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Frenzel L, Dartsch M, Balaguer GM, Westermeier F, Grübel G, Lehmkühler F. Glass-liquid and glass-gel transitions of soft-shell particles. Phys Rev E 2021; 104:L012602. [PMID: 34412357 DOI: 10.1103/physreve.104.l012602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 06/23/2021] [Indexed: 12/12/2022]
Abstract
We study the structure and dynamics of colloidal particles with a spherical hard core and a thermo-responsive soft shell over the whole phase diagram by means of small-angle x-ray scattering and x-ray photon correlation spectroscopy. By changing the effective volume fraction by temperature and particle concentration, liquid, repulsive glass. and attractive gel phases are observed. The dynamics slow down with increasing volume fraction in the liquid phase and reflect a Vogel-Fulcher-Tamann behavior known for fragile glass formers. We find a liquid-glass transition above 50 vol.% that is independent of the particles' concentration and temperature. In an overpacked state at effective volume fractions above 1, the dispersion does not show a liquid phase but undergoes a gel-glass transition at an effective volume fraction of 34 vol.%. At the same concentration, extrema of subdiffusive dynamics are found in the liquid phase at lower weight fractions. We interpret this as dynamic precursors of the glass-gel transition.
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Affiliation(s)
- Lara Frenzel
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany.,The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Michael Dartsch
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany.,The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| | | | - Fabian Westermeier
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Gerhard Grübel
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany.,The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Felix Lehmkühler
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany.,The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
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2
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Chaudhary G, Ghosh A, Kang JG, Braun PV, Ewoldt RH, Schweizer KS. Linear and nonlinear viscoelasticity of concentrated thermoresponsive microgel suspensions. J Colloid Interface Sci 2021; 601:886-898. [PMID: 34186277 DOI: 10.1016/j.jcis.2021.05.111] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 04/26/2021] [Accepted: 05/19/2021] [Indexed: 11/25/2022]
Abstract
We present an integrated experimental and theoretical study of the dynamics and rheology of self-crosslinked, slightly charged, temperature responsive soft poly(N-isopropylacrylamide) (pNIPAM) microgels over a wide range of concentration and temperature spanning the sharp change in particle size and intermolecular interactions across the lower critical solution temperature (LCST). Dramatic, non-monotonic changes in viscoelasticity are observed as a function of temperature, with distinct concentration dependence in the dense fluid, glassy, and soft-jammed regimes. Motivated by our experimental observations, we formulate a minimalistic model for the size dependence of a single microgel particle and the change of the interparticle interaction from purely repulsive to attractive upon heating. Using microscopic equilibrium and time-dependent statistical mechanical theories, theoretical predictions are quantitatively compared with experimental measurements of the shear modulus. Good agreement is found for the nonmonotonic temperature behavior that originates as a consequence of the competition between reduced microgel packing fraction and increasing interparticle attractions. Testable predictions are made for nonlinear rheological properties such as the yield stress and strain. To our knowledge, this is the first attempt to quantitatively understand in a unified manner the viscoelasticity of dense, temperature-responsive microgel suspensions spanning a wide range of temperatures and concentrations.
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Affiliation(s)
- Gaurav Chaudhary
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Ashesh Ghosh
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Jin Gu Kang
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Paul V Braun
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Randy H Ewoldt
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | - Kenneth S Schweizer
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Chemical & Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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3
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Nigro V, Angelini R, Bertoldo M, Buratti E, Franco S, Ruzicka B. Chemical-Physical Behaviour of Microgels Made of Interpenetrating Polymer Networks of PNIPAM and Poly(acrylic Acid). Polymers (Basel) 2021; 13:polym13091353. [PMID: 33919087 PMCID: PMC8122350 DOI: 10.3390/polym13091353] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 04/01/2021] [Accepted: 04/13/2021] [Indexed: 01/06/2023] Open
Abstract
Microgels composed of stimuli responsive polymers have attracted worthwhile interest as model colloids for theorethical and experimental studies and for nanotechnological applications. A deep knowledge of their behaviour is fundamental for the design of new materials. Here we report the current understanding of a dual responsive microgel composed of poly(N-isopropylacrylamide) (PNIPAM), a temperature sensitive polymer, and poly(acrylic acid) (PAAc), a pH sensitive polymer, at different temperatures, PAAc contents, concentrations, solvents and pH. The combination of multiple techniques as Dynamic Light Scattering (DLS), Raman spectroscopy, Small Angle Neutron Scattering (SANS), rheology and electrophoretic measurements allow to investigate the hydrodynamic radius behaviour across the typical Volume Phase Transition (VPT), the involved molecular mechanism and the internal particle structure together with the viscoelastic properties and the role of ionic charge in the aggregation phenomena.
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Affiliation(s)
- Valentina Nigro
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), Sede Sapienza, 00185 Roma, Italy; (V.N.); (E.B.)
| | - Roberta Angelini
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), Sede Sapienza, 00185 Roma, Italy; (V.N.); (E.B.)
- Dipartimento di Fisica, Sapienza Università, 00185 Rome, Italy
- Correspondence: (R.A.); (B.R.)
| | - Monica Bertoldo
- Dipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, Università degli Studi di Ferrara, 45121 Ferrara, Italy;
| | - Elena Buratti
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), Sede Sapienza, 00185 Roma, Italy; (V.N.); (E.B.)
| | - Silvia Franco
- Dipartimento di Scienze di Base e Applicate per l’Ingegneria (SBAI), Sapienza Università, 00185 Rome, Italy;
| | - Barbara Ruzicka
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), Sede Sapienza, 00185 Roma, Italy; (V.N.); (E.B.)
- Dipartimento di Fisica, Sapienza Università, 00185 Rome, Italy
- Correspondence: (R.A.); (B.R.)
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4
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Frenzel L, Lokteva I, Koof M, Narayanan S, Grübel G, Lehmkühler F. Influence of TMAO as co-solvent on the gelation of silica-PNIPAm core-shell nanogels at intermediate volume fractions. Chemphyschem 2020; 21:1318-1325. [PMID: 32250508 PMCID: PMC7318175 DOI: 10.1002/cphc.202000114] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 03/20/2020] [Indexed: 12/29/2022]
Abstract
We study the structure and dynamics of poly(N-isopropylacrylamide) (PNIPAm) core-shell nanogels dispersed in aqueous trimethylamine N-oxide (TMAO) solutions by means of small-angle X-ray scattering and X-ray photon correlation spectroscopy (XPCS). Upon increasing the temperature above the lower critical solution temperature of PNIPAm at 33 °C, a colloidal gel is formed as identified by an increase of I(q) at small q as well as a slowing down of sample dynamics by various orders of magnitude. With increasing TMAO concentration the gelation transition shifts linearly to lower temperatures. Above a TMAO concentration of approximately 0.40 mol/L corresponding to a 1 : 1 ratio of TMAO and NIPAm groups, collapsed PNIPAm states are found for all temperatures without any gelation transition. This suggests that reduction of PNIPAm-water hydrogen bonds due to the presence of TMAO results in a stabilisation of the collapsed PNIPAm state and suppresses gelation of the nanogel.
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Affiliation(s)
- Lara Frenzel
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
- The Hamburg Centre for Ultrafast ImagingLuruper Chaussee 14922761HamburgGermany
| | - Irina Lokteva
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
- The Hamburg Centre for Ultrafast ImagingLuruper Chaussee 14922761HamburgGermany
| | - Michael Koof
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
- The Hamburg Centre for Ultrafast ImagingLuruper Chaussee 14922761HamburgGermany
| | - Suresh Narayanan
- Advanced Photon SourceArgonne National LaboratoryArgonneIllinois60439United States
| | - Gerhard Grübel
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
- The Hamburg Centre for Ultrafast ImagingLuruper Chaussee 14922761HamburgGermany
| | - Felix Lehmkühler
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
- The Hamburg Centre for Ultrafast ImagingLuruper Chaussee 14922761HamburgGermany
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5
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Colloidal Probes of PNIPAM-Grafted SiO 2 in Studying the Microrheology of Thermally Sensitive Microgel Suspensions. ADVANCES IN POLYMER TECHNOLOGY 2020. [DOI: 10.1155/2020/3971953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The complex rheology and the phase behavior of thermally sensitive poly(N-isopropylacrylamide) (PNIPAM) microgels have been investigated in both the swollen and collapsed states by using microrheology. To avoid the interactions between the tracer probes and the PNIPAM microgels, such as the adsorption or the depletion effect, the probes of silica (SiO2) particles have been grafted with PNIPAM chains (SiO2-PNIPAM) and characterized with Fourier transform infrared spectroscopy (FTIR). The successful preparation of SiO2-PNIPAM has also been proved by the investigation of the particle size and morphology with dynamic light scattering (DLS) and transmission electron microscope (TEM) below and beyond the phase transition temperature of PNIPAM. The microrheology of the PNIPAM microgel suspension has been investigated by using the prepared SiO2-PNIPAM particles as microrheological probes, and the results show that the diffusive coefficient of the probes in the swollen state is one-fifth of that in the collapsed state, and the viscosity of the PNIPAM microgel suspension in the swollen state is four times higher than that in the collapsed state, indicating SiO2-PNIPAM is a good probe in the microrheological study of PNIPAM microgel suspensions.
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6
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Town A, Niezabitowska E, Kavanagh J, Barrow M, Kearns VR, García-Tuñón E, McDonald TO. Understanding the Phase and Morphological Behavior of Dispersions of Synergistic Dual-Stimuli-Responsive Poly( N-isopropylacrylamide) Nanogels. J Phys Chem B 2019; 123:6303-6313. [PMID: 31251624 PMCID: PMC7007235 DOI: 10.1021/acs.jpcb.9b04051] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 06/21/2019] [Indexed: 12/14/2022]
Abstract
This work represents a detailed investigation into the phase and morphological behavior of synergistic dual-stimuli-responsive poly(N-isopropylacrylamide) nanogels, a material that is of considerable interest as a matrix for in situ forming implants. Nanogels were synthesized with four different diameters (65, 160, 310, and 450 nm) as monodispersed particles. These different samples were then prepared and characterized as both dilute (0.1 wt %) and concentrated dispersions (2-22 wt %). In the dilute form, all of the nanogels had the same response to the triggers of the physiological temperature and ionic strength. In water, the nanogels would deswell when heated above 32 °C, while they would aggregate if heated above this temperature at the physiological ionic strength. In the concentrated form, the nanogels exhibited a wide range of morphological changes, with liquid, swollen gel, shrunken gel, and aggregate structures all possible. The occurrence of these structures was dependent on many factors such as the temperature, ionic strength of the solvent, size and ζ-potential of the nanogel, and dispersion concentration. We explored these factors in detail with techniques such as visual studies, rheology, effective volume fraction, and shape factor measurement. The different-sized nanogels displayed differing phase and morphological behavior, but generally higher concentrations of the nanogels (>7 wt %) yielded gels in water with the transitions depending on the temperature. The smallest nanogel (65 nm diameter) exhibited the most unique behavior; it did not form a swollen gel at any concentration tested. Shape factor measurement for the nanogel samples showed that two of the larger three samples (160 and 310 nm) had core-shell structures with denser core cross-linking, while the smallest nanogel sample displayed a homogeneous cross-linked structure. We hypothesize that the smallest nanogels are able to undergo more extensive interpenetration compared to the larger nanogels, which meant that the smallest nanogel was not able to form a swollen gel. In the presence of salt at 12 wt %, all of the nanogels formed aggregates when heated above 35 °C due to the screening of the electrostatic stabilization by the salt. This work revealed unique behavior of the smallest nanogel with a homogeneous cross-linked structure; its phase and morphological behavior were unlike a particle dispersion, rather these were more similar to those of a branched polymer solution. In total, these findings can be used to provide information about the design of poly(N-isopropylacrylamide) nanogel dispersions for different applications where highly specific spatiotemporal control of morphology is required, for example, in the formation of in situ forming implants or for pore blocking behavior.
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Affiliation(s)
- Adam Town
- Department
of Chemistry & Materials Innovation Factory and School of Engineering
& Materials Innovation Factory, University
of Liverpool, Oxford Street, Liverpool L69 7ZD, U.K.
| | - Edyta Niezabitowska
- Department
of Chemistry & Materials Innovation Factory and School of Engineering
& Materials Innovation Factory, University
of Liverpool, Oxford Street, Liverpool L69 7ZD, U.K.
| | - Janine Kavanagh
- Department
of Earth, Ocean and Ecological Sciences, University of Liverpool, Jane Herdman Laboratories, Liverpool L69 3GP, U.K.
| | - Michael Barrow
- Anton
Paar (UK) Ltd., Unit F, The Courtyard, St. Albans AL4 0LA, U.K.
| | - Victoria R. Kearns
- Department
of Eye and Vision Science, University of
Liverpool, Liverpool L7 8TX, U.K.
| | - Esther García-Tuñón
- Department
of Chemistry & Materials Innovation Factory and School of Engineering
& Materials Innovation Factory, University
of Liverpool, Oxford Street, Liverpool L69 7ZD, U.K.
| | - Tom O. McDonald
- Department
of Chemistry & Materials Innovation Factory and School of Engineering
& Materials Innovation Factory, University
of Liverpool, Oxford Street, Liverpool L69 7ZD, U.K.
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7
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Nigro V, Angelini R, Rosi B, Bertoldo M, Buratti E, Casciardi S, Sennato S, Ruzicka B. Study of network composition in interpenetrating polymer networks of poly(N isopropylacrylamide) microgels: The role of poly(acrylic acid). J Colloid Interface Sci 2019; 545:210-219. [PMID: 30889412 DOI: 10.1016/j.jcis.2019.03.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 03/01/2019] [Accepted: 03/02/2019] [Indexed: 12/20/2022]
Abstract
HYPOTHESIS The peculiar swelling behaviour of poly(N-isopropylacrylamide) (PNIPAM)4-based responsive microgels provides the possibility to tune both softness and volume fraction with temperature, making these systems of great interest for technological applications and theoretical implications. Their intriguing phase diagram can be even more complex if poly(acrylic acid) (PAAc)5 is interpenetrated within PNIPAM network to form Interpenetrating Polymer Network (IPN)6 microgels that exhibit an additional pH-sensitivity. The effect of the PAAc/PNIPAM polymeric ratio on both swelling capability and dynamics is still matter of investigation. EXPERIMENTS Here we investigate the role of PAAc in the behaviour of IPN microgels across the volume phase transition through dynamic light scattering (DLS),7 transmission electron microscopy (TEM)8 and electrophoretic measurements as a function of microgel concentration and pH. FINDINGS Our results highlight that aggregation is favored at increasing weight concentration, PAAc content and pH and that a crossover PAAc content CPAAc∗9 exists above which the ionic charges on the microgel become relevant. Moreover we show that the softness of IPN microgels can be tuned ad hoc by changing the PAAc/PNIPAM ratio. These findings provide new insights into the possibility to control experimentally aggregation properties, charge and softness of IPN microgels by varying PAAc content.
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Affiliation(s)
- Valentina Nigro
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), sede Sapienza, Pz.le Aldo Moro 5, I-00185 Roma, Italy; Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy.
| | - Roberta Angelini
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), sede Sapienza, Pz.le Aldo Moro 5, I-00185 Roma, Italy; Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy.
| | - Benedetta Rosi
- Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy
| | - Monica Bertoldo
- Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, Via G.Moruzzi 1, I-56124 Pisa, Italy
| | - Elena Buratti
- Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, Via G.Moruzzi 1, I-56124 Pisa, Italy
| | - Stefano Casciardi
- Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, National Institution for Insurance Against Accidents at Work (INAIL Research), Via Fontana Candida 1, Monte Porzio Catone, 00040 Rome, Italy
| | - Simona Sennato
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), sede Sapienza, Pz.le Aldo Moro 5, I-00185 Roma, Italy; Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy
| | - Barbara Ruzicka
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), sede Sapienza, Pz.le Aldo Moro 5, I-00185 Roma, Italy; Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy.
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8
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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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9
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Liu W, Gong X, Ngai T, Wu C. Near-surface microrheology reveals dynamics and viscoelasticity of soft matter. SOFT MATTER 2018; 14:9764-9776. [PMID: 30383062 DOI: 10.1039/c8sm01886c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The development of experimental techniques able to probe the microscale viscoelastic properties of soft matter over a broad time scale is essential to uncover the physics that govern their behavior. Herein, we report the development of a microrheology technique that can determine the near-surface dynamics and viscoelastic behaviors of soft matter like polymer solution/gels and colloidal dispersions. Our approach combines a magnetic-field-induced stimulator with total internal reflection microscopy (TIRM) to apply mechanical loading (∼pN) to a micro-sized probe particle and capture its axial displacement near the surface with nano-scaled sensitivity. We demonstrate the use of this technique to measure the detachment of a colloid to a solid substrate and identify three quantitatively different regimes of mechanical coupling that differ in colloid-surface separation and interaction: exclusion, aging, and non-exclusion. We also apply it to study a physical gelation process of a volume-phase transition in thermosensitive microgels and a chemically cross-linked sol-gel transition of 4-arm star polymers by monitoring the evolution of complex modulus near solid surface with frequency, time, and separation distance. In contrast to passive microrheology techniques that rely on particle tracking, we can probe the viscoelastic behavior over five orders of magnitude in stiffness, from 10-3 to 102 Pa, providing excellent coverage for dynamics and heterogeneous samples. We expect this technique will stimulate the development of new experimental methods to explore the complex microscale rheology of macromolecular networks, soft materials, and living cytoplasm.
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Affiliation(s)
- Wei Liu
- Department of Physics, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
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10
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Rivas-Barbosa R, Lázaro-Lázaro E, Mendoza-Méndez P, Still T, Piazza V, Ramírez-González PE, Medina-Noyola M, Laurati M. Different routes into the glass state for soft thermo-sensitive colloids. SOFT MATTER 2018; 14:5008-5018. [PMID: 29855653 DOI: 10.1039/c8sm00285a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report an experimental and theoretical investigation of glass formation in soft thermo-sensitive colloids following two different routes: a gradual increase of the particle number density at constant temperature and an increase of the radius in a fixed volume at constant particle number density. Confocal microscopy experiments and the non-equilibrium self-consistent generalized Langevin equation (NE-SCGLE) theory consistently show that the two routes lead to a dynamically comparable state at sufficiently long aging times. However, experiments reveal the presence of moderate but persistent structural differences. Successive cycles of radius decrease and increase lead instead to a reproducible glass state, indicating a suitable route to obtain rejuvenation without using shear fields.
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Affiliation(s)
- Rodrigo Rivas-Barbosa
- División de Ciencias e Ingenierías, Universidad de Guanajuato, Loma del Bosque 103, 37150 León, Mexico.
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11
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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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12
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Nigro V, Angelini R, Bertoldo M, Ruzicka B. Swelling of responsive-microgels: experiments versus models. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2017.04.059] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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13
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Nigro V, Angelini R, Bertoldo M, Bruni F, Ricci MA, Ruzicka B. Dynamical behavior of microgels of interpenetrated polymer networks. SOFT MATTER 2017; 13:5185-5193. [PMID: 28664963 PMCID: PMC5898610 DOI: 10.1039/c7sm00739f] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Microgel suspensions of an interpenetrated Polymer Network (IPN) of PNIPAM and PAAc in D2O have been investigated through dynamic light scattering as a function of temperature, pH and concentration across the Volume Phase Transition (VPT). The dynamics of the system is slowed down under H/D isotopic substitution due to different balance states between polymer/polymer and polymer/solvent interactions suggesting the crucial role played by H-bonding. The swelling behavior, reduced with respect to PNIPAM and water, has been described by the Flory-Rehner theory, tested for PNIPAM microgel and successfully expanded to higher order for IPN microgels. Moreover the concentration dependence of the relaxation time at neutral pH has highlighted two different routes to approach the glass transition: Arrhenius and super-Arrhenius (Vogel Fulcher Tammann) respectively below and above the VPT and a fragility plot has been derived. Fragility can be tuned by changing temperature: across the VPT particles undergo a transition from soft-strong to stiff-fragile.
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Affiliation(s)
- Valentina Nigro
- Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy.
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Sub-diffusive dynamics and two-step yielding in dense thermo-responsive microgel glasses. Colloid Polym Sci 2017. [DOI: 10.1007/s00396-017-4142-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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de Oliveira TE, Mukherji D, Kremer K, Netz PA. Effects of stereochemistry and copolymerization on the LCST of PNIPAm. J Chem Phys 2017; 146:034904. [DOI: 10.1063/1.4974165] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Tiago E. de Oliveira
- Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Max-Planck Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
| | - Debashish Mukherji
- Max-Planck Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
| | - Kurt Kremer
- Max-Planck Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
| | - Paulo A. Netz
- Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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Ouyang W, Fu C, Sun Z, Xu S. Polymorph selection and nucleation pathway in the crystallization of Hertzian spheres. Phys Rev E 2016; 94:042805. [PMID: 27841599 DOI: 10.1103/physreve.94.042805] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Indexed: 06/06/2023]
Abstract
The crystallization process of Hertzian spheres is studied by means of molecular dynamics simulations in an NPT ensemble where the total number of particles N, the pressure P, and the temperature T are kept constant. It has been observed that the bond orientational ordering rather than the translational ordering (density) plays a primary role. The crystal polymorphs are determined by the state points. Under the conditions of small supercooling, the system is likely to be nucleated into crystals that have a preference for the metastable bcc structure, which can be regarded as a manifestation of the Alexander-McTague mechanism. In contrast, small nuclei are found to have a preference for fcc symmetry under conditions of a high degree of supercooling. Prestructured precursors that act as seeds and wet on the nuclei during nucleation always have a high degree of bcc-like ordering, despite different state points. The results above may provide a clue to the understanding of the crystallization process in core-softened particles.
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Affiliation(s)
- Wenze Ouyang
- Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
| | - Cuiliu Fu
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Zhiwei Sun
- Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
| | - Shenghua Xu
- Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
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Nigro V, Angelini R, Bertoldo M, Bruni F, Castelvetro V, Ricci MA, Rogers S, Ruzicka B. Local structure of temperature and pH-sensitive colloidal microgels. J Chem Phys 2015; 143:114904. [PMID: 26395735 DOI: 10.1063/1.4930885] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The temperature dependence of the local intra-particle structure of colloidal microgel particles, composed of interpenetrated polymer networks, has been investigated by small-angle neutron scattering at different pH and concentrations, in the range (299÷315) K, where a volume phase transition from a swollen to a shrunken state takes place. Data are well described by a theoretical model that takes into account the presence of both interpenetrated polymer networks and cross-linkers. Two different behaviors are found across the volume phase transition. At neutral pH and T ≈ 307 K, a sharp change of the local structure from a water rich open inhomogeneous interpenetrated polymer network to a homogeneous porous solid-like structure after expelling water is observed. Differently, at acidic pH, the local structure changes almost continuously. These findings demonstrate that a fine control of the pH of the system allows to tune the sharpness of the volume-phase transition.
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Affiliation(s)
- Valentina Nigro
- Dipartimento di Scienze, Sezione di Nanoscienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy
| | - Roberta Angelini
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR) UOS Sapienza and Dipartimento di Fisica, Sapienza Università, Pz.le Aldo Moro 5, I-00185 Roma, Italy
| | - Monica Bertoldo
- Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, Via G. Moruzzi 1, I-56124 Pisa, Italy
| | - Fabio Bruni
- Dipartimento di Scienze, Sezione di Nanoscienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy
| | - Valter Castelvetro
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via G. Moruzzi 3, I-56126 Pisa, Italy
| | - Maria Antonietta Ricci
- Dipartimento di Scienze, Sezione di Nanoscienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy
| | - Sarah Rogers
- ISIS-STFC, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, United Kingdom
| | - Barbara Ruzicka
- Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR) UOS Sapienza and Dipartimento di Fisica, Sapienza Università, Pz.le Aldo Moro 5, I-00185 Roma, Italy
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Su W, Zhao K, Wei J, Ngai T. Dielectric relaxations of poly(N-isopropylacrylamide) microgels near the volume phase transition temperature: impact of cross-linking density distribution on the volume phase transition. SOFT MATTER 2014; 10:8711-8723. [PMID: 25263641 DOI: 10.1039/c4sm01516a] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Dielectric relaxation behaviors of three types of thermally sensitive poly(N-isopropylacrylamide) (PNIPAM) microgels with different cross-linking density distributions were investigated in a frequency range from 40 Hz to 110 MHz at temperatures from 15 °C to 55 °C. After eliminating the electrode polarization at low frequency, two remarkable relaxations were observed, one in the kHz frequency range and the other in the MHz range. The low-frequency relaxation is attributed to the counterion polarization in the whole measuring temperature range, while the relaxation at high-frequency is probably dominated by different polarization mechanisms depending on below or above the volume phase transition temperature (VPTT): it is considered as micro-Brownian motion of side groups of PNIPAM when T < VPTT and interfacial polarization when T > VPTT. The temperature dependence of the dielectric parameters for both the relaxations presents an abrupt change around 32.5 °C, indicating the occurrence of phase transition. Based on the analysis and discussion about the micro-Brownian motion of the side groups, a possible microstructure for the microgels before and after the collapse of PNIPAM was suggested. A dielectric model to describe the collapsing microgel suspension was proposed, from which the electrical and structural parameters of the suspension were calculated. The information on the internal structure and hydration dynamic behavior of microgels was obtained by using the thermodynamic parameters which were calculated based on the Eyring equation. Our results reveal that the spatial distribution of the cross-linking density distribution has almost no effect on the volume phase transition temperature, but markedly affects the swelling capacity of PNIPAM microgels at low temperatures.
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Affiliation(s)
- Wenjuan Su
- College of Chemistry, Beijing Normal University, Beijing 100875, China
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Yunker PJ, Chen K, Gratale MD, Lohr MA, Still T, Yodh AG. Physics in ordered and disordered colloidal matter composed of poly(N-isopropylacrylamide) microgel particles. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2014; 77:056601. [PMID: 24801604 DOI: 10.1088/0034-4885/77/5/056601] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
This review collects and describes experiments that employ colloidal suspensions to probe physics in ordered and disordered solids and related complex fluids. The unifying feature of this body of work is its clever usage of poly(N-isopropylacrylamide) (PNIPAM) microgel particles. These temperature-sensitive colloidal particles provide experimenters with a 'knob' for in situ control of particle size, particle interaction and particle packing fraction that, in turn, influence the structural and dynamical behavior of the complex fluids and solids. A brief summary of PNIPAM particle synthesis and properties is given, followed by a synopsis of current activity in the field. The latter discussion describes a variety of soft matter investigations including those that explore formation and melting of crystals and clusters, and those that probe structure, rearrangement and rheology of disordered (jammed/glassy) and partially ordered matter. The review, therefore, provides a snapshot of a broad range of physics phenomenology which benefits from the unique properties of responsive microgel particles.
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Affiliation(s)
- Peter J Yunker
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA. School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
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