51
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Migliozzi S, Meridiano G, Angeli P, Mazzei L. Investigation of the swollen state of Carbopol molecules in non-aqueous solvents through rheological characterization. SOFT MATTER 2020; 16:9799-9815. [PMID: 33005911 DOI: 10.1039/d0sm01196g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We explore how different types of solvent influence the rheological properties of non-aqueous Carbopol dispersions from the dilute to the jammed state. In novel non-aqueous formulations, polar solvents are used more and more frequently, because they can form Carbopol microgels without the need of any neutralizing agents. However, the swelling behaviour of Carbopol molecules in the absence of water, when ionic forces are weak, is still poorly understood. To this end, we study the swelling behaviour of Carbopol 974P NF in different polar solvents, i.e. glycerol, PEG400 and mixtures of the two solvents, by mapping the rheological behaviour of Carbopol suspensions from very dilute to highly concentrated conditions. The rheological study reveals that the onset of the jamming transition occurs at different critical polymer concentrations depending on the solvents used. Nevertheless, once the jammed state is reached, both elastic and yielding behaviours are scalable with the particle volume fraction. These results suggest that the type of solvent influences the final volume of the single Carbopol particles but does not alter the interactions between the particles. The final radius of the swollen particles is estimated from shear rheology measurements in dilute conditions, showing a decrease of the final swelling ratio of Carbopol molecules of almost 50% for PEG400 solutions, a result that confirms the shift to higher values of the critical jamming concentration obtained from linear viscoelasticity for the same solutions.
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Affiliation(s)
- Simona Migliozzi
- Department of Chemical Engineering, University College London, Torrington Place, London WC1E 7JE, UK.
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52
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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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53
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Abstract
Suspensions of soft and highly deformable microgels can be concentrated far more than suspensions of hard colloids, leading to their unusual mechanical properties. Microgels can accommodate compression in suspensions in a variety of ways such as interpenetration, deformation, and shrinking. Previous experiments have offered insightful, but somewhat conflicting, accounts of the behavior of individual microgels in compressed suspensions. We develop a mesoscale computational model to probe the behavior of compressed suspensions consisting of microgels with different architectures at a variety of packing fractions and solvent conditions. We find that microgels predominantly change shape and mildly shrink above random close packing. Interpenetration is only appreciable above space filling, remaining small relative to the mean distance between cross-links. At even higher packing fractions, microgels solely shrink. Remarkably, irrespective of the single-microgel properties, and whether the suspension concentration is changed via changing the particle number density or the swelling state of the particles, which can even result in colloidal gelation, the mechanics of the suspension can be quantified in terms of the single-microgel bulk modulus, which thus emerges as the correct mechanical measure for these type of soft-colloidal suspensions. Our results rationalize the many and varied experimental results, providing insights into the relative importance of effects defining the mechanics of suspensions comprising soft particles.
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54
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Scheffold F. Pathways and challenges towards a complete characterization of microgels. Nat Commun 2020; 11:4315. [PMID: 32887886 PMCID: PMC7473851 DOI: 10.1038/s41467-020-17774-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Accepted: 07/20/2020] [Indexed: 01/07/2023] Open
Abstract
Due to their controlled size, sensitivity to external stimuli, and ease-of-use, microgel colloids are unique building blocks for soft materials made by crosslinking polymers on the micrometer scale. Despite the plethora of work published, many questions about their internal structure, interactions, and phase behavior are still open. The reasons for this lack of understanding are the challenges arising from the small size of the microgel particles, complex pairwise interactions, and their solvent permeability. Here we describe pathways toward a complete understanding of microgel colloids based on recent experimental advances in nanoscale characterization, such as super-resolution microscopy, scattering methods, and modeling.
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Affiliation(s)
- Frank Scheffold
- Department of Physics, University of Fribourg, Chemin du Musée 3, 1700, Fribourg, Switzerland.
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55
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Minato H, Nishizawa Y, Uchihashi T, Suzuki D. Thermoresponsive structural changes of single poly(N-isopropyl acrylamide) hydrogel microspheres under densely packed conditions on a solid substrate. Polym J 2020. [DOI: 10.1038/s41428-020-0372-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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56
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Minami S, Watanabe T, Sasaki Y, Minato H, Yamamoto A, Suzuki D, Urayama K. Two-step yielding behavior of densely packed microgel mixtures with chemically dissimilar surfaces and largely different sizes. SOFT MATTER 2020; 16:7400-7413. [PMID: 32699868 DOI: 10.1039/d0sm00366b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Steady-state flow and elastic behavior is investigated for the moderately concentrated binary suspensions of soft microgels (pastes) with chemically dissimilar surfaces, and various degrees of size- and stiffness disparities. The pastes of poly(N-isopropyl acrylamide) (N) and poly(N-isopropyl methacrylamide) (NM) microgels with different values of yield strain γc (γNc > γNMc) are employed as the components. For the single microgel pastes (φ ≈ 1 where φ is apparent volume fraction), the values of γc are governed by the chemical species of constituent polymer in microgel surface whereas γc is insensitive to cross-link density and particle size. We demonstrate that the binary N/NM pastes with large size disparity (RN/NM = DN/DNM < 0.26 where D is the microgel diameter) at low φN (φN: weight fraction of small N microgels) exhibit the peculiarities in several rheological aspects, i.e., the two-step yielding in steady-state flow, and their values of γc and equilibrium shear modulus (G0) being equivalent to those of the single large NM microgel paste. These peculiarities are attributed to the characteristic packing resulting from large size disparity in which all or almost of the small N microgels tend to be accommodated in the gap between the large NM microgels even in moderately concentrated state. This characteristic packing substantially masks the contribution of the small N microgels at low φN, explaining the φN-independent G0 and γc as well as the first yielding governed solely by the large NM microgels. The second yielding results from the emerged contribution of the small N microgels expelled out from the gap by the positional rearrangements after the first yielding. The binary homo-N/N pastes with the similarly large size disparity at low φsmall also exhibit the φsmall-independent values of G0, but they show one-step yielding, indicating that the two-step yielding requires not only sufficiently large size disparity but also chemical dissimilarity (different values of γc) between the two components.
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Affiliation(s)
- Saori Minami
- Department of Macromolecular Science and Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan.
| | - Takumi Watanabe
- Graduate School of Textile Science & Technology, Shinshu University, Ueda 386-8567, Japan.
| | - Yuma Sasaki
- Graduate School of Textile Science & Technology, Shinshu University, Ueda 386-8567, Japan.
| | - Haruka Minato
- Graduate School of Textile Science & Technology, Shinshu University, Ueda 386-8567, Japan.
| | - Atsushi Yamamoto
- Department of Macromolecular Science and Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan.
| | - Daisuke Suzuki
- Graduate School of Textile Science & Technology, Shinshu University, Ueda 386-8567, Japan. and Research Initiative for Supra-Materials, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, Ueda 386-8567, Japan
| | - Kenji Urayama
- Department of Macromolecular Science and Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan.
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57
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Di Napoli B, Franco S, Severini L, Tumiati M, Buratti E, Titubante M, Nigro V, Gnan N, Micheli L, Ruzicka B, Mazzuca C, Angelini R, Missori M, Zaccarelli E. Gellan Gum Microgels as Effective Agents for a Rapid Cleaning of Paper. ACS APPLIED POLYMER MATERIALS 2020; 2:2791-2801. [PMID: 32685926 PMCID: PMC7359273 DOI: 10.1021/acsapm.0c00342] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 05/27/2020] [Indexed: 05/21/2023]
Abstract
Microgel particles have emerged in the past few years as a favorite model system for fundamental science and for innovative applications ranging from the industrial to biomedical fields. Despite their potentialities, no works so far have focused on the application of microgels for cultural heritage preservation. Here we show their first use for this purpose, focusing on wet paper cleaning. Exploiting their retentive properties, microgels are able to clean paper, ensuring more controlled water release from the gel matrix, in analogy to their macroscopic counterpart, i.e., hydrogels. However, differently from these, the reduced size of microgels makes them suitable to efficiently penetrate in the porous structure of the paper and to easily adapt to the irregular surfaces of the artifacts. To test their cleaning abilities, we prepare microgels made of Gellan gum, a natural and widespread material already used as a hydrogel for paper cleaning, and apply them to modern and ancient paper samples. Combining several diagnostic methods, we show that microgels performances in the removal of cellulose degradation byproducts for ancient samples are superior to commonly employed hydrogels and water bath treatments. This is due to the composition and morphology of ancient paper, which facilitates microgels penetration. For modern paper cleaning, performances are at least comparable to the other methods. In all cases, the application of microgels takes place on a time scale of a few minutes, opening the way for widespread use as a rapid and efficient cleaning protocol.
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Affiliation(s)
- Benedetta Di Napoli
- Institute
for Complex Systems, National Research Council (CNR-ISC) and Department
of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy
- Department
of Chemical Sciences and Technologies, University
of Rome Tor Vergata, Via della Ricerca Scientifica I, 00133 Rome, Italy
| | - Silvia Franco
- Institute
for Complex Systems, National Research Council (CNR-ISC) and Department
of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy
| | - Leonardo Severini
- Department
of Chemical Sciences and Technologies, University
of Rome Tor Vergata, Via della Ricerca Scientifica I, 00133 Rome, Italy
| | - Manuel Tumiati
- Department
of Chemical Sciences and Technologies, University
of Rome Tor Vergata, Via della Ricerca Scientifica I, 00133 Rome, Italy
| | - Elena Buratti
- Institute
for Complex Systems, National Research Council (CNR-ISC) and Department
of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy
| | - Mattia Titubante
- Department
of Chemical Sciences and Technologies, University
of Rome Tor Vergata, Via della Ricerca Scientifica I, 00133 Rome, Italy
| | - Valentina Nigro
- Institute
for Complex Systems, National Research Council (CNR-ISC) and Department
of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy
- ENEA
C.R. Frascati, FSN-TECFIS-MNF
Photonics Micro and Nanostructures Laboratory, Via E. Fermi 45, 00044 Frascati, Roma, Italy
| | - Nicoletta Gnan
- Institute
for Complex Systems, National Research Council (CNR-ISC) and Department
of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy
| | - Laura Micheli
- Department
of Chemical Sciences and Technologies, University
of Rome Tor Vergata, Via della Ricerca Scientifica I, 00133 Rome, Italy
| | - Barbara Ruzicka
- Institute
for Complex Systems, National Research Council (CNR-ISC) and Department
of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy
| | - Claudia Mazzuca
- Department
of Chemical Sciences and Technologies, University
of Rome Tor Vergata, Via della Ricerca Scientifica I, 00133 Rome, Italy
| | - Roberta Angelini
- Institute
for Complex Systems, National Research Council (CNR-ISC) and Department
of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy
| | - Mauro Missori
- Institute
for Complex Systems, National Research Council (CNR-ISC) and Department
of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy
| | - Emanuela Zaccarelli
- Institute
for Complex Systems, National Research Council (CNR-ISC) and Department
of Physics, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy
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58
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Zanatta M, Tavagnacco L, Buratti E, Chiessi E, Natali F, Bertoldo M, Orecchini A, Zaccarelli E. Atomic scale investigation of the volume phase transition in concentrated PNIPAM microgels. J Chem Phys 2020; 152:204904. [PMID: 32486676 DOI: 10.1063/5.0007112] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Combining elastic incoherent neutron scattering and differential scanning calorimetry, we investigate the occurrence of the volume phase transition (VPT) in very concentrated poly-(N-isopropyl-acrylamide) (PNIPAM) microgel suspensions, from a polymer weight fraction of 30 wt. % up to dry conditions. Although samples are arrested at the macroscopic scale, atomic degrees of freedom are equilibrated and can be probed in a reproducible way. A clear signature of the VPT is present as a sharp drop in the mean square displacement of PNIPAM hydrogen atoms obtained by neutron scattering. As a function of concentration, the VPT gets smoother as dry conditions are approached, whereas the VPT temperature shows a minimum at about 43 wt. %. This behavior is qualitatively confirmed by calorimetry measurements. Molecular dynamics simulations are employed to complement experimental results and gain further insights into the nature of the VPT, confirming that it involves the formation of an attractive gel state between the microgels. Overall, these results provide evidence that the VPT in PNIPAM-based systems can be detected at different time- and length-scales as well as under overcrowded conditions.
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Affiliation(s)
- M Zanatta
- Department of Physics, University of Trento, I-38123 Trento, Italy
| | - L Tavagnacco
- CNR-ISC and Department of Physics, Sapienza University of Rome, I-00185 Roma, Italy
| | - E Buratti
- CNR-ISC and Department of Physics, Sapienza University of Rome, I-00185 Roma, Italy
| | - E Chiessi
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, I-00133 Roma, Italy
| | - F Natali
- CNR-IOM, Operative Group in Grenoble (OGG), c/o Institut Laue Langevin, F-38042 Grenoble, France
| | - M Bertoldo
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, I-44121 Ferrara, Italy
| | - A Orecchini
- Department of Physics and Geology, University of Perugia, I-06123 Perugia, Italy
| | - E Zaccarelli
- CNR-ISC and Department of Physics, Sapienza University of Rome, I-00185 Roma, Italy
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59
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Minami S, Yamamoto A, Oura S, Watanabe T, Suzuki D, Urayama K. Criteria for colloidal gelation of thermo-sensitive poly(N-isopropylacrylamide) based microgels. J Colloid Interface Sci 2020; 568:165-175. [DOI: 10.1016/j.jcis.2020.02.047] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 02/12/2020] [Accepted: 02/13/2020] [Indexed: 11/24/2022]
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60
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Su YX, Xu L, Xu XH, Hou XH, Liu N, Wu ZQ. Controlled Synthesis of Densely Grafted Bottlebrushes That Bear Helical Polyisocyanide Side Chains on Polyisocyanide Backbones and Exhibit Greatly Increased Viscosity. Macromolecules 2020. [DOI: 10.1021/acs.macromol.9b02032] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Yi-Xu Su
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009, Anhui Province, China
| | - Lei Xu
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009, Anhui Province, China
| | - Xun-Hui Xu
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009, Anhui Province, China
| | - Xiao-Hua Hou
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009, Anhui Province, China
| | - Na Liu
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009, Anhui Province, China
| | - Zong-Quan Wu
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009, Anhui Province, China
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61
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Scotti A, Brugnoni M, G Lopez C, Bochenek S, Crassous JJ, Richtering W. Flow properties reveal the particle-to-polymer transition of ultra-low crosslinked microgels. SOFT MATTER 2020; 16:668-678. [PMID: 31815271 DOI: 10.1039/c9sm01451a] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Exploiting soft, adaptive microgels as building blocks for soft materials with controlled and predictable viscoelastic properties is of great interest for both industry and fundamental research. Here the flow properties of different poly(N-isopropylacrylamide) (pNIPAM) microgels are compared: regularly crosslinked versus ultra-low crosslinked (ULC) microgels. The latter are the softest microgels that can be produced via precipitation polymerization. The viscosity of ULC microgel suspensions at low concentrations can be described with models typically used for hard spheres and regularly crosslinked microgels. In contrast, at higher concentrations, ULC microgels show a much softer behavior compared to regularly crosslinked microgels. The increase of the storage modulus with concentration discloses that while for regularly crosslinked microgels the flow properties are mainly determined by the more crosslinked core, for ULC microgels the brush-like interaction is dominant at high packing fractions. Both the flow curves and the increase of the storage modulus with concentration indicates that ULC microgels can form glass and even reach an apparent jammed state despite their extreme softness. In contrast, the analysis of oscillatory frequency sweep measurements show that when approaching the glass transition the ultra-low crosslinked microgels behave as the regularly crosslinked microgels. This is consistent with a recent study showing that in this concentration range the equilibrium phase behavior of these ULC microgels is the one expected for regularly crosslinked microgels.
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Affiliation(s)
- Andrea Scotti
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany.
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62
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Schulte MF, Scotti A, Brugnoni M, Bochenek S, Mourran A, Richtering W. Tuning the Structure and Properties of Ultra-Low Cross-Linked Temperature-Sensitive Microgels at Interfaces via the Adsorption Pathway. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:14769-14781. [PMID: 31638406 DOI: 10.1021/acs.langmuir.9b02478] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The structure of poly(N-isopropylacrylamide) (PNIPAM) microgels adsorbed onto a solid substrate is investigated in the dry and hydrated states by means of atomic force microscopy (AFM). We compare two different systems: a regularly cross-linked microgel containing 5 mol % cross-linker and ultra-low cross-linked microgels (ULC) prepared without a dedicated cross-linker. Furthermore, we compare three different adsorption processes: (i) in situ adsorption from solution, (ii) spin-coating, and (iii) Langmuir-Blodgett deposition from an oil-water interface. The results demonstrate that the morphology and the temperature-induced collapse of microgels adsorbed onto a solid substrate are very different for ultra-low cross-linked microgels as compared to regularly cross-linked microgels, despite the fact that their general behavior in solution is very similar. Furthermore, the morphology of ULC microgels can be controlled by the adsorption pathway onto the substrate. Absorbed ULC microgels are strongly deformed when being prepared either by spin-coating or by Langmuir-Blodgett deposition from an oil-water interface. After rehydration, the ULC microgels cannot collapse as entire objects, instead small globules are formed. Such a strong deformation can be avoided by in situ adsorption onto the substrate. Then, the ULC microgels exhibit half-ellipsoidal shapes with a smooth surface in the collapsed state similar to the more cross-linked microgels. As ULC microgels can be selectively trapped either in a more particle-like or in a more polymer-like behavior, coatings with strongly different topographies and properties can be prepared by one and the same ultra-low cross-linked microgel. This provides new opportunities for the development of smart polymeric coatings.
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Affiliation(s)
- M Friederike Schulte
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , 52056 Aachen , Germany
- DWI-Leibniz Institute for Interactive Materials , Forckenbeckstr. 50 , 52056 Aachen , Germany
| | - Andrea Scotti
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , 52056 Aachen , Germany
| | - Monia Brugnoni
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , 52056 Aachen , Germany
| | - Steffen Bochenek
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , 52056 Aachen , Germany
| | - Ahmed Mourran
- DWI-Leibniz Institute for Interactive Materials , Forckenbeckstr. 50 , 52056 Aachen , Germany
| | - Walter Richtering
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , 52056 Aachen , Germany
- DWI-Leibniz Institute for Interactive Materials , Forckenbeckstr. 50 , 52056 Aachen , Germany
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63
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Del Monte G, Ninarello A, Camerin F, Rovigatti L, Gnan N, Zaccarelli E. Numerical insights on ionic microgels: structure and swelling behaviour. SOFT MATTER 2019; 15:8113-8128. [PMID: 31589214 DOI: 10.1039/c9sm01253b] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Recent progress has been made in the numerical modelling of neutral microgel particles with a realistic, disordered structure. In this work we extend this approach to the case of co-polymerised microgels where a thermoresponsive polymer is mixed with acidic groups. We compare the cases where counterions directly interact with microgel charges or are modelled implicitly through a Debye-Hückel description. We do so by performing extensive numerical simulations of single microgels across the volume phase transition (VPT) varying the temperature and the fraction of charged monomers. We find that the presence of charges considerably alters the microgel structure, quantified by the monomer density profiles and by the form factors of the microgels, particularly close to the VPT. We observe significant deviations between the implicit and explicit models, with the latter comparing more favourably to available experiments. In particular, we observe a shift of the VPT temperature to larger values as the amount of charged monomers increases. We also find that below the VPT the microgel-counterion complex is almost neutral, while it develops a net charge above the VPT. Interestingly, under these conditions the collapsed microgel still retains a large amount of counterions inside its structure. Since these interesting features cannot be captured by the implicit model, our results show that it is crucial to explicitly include the counterions in order to realistically model ionic thermoresponsive microgels.
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Affiliation(s)
- Giovanni Del Monte
- Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Center for Life NanoScience, Istituto Italiano di Tecnologia, Rome, Italy
| | - Andrea Ninarello
- CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy.
| | - Fabrizio Camerin
- CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Department of Basic and Applied Sciences for Engineering, Sapienza University of Rome, via A. Scarpa 14, 00161 Rome, Italy
| | - Lorenzo Rovigatti
- Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy.
| | - Nicoletta Gnan
- CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy.
| | - Emanuela Zaccarelli
- CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy.
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64
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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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