo 180, 02200 Ciudad de México, Mexico
| | - M Quesada-Pérez
- Departamento de Física, Universidad de Jaén, Escuela Politécnica Superior de Linares, 23700 Linares, Spain
| | - L F Rojas-Ochoa
- Departamento de Física, CINVESTAV-IPN, Avenida Instituto Politécnico Nacional 2508, 07360 Ciudad de México, Mexico
| | - V Trappe
- Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland
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38
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Verma SK, Jha E, Kiran K, Bhat S, Suar M, Mohanty PS. Synthesis and characterization of novel polymer-hybrid silver nanoparticles and its biomedical study. ACTA ACUST UNITED AC 2016. [DOI: 10.1016/j.matpr.2016.04.096] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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39
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Gawlitza K, Ivanova O, Radulescu A, Holderer O, von Klitzing R, Wellert S. Bulk Phase and Surface Dynamics of PEG Microgel Particles. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00788] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Kornelia Gawlitza
- Stranski-Laboratory
for Physical and Theoretical Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Oxana Ivanova
- Forschungszentrum Jülich Outstation at the Heinz Maier-Leibniz-Zentrum, Jülich Center for Neutron Science JCNS-MLZ , Lichtenbergstraße 1, 85747 Garching, Germany
| | - Aurel Radulescu
- Forschungszentrum Jülich Outstation at the Heinz Maier-Leibniz-Zentrum, Jülich Center for Neutron Science JCNS-MLZ , Lichtenbergstraße 1, 85747 Garching, Germany
| | - Olaf Holderer
- Forschungszentrum Jülich Outstation at the Heinz Maier-Leibniz-Zentrum, Jülich Center for Neutron Science JCNS-MLZ , Lichtenbergstraße 1, 85747 Garching, Germany
| | - Regine von Klitzing
- Stranski-Laboratory
for Physical and Theoretical Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Stefan Wellert
- Stranski-Laboratory
for Physical and Theoretical Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
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40
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Brijitta J, Tata BVR, Joshi RG. Controlled synthesis of monodisperse thermo-responsive nanogel particles. JOURNAL OF POLYMER RESEARCH 2015. [DOI: 10.1007/s10965-015-0674-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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41
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Wellert S, Hertle Y, Richter M, Medebach M, Magerl D, Wang W, Demé B, Radulescu A, Müller-Buschbaum P, Hellweg T, von Klitzing R. Inner structure of adsorbed ionic microgel particles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:7168-7176. [PMID: 24920223 DOI: 10.1021/la500390j] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Microgel particles of cross-linked poly(NIPAM-co-acrylic acid) with different acrylic acid contents are investigated in solution and in the adsorbed state. As a substrate, silicon with a poly(allylamine hydrochloride) (PAH) coating is used. The temperature dependence of the deswelling of the microgel particles was probed with atomic force microscopy (AFM). The inner structure of the adsorbed microgel particles was detected with grazing incidence small angle neutron scattering (GISANS). Small angle neutron scattering (SANS) on corresponding microgel suspensions was performed for comparison. Whereas the correlation length of the polymer network shows a divergence in the bulk samples, in the adsorbed microgel particles it remains unchanged over the entire temperature range. In addition, GISANS indicates changes in the particles along the surface normal. This suggests that the presence of a solid surface suppresses the divergence of internal fluctuations in the adsorbed microgels close to the volume phase transition.
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Affiliation(s)
- Stefan Wellert
- Stranski Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin , Straße des 17 Juni 124, 10623 Berlin, Germany
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42
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Geisel K, Isa L, Richtering W. The Compressibility of pH-Sensitive Microgels at the Oil-Water Interface: Higher Charge Leads to Less Repulsion. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201402254] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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43
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Geisel K, Isa L, Richtering W. The Compressibility of pH-Sensitive Microgels at the Oil-Water Interface: Higher Charge Leads to Less Repulsion. Angew Chem Int Ed Engl 2014; 53:4905-9. [DOI: 10.1002/anie.201402254] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Indexed: 11/09/2022]
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44
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Mohanty PS, Paloli D, Crassous JJ, Zaccarelli E, Schurtenberger P. Effective interactions between soft-repulsive colloids: Experiments, theory, and simulations. J Chem Phys 2014; 140:094901. [DOI: 10.1063/1.4866644] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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45
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Gasser U, Lietor-Santos JJ, Scotti A, Bunk O, Menzel A, Fernandez-Nieves A. Transient formation of bcc crystals in suspensions of poly(N-isopropylacrylamide)-based microgels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:052308. [PMID: 24329265 DOI: 10.1103/physreve.88.052308] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Indexed: 06/03/2023]
Abstract
We present a small-angle x-ray scattering study of crystals formed by temperature-sensitive, swollen microgel particles consisting of poly(N-isopropylacrylamide) copolymerized with acrylic acid and 5 mol % of a cross-linker. As for hard spheres, the random hexagonal close-packed structure is predominant during crystal growth and slowly transforms toward the face-centered-cubic structure. However, a transient phase of body-centered-cubic crystal is observed in an intermediate range of effective volume fractions. We estimate that the studied suspensions are close to a transition from face-centered-cubic to body-centered-cubic structure that can be understood by the tendency of the system to maximize the excluded volume and minimize the contact area between the particles.
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Affiliation(s)
- U Gasser
- Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - J-J Lietor-Santos
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA
| | - A Scotti
- Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - O Bunk
- Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - A Menzel
- Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - A Fernandez-Nieves
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA
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46
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47
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Richtering W. Responsive emulsions stabilized by stimuli-sensitive microgels: emulsions with special non-Pickering properties. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:17218-29. [PMID: 23020623 DOI: 10.1021/la302331s] [Citation(s) in RCA: 212] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Recent studies revealing the unique properties of microgel-stabilized responsive emulsions are discussed, and microgels are compared to classical rigid-particle Pickering stabilizers. Microgels are strongly swollen, lyophilic particles that become deformed at the oil-water interface and protrude only a little into the oil phase. Temperature- and pH-sensitive microgels allow us to prepare temperature- and pH-sensitive emulsions and thus enable us to prepare and break emulsions on demand. Although such emulsions are sensitive to pH, the stabilization of droplets is not due to electrostatic repulsion, instead the viscoelastic properties of the interface seem to dominate droplet stability. Being soft and porous, microgels behave distinctly differently from rigid particles at the interface: they are deformed and strongly flattened especially in the case of oil-in-water emulsions. The microgels are located mainly on the water side of the interface for both oil-in-water and water-in-oil emulsions. In contrast to rigid, solid particles, the behavior of microgels at oil-water interfaces does not depend only on the interfacial tension but also on the balance among the interfacial tension, swelling, elasticity, and deformability of the microgel, which needs to be considered. It is obvious that microgels as soft, porous particles are significantly different from classical rigid colloidal stabilizers in Pickering emulsions and we suggest avoiding the term Pickering emulsion when swollen microgels are employed. Microgel-stabilized emulsions require the development of new theoretical models to understand their properties. They open the door to new sophisticated applications.
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Affiliation(s)
- Walter Richtering
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52056 Aachen, Germany.
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48
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Holmqvist P, Mohanty PS, Nägele G, Schurtenberger P, Heinen M. Structure and dynamics of loosely cross-linked ionic microgel dispersions in the fluid regime. PHYSICAL REVIEW LETTERS 2012; 109:048302. [PMID: 23006114 DOI: 10.1103/physrevlett.109.048302] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Indexed: 06/01/2023]
Abstract
We report a comprehensive experimental-theoretical study of the temperature- and concentration-dependent swelling behavior of weakly cross-linked PNiPAm ionic microgel particles in the deionized fluid phase. The particles swell reversibly when the dispersion is cooled from the collapsed state to lower temperatures. While the collapsed state shows no dependence on the microgel number density, the swelling at lower T is more pronounced at lower concentrations. The static pair correlations and short-time diffusion functions, and the concentration and temperature dependence of the microgel radius and effective charge, are studied using static and dynamic light scattering in combination with state-of-the-art analytical theoretical schemes based on a Yukawa-type effective pair potential and a core-shell model. We show that only such a combined, simultaneous fit of static and dynamic scattering functions allows for an unambiguous determination of the microgel radius and effective charge.
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Affiliation(s)
- P Holmqvist
- Institute of Complex Systems (ICS-3), Forschungszentrum Jülich, Jülich D-52425, Germany.
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49
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Riest J, Mohanty P, Schurtenberger P, Likos CN. Coarse-Graining of Ionic Microgels: Theory and Experiment. ACTA ACUST UNITED AC 2012. [DOI: 10.1524/zpch.2012.0258] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
In this work, we discuss the statistical mechanics of many-body systems consisting of electrically charged microgels, and we show that their collective behavior is determined by an interplay between the screened electrostatic and the elastic contributions to their effective interaction potential. The former is derived by means of a statistical-mechanical approach due to Denton [A. R. Denton, Phys. Rev. E 67, 011804 (2003)], and it includes the screened electrostatic potential between penetrable spheres and the counterion entropic contribution. The latter is based on the Hertzian model of the theory of elasticity. Comparisons with experimental results demonstrate the realistic nature of the coarse-graining procedure, which makes it possible to put forward theoretical predictions on the phase diagram of ionic microgels and on the behavior of soft, neutral microgels under confinement in narrow pores.
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Affiliation(s)
- Jonas Riest
- University of Vienna, Faculty of Physics, Vienna, Österreich
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50
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Muluneh M, Weitz DA. Direct visualization of three-dimensional crystallization behavior in microgels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:021405. [PMID: 22463210 DOI: 10.1103/physreve.85.021405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 12/27/2011] [Indexed: 05/28/2023]
Abstract
We use confocal microscopy to study the three-dimensional (3D) structure of colloidal crystals formed by poly(N-isopropylacrylamide)-co-(acrylic acid) microgels of diameter 1.0-1.5 μm. The confocal images are tracked to locate particle positions in 3D, which are used to compute pair-correlation functions g(r), bond order parameters, and structure factors s(q). We find that the structure remains fcc for a range of charge, size, and concentration of the particles. When the particles are weakly attractive and are at low concentrations, polycrystalline solids result. In addition, owing to the compressibility of the colloids, the crystals display remarkable structural stability when subjected to external stress.
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Affiliation(s)
- Melaku Muluneh
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
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