1
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Otten M, Hildebrandt M, Pfeffing B, Voigt VC, Scheffold F, Hellweg T, Karg M. Volume Phase Transition of Thermoresponsive Microgels Scrutinized by Dynamic Light Scattering and Turbidity: Correlations Depend on Microgel Homogeneity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:14515-14526. [PMID: 38951962 DOI: 10.1021/acs.langmuir.4c01344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/03/2024]
Abstract
Thermoresponsive microgels experience a volume phase transition triggered by temperature changes, a phenomenon often analyzed using dynamic light scattering to observe overall size alterations via the diffusion coefficient. However, local structural changes are typically assessed using more intricate and expensive techniques like small-angle neutron or X-ray scattering. In our research, we investigate the volume phase transition of poly-N-isopropylacrylamide (PNIPAM)-based microgels by employing a combination of temperature-dependent dynamic light scattering and simpler, faster, and more efficient attenuation measurements. We utilize attenuation at a fixed wavelength as a direct measure of dispersion turbidity, linking the absolute changes in hydrodynamic radius to the absolute changes in turbidity. This approach allows us to compare "classical" PNIPAM microgels from precipitation polymerization, charged copolymer microgels from precipitation copolymerization, and core-shell microgels from seeded precipitation polymerization. Our study includes a systematic analysis and comparison of 30 different microgels. By directly comparing data from dynamic light scattering and attenuation spectroscopy, we gain insights into structural heterogeneity and deviations from the established fuzzy sphere morphology. Furthermore, we demonstrate how turbidity data can be converted to swelling curves.
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Affiliation(s)
- Marius Otten
- Institut für Physikalische Chemie I: Kolloide und Nanooptik, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - Marco Hildebrandt
- Institut für Physikalische Chemie I: Kolloide und Nanooptik, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - Ben Pfeffing
- Institut für Physikalische Chemie I: Kolloide und Nanooptik, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - Victoria Carina Voigt
- Institut für Physikalische Chemie I: Kolloide und Nanooptik, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - Frank Scheffold
- Department of Physics, University of Fribourg, Chem. Du Musée, 1700 Fribourg, Switzerland
| | - Thomas Hellweg
- Fakultät für Chemie, Physikalische und Biophysikalische Chemie, Universität Bielefeld, Universitätsstr. 25, 33615 Bielefeld, Germany
| | - Matthias Karg
- Institut für Physikalische Chemie I: Kolloide und Nanooptik, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
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2
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Uredat S, Gujare A, Runge J, Truzzolillo D, Oberdisse J, Hellweg T. A review of stimuli-responsive polymer-based gating membranes. Phys Chem Chem Phys 2024; 26:2732-2744. [PMID: 38193196 DOI: 10.1039/d3cp05143a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
The formation and properties of smart (stimuli-responsive) membranes are reviewed, with a special focus on temperature and pH triggering of gating to water, ions, polymers, nanoparticles, or other molecules of interest. The review is organized in two parts, starting with all-smart membranes based on intrinsically smart materials, in particular of the poly(N-isopropylacrylamide) family and similar polymers. The key steps of membrane fabrication are discussed, namely the deposition into thin films, functionalization of pores, and the secondary crosslinking of pre-existing microgel particles into membranes. The latter may be free-standing and do not necessitate the presence of a porous support layer. The temperature-dependent swelling properties of polymers provide a means of controlling the size of pores, and thus size-sensitive gating. Throughout the review, we highlight "positive" (gates open) or "negative" (closed) gating effects with respect to increasing temperature. In the second part, the functionalization of porous organic or inorganic membranes of various origins by either microgel particles or linear polymer brushes is discussed. In this case, the key steps are the adsorption or grafting mechanisms. Finally, whenever provided by the authors, the suitability of smart gating membranes for specific applications is highlighted.
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Affiliation(s)
- Stefanie Uredat
- Department of Physical and Biophysical Chemistry, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany.
| | - Aditi Gujare
- Laboratoire Charles Coulomb (L2C), University of Montpellier, CNRS, 34095 Montpellier, France.
| | - Jonas Runge
- Department of Physical and Biophysical Chemistry, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany.
| | - Domenico Truzzolillo
- Laboratoire Charles Coulomb (L2C), University of Montpellier, CNRS, 34095 Montpellier, France.
| | - Julian Oberdisse
- Laboratoire Charles Coulomb (L2C), University of Montpellier, CNRS, 34095 Montpellier, France.
| | - Thomas Hellweg
- Department of Physical and Biophysical Chemistry, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany.
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3
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Ruiz-Franco J, Rivas-Barbosa R, Lara-Peña MA, Villanueva-Valencia JR, Licea-Claverie A, Zaccarelli E, Laurati M. Concentration and temperature dependent interactions and state diagram of dispersions of copolymer microgels. SOFT MATTER 2023; 19:3614-3628. [PMID: 37161724 DOI: 10.1039/d3sm00120b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We investigate by means of small angle neutron scattering experiments and numerical simulations the interactions and inter-particle arrangements of concentrated dispersions of copolymer poly(N-isopropylacrylamide)-poly(ethylene glycol methyl ether methacrylate) (PNIPAM-PEGMA) microgels across the volume phase transition (VPT). The scattering data of moderately concentrated dispersions are accurately modeled at all temperatures by using a star polymer form factor and static structure factors calculated from the effective potential obtained from simulations. Interestingly, for temperatures below the VPT temperature (VPTT), the radius of gyration and blob size of the particles significantly decrease with increasing the effective packing fraction in the non-overlapping regime. This is attributed to the presence of charges in the system associated with the use of an ionic initiator in the synthesis. Simulations using the experimentally corroborated interaction potential are used to explore the state diagram in a wide range of effective packing fractions. Below and slightly above the VPTT, the system undergoes an arrest transition mainly driven by the soft repulsion between the particles. Only well above the VPTT the system is found to phase separate before arresting. Our results highlight the versatility and potential of copolymer PNIPAM-PEGMA microgels to explore different kinds of arrested states balancing attraction and repulsion by changing temperature and packing fraction.
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Affiliation(s)
- José Ruiz-Franco
- CNR Institute of Complex Systems, Uos Sapienza, Piazzale Aldo Moro 2, 00185, Roma, Italy.
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Roma, Italy
- Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, 6708WE Wageningen, The Netherlands
| | - Rodrigo Rivas-Barbosa
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Roma, Italy
- División de Ciencias e Ingenierías, Universidad de Guanajuato, Lomas del Bosque 103, 37150 León, Mexico
| | - Mayra A Lara-Peña
- División de Ciencias e Ingenierías, Universidad de Guanajuato, Lomas del Bosque 103, 37150 León, Mexico
- Dipartimento di Chimica and CSGI, Università di Firenze, 50019 Sesto Fiorentino, Italy.
| | | | - Angel Licea-Claverie
- Centro de Graduados e Investigación en Química del Tecnológico Nacional de México/Instituto Tecnológico de Tijuana, 22500 Tijuana, Mexico
| | - Emanuela Zaccarelli
- CNR Institute of Complex Systems, Uos Sapienza, Piazzale Aldo Moro 2, 00185, Roma, Italy.
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Roma, Italy
| | - Marco Laurati
- Dipartimento di Chimica and CSGI, Università di Firenze, 50019 Sesto Fiorentino, Italy.
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Izak‐Nau E, Braun S, Pich A, Göstl R. Mechanically Resistant Poly(N-vinylcaprolactam) Microgels with Sacrificial Supramolecular Catechin Hydrogen Bonds. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2104004. [PMID: 35187862 PMCID: PMC9036020 DOI: 10.1002/advs.202104004] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 01/10/2022] [Indexed: 06/14/2023]
Abstract
Microgels (μgels) swiftly undergo structural and functional degradation when they are exposed to shear forces, which potentially limit their applicability in, e.g., biomedicine and engineering. Here, poly(N-vinylcaprolactam) μgels that resist mechanical disruption through supramolecular hydrogen bonds provided by (+)-catechin hydrate (+C) are synthesized. When +C is added to the microgel structure, an increased resistance against shear force exerted by ultrasonication is observed compared to μgels crosslinked by covalent bonds. While covalently crosslinked μgels degrade already after a few seconds, it is found that μgels having both supramolecular interchain interactions and covalent crosslinks show the highest mechanical durability. By the incorporation of optical force probes, it is found that the covalent bonds of the μgels are not stressed beyond their scission threshold and mechanical energy is dissipated by the force-induced reversible dissociation of the sacrificial +C bonds for at least 20 min of ultrasonication. Additionally, +C renders the μgels pH-sensitive and introduces multiresponsivity. The μgels are extensively characterized using Fourier-transform infrared, Raman and quantitative nuclear magnetic resonance spectroscopy, dynamic light scattering, and cryogenic transmission electron microscopy. These results may serve as blueprint for the preparation of many mechanically durable μgels.
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Affiliation(s)
- Emilia Izak‐Nau
- DWI – Leibniz Institute for Interactive MaterialsForckenbeckstr. 50Aachen52056Germany
| | - Susanne Braun
- DWI – Leibniz Institute for Interactive MaterialsForckenbeckstr. 50Aachen52056Germany
- Institute of Technical and Macromolecular ChemistryRWTH Aachen UniversityWorringerweg 1Aachen52074Germany
| | - Andrij Pich
- DWI – Leibniz Institute for Interactive MaterialsForckenbeckstr. 50Aachen52056Germany
- Institute of Technical and Macromolecular ChemistryRWTH Aachen UniversityWorringerweg 1Aachen52074Germany
- Aachen Maastricht Institute for Biobased Materials (AMIBM) Maastricht UniversityBrightlands Chemelot CampusGeleen6167 RDThe Netherlands
| | - Robert Göstl
- DWI – Leibniz Institute for Interactive MaterialsForckenbeckstr. 50Aachen52056Germany
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Dirksen M, Fandrich P, Goett-Zink L, Cremer J, Anselmetti D, Hellweg T. Thermoresponsive Microgel-Based Free-Standing Membranes: Influence of Different Microgel Cross-Linkers on Membrane Function. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:638-651. [PMID: 34982566 DOI: 10.1021/acs.langmuir.1c02195] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In this study we show a possibility to produce thermoresponsive, free-standing microgel membranes based on N-isopropylacrylamide (NIPAM) and the UV-sensitive comonomer 2-hydroxy-4-(methacryloyloxy)benzophenone (HMABP). To influence the final network structure and functionality of the membranes, we use different cross-linkers in the microgel syntheses and characterize the resulting structural microgel properties and the swelling behavior by means of AFM, FTIR, and PCS measurements. Varying the cross-linker results in significant changes in the structure and swelling behavior of the individual microgels and has an influence on the incorporation of the comonomer, which is essential for subsequent photochemical membrane formation. We investigate the ion transport through the different membranes by temperature-dependent resistance measurements revealing a sharp increase in resistance when the copolymer microgels reach their collapsed state. The resistance of the membranes can be adjusted by different cross-linkers and the associated incorporation of the comonomer. Furthermore, we show that transferring a reversible cross-linker from a cross-linked state to an un-cross-linked state strongly influences the membrane properties and even reverses the switching behavior, while the mechanical stability of the membrane is maintained.
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6
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Suarez IJ, Sierra-Martin B, Fernandez-Barbero A. Using Plasma Etching to Access the Polymer Density Distribution and Diffusivity of Gel Particles. Polymers (Basel) 2021; 13:2537. [PMID: 34372139 PMCID: PMC8347704 DOI: 10.3390/polym13152537] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Revised: 07/27/2021] [Accepted: 07/27/2021] [Indexed: 11/16/2022] Open
Abstract
In this paper we examine the polymer density distribution of gel particles and its effect on solvent diffusivity through the polymer network. In order to access the inner particle regions, external polymer layers were removed by plasma etching, thus reducing them from the outside. Higher polymer densities after erosion showed internal heterogeneity, with the density increasing towards the center of the particles. An exponential decay polymer density model is proposed, and the spatial relaxation length measured. The diffusion of solvent through the particles, before and after the plasma oxidation, revealed a correlation between the diffusion coefficient and the internal density.
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Affiliation(s)
- Ivan J. Suarez
- NanoLab, Department of Chemistry and Physics, University of Almeria, 04120 Almeria, Spain; (I.J.S.); (B.S.-M.)
| | - Benjamin Sierra-Martin
- NanoLab, Department of Chemistry and Physics, University of Almeria, 04120 Almeria, Spain; (I.J.S.); (B.S.-M.)
| | - Antonio Fernandez-Barbero
- NanoLab, Department of Chemistry and Physics, University of Almeria, 04120 Almeria, Spain; (I.J.S.); (B.S.-M.)
- Institute of Applied Chemical Sciences, Universidad Autonoma de Chile, Santiago 7500138, Chile
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7
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Wilms D, Adler Y, Schröer F, Bunnemann L, Schmidt S. Elastic modulus distribution in poly( N-isopopylacrylamide) and oligo(ethylene glycol methacrylate)-based microgels studied by AFM. SOFT MATTER 2021; 17:5711-5717. [PMID: 34013309 DOI: 10.1039/d1sm00291k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The spatial elastic modulus distribution of microgel networks in presence and absence of bifunctional crosslinkers is studied by AFM. Thermoresponsive poly(N-isopopylacrylamide) (PNIPAM) and poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol)methacrylate) (P(MEO2MA-co-OEGMA)) microgels are synthesized via precipitation polymerization above their lower critical solution temperature (LCST). High-resolution elastic modulus profiles are acquired using AFM force-indentation mapping of surface-deposited microgels at 25 °C. For both microgel systems, the use of a bifunctional crosslinker leads to a strong elastic modulus gradient with stiff microgel cores and soft networks toward the edge. In absence of a dedicated crosslinker (self-crosslinking), PNIPAM microgels show a homogeneous elastic modulus distribution, whereas self-crosslinked P(MEO2MA-co-OEGMA) microgels still show decreasing elastic moduli from the centre to the edge of the microgels. However, POEGMA microgels without comonomer showed no elastic modulus gradient suggesting that different incorporation rates of MEO2MA and OEGMA result in a radial variation of the polymer segment density. In addition, when varying the molecular weight of OEGMA the overall elastic modulus was affected, possibly due to molecular weight-dependent phase behavior and different reactivity. This shows that quite different microgel architectures can be obtained by the simple "one-pot" precipitation reaction of microgels which may open to new avenues toward advanced applications.
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Affiliation(s)
- Dimitri Wilms
- Institute for Organic Chemistry and Macromolecular Chemistry, Heinrich-Heine-University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
| | - Yanik Adler
- Institute for Organic Chemistry and Macromolecular Chemistry, Heinrich-Heine-University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
| | - Fabian Schröer
- Institute for Organic Chemistry and Macromolecular Chemistry, Heinrich-Heine-University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
| | - Lennart Bunnemann
- Institute for Organic Chemistry and Macromolecular Chemistry, Heinrich-Heine-University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
| | - Stephan Schmidt
- Institute for Organic Chemistry and Macromolecular Chemistry, Heinrich-Heine-University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
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8
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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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9
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Functional Glyco-Nanogels for Multivalent Interaction with Lectins. Molecules 2019; 24:molecules24101865. [PMID: 31096570 PMCID: PMC6572176 DOI: 10.3390/molecules24101865] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/03/2019] [Accepted: 05/14/2019] [Indexed: 12/31/2022] Open
Abstract
Interactions between glycans and proteins have tremendous impact in biomolecular interactions. They are important for cell–cell interactions, proliferation and much more. Here, we emphasize the glycan-mediated interactions between pathogens and host cells. Pseudomonas aeruginosa, responsible for a huge number of nosocomial infections, is especially the focus when it comes to glycan-derivatives as pathoblockers. We present a microwave assisted protecting group free synthesis of glycomonomers based on lactose, melibiose and fucose. The monomers were polymerized in a precipitation polymerization in the presence of NiPAm to form crosslinked glyco-nanogels. The influence of reaction parameters like crosslinker type or stabilizer amount was investigated. The gels were characterized in lectin binding studies using model lectins and showed size and composition-dependent inhibition of lectin binding. Due to multivalent presentation of glycans in the gel, the inhibition was clearly stronger than with unmodified saccharides, which was compared after determination of the glycan loading. First studies with Pseudomonas aeruginosa revealed a surprising influence on the secretion of virulence factors. Functional glycogels may be in the future potent alternatives or adjuvants for antibiotic treatment of infections based on glycan interactions between host and pathogen.
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Witte J, Kyrey T, Lutzki J, Dahl AM, Houston J, Radulescu A, Pipich V, Stingaciu L, Kühnhammer M, Witt MU, von Klitzing R, Holderer O, Wellert S. A comparison of the network structure and inner dynamics of homogeneously and heterogeneously crosslinked PNIPAM microgels with high crosslinker content. SOFT MATTER 2019; 15:1053-1064. [PMID: 30663759 DOI: 10.1039/c8sm02141d] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Poly(N-isopropylacrylamide) microgel particles were prepared via a "classical" surfactant-free precipitation polymerization and a continuous monomer feeding approach. It is anticipated that this yields microgel particles with different internal structures, namely a dense core with a fluffy shell for the classical approach and a more even crosslink distribution in the case of the continuous monomer feeding approach. A thorough structural investigation of the resulting microgels with dynamic light scattering, atomic force microscopy and small angle neutron scattering was conducted and related to neutron spin echo spectroscopy data. In this way a link between structural and dynamic features of the internal polymer network was made.
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Affiliation(s)
- Judith Witte
- Institute of Chemistry, TU Berlin, Strasse des 17. Juni 124, 10623 Berlin, Germany.
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11
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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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12
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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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13
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Kim S, Lee K, Cha C. Refined control of thermoresponsive swelling/deswelling and drug release properties of poly(N-isopropylacrylamide) hydrogels using hydrophilic polymer crosslinkers. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2016; 27:1698-1711. [DOI: 10.1080/09205063.2016.1230933] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Suntae Kim
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea
| | - Kangseok Lee
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, South Korea
| | - Chaenyung Cha
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, South Korea
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14
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Aqueous dispersions of cross-linked poly-N-vinylcaprolactam stabilized with hydrophobically modified polyacrylamide: synthesis, colloidal stability, and thermosensitive properties. Colloid Polym Sci 2016. [DOI: 10.1007/s00396-016-3843-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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15
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Effect of cross-linker and charge on the scattered light by dilute aqueous dispersions of nanogel particles. Colloids Surf A Physicochem Eng Asp 2015. [DOI: 10.1016/j.colsurfa.2015.08.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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16
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Wellert S, Radulescu A, Carl A, Klitzing RV, Gawlitza K. Evolution of Size and Structure during the Polymerization Process: A SANS Study on EG-Based Microgels. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00686] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stefan Wellert
- Stranski-Laboratory
for Physical and Theoretical Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Aurel Radulescu
- Outstation
at MLZ, Forschungszentrum Jülich GmbH, Lichtenbergstraße
1, 85747 Garching, Germany
| | - Adrian Carl
- Stranski-Laboratory
for Physical and Theoretical Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Regine von Klitzing
- Stranski-Laboratory
for Physical and Theoretical Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Kornelia Gawlitza
- Stranski-Laboratory
for Physical and Theoretical Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
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17
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18
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Callejas-Fernández J, Ramos J, Forcada J, Moncho-Jordá A. On the scattered light by dilute aqueous dispersions of nanogel particles. J Colloid Interface Sci 2015; 450:310-315. [PMID: 25837408 DOI: 10.1016/j.jcis.2015.03.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 02/12/2015] [Accepted: 03/13/2015] [Indexed: 11/17/2022]
Abstract
This work deals with the scattered light by nanoparticles formed by a temperature sensitive polymer networks, namely nanogel particles. The scattered light is measured as a function of the scattering angle at temperatures below and above the volume phase transition temperature (VPTT) of nanogel particles. Our experimental results indicate that nanogel particles have a core-shell structure, formed by a uniform highly cross-linked core surrounded by a fuzzy shell where the polymer density decays to zero gradually for swollen configurations and sharply for shrunken states. The theoretical fitting of the experimental curves shows that the scattered light at low angle obeys a decreasing power law with the scattering vector, q(-α). The value of exponent α provides information about the radial dependence of the polymer density at the external shell of the particles for swollen nanogels, and about the degree of roughness of the surface for the case of shrunken nanogels. On the one hand, at low temperatures (below the VPPT), the nanogel particle is in the swollen state and the light scattering data show that its shell structure follows a fractal behaviour, with a polymer density that decays as r(α-3), where r is the distance to the particle centre. On the other hand, above the VPPT the results indicate that nanogel collapses into a core of uniform polymer density and a rough shell, with a fractal surface dimension of 2.5.
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Affiliation(s)
- J Callejas-Fernández
- Grupo de Física de Fluidos y Biocoloides, Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain.
| | - J Ramos
- Department of Materials, Department of Bioengineering, and the Institute for Biomedical Engineering, Imperial College London, London SW7 2AZ, United Kingdom; POLYMAT, Bionanoparticles Group, Departamento de Química Aplicada, UFI/56, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, Apdo. 1072, 20080 Donostia-San Sebastián, Spain
| | - J Forcada
- POLYMAT, Bionanoparticles Group, Departamento de Química Aplicada, UFI/56, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, Apdo. 1072, 20080 Donostia-San Sebastián, Spain
| | - A Moncho-Jordá
- Grupo de Física de Fluidos y Biocoloides, Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
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Schneider F, Balaceanu A, Feoktystov A, Pipich V, Wu Y, Allgaier J, Pyckhout-Hintzen W, Pich A, Schneider GJ. Monitoring the internal structure of poly(N-vinylcaprolactam) microgels with variable cross-link concentration. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:15317-15326. [PMID: 25493607 DOI: 10.1021/la503830w] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The combination of a set of complementary techniques allows us to construct an unprecedented and comprehensive picture of the internal structure, temperature dependent swelling behavior, and the dependence of these properties on the cross-linker concentration of microgel particles based on N-vinylcaprolactam (VCL). The microgels were synthesized by precipitation polymerization using different amounts of cross-linking agent. Characterization was performed by small-angle neutron scattering (SANS) using two complementary neutron instruments to cover a uniquely broad Q-range with one probe. Additionally we used dynamic light scattering (DLS), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). Previously obtained nuclear magnetic resonance spectroscopy (NMR) results on the same PVCL particles are utilized to round the picture off. Our study shows that both the particle radius and the cross-link density and therefore also the stiffness of the microgels rises with increasing cross-linker content. Hence, more cross-linker reduces the swelling capability distinctly. These findings are supported by SANS and AFM measurements. Independent DLS experiments also found the increase in particle size but suggest an unchanged cross-link density. The reason for the apparent contradiction is the indirect extraction of the parameters via a model in the evaluation of DLS measurements. The more direct approach in AFM by evaluating the cross section profiles of observed microgel particles gives evidence of significantly softer and more deformable particles at lower cross-linker concentrations and therefore verifies the change in cross-link density. DSC data indicate a minor but unexpected shift of the volume phase transition temperature (VPTT) to higher temperatures and exposes a more heterogeneous internal structure of the microgels with increasing cross-link density. Moreover, a change in the total energy transfer during the VPT gives evidence that the strength of hydrogen bonds is significantly affected by the cross-link density. A strong and reproducible deviation of the material density of the cross-linked microgel polymer chains toward a higher value compared to the respective linear chains has yet to be explained.
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Affiliation(s)
- Florian Schneider
- Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstraße 1, 85747 Garching, Germany
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20
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Gawlitza K, Radulescu A, von Klitzing R, Wellert S. On the structure of biocompatible, thermoresponsive poly(ethylene glycol) microgels. POLYMER 2014. [DOI: 10.1016/j.polymer.2014.10.069] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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21
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Synthesis and characterization of thermosensitive poly(N-isopropylacrylamide-co-hydroxyethylacrylamide) microgels as potential carriers for drug delivery. JOURNAL OF POLYMER RESEARCH 2014. [DOI: 10.1007/s10965-014-0580-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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22
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Bhat KA, Leo Prakash P, Manoharan N, Lakshmibai A, Sangeetha D. Fabrication of polymethyl methacrylate/polysulfone/nanoceramic composites for orthopedic applications. J Appl Polym Sci 2013. [DOI: 10.1002/app.37581] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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23
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Wu Q, Su T, Mao Y, Wang Q. Thermal responsive microgels as recyclable carriers to immobilize active proteins with enhanced nonaqueous biocatalytic performance. Chem Commun (Camb) 2013; 49:11299-301. [DOI: 10.1039/c3cc46161k] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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24
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Gawlitza K, Wu C, Georgieva R, Ansorge-Schumacher M, von Klitzing R. Temperature Controlled Activity of Lipase B from Candida Antarctica after Immobilization within p-NIPAM Microgel Particles. ACTA ACUST UNITED AC 2012. [DOI: 10.1524/zpch.2012.0271] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
The immobilization of lipase B from Candida antarctica (CalB) within micronsized poly-N-Isopropylacrylamide (p-NIPAM) microgel particles with a crosslinker content of 5% is reported. The immobilization of the enzyme was reached by an exchange from polar to organic solvents. After determining the embedded amount of CalB within the polymer network, an enhanced specific activity in n-hexane was obtained. Due to the thermoresponsibility of the polymer particles, the activity reaction was done at 25 ºC and 50 ºC. The results presented show that the reversible collapse of the microgel leads to a decreased activity with increasing temperature. Hence, p-NIPAM microgels display a good opportunity to tailor the activity of CalB. An interesting side effect is that CalB presents a suitable probe to estimate the mesh size of the polymer network, since it penetrates in the unlabeled form but not after labeling with FITC.
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Affiliation(s)
| | - Changzhu Wu
- Technische Universität Berlin, Department of Enzyme Technology, Institute of Chemistry, Berlin, Deutschland
| | - Radostina Georgieva
- Trakia University Stara Zagora, Medical Faculty, Department of Medical Physics, Biophysics and Radiology, Stara Zagora, Bulgarien
| | - Marion Ansorge-Schumacher
- Technische Universität Berlin, Department of Enzyme Technology, Institute of Chemistry, Berlin, Deutschland
| | - Regine von Klitzing
- Technische Universität Berlin, Stranski-Laboratory f. Phys./Theoret. Chemistry, Berlin, Deutschland
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25
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Holmqvist P, Mohanty PS, Nägele G, Schurtenberger P, Heinen M. Structure and dynamics of loosely cross-linked ionic microgel dispersions in the fluid regime. PHYSICAL REVIEW LETTERS 2012; 109:048302. [PMID: 23006114 DOI: 10.1103/physrevlett.109.048302] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Indexed: 06/01/2023]
Abstract
We report a comprehensive experimental-theoretical study of the temperature- and concentration-dependent swelling behavior of weakly cross-linked PNiPAm ionic microgel particles in the deionized fluid phase. The particles swell reversibly when the dispersion is cooled from the collapsed state to lower temperatures. While the collapsed state shows no dependence on the microgel number density, the swelling at lower T is more pronounced at lower concentrations. The static pair correlations and short-time diffusion functions, and the concentration and temperature dependence of the microgel radius and effective charge, are studied using static and dynamic light scattering in combination with state-of-the-art analytical theoretical schemes based on a Yukawa-type effective pair potential and a core-shell model. We show that only such a combined, simultaneous fit of static and dynamic scattering functions allows for an unambiguous determination of the microgel radius and effective charge.
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Affiliation(s)
- P Holmqvist
- Institute of Complex Systems (ICS-3), Forschungszentrum Jülich, Jülich D-52425, Germany.
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26
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Balaceanu A, Mayorga V, Lin W, Schürings MP, Demco DE, Böker A, Winnik MA, Pich A. Copolymer microgels by precipitation polymerisation of N-vinylcaprolactam and N-isopropylacrylamides in aqueous medium. Colloid Polym Sci 2012. [DOI: 10.1007/s00396-012-2659-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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27
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Zhang Y, Liu T, Wang Q, Zhao J, Fang J, Shen W. Synthesis of novel poly(N,N-diethylacrylamide-co-acrylic acid) (P(DEA-co-AA)) microgels as carrier of horseradish peroxidase immobilization for pollution treatment. Macromol Res 2012. [DOI: 10.1007/s13233-012-0044-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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28
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Gawlitza K, Wu C, Georgieva R, Wang D, Ansorge-Schumacher MB, Klitzing RV. Immobilization of lipase B within micron-sized poly-N-isopropylacrylamide hydrogel particles by solvent exchange. Phys Chem Chem Phys 2012; 14:9594-600. [DOI: 10.1039/c2cp40624a] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Deshmukh S, Mooney DA, MacElroy JM. Molecular simulation study of the effect of cross-linker on the properties of poly(N-isopropyl acrylamide) hydrogel. MOLECULAR SIMULATION 2011. [DOI: 10.1080/08927022.2011.566608] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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30
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One-step method for monodisperse microbiogels by glass capillary microfluidics. Colloids Surf A Physicochem Eng Asp 2011. [DOI: 10.1016/j.colsurfa.2011.04.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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31
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Acciaro R, Gilányi T, Varga I. Preparation of monodisperse poly(N-isopropylacrylamide) microgel particles with homogenous cross-link density distribution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:7917-25. [PMID: 21591700 DOI: 10.1021/la2010387] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Monodisperse microgel latex with homogeneous cross-link density distribution within the particles was prepared by feeding the monomer and cross-linker into the reaction mixture in a regulated way during the polymerization. To determine the appropriate monomer feeding parameters, the kinetics of the particle formation was investigated by HPLC. The swelling and optical characteristics of the prepared homogenously cross-linked microgel particles were compared to the properties of inhomogenously cross-linked microgels prepared by the normal precipitation polymerization method. The distribution of the cross-link density within the particles inserts a great influence on the characteristics of the system. The degree of swelling of the homogeneous particles is significantly higher than that of the heterogeneous microgel particles. Furthermore, at room temperature the pNIPAm latex containing the homogeneously cross-linked particles is transparent, while the heterogeneously cross-linked particles form a highly turbid system at the same 0.1 wt% concentration.
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Affiliation(s)
- Roberta Acciaro
- Institute of Chemistry, Eötvös University, 1117 Budapest, Pázmány s. 1/A, Hungary
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32
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Chen S, Jiang L, Dan Y. Preparation and thermal response behavior of poly(N-isopropylacrylamide-co-a crylic acid) microgels via soap-free emulsion polymerization based on AIBN initiator. J Appl Polym Sci 2011. [DOI: 10.1002/app.33938] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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33
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Karg M, Jaber S, Hellweg T, Mulvaney P. Surface plasmon spectroscopy of gold-poly-N-isopropylacrylamide core-shell particles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:820-7. [PMID: 21155547 DOI: 10.1021/la1039249] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Highly uniform, core-shell microgels consisting of single gold nanoparticle cores and cross-linked poly-N-isopropylacrylamide (PNIPAM) shells were prepared by a novel, versatile protocol. The synthetic pathway allows control over the polymer shell thickness and its swelling behavior. The core-shell structure was investigated by electron microscopy and atomic force microscopy, whereas the swelling behavior of the shell was studied by means of dynamic light scattering and UV-vis spectroscopy. Furthermore, the latter method was used to investigate the optical properties of the hybrid particles. By modeling the scattering contribution from the PNIPAM shells, the absorption spectra of the gold nanoparticle cores could be recovered. This allows the particle concentration to be determined, and this in turn permits the calculation of the molar mass of the hybrid particles as well as the refractive index of the shells.
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Affiliation(s)
- Matthias Karg
- School of Chemistry & Bio21 Institute, University of Melbourne, 30 Flemington Road, 3010 Victoria, Australia.
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34
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Burmistrova A, Steitz R, von Klitzing R. Temperature Response of PNIPAM Derivatives at Planar Surfaces: Comparison between Polyelectrolyte Multilayers and Adsorbed Microgels. Chemphyschem 2010; 11:3571-9. [DOI: 10.1002/cphc.201000378] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Anna Burmistrova
- Stranski‐Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 124, D‐10623 Berlin (Germany), Fax: (+49) 30‐314‐26602
| | - Roland Steitz
- Helmholtz‐Zentrum Berlin, Lise‐Meitner Campu, Hahn‐Meitner‐Platz 1, 14109 Berlin (Germany)
| | - Regine von Klitzing
- Stranski‐Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 124, D‐10623 Berlin (Germany), Fax: (+49) 30‐314‐26602
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35
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Karg M, Wellert S, Prevost S, Schweins R, Dewhurst C, Liz-Marzán LM, Hellweg T. Well defined hybrid PNIPAM core-shell microgels: size variation of the silica nanoparticle core. Colloid Polym Sci 2010. [DOI: 10.1007/s00396-010-2327-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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36
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SYNTHESIS AND PROPERTIES OF TEMPERATURE-SENSITIVE <I>N</I>-ISOPROPYLACRYLAMIDE COPOLYMER MICROGELS WITH TUNABLE PHASE TRANSITION TEMPERATURE. ACTA POLYM SIN 2010. [DOI: 10.3724/sp.j.1105.2006.00897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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37
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Pich A, Richtering W. Microgels by Precipitation Polymerization: Synthesis, Characterization, and Functionalization. CHEMICAL DESIGN OF RESPONSIVE MICROGELS 2010. [DOI: 10.1007/12_2010_70] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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38
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Burmistrova A, von Klitzing R. Control of number density and swelling/shrinking behavior of P(NIPAM–AAc) particles at solid surfaces. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/b923969c] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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39
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Preparation and characterization of poly (N-isopropylacrylamide)/polyvinylamine core-shell microgels. Colloid Polym Sci 2009. [DOI: 10.1007/s00396-009-2095-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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40
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Karg M, Hellweg T. Smart inorganic/organic hybrid microgels: Synthesis and characterisation. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b820292n] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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41
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Karg M, Pastoriza-Santos I, Rodriguez-González B, von Klitzing R, Wellert S, Hellweg T. Temperature, pH, and ionic strength induced changes of the swelling behavior of PNIPAM-poly(allylacetic acid) copolymer microgels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:6300-6306. [PMID: 18489184 DOI: 10.1021/la702996p] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The volume phase transition of colloidal microgels made of N-isopropylacrylamide (NIPAM) is well-studied and it is known that the transition temperature can be influenced by copolymerization. A series of poly( N-isopropylacrylamide- co-allylacetic acid) copolymers with different contents of allylacetic acid (AAA) was synthesized by means of a simple radical polymerization approach. The thermoresponsive behavior of these particles was studied using dynamic light scattering (DLS). Further characterization was done by employing transmission electron microscopy (TEM) and zeta potential measurements. TEM observations reveal the approximately spherical shape and low polydispersity of the copolymer particles. In addition, the measured zeta potentials provide information about the relative surface charge. Since these copolymers are much more sensitive to external stimuli such as pH and ionic strength than their pure PNIPAM counterparts, the volume phase transition was investigated at two different pH values and various salt concentrations. At pH 10 for the copolymer microgels with the highest AAA content, a significant shift of the volume phase transition temperature toward higher values is found. For higher AAA content, a change in pH from 8 to 10 can induce a change in radius of up to 100 nm making the particles interesting as pH controlled actuators.
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Affiliation(s)
- Matthias Karg
- Universität Bayreuth, Physikalische Chemie I, Universitätsstrasse 30, D-95440 Bayreuth, Germany
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42
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Imaz A, Forcada J. N-vinylcaprolactam-based microgels: Effect of the concentration and type of cross-linker. ACTA ACUST UNITED AC 2008. [DOI: 10.1002/pola.22609] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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43
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Karg M, Wellert S, Pastoriza-Santos I, Lapp A, Liz-Marzán LM, Hellweg T. Thermoresponsive core–shell microgels with silica nanoparticle cores: size, structure, and volume phase transition of the polymer shell. Phys Chem Chem Phys 2008; 10:6708-16. [DOI: 10.1039/b802676a] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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44
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Elmas B, Tuncel M, Senel S, Patir S, Tuncel A. Hydroxyl functionalized thermosensitive microgels with quadratic crosslinking density distribution. J Colloid Interface Sci 2007; 313:174-83. [PMID: 17532327 DOI: 10.1016/j.jcis.2007.04.052] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Revised: 04/08/2007] [Accepted: 04/17/2007] [Indexed: 11/16/2022]
Abstract
N-isopropylacrylamide (NIPA) based uniform thermosensitive microgels were synthesized by dispersion polymerization by using relatively hydrophilic crosslinking agents with hydroxyl functionality. Glycerol dimethacrylate (GDMA), pentaerythritol triacrylate (PETA) and pentaerythritol propoxylate triacrylate (PEPTA) were used as crosslinking agents with different hydrophilicities. A protocol was first proposed to determine the crosslinking density distribution in the thermosensitive microgel particles by confocal laser scanning microscopy (CLSM). The microgels were fluorescently labeled by using hydroxyl group of the crosslinking agent. The CLSM observations performed with the microgels synthesized by three different crosslinking agents showed that the crosslinking density exhibited a quadratic decrease with the increasing radial distance in the spherical microgel particles. This structure led to the formation of more loose gel structure on the particle surface with respect to the center. Then the use of hydrophilic crosslinking agents in the dispersion polymerization of NIPA made possible the synthesis of thermosensitive microgels carrying long, flexible and chemically derivatizable (i.e., hydroxyl functionalized) fringes on the surface by a single-stage dispersion polymerization. The microgels with all crosslinking agents exhibited volume phase transition with the increasing temperature. The microgel obtained by the most hydrophilic crosslinking agent, GDMA exhibited higher hydrodynamic diameters in the fully swollen form at low temperatures than those obtained by PETA and PEPTA. Higher hydrodynamic size decrease from fully swollen form to the fully shrunken form was also observed with the same microgel.
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Affiliation(s)
- Begum Elmas
- Hacettepe University, Department of Chemistry, Ankara, Turkey
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45
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Khan A. Preparation and characterization of N-isopropylacrylamide/acrylic acid copolymer core–shell microgel particles. J Colloid Interface Sci 2007; 313:697-704. [PMID: 17561067 DOI: 10.1016/j.jcis.2007.05.027] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2006] [Revised: 04/30/2007] [Accepted: 05/04/2007] [Indexed: 11/22/2022]
Abstract
A new method has been developed to prepare smart copolymer microgels that consist of well defined temperature sensitive cores and pH sensitive shells. The microgels were obtained from N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc), containing different mole ratios of AAc. Transmission electron micrographs of the microgels show that the colloidal copolymers are nearly monodisperse spheres (core-shell structures). The lower critical solution temperatures (LCSTs) (or phase separation temperatures) of the aqueous microgel solutions were measured by cloud-point method. At slight acidic conditions, the LCST decreased with increase in AAc content, which suggests that the hydrophobic group of NIPAAm has a greater influence on the LCST than the polar COOH group at those conditions. An increase of pH value leads to a significant increase in LCST due to the formation of a more hydrophilic copolymer. The LCST were studied as a function of copolymer composition over the pH range from 4.0 to 6.5. Because the pK(a) of the polymers can be tuned to fall close to neutral pH, these polymer compositions can be dispersed to have phase transitions triggered near physiological pH or at slight acidic pH values that fall within acidic gradients found in biology. Because of their stimuli-responsive behavior, these nanoscale materials are excellent candidates for biotechnology and biomedical applications where small changes in pH or temperature are of great consequence.
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Affiliation(s)
- Aslam Khan
- Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781 039, India.
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46
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Hoare T, Pelton R. Calorimetric Analysis of Thermal Phase Transitions in Functionalized Microgels. J Phys Chem B 2007; 111:1334-42. [PMID: 17253739 DOI: 10.1021/jp066916v] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Differential scanning calorimetry (DSC) is used to investigate the thermal phase transitions of a range of N-isopropylacrylamide (NIPAM)-based, carboxylic acid-functionalized microgels with well-defined radial and chain functional group distributions. The transition enthalpies of protonated microgels can be correlated with the hydrophobicity of the functional comonomer, while the transition enthalpies for ionized microgels can be correlated with the degree of microgel deswelling achieved across the thermal phase transition. The peak widths at half-height vary inversely with the average length of NIPAM blocks in each of the microgels, as calculated using a kinetic copolymerization model. Deconvolution of the asymmetric DSC thermograms is accomplished using a two-transition model, thought to relate to core-shell-type transitions induced by the significant local heterogeneities within the functionalized microgels. The ratio between the two transition temperatures of these deconvoluted peaks is a useful quantitative probe of the radial functional group distribution. An additional, low-temperature transition is also observed in the thermogram of the vinylacetic acid-functionalized microgel, indicative of the occurrence of local chain rearrangements prior to the macroscopic phase transition in this microgel. Complementary light scattering analysis suggests that microphase separation may account for this additional transition peak.
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Affiliation(s)
- Todd Hoare
- Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7.
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Höfl S, Zitzler L, Hellweg T, Herminghaus S, Mugele F. Volume phase transition of “smart” microgels in bulk solution and adsorbed at an interface: A combined AFM, dynamic light, and small angle neutron scattering study. POLYMER 2007. [DOI: 10.1016/j.polymer.2006.10.026] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Hoare T, McLean D. Kinetic Prediction of Functional Group Distributions in Thermosensitive Microgels. J Phys Chem B 2006; 110:20327-36. [PMID: 17034214 DOI: 10.1021/jp0643451] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A kinetic model accounting for the copolymerization of up to four comonomers is applied to predict both chain and radial functional group distributions in carboxylic-acid-functionalized poly(N-isopropylacrylamide) (NIPAM)-based microgels. The model can accurately predict the experimentally observed radial distributions of functional monomers in microgels prepared using a variety of different carboxylic-acid-functionalized monomers with significantly different hydrophobicities, copolymerization kinetics, and reactivities, without requiring the use of adjustable parameters. Multimodal distributions can both be predicted and experimentally generated by copolymerizing two -COOH-containing monomers with widely different reactivities. Chain distributions and monomer block formation can also be probed using the kinetic model, allowing for qualitative predictions of the potentiometric titration behavior of the microgels. The kinetic model reported herein therefore provides the first available analytical method for semiquantitatively predicting and controlling functional group distributions in bulk-polymerized microgel systems.
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Affiliation(s)
- Todd Hoare
- Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L7, Canada.
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Ma X, Tang X. Flocculation behavior of temperature-sensitive poly(N-isopropylacrylamide) microgels containing polar side chains with OH groups. J Colloid Interface Sci 2006; 299:217-24. [PMID: 16500668 DOI: 10.1016/j.jcis.2006.01.036] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2005] [Revised: 01/16/2006] [Accepted: 01/18/2006] [Indexed: 11/17/2022]
Abstract
The flocculation behavior of poly(N-isopropylacrylamide) (pNIPAM) microgels containing polar -(OCH(2)CH(2))(3)OH chains, incorporated by the copolymeric components (triethyleneglycol methacrylate, TREGMA), in aqueous NaCl solution was investigated. Determination of the critical flocculation temperatures (CFTs) and the critical flocculation concentrations (CFCs) of the microgels at 45 degrees C shows that polar -(OCH(2)CH(2))(3)OH chains have different influence on the flocculation behavior of the microgels at temperatures below and above their volume phase transition temperatures (VPTTs). The flocculation of the microgels becomes more difficult with the increase of -(OCH(2)CH(2))(3)OH chains below the VPTT. In contrast, the microgels flocculate more easily with more -(OCH(2)CH(2))(3)OH chains above the VPTT. Preliminary investigation on the flocculation kinetics of the microgels further shows that -(OCH(2)CH(2))(3)OH chains have different effects on the flocculation rate at temperatures below and above the VPTT. The flocculating rate of the microgels at 25 degrees C decreases with the increase of -(OCH(2)CH(2))(3)OH chains. While the flocculation rate at 45 degrees C increases with the increase of -(OCH(2)CH(2))(3)OH chains due to their enrichment on the surface of the microgels as a result of the temperature-induced volume-phase transition, which was verified by variable temperature (1)H NMR spectroscopy. The polar -(OCH(2)CH(2))(3)OH chains rich in the surface increase the attractive force between the microgels, promoting the flocculation.
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Affiliation(s)
- Xiaomei Ma
- School of Chemical Engineering, Qingdao University, Qingdao 266071, PR China.
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Ma X, Xing Y. The preparation and characterization of co-polymer microgels with transition temperature at or near physiological values. Polym Bull (Berl) 2006. [DOI: 10.1007/s00289-006-0548-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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