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Kureha T, Ohira M, Takahashi Y, Li X, Gilbert EP, Shibayama M. Nanoscale Structures of Poly(oligo ethylene glycol methyl ether methacrylate) Hydrogels Revealed by Small-Angle Neutron Scattering. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c02259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Takuma Kureha
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan
| | - Masashi Ohira
- Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8685, Japan
| | - Yuki Takahashi
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan
| | - Xiang Li
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan
| | - Elliot P. Gilbert
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, New South Wales 2234, Australia
| | - Mitsuhiro Shibayama
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Tokai, Ibaraki 319-1106, Japan
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2
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Fernandez Bordín SP, Andrada HE, Carreras AC, Castellano G, Schweins R, Cuello GJ, Mondelli C, Galván Josa VM. Water channel structure of alternative perfluorosulfonic acid membranes for fuel cells. J Memb Sci 2021. [DOI: 10.1016/j.memsci.2021.119559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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3
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Kureha T, Hayashi K, Li X, Shibayama M. Mechanical properties of temperature-responsive gels containing ethylene glycol in their side chains. SOFT MATTER 2020; 16:10946-10953. [PMID: 33146225 DOI: 10.1039/d0sm01436b] [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
The mechanical properties of temperature-responsive and biocompatible poly(oligo-ethylene glycol methyl ether methacrylate)-based gels were investigated using dynamic viscoelasticity measurements so as to find applications in tissue and biomedical engineering. The gels were copolymerized using two ethylene glycol methacrylate monomers with diethylene glycol side chains: diethylene glycol methacrylate (MeO2MA), which contains two ethylene oxide units, and oligo-ethylene glycol methyl ether methacrylate (OEGMA) with either four or five ethylene oxide units. The storage (G') and loss (G'') moduli of these gels exhibit unique temperature-responsive behavior and depend on the copolymerization ratio. In MeO2MA-rich gels, phase separation occurred with increasing temperature, resulting in a significant increase in G' and the disappearance of the frequency dependence of G''. Although phase separation of OEGMA-rich gels was also observed with increasing temperature, it resulted in only a slight increase in the storage modulus due to the steric hindrance of the side chain. The mechanical properties of these gels are thus found to be strongly affected by a slight difference in the number of ethylene oxide groups in their side chains.
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Affiliation(s)
- Takuma Kureha
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki 036-8561, Japan.
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5
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Anakhov MV, Gumerov RA, Richtering W, Pich A, Potemkin II. Scavenging One of the Liquids versus Emulsion Stabilization by Microgels in a Mixture of Two Immiscible Liquids. ACS Macro Lett 2020; 9:736-742. [PMID: 35648562 DOI: 10.1021/acsmacrolett.0c00191] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
It is known that microgels can serve as soft, permeable and stimuli-responsive alternative of solid colloidal particles to stabilize oil-water emulsions. The driving force for the adsorption of the microgels on interface of two immiscible liquids is a shielding of unfavorable oil-water contacts by adsorbed subchains, that is, the decrease of the surface tension between the liquids. Such phenomenon usually proceeds if volume fractions of the two liquids are comparable with each other and the microgel concentration is not high enough. The natural question arises: what is going on with the system in the opposite case of strongly asymmetric mixture (one of the liquids (oil) has a very small fraction) or high microgel concentration (the overall volume of the microgels exceeds the volume of the minor oil component)? Here we demonstrate that the microgels uptake the oil whose concentration within the microgels can be orders of magnitude higher than outside, leading to the additional microgel swelling (in comparison with the swelling in water). Thus, the microgels can serve as scavengers and concentrators of liquids dissolved in water. At first glance, this effect seems counterintuitive. However, it has a clear physical reason related to the incompatibility of oil and water. Absorption of the oil by microgels reduces unfavorable oil-water contacts by microgel segments: the microgels have a higher concentration of the segments at the periphery, forming a shell. The microgels with uptaken oil are stable toward aggregation at very small oil concentration in the mixture. However, an increase in the oil concentration can lead to aggregation of the microgels into dimers, trimers, and so on. The increasing concentration of oil mediates the attraction between the microgels: the oil in the aggregates appears to be localized in-between the microgels instead of their interior, which is accompanied by the release of the elastic stress of the microgels. A further increase in the oil concentration results in a growth of the size of the oil droplets between the microgels and the number of the microgels at the droplet's periphery, that is, the emulsion is formed.
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Affiliation(s)
- Mikhail V. Anakhov
- Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991, Russian Federation
| | - Rustam A. Gumerov
- Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991, Russian Federation
- DWI - Leibniz Institute for Interactive Materials e.V., Forckenbeckstraße 50, Aachen 52056, Germany
| | - Walter Richtering
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, Aachen 52056, Germany
| | - Andrij Pich
- DWI - Leibniz Institute for Interactive Materials e.V., Forckenbeckstraße 50, Aachen 52056, Germany
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany
- Aachen Maastricht Institute for Biobased Materials (AMIBM), Maastricht University, Urmonderbaan 22, 6167 RD Geleen, The Netherlands
| | - Igor I. Potemkin
- Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991, Russian Federation
- DWI - Leibniz Institute for Interactive Materials e.V., Forckenbeckstraße 50, Aachen 52056, Germany
- National Research South Ural State University, Chelyabinsk 454080, Russian Federation
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6
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Lopez CG, Scotti A, Brugnoni M, Richtering W. The Swelling of Poly(Isopropylacrylamide) Near the θ Temperature: A Comparison between Linear and Cross‐Linked Chains. MACROMOL CHEM PHYS 2018. [DOI: 10.1002/macp.201800421] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Carlos G. Lopez
- Dr. C. G. Lopez, Dr. A. Scotti, M. Brugnoni, Prof. W. RichteringInstitute of Physical ChemistryRWTH Aachen University Landoltweg 2 52056 Aachen Germany
| | - Andrea Scotti
- Dr. C. G. Lopez, Dr. A. Scotti, M. Brugnoni, Prof. W. RichteringInstitute of Physical ChemistryRWTH Aachen University Landoltweg 2 52056 Aachen Germany
| | - Monia Brugnoni
- Dr. C. G. Lopez, Dr. A. Scotti, M. Brugnoni, Prof. W. RichteringInstitute of Physical ChemistryRWTH Aachen University Landoltweg 2 52056 Aachen Germany
| | - Walter Richtering
- Dr. C. G. Lopez, Dr. A. Scotti, M. Brugnoni, Prof. W. RichteringInstitute of Physical ChemistryRWTH Aachen University Landoltweg 2 52056 Aachen Germany
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Matsui S, Nishizawa Y, Uchihashi T, Suzuki D. Monitoring Thermoresponsive Morphological Changes in Individual Hydrogel Microspheres. ACS OMEGA 2018; 3:10836-10842. [PMID: 31459195 PMCID: PMC6645467 DOI: 10.1021/acsomega.8b01770] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 08/24/2018] [Indexed: 06/10/2023]
Abstract
Real-time morphology/structure changes in individual hydrogel microspheres (microgels) were directly visualized at high spatiotemporal resolution using high-speed atomic force microscopy (HS-AFM) under temperature control ranging from room temperature to ∼40 °C. The recorded HS-AFM movies demonstrate that the size and morphology of thermoresponsive poly(N-isopropyl acrylamide)-based microgels change with increasing temperature at the individual microgel level. Specifically, the height of the microgels gradually decreases and domain structures appeared even below the volume phase transition temperature. Moreover, the domain structure is retained, even after the microgels have fully collapsed. The present study thus demonstrates that temperature-controlled HS-AFM is a useful tool for monitoring stimulus-responsiveness of microgels. In the near future, it should furthermore be possible to extend this temperature-controlled HS-AFM to other stimulus-responsive materials, including autonomously oscillating microgels.
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Affiliation(s)
- Shusuke Matsui
- Graduate
School of Textile Science & Technology and Division of Smart Textile, Institute
for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge
Research, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
| | - Yuichiro Nishizawa
- Graduate
School of Textile Science & Technology and Division of Smart Textile, Institute
for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge
Research, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
| | - Takayuki Uchihashi
- Department
of Physics and Structural Biology Research Center, Graduate School
of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Daisuke Suzuki
- Graduate
School of Textile Science & Technology and Division of Smart Textile, Institute
for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge
Research, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
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Matsui S, Inui K, Kumai Y, Yoshida R, Suzuki D. Autonomously Oscillating Hydrogel Microspheres with High-Frequency Swelling/Deswelling and Dispersing/Flocculating Oscillations. ACS Biomater Sci Eng 2018; 5:5615-5622. [DOI: 10.1021/acsbiomaterials.8b00850] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Shusuke Matsui
- Graduate School of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
| | - Kohei Inui
- Graduate School of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
| | - Yuki Kumai
- Graduate School of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
| | - Ryo Yoshida
- Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku 113-8656, Japan
| | - Daisuke Suzuki
- Graduate School of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
- Division of Smart Textiles, Institute for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
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9
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Mueller E, Alsop RJ, Scotti A, Bleuel M, Rheinstädter MC, Richtering W, Hoare T. Dynamically Cross-Linked Self-Assembled Thermoresponsive Microgels with Homogeneous Internal Structures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:1601-1612. [PMID: 29261314 DOI: 10.1021/acs.langmuir.7b03664] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The internal morphology of temperature-responsive degradable poly(N-isopropylacrylamide) (PNIPAM) microgels formed via an aqueous self-assembly process based on hydrazide and aldehyde-functionalized PNIPAM oligomers is investigated. A combination of surface force measurements, small angle neutron scattering (SANS), and ultrasmall angle neutron scattering (USANS) was used to demonstrate that the self-assembled microgels have a homogeneously cross-linked internal structure. This result is surprising given the sequential addition process used to fabricate the microgels, which was expected to result in a densely cross-linked shell-diffuse core structure. The homogeneous internal structure identified is also significantly different than conventional microgels prepared via precipitation polymerization, which typically exhibit a diffuse shell-dense core structure. The homogeneous structure is hypothesized to result from the dynamic nature of the hydrazone cross-linking chemistry used to couple with the assembly conditions chosen that promote polymer interdiffusion. The lack of an internal cross-linking gradient within these degradable and monodisperse microgels is expected to facilitate more consistent drug release over time, improved optical properties, and other potential application benefits.
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Affiliation(s)
- Eva Mueller
- Department of Chemical Engineering, McMaster University , 1280 Main Street W, Hamilton, Ontario L8S 4L7, Canada
| | - Richard J Alsop
- Department of Physics and Astronomy, McMaster University , 1280 Main Street W, Hamilton, Ontario L8S 4M1, Canada
| | - Andrea Scotti
- Department of Physical Chemistry (IPC), RWTH Aachen , Landoltweg 2, 52074 Aachen, Germany
| | - Markus Bleuel
- Neutron-Condensed Matter Science Group, National Institute of Standards and Technology (NIST) , 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
- Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742-2115, United States
| | - Maikel C Rheinstädter
- Department of Physics and Astronomy, McMaster University , 1280 Main Street W, Hamilton, Ontario L8S 4M1, Canada
| | - Walter Richtering
- Department of Physical Chemistry (IPC), RWTH Aachen , Landoltweg 2, 52074 Aachen, Germany
| | - Todd Hoare
- Department of Chemical Engineering, McMaster University , 1280 Main Street W, Hamilton, Ontario L8S 4L7, Canada
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10
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Kureha T, Suzuki D. Nanocomposite Microgels for the Selective Separation of Halogen Compounds from Aqueous Solution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:837-846. [PMID: 28618227 DOI: 10.1021/acs.langmuir.7b01485] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Nanocomposite microgels that selectively adsorb and release halogen compounds were developed. These nanocomposite microgels consist of poly(2-methoxyethyl acrylate) (pMEA) and a poly(oligo ethylene glycol methacrylate) hydrogel matrix. Therefore, the methoxy groups of the former are crucial for the halogen bonding, while the presence of the latter adds colloidal stability and allows controlled uptake/release of the halogen compounds. Such nanocomposite microgels may not only be used as dispersed carriers, but also in films and columnar formations. Thus, these unprecedented polymer/polymer nanocomposite microgels resolve a variety of problems associated with, e.g., the removal of halogen compounds from wastewater, or with the delivery of halogen-containing drugs.
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Affiliation(s)
- Takuma Kureha
- Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida, Ueda 386-8567, Japan
| | - Daisuke Suzuki
- Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida, Ueda 386-8567, Japan
- Division of Smart Textiles, Institute for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University , 3-15-1 Tokida, Ueda 386-8567, Japan
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11
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Naseem K, Hussain Farooqi Z, Zia Ur Rehman M, Atiq Ur Rehman M, Ghufran M. Microgels as efficient adsorbents for the removal of pollutants from aqueous medium. REV CHEM ENG 2018. [DOI: 10.1515/revce-2017-0042] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Abstract
Due to their responsive behavior, high stability, and reusability, microgels have gained importance as adsorbents for the removal of aqueous pollutants such as heavy metals, nitroarenes, organic matter, and toxic dyes. However, there are few challenges that need to be addressed to make microgels as potential adsorbents for the removal of aqueous pollutants. This review article encircles the recent developments in the field of microgel usage as adsorbents for the extraction of aqueous pollutants. Many factors that influence the adsorption of pollutants such as pH, temperature of the medium, agitation time, pollutant concentration, microgel dose, and feed contents of microgels have been discussed in detail. Different adsorption isotherms as well as the kinetic and thermodynamic aspects of the adsorption process have also been enlightened to interpret the insight of the adsorption process. Microgel recovery from the reaction mixture as well as reusability is discussed from the financial point of view. The biodegradability of microgels induced due to the incorporation of specific biomacromolecules is also discussed.
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Affiliation(s)
- Khalida Naseem
- Institute of Chemistry , University of the Punjab, New Campus , Lahore 54590 , Pakistan
- Department of Chemistry , Kinnaird College for Women , Lahore 54000 , Pakistan
| | | | - Muhammad Zia Ur Rehman
- Department of Chemical Engineering , University of Engineering and Technology , Lahore 54890 , Pakistan
| | | | - Maida Ghufran
- Department of Chemistry , Kinnaird College for Women , Lahore 54000 , Pakistan
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12
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Hernandez-Martínez A, Lujan-Montelongo J, Silva-Cuevas C, Mota-Morales JD, Cortez-Valadez M, Ruíz-Baltazar ÁDJ, Cruz M, Herrera-Ordonez J. Swelling and methylene blue adsorption of poly(N,N-dimethylacrylamide-co-2-hydroxyethyl methacrylate) hydrogel. REACT FUNCT POLYM 2018. [DOI: 10.1016/j.reactfunctpolym.2017.11.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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13
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Kureha T, Nishizawa Y, Suzuki D. Controlled Separation and Release of Organoiodine Compounds Using Poly(2-methoxyethyl acrylate)-Analogue Microspheres. ACS OMEGA 2017; 2:7686-7694. [PMID: 31457326 PMCID: PMC6645105 DOI: 10.1021/acsomega.7b01556] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Accepted: 10/30/2017] [Indexed: 05/16/2023]
Abstract
A selective adsorption/desorption of organoiodine compounds was achieved on poly(2-methoxyethyl acrylate)-analogue microspheres, wherein the side chains in the polymers act as halogen-bonding sites. These results demonstrate that the halogen-bonding sites in the side chains exhibit adequate specific affinity for organoiodine compounds. In addition, the water-swollen pMEA-analogue microspheres (microgels) showed a thermoresponsive swelling/deswelling behavior that permitted a controlled release of the organoiodine compounds upon changing the temperature. Thus, it seems plausible that a variety of problems associated with, e.g., the recovery of rare iodine-containing compounds, such as the marine-derived iodine compounds, the delivery of iodine-containing drugs, or the removal of halogen compounds from wastewater, could be resolved by polymer microspheres that exhibit controlled halogen bonding.
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Affiliation(s)
- Takuma Kureha
- Graduate
School of Textile Science & Technology and Division of Smart Textiles, Institute
for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge
Research, Shinshu University, 3-15-1 Tokida, Ueda 386-8567, Japan
| | - Yuichiro Nishizawa
- Graduate
School of Textile Science & Technology and Division of Smart Textiles, Institute
for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge
Research, Shinshu University, 3-15-1 Tokida, Ueda 386-8567, Japan
| | - Daisuke Suzuki
- Graduate
School of Textile Science & Technology and Division of Smart Textiles, Institute
for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge
Research, Shinshu University, 3-15-1 Tokida, Ueda 386-8567, Japan
- E-mail:
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14
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Lopez CG, Richtering W. Does Flory-Rehner theory quantitatively describe the swelling of thermoresponsive microgels? SOFT MATTER 2017; 13:8271-8280. [PMID: 29071323 DOI: 10.1039/c7sm01274h] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The swelling of thermoresponsive microgels is widely modelled through Flory-Rehner theory, which combines Flory-Huggins solution thermodynamics with the affine network model of elasticity. While it has been shown that FR theory closely follows experimental results for a range of systems, the large number of free parameters required to fit size vs. temperature data make a proper evaluation of the theory difficult. In order to test the applicability of FR theory to microgel particles, we analyse viscosity and light scattering data for PNIPAM microgels as a function of temperature, cross-linking degree (f) and molar mass. In the collapsed state, the polymer volume fraction is estimated to be ϕC ≃ 0.44, independent of cross linking degree and molar mass. Fixing ϕC, f and the θ temperature to independent estimates, the FR model appears to describe microgel swelling well, particularly for high cross-linking densities. Estimates for the various fit parameters differ from earlier reports by an order of magnitude. A comparison of the χ parameter obtained from FR theory with values for the linear polymer reveals that the agreement between experiment and theory is somewhat fortuitous. Although the FR model can accurately describe experimental data, the accuracy of the obtained fit parameters is significantly poorer.
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Affiliation(s)
- Carlos G Lopez
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52056 Aachen, Germany.
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15
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Kureha T, Aoki D, Hiroshige S, Iijima K, Aoki D, Takata T, Suzuki D. Decoupled Thermo- and pH-Responsive Hydrogel Microspheres Cross-Linked by Rotaxane Networks. Angew Chem Int Ed Engl 2017; 56:15393-15396. [DOI: 10.1002/anie.201709633] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Indexed: 12/28/2022]
Affiliation(s)
- Takuma Kureha
- Graduate School of Textile Science & Technology; Shinshu University; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
| | - Daichi Aoki
- Graduate School of Textile Science & Technology; Shinshu University; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
| | - Seina Hiroshige
- Graduate School of Textile Science & Technology; Shinshu University; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
| | - Keisuke Iijima
- Department of Chemical Science and Engineering; Tokyo Institute of Technology, and JST-CREST; 2-12-1 O-okayama Meguro Tokyo 152-8552 Japan
| | - Daisuke Aoki
- Department of Chemical Science and Engineering; Tokyo Institute of Technology, and JST-CREST; 2-12-1 O-okayama Meguro Tokyo 152-8552 Japan
| | - Toshikazu Takata
- Department of Chemical Science and Engineering; Tokyo Institute of Technology, and JST-CREST; 2-12-1 O-okayama Meguro Tokyo 152-8552 Japan
| | - Daisuke Suzuki
- Graduate School of Textile Science & Technology; Shinshu University; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
- Division of Smart Textiles; Institute for Fiber Engineering; Interdisciplinary Cluster for Cutting Edge Research; Shinshu University, and JST-CREST; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
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16
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Kureha T, Aoki D, Hiroshige S, Iijima K, Aoki D, Takata T, Suzuki D. Decoupled Thermo- and pH-Responsive Hydrogel Microspheres Cross-Linked by Rotaxane Networks. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201709633] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Takuma Kureha
- Graduate School of Textile Science & Technology; Shinshu University; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
| | - Daichi Aoki
- Graduate School of Textile Science & Technology; Shinshu University; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
| | - Seina Hiroshige
- Graduate School of Textile Science & Technology; Shinshu University; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
| | - Keisuke Iijima
- Department of Chemical Science and Engineering; Tokyo Institute of Technology, and JST-CREST; 2-12-1 O-okayama Meguro Tokyo 152-8552 Japan
| | - Daisuke Aoki
- Department of Chemical Science and Engineering; Tokyo Institute of Technology, and JST-CREST; 2-12-1 O-okayama Meguro Tokyo 152-8552 Japan
| | - Toshikazu Takata
- Department of Chemical Science and Engineering; Tokyo Institute of Technology, and JST-CREST; 2-12-1 O-okayama Meguro Tokyo 152-8552 Japan
| | - Daisuke Suzuki
- Graduate School of Textile Science & Technology; Shinshu University; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
- Division of Smart Textiles; Institute for Fiber Engineering; Interdisciplinary Cluster for Cutting Edge Research; Shinshu University, and JST-CREST; 3-15-1 Tokida Ueda Nagano 386-8567 Japan
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17
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Suzuki D, Horigome K, Kureha T, Matsui S, Watanabe T. Polymeric hydrogel microspheres: design, synthesis, characterization, assembly and applications. Polym J 2017. [DOI: 10.1038/pj.2017.39] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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18
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Water-immiscible bioinert coatings and film formation from aqueous dispersions of poly(2-methoxyethyl acrylate) microspheres. Colloids Surf B Biointerfaces 2017; 155:166-172. [DOI: 10.1016/j.colsurfb.2017.04.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/31/2017] [Accepted: 04/01/2017] [Indexed: 11/22/2022]
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19
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Tang S, Bhandari R, Delaney SP, Munson EJ, Dziubla TD, Hilt JZ. Synthesis and characterization of thermally responsive N-isopropylacrylamide hydrogels copolymerized with novel hydrophobic polyphenolic crosslinkers. MATERIALS TODAY. COMMUNICATIONS 2017; 10:46-53. [PMID: 28989952 PMCID: PMC5628756 DOI: 10.1016/j.mtcomm.2016.12.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Two series of thermosensitive hydrogels were synthesized by copolymerizing N-isopropylacrylamide (NIPAAm) with various contents of novel hydrophobic crosslinkers, curcumin multiacrylate (CMA) and quercetin multiacrylate (QMA). The compositions of the resulting hydrogels were characterized using solid state-NMR (ss-NMR), and the temperature dependent swelling behavior and lower critical solution temperature (LCST) were characterized using swelling studies and differential scanning calorimetry (DSC). Increasing the crosslinker content resulted in a significant decrease in the LCST and swelling ratio of hydrogels, which could be attributed to the increased hydrophobicity introduced by CMA or QMA. All of the hydrogels demonstrated temperature responsive swelling with the extent of swelling decreasing with increasing crosslinker content. The lower crosslinker content gels displayed sharper phase transitions, while the high crosslinker content gels had broader phase transitions.
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Affiliation(s)
- Shuo Tang
- Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Rohit Bhandari
- Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Sean P Delaney
- Department of Pharmaceutical Sciences, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Eric J Munson
- Department of Pharmaceutical Sciences, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Thomas D Dziubla
- Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506, USA
| | - J Zach Hilt
- Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506, USA
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20
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Kureha T, Shibamoto T, Matsui S, Sato T, Suzuki D. Investigation of Changes in the Microscopic Structure of Anionic Poly(N-isopropylacrylamide-co-Acrylic acid) Microgels in the Presence of Cationic Organic Dyes toward Precisely Controlled Uptake/Release of Low-Molecular-Weight Chemical Compound. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:4575-85. [PMID: 27101468 DOI: 10.1021/acs.langmuir.6b00760] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Changes in a microscopic structure of an anionic poly(N-isopropylacrylamide-co-acrylic acid) microgel were investigated using small- and wide-angle X-ray scattering (SWAXS). The scattering profiles of the microgels were analyzed in a wide scattering vector (q) range of 0.07 ≤ q/nm(-1) ≤ 20. In particular, the microscopic structure of the microgel in the presence of a cationic dye rhodamine 6G (R6G) was characterized in terms of its correlation length (ξ), which represents the length scale of the spatial correlation of the network density fluctuations, and characteristic distance (d*), which originated from the local packing of isopropyl groups of two neighboring chains. In the presence of cationic R6G, ξ exhibited a divergent-like behavior, which was not seen in the absence of R6G, and d* was decreased with decreasing the volume of the microgel upon increasing temperature. At the same time, the amount of R6G adsorbed per unit mass of the microgel increased upon heating. These results suggested that a coil-to-globule transition of the poly(N-isopropylacrylamide) chains in the present anionic microgel occurred because of efficiently screened, thus, short ranged electrostatic repulsion between the charged groups, and hydrophobic interaction between the isopropyl groups in the presence of cationic R6G. The combination of hydrophobic and electrostatic interaction between the cationic dye and the microgel affected the separation and volume transition behavior of the microgel.
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Affiliation(s)
- Takuma Kureha
- Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan
| | - Takahisa Shibamoto
- Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan
| | - Shusuke Matsui
- Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan
| | - Takaaki Sato
- Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan
| | - Daisuke Suzuki
- Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan
- Division of Smart Textiles, Institute for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University , 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
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21
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Virtanen OLJ, Mourran A, Pinard PT, Richtering W. Persulfate initiated ultra-low cross-linked poly(N-isopropylacrylamide) microgels possess an unusual inverted cross-linking structure. SOFT MATTER 2016; 12:3919-28. [PMID: 27033731 DOI: 10.1039/c6sm00140h] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Cross-linking density and distribution are decisive for the mechanical and other properties of stimuli-sensitive poly(N-isopropylacrylamide) microgels. Here we investigate the structure of ultra-low cross-linked microgels by static light scattering and scanning force microscopy, and show that they have an inverted cross-linking structure with respect to conventional microgels, contrary to what has been assumed previously. The conventional microgels have the largest polymer volume fraction in the core from where the particle density decays radially outwards, whereas ultra-low cross-linked particles have the highest polymer volume fraction close to the surface. On a solid substrate these particles form buckled shapes at high surface coverage, as shown by scanning force micrographs. The special structure of ultra-low cross-linked microgels is attributed to cross-linking of the particle surface, which is exposed to hydrogen abstraction by radicals generated from persulfate initiators during and after polymerization. The particle core, which is less accessible to the diffusion of radicals, has consequently a lower polymer volume fraction in the swollen state. By systematic variation of the cross-linker concentration it is shown that the cross-linking contribution from peroxide under typical synthesis conditions is weaker than that from the use of 1 mol% N,N'-methylenebisacrylamide. Soft deformable hydrogel particles are of interest because they emulate biological tissues, and understanding the underlying synthesis principle enables tailoring the microgel structure for biomimetic applications. Deformability of microgels is usually controlled by the amount of added cross-linker; here we however highlight an alternative approach through structural softness.
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Affiliation(s)
- O L J Virtanen
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52064 Aachen, Germany.
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22
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Picco AS, Yameen B, Knoll W, Ceolín MR, Azzaroni O. Temperature-driven self-assembly of self-limiting uniform supraparticles from non-uniform unimolecular micelles. J Colloid Interface Sci 2016; 471:71-75. [PMID: 26990953 DOI: 10.1016/j.jcis.2016.03.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 03/03/2016] [Accepted: 03/03/2016] [Indexed: 01/31/2023]
Abstract
In this work, the self-assembly of non-uniform unimolecular micelles constituted of a hyperbranched polyester core decorated with a corona of thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) chains has been studied. As revealed by dynamic light scattering (DLS), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS), these unimicelles form uniform supraparticles through a thermally-induced self-limited process, as well as exhibit molecular features commonly observed in PNIPAm-based gels. We believe that these results provide new insights into the application of stimuli-responsive polymeric materials as versatile building blocks to build up soft supraparticles displaying well-defined dimensional characteristics.
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Affiliation(s)
- Agustín S Picco
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata (UNLP), CONICET, CC. 16 Suc. 4, 1900 La Plata, Argentina
| | - Basit Yameen
- Laboratory of Nanomedicine and Biomaterials, Harvard Medical School, Boston, MA 02115, USA; Department of Chemistry, SBA School of Science and Engineering, LUMS, Lahore 54792, Pakistan
| | - Wolfgang Knoll
- Austrian Institute of Technology (AIT), Donau-City-Strasse 1, 1220 Vienna, Austria
| | - Marcelo R Ceolín
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata (UNLP), CONICET, CC. 16 Suc. 4, 1900 La Plata, Argentina.
| | - Omar Azzaroni
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata (UNLP), CONICET, CC. 16 Suc. 4, 1900 La Plata, Argentina.
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23
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Kobayashi C, Watanabe T, Murata K, Kureha T, Suzuki D. Localization of Polystyrene Particles on the Surface of Poly(N-isopropylacrylamide-co-methacrylic acid) Microgels Prepared by Seeded Emulsion Polymerization of Styrene. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:1429-1439. [PMID: 26794923 DOI: 10.1021/acs.langmuir.5b03698] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Composite microgels with polystyrene nanoparticles were synthesized by seeded emulsion polymerization of styrene in the presence of pH- and temperature-responsive poly(N-isopropylacrylamide-co-methacrylic acid) microgels as seeds. In particular, the core microgels maintained their swelled state as the pH was increased to 10 during seeded emulsion polymerization conducted at an elevated temperature. Furthermore, we tuned the swelling degree of the core microgels at pH 10 by changing the amount of methacrylic acid incorporated during the synthesis of the core microgels. Unlike deswollen microgels, during the seeded emulsion polymerization, the swollen microgels were covered with a monolayer of non-close-packed polystyrene particles on their surface, as confirmed by electron microscopy. A possible mechanism for the seeded emulsion polymerization of styrene in the presence of swollen microgels under alkaline conditions is proposed.
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Affiliation(s)
| | | | - Kazuyoshi Murata
- National Institute for Physiological Sciences , 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
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24
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Jiang Y, Tan P, Cheng L, Shan SF, Liu XQ, Sun LB. Selective adsorption and efficient regeneration via smart adsorbents possessing thermo-controlled molecular switches. Phys Chem Chem Phys 2016; 18:9883-7. [DOI: 10.1039/c6cp00351f] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new generation of adsorbents possessing thermo-controlled molecular switches was fabricated and consequently realized selective adsorption and efficient desorption simultaneously.
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Affiliation(s)
- Yao Jiang
- State Key Laboratory of Materials-Oriented Chemical Engineering
- College of Chemistry and Chemical Engineering
- Nanjing Tech University
- Nanjing 210009
- China
| | - Peng Tan
- State Key Laboratory of Materials-Oriented Chemical Engineering
- College of Chemistry and Chemical Engineering
- Nanjing Tech University
- Nanjing 210009
- China
| | - Lei Cheng
- State Key Laboratory of Materials-Oriented Chemical Engineering
- College of Chemistry and Chemical Engineering
- Nanjing Tech University
- Nanjing 210009
- China
| | - Shu-Feng Shan
- State Key Laboratory of Materials-Oriented Chemical Engineering
- College of Chemistry and Chemical Engineering
- Nanjing Tech University
- Nanjing 210009
- China
| | - Xiao-Qin Liu
- State Key Laboratory of Materials-Oriented Chemical Engineering
- College of Chemistry and Chemical Engineering
- Nanjing Tech University
- Nanjing 210009
- China
| | - Lin-Bing Sun
- State Key Laboratory of Materials-Oriented Chemical Engineering
- College of Chemistry and Chemical Engineering
- Nanjing Tech University
- Nanjing 210009
- China
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25
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Geisel K, Rudov AA, Potemkin II, Richtering W. Hollow and Core-Shell Microgels at Oil-Water Interfaces: Spreading of Soft Particles Reduces the Compressibility of the Monolayer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:13145-54. [PMID: 26575794 DOI: 10.1021/acs.langmuir.5b03530] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We investigate the influence of a solid core and of the cross-link density on the compression of microgel particles at oil-water interfaces by means of compression isotherms and computer simulations. We investigate particles with different morphology, namely core-shell particles containing a solid silica core surrounded by a cross-linked polymer shell of poly(N-isopropylacrylamide), and the corresponding hollow microgels where the core was dissolved. The polymer shell contains different amounts of cross-linker. The compression isotherms show that the removal of the core leads to an increase of the surface pressure at low compression, and the same effect can be observed when the polymer cross-link density is decreased. Low cross-link density and a missing core thus facilitate spreading of the polymer chains at the interface and, at high compression, hinder the transition to close hexagonal packing. Furthermore, the compression modulus only depends on the cross-link density at low compression, and no difference can be observed between the core-shell particles and the corresponding hollow microgels. It is especially remarkable that a low cross-link density leads to a high compression modulus at low compression, while this behavior is reversed at high compression. Thus, the core does not influence the particle behavior until the polymer shell is highly compressed and the core is directly exposed to the pressure. This is related to an enhanced spreading of polymer chains at the interface and thus high adsorption energy. These conclusions are fully supported by computer simulations which show that the cross-link density of the polymer shell defines the degree of deformation at the interface. Additionally, the core restricts the spreading of polymer chains at the interface. These results illustrate the special behavior of soft microgels at liquid interfaces.
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Affiliation(s)
- Karen Geisel
- Institute of Physical Chemistry, RWTH Aachen University , Aachen, Germany
| | - Andrey A Rudov
- Physics Department, Lomonosov Moscow State University , Moscow 119991, Russian Federation
- DWI-Leibniz Institute for Interactive Materials e.V., Aachen, Germany
| | - Igor I Potemkin
- Physics Department, Lomonosov Moscow State University , Moscow 119991, Russian Federation
- DWI-Leibniz Institute for Interactive Materials e.V., Aachen, Germany
| | - Walter Richtering
- Institute of Physical Chemistry, RWTH Aachen University , Aachen, Germany
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26
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Matsui S, Kureha T, Nagase Y, Okeyoshi K, Yoshida R, Sato T, Suzuki D. Small-Angle X-ray Scattering Study on Internal Microscopic Structures of Poly(N-isopropylacrylamide-co-tris(2,2'-bipyridyl))ruthenium(II) Complex Microgels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:7228-7237. [PMID: 26065589 DOI: 10.1021/acs.langmuir.5b01164] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Internal microscopic structures of poly(N-isopropylacrylamide-co-tris(2,2'-bipyridyl))ruthenium(II) complex microgels were investigated using small-angle X-ray scattering (SAXS) in the extended q-range of 0.07 ≤ q/nm(-1) ≤ 20. The microgels were prepared by aqueous free-radical precipitation polymerization, resulting in formation of monodispersed, submicrometer-sized microgels, which was confirmed by transmission electron microscopy and dynamic light scattering. To reveal the changes in the microscopic structures of the microgels during swelling/deswelling or dispersing/flocculating oscillation, the redox state of Ru(bpy)3 complexes was fixed in the microgels using Ce(IV) or Ce(III) ions under high ionic strength (1.5 M) during the SAXS measurements. The scattering intensity of the microgels manifested five different structural features. In particular, the correlation length (ξ), which was obtained from the fitting analysis using the Ornstein-Zernike equation, of the microgels both in the reduced and oxidized Ru(bpy)3 states exhibited divergent-like behavior. In addition, a low-q peak centered at q ≈ 5 nm(-1) did not appear clearly in both the reduced [Ru(bpy)3](2+) and oxidized [Ru(bpy)3](3+) states, indicating that the formation of a polymer-rich domain was suppressed; thus, Ru(bpy)3 complexes can be active even though the microgels are deswollen or flocculated during the oscillation reaction.
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Affiliation(s)
| | | | | | - Kosuke Okeyoshi
- §School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi 923-1292, Japan
| | - Ryo Yoshida
- ∥Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku 113-8656, Japan
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27
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Habicht A, Schmolke W, Goerigk G, Lange F, Saalwächter K, Ballauff M, Seiffert S. Critical fluctuations and static inhomogeneities in polymer gel volume phase transitions. ACTA ACUST UNITED AC 2015. [DOI: 10.1002/polb.23743] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Axel Habicht
- Helmholtz-Zentrum Berlin; Soft Matter and Functional Materials; Hahn-Meitner-Platz 1 D-14109 Berlin Germany
- Freie Universität Berlin, Institute of Chemistry and Biochemistry; Takustr. 3 D-14195 Berlin Germany
| | - Willi Schmolke
- Helmholtz-Zentrum Berlin; Soft Matter and Functional Materials; Hahn-Meitner-Platz 1 D-14109 Berlin Germany
- Freie Universität Berlin, Institute of Chemistry and Biochemistry; Takustr. 3 D-14195 Berlin Germany
| | - Günter Goerigk
- Helmholtz-Zentrum Berlin; Soft Matter and Functional Materials; Hahn-Meitner-Platz 1 D-14109 Berlin Germany
- Humboldt-Universität zu Berlin; Department of Physics; Newtonstr. 15 D-12489 Berlin Germany
| | - Frank Lange
- Martin-Luther-Universität Halle-Wittenberg, Institute of Physics-NMR; Betty-Heimann-Str. 7 D-06120 Halle/Saale Germany
| | - Kay Saalwächter
- Martin-Luther-Universität Halle-Wittenberg, Institute of Physics-NMR; Betty-Heimann-Str. 7 D-06120 Halle/Saale Germany
| | - Matthias Ballauff
- Helmholtz-Zentrum Berlin; Soft Matter and Functional Materials; Hahn-Meitner-Platz 1 D-14109 Berlin Germany
- Humboldt-Universität zu Berlin; Department of Physics; Newtonstr. 15 D-12489 Berlin Germany
| | - Sebastian Seiffert
- Helmholtz-Zentrum Berlin; Soft Matter and Functional Materials; Hahn-Meitner-Platz 1 D-14109 Berlin Germany
- Freie Universität Berlin, Institute of Chemistry and Biochemistry; Takustr. 3 D-14195 Berlin Germany
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