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Brunchi CE, Morariu S. Laponite ®-From Dispersion to Gel-Structure, Properties, and Applications. Molecules 2024; 29:2823. [PMID: 38930887 PMCID: PMC11206873 DOI: 10.3390/molecules29122823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Revised: 06/05/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024] Open
Abstract
Laponite® (LAP) is an intensively studied synthetic clay due to the versatility given by its layered structure, which makes it usable in various applications. This review describes the multifaceted properties and applications of LAP in aqueous dispersions and gel systems. The first sections of the review discuss the LAP structure and the interactions between clay discs in an aqueous medium under different conditions (such as ionic strength, pH, temperature, and the addition of polymers) in order to understand the function of clay in tailoring the properties of the designed material. Additionally, the review explores the aging phenomenon characteristic of LAP aqueous dispersions as well as the development of shake-gels by incorporating LAP. The second part shows the most recent studies on materials containing LAP with possible applicability in the drilling industry, cosmetics or care products industry, and biomedical fields. By elucidating the remarkable versatility and ease of integration of LAP into various matrices, this review underscores its significance as a key ingredient for the creation of next-generation materials with tailored functionalities.
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Affiliation(s)
| | - Simona Morariu
- “Petru Poni” Institute of Macromolecular Chemistry, Grigore Ghica Voda Alley 41A, 700487 Iasi, Romania;
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2
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Hill EH. Investigating Solvent-Induced Aggregation in Edge-Functionalized Layered Silicates via All-Atom Molecular Dynamics Simulations. J Phys Chem B 2023; 127:8066-8073. [PMID: 37672482 DOI: 10.1021/acs.jpcb.3c04432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/08/2023]
Abstract
Molecular dynamics simulations can provide the means to visualize and understand the role of intermolecular interactions in the mechanisms involved in molecular aggregation. Along these lines, simulations can allow the study of how surface chemical modifications can influence nanomaterial assembly at the molecular level. Layered silicate clays have been of significant interest for some time, particularly with regard to their use in organic/inorganic nanocomposites. However, despite numerous reports on the covalent linkage of organic moieties via silanol condensation, the theoretical understanding of these systems has heretofore been limited to noncovalent interactions, specifically ionic interactions at the charged basal surfaces. Herein, a model for edge-functionalized layered aluminosilicate clay, based on the siloxane linkage, is presented. In addition to reproducing experimentally observed degrees of molecular aggregation of clay-linked perylene diimide derivatives with different terminal functional groups as a function of solvent composition, a molecular-level understanding of the role of van der Waals interactions and hydrogen bonding of the different end-groups on the aggregation state in different water/N,N-dimethylformamide mixtures is obtained. The reported model provides a means to simulate organic moieties covalently bound to the layered silicate edge, which will enable future simulations of nanocomposites and organic/inorganic hybrids based on this system.
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Affiliation(s)
- Eric H Hill
- Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, Hamburg 20146, Germany
- The Hamburg Center for Ultrafast Imaging (CUI), Luruper Chausee 149, Hamburg 22761, Germany
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Bednarz S, Bujok S, Mielczarek K, Świergosz T, Wierzbicki S, Konefał R, Konefał M, Nevoralová M, Pavlova E, Beneš H. Synthesis of low-molecular weight itaconic acid polymers as nanoclay dispersants and dispersion stabilizers. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.125614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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4
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Brunier B, Chevalier Y, Bourgeat‐Lami E, Sheibat‐Othman N. Modeling polystyrene homogeneous‐coagulative nucleation in Pickering emulsion polymerization. MACROMOL REACT ENG 2022. [DOI: 10.1002/mren.202200016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Barthélémy Brunier
- Université de Lyon Université Claude Bernard Lyon 1 CNRS LAGEPP UMR 5007 Villeurbanne 69616 France
| | - Yves Chevalier
- Université de Lyon Université Claude Bernard Lyon 1 CNRS LAGEPP UMR 5007 Villeurbanne 69616 France
| | - Elodie Bourgeat‐Lami
- Université de Lyon Université Claude Bernard Lyon 1 CPE Lyon CNRS CP2M UMR 5128 Villeurbanne 69616 France
| | - Nida Sheibat‐Othman
- Université de Lyon Université Claude Bernard Lyon 1 CNRS LAGEPP UMR 5007 Villeurbanne 69616 France
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Bujok S, Konefał M, Konefał R, Nevoralová M, Bednarz S, Mielczarek K, Beneš H. Insight into the aqueous Laponite® nanodispersions for self-assembled poly(itaconic acid) nanocomposite hydrogels: The effect of multivalent phosphate dispersants. J Colloid Interface Sci 2021; 610:1-12. [PMID: 34922067 DOI: 10.1016/j.jcis.2021.12.055] [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: 05/20/2021] [Revised: 08/31/2021] [Accepted: 12/08/2021] [Indexed: 10/19/2022]
Abstract
HYPOTHESIS We hypothesize, that physical network between Laponite® nanoparticles and high molecular weight polyelectrolyte formed by mixing of Laponite® nanodispersion (containing multivalent phosphate dispersant) and polyelectrolyte solution is strongly influenced by the type and content of dispersant, which forms electric double layer (EDL) closely to the Laponite® edges. Thus, optimum dispersant concentration is necessary to overcome clay-clay interactions (excellent clay delamination), but should not be exceeded, what would result in the EDL compression and weakening of attractions forming clay-polyelectrolyte network. Thus, deeper investigation of Laponite® nanodispersions is highly demanded since it would enable to better design the self-assembled clay-polyelectrolyte hydrogels. EXPERIMENTS To study clay interparticle interactions in the presence of various multivalent phosphates, complementary methods providing wide nanodispersion characterization have been applied: zeta potential measurement and SAXS technique (electrostatic interactions), oscillatory rheology (nanodispersion physical state) and NMR experiments (ion immobilization degree). FINDINGS It was found that multivalent phosphates induce and tune strength of clay-polyelectrolyte interactions forming hydrogel network in terms of varying EDL on the Laponite® edges. Moreover, phosphate dispersing efficiency depends on the molecular size, chemical structure, and valence of the anion; its potential as efficient dispersant for hydrogel preparation can be evaluated by estimation of anion charge density.
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Affiliation(s)
- Sonia Bujok
- Institute of Macromolecular Chemistry, CAS, Heyrovského nám. 2, Prague 6 162 06, Czech Republic.
| | - Magdalena Konefał
- Institute of Macromolecular Chemistry, CAS, Heyrovského nám. 2, Prague 6 162 06, Czech Republic
| | - Rafał Konefał
- Institute of Macromolecular Chemistry, CAS, Heyrovského nám. 2, Prague 6 162 06, Czech Republic
| | - Martina Nevoralová
- Institute of Macromolecular Chemistry, CAS, Heyrovského nám. 2, Prague 6 162 06, Czech Republic
| | - Szczepan Bednarz
- Faculty of Chemical Engineering and Technology, Cracow University of Technology, Warszawska 24, Cracow 31-155, Poland
| | - Kacper Mielczarek
- Faculty of Chemical Engineering and Technology, Cracow University of Technology, Warszawska 24, Cracow 31-155, Poland
| | - Hynek Beneš
- Institute of Macromolecular Chemistry, CAS, Heyrovského nám. 2, Prague 6 162 06, Czech Republic
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6
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Bolze J, Gateshki M. Highly versatile laboratory X-ray scattering instrument enabling (nano-)material structure analysis on multiple length scales by covering a scattering vector range of almost five decades. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:123103. [PMID: 31893848 DOI: 10.1063/1.5130061] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 11/12/2019] [Indexed: 06/10/2023]
Abstract
A compact laboratory X-ray scattering platform that uniquely enables for high-performance ultra-small-angle X-ray scattering (USAXS), small- and wide-angle X-ray scattering (SAXS/WAXS), and total scattering (atomic pair distribution function analysis; PDF) experiments was developed. It covers Bragg spacings from sub-Angstroms to 1.7 μm, thus allowing the analysis of dimensions and complex structures in (nano-)materials on multiple length scales. The accessible scattering vector q-range spans over almost five decades (qmin = 0.0036 nm-1, qmax = 215 nm-1), without any gaps. Whereas SAXS is suitable to characterize materials on a length scale of 1-100 nm, with USAXS, this range can be significantly extended to the micrometer range. On the other end, from WAXS and particularly from PDF measurements, information about the local atomic order and disorder can be obtained. The high performance, exceptional versatility, and ease-of-use of the instrument are enabled by a high-resolution 2-circle goniometer with kinematic mounts, a modular concept based on prealigned, quickly interchangeable X-ray components, and advanced detector technology. For USAXS measurements, a modified Bonse-Hart experimental setup with single crystal collimator and analyzer optics is used. SAXS/WAXS measurements are enabled by focusing optics, an evacuated beam path, and a 2D detector. For total scattering experiments, a high-energy X-ray source is used in combination with a hybrid pixel array detector that is based on a CdTe sensor for the highest counting efficiency. To ensure high resolution and sensitivity in these various applications, special care is taken to suppress any type of background scattering signal. The high resolution that can be achieved with the USAXS collimation system is demonstrated on a set of monodisperse, colloidal silica dispersions and derived colloidal crystals, with particle diameters in the range of hundreds of nanometers up to 1.6 µm. USAXS and SAXS results are shown to be consistent with those obtained by static light scattering (SLS) and dynamic light scattering. It is demonstrated that the obtainable USAXS data bridge the gap in q between SAXS and SLS. The capabilities of the instrument to acquire high-quality total scattering data for PDF analysis are demonstrated on amorphous SiO2 nanoparticles as well as on NaYF4 upconversion nanocrystals. To the best of our knowledge, it is for the first time that we present a single laboratory instrument that enables measurements of high-quality X-ray scattering data within such a wide q-range, by combining four complementary elastic X-ray scattering techniques. The modular design concept of the instrument allows for incremental improvements as well as to add more applications in the future.
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Affiliation(s)
- Joerg Bolze
- Malvern Panalytical, Lelyweg 1, Almelo 7602 EA, The Netherlands
| | - Milen Gateshki
- Malvern Panalytical, Lelyweg 1, Almelo 7602 EA, The Netherlands
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Suman K, Joshi YM. Microstructure and Soft Glassy Dynamics of an Aqueous Laponite Dispersion. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:13079-13103. [PMID: 30180583 DOI: 10.1021/acs.langmuir.8b01830] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Synthetic hectorite clay Laponite RD/XLG is composed of disk-shaped nanoparticles that acquire dissimilar charges when suspended in an aqueous medium. Owing to their property to spontaneously self-assemble, Laponite is used as a rheology modifier in a variety of commercial water-based products. In particular, an aqueous dispersion of Laponite undergoes a liquid-to-solid transition at about 1 vol % concentration. The evolution of the physical properties as the dispersion transforms to the solid state is reminiscent of physical aging in molecular as well as colloidal glasses. The corresponding soft glassy dynamics of an aqueous Laponite dispersion, including the rheological behavior, has been extensively studied in the literature. In this feature article, we take an overview of recent advances in understanding soft glassy dynamics and various efforts taken to understand the peculiar rheological behavior. Furthermore, the continuously developing microstructure that is responsible for the eventual formation of a soft solid state that supports its own weight against gravity has also been a topic of intense debate and discussion. In particularly, extensive experimental and theoretical studies lead to two types of microstructures for this system: an attractive gel-like or a repulsive glass-like structure. We carefully examine and critically analyze the literature and propose a state (phase) diagram that suggests an aqueous Laponite dispersion to be present in an attractive gel state.
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Affiliation(s)
- Khushboo Suman
- Department of Chemical Engineering , Indian Institute of Technology Kanpur , India
| | - Yogesh M Joshi
- Department of Chemical Engineering , Indian Institute of Technology Kanpur , India
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8
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Heinemann T, Klapp SHL. Coarse-graining strategy for molecular pair interactions: A reaction coordinate study for two- and three-dimensional systems. J Chem Phys 2017; 146:164107. [PMID: 28456203 DOI: 10.1063/1.4981207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We investigate and provide optimal sets of reaction coordinates for mixed pairs of molecules displaying polar, uniaxial, or spherical symmetry in two and three dimensions. These coordinates are non-redundant, i.e., they implicitly involve the molecules' symmetries. By tabulating pair interactions in these coordinates, resulting tables are thus minimal in length and require a minimal memory space. The intended fields of application are computer simulations of large ensembles of molecules or colloids with rather complex interactions in a fluid or liquid crystalline phase at low densities. Using effective interactions directly in the form of tables can help bridging the time and length scales without introducing errors stemming from any modeling procedure. Finally, we outline an exemplary computational methodology for gaining an effective pair potential in these coordinates, based on the Boltzmann inversion principle, by providing a step-by-step recipe.
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Affiliation(s)
- Thomas Heinemann
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
| | - Sabine H L Klapp
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
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9
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Mechanical, Swelling, and Structural Properties of Mechanically Tough Clay-Sodium Polyacrylate Blend Hydrogels. Gels 2017; 3:gels3010010. [PMID: 30920507 PMCID: PMC6318653 DOI: 10.3390/gels3010010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 02/13/2017] [Accepted: 02/20/2017] [Indexed: 11/17/2022] Open
Abstract
We investigated the mechanical, swelling, and structural properties of mechanically tough clay/sodium polyacrylate (PAAS) hydrogels prepared by simple mixing. The gels had large swelling ratios, reflecting the characteristics of the constituent polymer. The swelling ratios initially increased with the increase of the swelling time, and then attained maximum values. Afterwards, they decreased with an increase of the swelling time and finally became constant. An increase in the clay concentration lead to a decrease in the swelling ratios, whereas an increase in the PAAS concentration lead to an increase in the swelling ratios. Tensile measurements indicated that the toughness for clay/PAAS (Mw = 3.50 × 106) gels was several hundred times larger than that of clay/PAAS (Mw = 5.07 × 105) gels, i.e., the use of ultra-high molecular weight PAAS is essential for fabricating mechanically tough clay/PAAS blend hydrogels. Synchrotron small-angle X-ray scattering (SAXS) results showed that the SAXS intensity measured at small scattering angles decreased with an increase in the clay concentration, indicating that the interparticle interactions were more repulsive at higher concentrations. The decrease of the scattering intensity at high clay concentrations was larger for the clay/PAAS (Mw = 5.07 × 105) gel system than for the clay/PAAS (Mw = 3.50 × 106) gel system.
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10
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Kensbock P, Demco DE, Singh S, Rahimi K, Fechete R, Walther A, Schmidt AM, Möller M. Peptizing Mechanism at the Molecular Level of Laponite Nanoclay Gels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:66-74. [PMID: 27936777 DOI: 10.1021/acs.langmuir.6b03592] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In the presence of additives such as etidronic acid (1-hydroxyethane-1,1-diphosphonic acid, HEDP), a process of peptizing of Laponite clay gels takes place. The peptizing process at the molecular level was directly revealed by 31P and 1H high-resolution magic-angle sample spinning (HRMAS) NMR spectroscopy. Two NMR spectral components were detected and assigned to free etidronic acid and bound to the Laponite disk edges. Furthermore, with increase of temperature the ratio of bound-to-free etidronic acid increases. This thermal activation process could be explained by the increase in electrical polarization of the hydroxyl group at the edges and by the exfoliation of the tactoids that leads to more access to the additive molecules to the electrical charges of platelet edges. 31P HRNMR spectroscopy on sodium fluorohectorite with an aspect ratio of ∼750 shows a reduction of the bound etidronic acid molecules. Transmission electron microscopy (TEM), field-emission scanning microscopy (FESEM), UV-vis spectrophotometry, dynamic light scattering (DLS), and zeta potential results support the proposed peptizing mechanisms.
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Affiliation(s)
- Philip Kensbock
- DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University , Forckenbeckstraße 50, D-52074 Aachen, Germany
| | - Dan Eugen Demco
- DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University , Forckenbeckstraße 50, D-52074 Aachen, Germany
- Institute of Physical Chemistry, University of Köln , Luxemburger Str. 116, D-50939 Köln, Germany
| | - Smriti Singh
- DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University , Forckenbeckstraße 50, D-52074 Aachen, Germany
| | - Khosrow Rahimi
- DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University , Forckenbeckstraße 50, D-52074 Aachen, Germany
| | - Radu Fechete
- Department of Physics and Chemistry, Technical University of Cluj-Napoca , 25 G. Baritiu Str., RO-400027, Cluj-Napoca, Romania
| | - Andreas Walther
- DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University , Forckenbeckstraße 50, D-52074 Aachen, Germany
| | - Annette Monika Schmidt
- Institute of Physical Chemistry, University of Köln , Luxemburger Str. 116, D-50939 Köln, Germany
| | - Martin Möller
- DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University , Forckenbeckstraße 50, D-52074 Aachen, Germany
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11
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Jabbari-Farouji S, Weis JJ, Davidson P, Levitz P, Trizac E. Interplay of anisotropy in shape and interactions in charged platelet suspensions. J Chem Phys 2015; 141:224510. [PMID: 25494763 DOI: 10.1063/1.4903045] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Motivated by the intriguing phase behavior of charged colloidal platelets, we investigate the structure and dynamics of charged repulsive disks by means of Monte Carlo simulations. The electrostatic interactions are taken into account through an effective two-body potential, obtained within the nonlinear Poisson-Boltzmann formalism, which has the form of anisotropic screened Coulomb potential. Recently, we showed that the original intrinsic anisotropy of the electrostatic potential in competition with excluded volume effects leads to a rich phase behavior that not only includes various liquid-crystalline phases but also predicts the existence of novel structures composed of alternating nematic-antinematic sheets. Here, we examine the structural and dynamical signatures of each of the observed structures for both translational and rotational degrees of freedom. Finally, we discuss the influence of effective charge value and our results in relation to experimental findings on charged platelet suspensions.
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Affiliation(s)
- Sara Jabbari-Farouji
- LPTMS, CNRS and Université Paris-Sud, UMR8626, Bat. 100, 91405 Orsay, France and Laboratoire Interdisciplinaire de Physique, UMR 5588, F-38041 Grenoble, France
| | - Jean-Jacques Weis
- Laboratoire de Physique Théorique, Université Paris-Sud, UMR 8627 Bâtiment 210, 91405 Orsay Cedex, France
| | - Patrick Davidson
- Laboratoire de Physique des Solides, Université Paris-Sud, UMR 8502 Bâtiment 510, 91405 Orsay Cedex, France
| | - Pierre Levitz
- Laboratoire PECSA, UMR 7195, Université Pierre et Marie Curie, Case Courrier 51, 4 place Jussieu, 72522 Paris Cedex 5, France
| | - Emmanuel Trizac
- LPTMS, CNRS and Université Paris-Sud, UMR8626, Bat. 100, 91405 Orsay, France
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12
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Stöter M, Biersack B, Rosenfeldt S, Leitl MJ, Kalo H, Schobert R, Yersin H, Ozin GA, Förster S, Breu J. Encapsulation of Functional Organic Compounds in Nanoglass for Optically Anisotropic Coatings. Angew Chem Int Ed Engl 2015; 54:4963-7. [DOI: 10.1002/anie.201411137] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Indexed: 11/09/2022]
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13
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Stöter M, Biersack B, Rosenfeldt S, Leitl MJ, Kalo H, Schobert R, Yersin H, Ozin GA, Förster S, Breu J. Nanoglas-Verkapselung funktionaler organischer Verbindungen für optisch anisotrope Beschichtungen. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201411137] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Heinemann T, Palczynski K, Dzubiella J, Klapp SHL. Angle-resolved effective potentials for disk-shaped molecules. J Chem Phys 2014; 141:214110. [DOI: 10.1063/1.4902824] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Affiliation(s)
- Thomas Heinemann
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
| | - Karol Palczynski
- Institut für Physik, Humboldt Universität zu Berlin, Newtonstraße 15, 12489 Berlin, Germany
- Helmholtz Zentrum Berlin (HZB), Institute of Soft Matter and Functional Materials, Hahn-Meitner Platz 1, 14109 Berlin, Germany
| | - Joachim Dzubiella
- Institut für Physik, Humboldt Universität zu Berlin, Newtonstraße 15, 12489 Berlin, Germany
- Helmholtz Zentrum Berlin (HZB), Institute of Soft Matter and Functional Materials, Hahn-Meitner Platz 1, 14109 Berlin, Germany
| | - Sabine H. L. Klapp
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
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15
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Tudisca V, Bruni F, Scoppola E, Angelini R, Ruzicka B, Zulian L, Soper AK, Ricci MA. Neutron diffraction study of aqueous Laponite suspensions at the NIMROD diffractometer. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:032301. [PMID: 25314440 DOI: 10.1103/physreve.90.032301] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Indexed: 06/04/2023]
Abstract
The process of dynamical arrest, leading to formation of different arrested states such as glasses and gels, along with the closely related process of aging, is central for both basic research and technology. Here we report on a study of the time-dependent structural evolution of two aqueous Laponite clay suspensions at different weight concentrations. Neutron diffraction experiments have been performed with the near and intermediate range order diffractometer (NIMROD) that allows studies of the structure of liquids and disordered materials over a continuous length scale ranging from 1 to 300 Å, i.e., from the atomistic to the mesoscopic scales. NIMROD is presently a unique diffractometer, bridging the length scales traditionally investigated by small angle neutron scattering or small angle x-ray scattering with that accessible by traditional diffractometers for liquids. Interestingly, we have unveiled a signature of aging of both suspensions in the length scale region of NIMROD. This phenomenon, ascribed to sporadic contacts between Laponite platelets at long times, has been observed with the sample arrested as gel or as repulsive glass. Moreover, water molecules within the layers closest to Laponite platelets surface show orientational and translational order, which maps into the crystalline structure of Laponite.
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Affiliation(s)
- V Tudisca
- Dipartimento di Scienze, Università degli Studi "Roma Tre", Via della Vasca Navale 84, 00146 Roma, Italy
| | - F Bruni
- Dipartimento di Scienze, Università degli Studi "Roma Tre", Via della Vasca Navale 84, 00146 Roma, Italy
| | - E Scoppola
- Dipartimento di Scienze, Università degli Studi "Roma Tre", Via della Vasca Navale 84, 00146 Roma, Italy
| | - R Angelini
- IPCF-CNR and Dipartimento di Fisica, Università di Roma "La Sapienza", Piazzale A. Moro 2, I-00185, Rome, Italy
| | - B Ruzicka
- IPCF-CNR and Dipartimento di Fisica, Università di Roma "La Sapienza", Piazzale A. Moro 2, I-00185, Rome, Italy
| | - L Zulian
- Dipartimento di Scienza dei Materiali, Università degli Studi Milano Bicocca, Via Roberto Cozzi, 53 20125 Milano, Italy
| | - A K Soper
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - M A Ricci
- Dipartimento di Scienze, Università degli Studi "Roma Tre", Via della Vasca Navale 84, 00146 Roma, Italy
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16
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Abstract
Abstract
The influence of dilute impurities on the structure of a fluid solvent is investigated theoretically. General arguments, which do not rely on particular models, are used to derive an extension of the Ornstein–Zernike form for the solvent structure factor at small scattering vectors. It is shown that dilute impurities can influence the solvent structure only if they are composed of ions with significantly different sizes. Non-ionic impurities or ions of similar size are shown to not alter the solvent structure qualitatively. This picture is compatible with available experimental data. The derived form of the solvent structure factor is expected to be useful to infer information on the impurity-solvent interactions form measured scattering intensities.
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Affiliation(s)
- Markus Bier
- Max-Planck-Institut für Intelligente Systeme, Stuttgart, Deutschland
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17
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Henzler K, Haupt B, Rosenfeldt S, Harnau L, Narayanan T, Ballauff M. Interaction strength between proteins and polyelectrolyte brushes: a small angle X-ray scattering study. Phys Chem Chem Phys 2011; 13:17599-605. [PMID: 21892474 DOI: 10.1039/c1cp20663j] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present an investigation of β-lactoglobulin adsorption onto spherical polyelectrolyte brushes (SPBs) by small angle X-ray scattering (SAXS). The SPB consists of a polystyrene core onto which long chains of poly(styrene sulfonate) are grafted. The amount and the distribution of proteins adsorbed in the brush layer at low ionic strength can be derived from SAXS. The analysis of the SAXS data reveals additionally that some of the protein molecules form aggregates of about six monomers in the adsorbed state. Furthermore, the position and the amount of slightly bound protein can be detected by the combination of the SAXS results and the SPB loading after extensive ultrafiltration. The total amount of adsorbed protein is compared to data derived from isothermal titration calorimetry. The comparison of both sets of data demonstrates that the protein molecules in the inner layers of the spherical polyelectrolyte brush are firmly bound. Proteins located in the outer layers are only weakly bound and can be washed out by prolonged ultrafiltration.
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Affiliation(s)
- Katja Henzler
- Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
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Takeda M, Matsunaga T, Nishida T, Endo H, Takahashi T, Shibayama M. Rheo-SANS Studies on Shear Thickening in Clay−Poly(ethylene oxide) Mixed Solutions. Macromolecules 2010. [DOI: 10.1021/ma101319j] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Makiko Takeda
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Takuro Matsunaga
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Toshihiko Nishida
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Hitoshi Endo
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Tsutomu Takahashi
- Department of Mechanical Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan
| | - Mitsuhiro Shibayama
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
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19
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Shahin A, Joshi YM. Irreversible aging dynamics and generic phase behavior of aqueous suspensions of Laponite. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:4219-4225. [PMID: 20099829 DOI: 10.1021/la9032749] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We study the aging behavior of aqueous suspension of Laponite having 2.8 wt % concentration using rheological tools. At various salt concentration all the samples demonstrate orientational order when observed using crossed polarizers. In rheological experiments we observe inherent irreversibility in the aging dynamics which forces the system not to rejuvenate to the same state in the shear melting experiment carried out at a later date since preparation. The extensive rheological experiments carried out as a function of time elapsed since preparation demonstrate the self-similar trend in the aging behavior irrespective of the concentration of salt. We observe that the exploration of the low-energy states as a function of aging time is only kinetically affected by the presence of salt. We estimate that the energy barrier to attain the low-energy states decreases linearly with increase in the concentration of salt. The observed superposition of all the elapsed time and the salt-concentration-dependent data suggests that the aging that occurs in low salt concentration systems over a very long period is qualitatively similar to the aging behavior observed in systems with high salt concentration over a shorter period.
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Affiliation(s)
- A Shahin
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
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20
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Lei S, Ver Heyen A, De Feyter S, Surin M, Lazzaroni R, Rosenfeldt S, Ballauff M, Lindner P, Mössinger D, Höger S. Two-dimensional oligo(phenylene-ethynylene-butadiynylene)s: all-covalent nanoscale spoked wheels. Chemistry 2009; 15:2518-35. [PMID: 19191234 DOI: 10.1002/chem.200801939] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Round and round: Covalently bound spokes induce an efficient template-directed cyclization towards a rigid molecular wheel (see figure) and afford dramatically increased shape-persistence properties compared with non-strutted macrocycles.The synthesis and characterization of a shape-persistent two-dimensional (2D) organic compound is described in detail. In a rational modular synthesis of a dodecaacetylene precursor and its subsequent template-aided cyclization, we obtained a molecularly defined, stable, C(6)-symmetric, rigid, spoked wheel. Peripheral tert-butyl groups and alkyl chains attached to the plane of the molecule provide sufficient solubility, so that the 2D oligomer can be fully characterized by MALDI-MS, GPC, and (1)H NMR, UV/Vis absorption, and fluorescence spectroscopy. Molecular mechanics and dynamics simulations indicate that the most stable conformer of the molecule in vacuum is a shallow boat conformation with a small dihedral angle. Comparisons with the precursor as well as a ring-only structure clearly reveal the high rigidity of the title compound. Small-angle neutron scattering (SANS) experiments in [D(8)]THF and CDCl(3) affirm the rigid backbone structure in solution, that is, a radius of about 2.7 nm and a thickness of about 0.22 nm. STM investigations illustrate that the wheel molecules adsorb with their molecular plane parallel to the surface and can form hexagonal crystalline domains (unit cell parameters are a=b=6.0+/-0.2 nm and theta=60+/-2 degrees ), with the tert-butyl groups on the apexes staggered. Such staggering induces chirality in the organized domains. AFM investigations demonstrate that the wheel molecules inside overlayers organize in the same way as in the layer directly in contact with the surface. This indicates an epitaxial growth characteristic of the film.
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Affiliation(s)
- Shengbin Lei
- Department of Chemistry, Laboratory of Photochemistry and Spectroscopy, and Institute for Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200-F, 3001 Leuven, Belgium
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21
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Joshi YM. Modeling Dependence of Creep Recovery Behavior on Relaxation Time Distribution of Aging Colloidal Suspensions. Ind Eng Chem Res 2009. [DOI: 10.1021/ie801894z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yogesh M. Joshi
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
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22
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Bolisetty S, Rosenfeldt S, Rochette CN, Harnau L, Lindner P, Xu Y, Müller AHE, Ballauff M. Interaction of cylindrical polymer brushes in dilute and semi-dilute solution. Colloid Polym Sci 2008; 287:129-138. [PMID: 19816531 PMCID: PMC2755784 DOI: 10.1007/s00396-008-1962-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 10/24/2008] [Accepted: 10/29/2008] [Indexed: 10/29/2022]
Abstract
We present a systematic study of flexible cylindrical brush-shaped macromolecules in a good solvent by small-angle neutron scattering (SANS), static light scattering (SLS), and by dynamic light scattering (DLS) in dilute and semi-dilute solution. The SLS and SANS data extrapolated to infinite dilution lead to the shape of the polymer that can be modeled in terms of a worm-like chain with a contour length of 380 nm and a persistence length of 17.5 nm. SANS data taken at higher polymer concentration were evaluated by using the polymer reference interaction site model (PRISM). We find that the persistence length reduce from 17.5 nm at infinite dilution to 5.3 nm at the highest concentration (volume fraction 0.038). This is comparable with the decrease of the persistence length in semi-dilute concentration predicted theoretically for polyelectrolytes. This finding reveals a softening of stiffness of the polymer brushes caused by their mutual interaction.
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23
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Seydel T, Wiegart L, Juranyi F, Struth B, Schober H. Unaffected microscopic dynamics of macroscopically arrested water in dilute clay gels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:061403. [PMID: 19256837 DOI: 10.1103/physreve.78.061403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Indexed: 05/27/2023]
Abstract
Adequate clay minerals considerably affect the macroscopic mechanical behavior of water even at concentrations of a few percent. Thus when 2 wt. % laponite clay mineral nanoparticles are added to water, the resulting colloidal suspension after some time takes on the semisolid characteristics of a jellylike material at room temperature. Cold neutron time-of-flight spectroscopy data are in agreement with the assumption that notwithstanding this macroscopic change, the mobility of the water molecules on intermolecular and intramolecular length scales remains largely unaffected. This observation is discussed in the context of the properties and the role of water in different more or less dilute ionic environments. The result contributes to the ongoing debate of the properties and role of water in living cells.
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Affiliation(s)
- Tilo Seydel
- Institut Max von Laue-Paul Langevin, Boîte Postale 156, F-38042 Grenoble Cedex 9, France.
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24
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Jabbari-Farouji S, Tanaka H, Wegdam GH, Bonn D. Multiple nonergodic disordered states in Laponite suspensions: a phase diagram. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:061405. [PMID: 19256839 DOI: 10.1103/physreve.78.061405] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 09/22/2008] [Indexed: 05/27/2023]
Abstract
We study the time evolution of different Laponite suspensions from a low-viscosity ergodic state to a viscoelastic nonergodic state over a wide range of volume fractions and salt contents. We find that the evolution of nonergodicity parameter (Debye-Waller factor) splits into two branches for all the samples, which correspond to two distinct dynamically arrested states. At moderately high salt concentrations, on the other hand, a third nonergodic state appears that is different from the above two nonergodic states. Measurement of the conductivity of Laponite solutions in pure water shows that the contribution of counterions in the ionic strength is considerable and their role should be taken into account in interpretations of aging dynamics and the phase diagram. Based on these data and available data in the literature, we propose a (nonequilibrium) phase diagram for Laponite suspensions.
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Affiliation(s)
- S Jabbari-Farouji
- Van der Waals-Zeeman Institute, University of Amsterdam, 1018XE Amsterdam, The Netherlands
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25
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26
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Whitby CP, Fornasiero D, Ralston J. Effect of oil soluble surfactant in emulsions stabilised by clay particles. J Colloid Interface Sci 2008; 323:410-9. [DOI: 10.1016/j.jcis.2008.04.038] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Revised: 04/17/2008] [Accepted: 04/18/2008] [Indexed: 10/22/2022]
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27
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Affiliation(s)
- Sujata Tarafdar
- Condensed Matter Physics Research Centre, Physics Department, Jadavpur University, Kolkata 700032, India
| | - Suparna Sinha
- Condensed Matter Physics Research Centre, Physics Department, Jadavpur University, Kolkata 700032, India
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28
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Toomey R, Tirrell M. Functional Polymer Brushes in Aqueous Media from Self-Assembled and Surface-Initiated Polymers. Annu Rev Phys Chem 2008; 59:493-517. [DOI: 10.1146/annurev.physchem.59.032607.093623] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ryan Toomey
- Department of Chemical Engineering, University of South Florida, Tampa, Florida 33620;
| | - Matthew Tirrell
- Department of Chemical Engineering and the Materials Research Laboratory, University of California, Santa Barbara, California 93106;
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29
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Ruzicka B, Zulian L, Angelini R, Sztucki M, Moussaïd A, Ruocco G. Arrested state of clay-water suspensions: gel or glass? PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:020402. [PMID: 18351973 DOI: 10.1103/physreve.77.020402] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Revised: 01/09/2008] [Indexed: 05/26/2023]
Abstract
The aging of a charged colloidal system has been studied by small-angle x-ray scattering, in the exchanged momentum range Q=0.03-5 nm(-1) , and by dynamic light scattering, at different clay concentrations (C(w)=0.6-2.8%) . The static structure factor S(Q) has been determined as a function of both aging time and concentration. This is the direct experimental evidence of the existence and evolution with aging time of two different arrested states in a single system simply obtained only by changing its volume fraction: an inhomogeneous state is reached at low concentrations, while a homogeneous one is found at high concentrations.
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Affiliation(s)
- B Ruzicka
- SOFT INFM-CNR and Dipartimento di Fisica, Università di Roma La Sapienza, Rome, Italy
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30
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Kätzel U, Richter T, Stintz M, Barthel H, Gottschalk-Gaudig T. Phase transitions of pyrogenic silica suspensions: a comparison to model laponite. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:031402. [PMID: 17930242 DOI: 10.1103/physreve.76.031402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2006] [Revised: 06/18/2007] [Indexed: 05/25/2023]
Abstract
Pyrogenic silica is often used as a thickening agent in paints, pastes, adhesives, or resins. Other applications include, e.g., abrasives in chemical mechanical planarization in the microelectronics industry. In all these applications it is essential to control the state of dispersion. Sometimes, phase transitions from the liquid to the solid state are required while in other cases they have to be completely avoided for the whole shelf life. The nature and influencing parameters of the fluid-solid transition for pyrogenic silica have not been investigated so far. Most investigations deal with the phase transitions of small clay particles such as laponite. Here, we dedicate our interest to the behavior of pyrogenic silica suspensions with varying specific surface area and ionic background concentration. To get an impression of the phase transition behavior we compare our results to model laponite suspensions. We apply dynamic light scattering measurements in the backscattering regime to minimize multiple scattering contributions from concentrated pyrogenic silica suspensions. Further on we exert a decomposition of the measured autocorrelation functions into an ergodic and nonergodic contribution. The analysis of the ergodic spectrum yields two different gelation kinetics for both systems, laponite and pyrogenic silica. For laponite these are in accordance with earlier investigations. The kinetics depend on the ionic background and the solids content of the suspensions. Additionally, we used dynamic extinction spectroscopy to follow the phase transitions of pyrogenic silica on a macroscale.
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Affiliation(s)
- Uwe Kätzel
- Research Group Mechanical Process Engineering, Institute of Process Engineering and Environmental Technology, TU Dresden, D-01062 Dresden, Germany
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31
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Bier M, van Roij R. Relaxation dynamics in fluids of platelike colloidal particles. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:021405. [PMID: 17930037 DOI: 10.1103/physreve.76.021405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Revised: 06/08/2007] [Indexed: 05/25/2023]
Abstract
The relaxation dynamics of a model fluid of platelike colloidal particles is investigated by means of a phenomenological dynamic density functional theory. The model fluid approximates the particles within the Zwanzig model of restricted orientations. The driving force for time dependence is expressed completely by gradients of the local chemical potential, which in turn is derived from a density functional-hydrodynamic interactions are not taken into account. These approximations are expected to lead to qualitatively reliable results for low densities like those within the isotropic-nematic two-phase region. The formalism is applied to model an initially spatially homogeneous stable or metastable isotropic fluid which is perturbed by switching a two-dimensional array of Gaussian laser beams. Switching on the laser beams leads to an accumulation of colloidal particles in the beam centers. If the initial chemical potential and the laser power are large enough, a preferred orientation of particles occurs, breaking the symmetry of the laser potential. After switching off the laser beams again, the system can follow different relaxation paths: It either relaxes back to the homogeneous isotropic state or it forms an approximately elliptical high-density core which is elongated perpendicular to the dominating orientation in order to minimize the surface free energy. For large supersaturations of the initial isotropic fluid, the high-density cores of neighboring laser beams of the two-dimensional array merge into complex superstructures.
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Affiliation(s)
- Markus Bier
- Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584CE Utrecht, The Netherlands.
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32
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Harnau L, Rosenfeldt S, Ballauff M. Structure factor and thermodynamics of rigid dendrimers in solution. J Chem Phys 2007; 127:014901. [PMID: 17627363 DOI: 10.1063/1.2750339] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The "polymer reference interaction site model" (PRISM) integral equation theory is used to determine the structure factor of rigid dendrimers in solution. The theory is quite successful in reproducing experimental structure factors for various dendrimer concentrations. In addition, the structure factor at vanishing scattering vector is calculated via the compressibility equation using scaled particle theory and fundamental measure theory. The results as predicted by both theories are systematically smaller than the experimental and PRISM data for platelike dendrimers.
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Affiliation(s)
- L Harnau
- Max-Planck-Institut für Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart, Germany
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33
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Weber CHM, Chiche A, Krausch G, Rosenfeldt S, Ballauff M, Harnau L, Göttker-Schnetmann I, Tong Q, Mecking S. Single lamella nanoparticles of polyethylene. NANO LETTERS 2007; 7:2024-9. [PMID: 17564476 DOI: 10.1021/nl070859f] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We present a complete analysis of the structure of polyethylene (PE) nanoparticles synthesized and stabilized in water under very mild conditions (15 degrees C, 40 atm) by a nickel-catalyzed polymerization in aqueous solution. Combining cryogenic transmission electron microscopy (cryo-TEM) with X-ray scattering, we demonstrate that this new synthetic route leads to a stable dispersion of individual PE nanoparticles with a narrow size distribution. Most of the semicrystalline particles have a hexagonal shape (lateral size 25 nm, thickness 9 nm) and exhibit the habit of a truncated lozenge. The combination of cryo-TEM and small-angle X-ray scattering demonstrates that the particles consist of a single crystalline lamella sandwiched between two thin amorphous polymer layers ("nanohamburgers"). Hence, these nanocrystals that comprise only ca. 14 chains present the smallest single crystals of PE ever reported. The very small thickness of the crystalline lamella (6.3 nm) is related to the extreme undercooling (more than 100 degrees C) that is due to the low temperature at which the polymerization takes place. This strong undercooling cannot be achieved by any other method so far. Dispersions of polyethylene nanocrystals may have a high potential for a further understanding of polymer crystallization as well as for materials science as, e.g., for the fabrication of extremely thin crystalline layers.
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Affiliation(s)
- C H M Weber
- Physikalische Chemie II, University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany
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34
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Bolisetty S, Airaud C, Xu Y, Müller AHE, Harnau L, Rosenfeldt S, Lindner P, Ballauff M. Softening of the stiffness of bottle-brush polymers by mutual interaction. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:040803. [PMID: 17500856 DOI: 10.1103/physreve.75.040803] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Indexed: 05/15/2023]
Abstract
We study bottle-brush macromolecules in a good solvent by small-angle neutron scattering (SANS), static light scattering (SLS), and dynamic light scattering (DLS). These polymers consist of a linear backbone to which long side chains are chemically grafted. The backbone contains about 1600 monomer units (weight average) and every second monomer unit carries side chains with approximately 60 monomer units. The SLS and SANS data extrapolated to infinite dilution lead to the form factor of the polymer that can be described in terms of a wormlike chain with a contour length of 380 nm and a persistence length of 17.5 nm. An analysis of the DLS data confirms these model parameters. The scattering intensities taken at finite concentration can be modeled using the polymer reference interaction site model. It reveals a softening of the bottle-brush polymers caused by their mutual interaction. We demonstrate that the persistence decreases from 17.5 nm down to 5 nm upon increasing the concentration from dilute solution to the highest concentration (40.59 gl) under consideration. The observed softening of the chains is comparable to the theoretically predicted decrease of the electrostatic persistence length of linear polyelectrolyte chains at finite concentrations.
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Affiliation(s)
- S Bolisetty
- Physikalische Chemie I, University of Bayreuth, D-95440 Bayreuth, Germany
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35
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Mossa S, De Michele C, Sciortino F. Aging in a Laponite colloidal suspension: A Brownian dynamics simulation study. J Chem Phys 2007; 126:014905. [PMID: 17212517 DOI: 10.1063/1.2408418] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The authors report Brownian dynamics simulation of the out-of-equilibrium dynamics (aging) in a colloidal suspension composed of rigid charged disks, one possible model for Laponite, a synthetic clay deeply investigated in the last few years by means of various experimental techniques. At variance with previous numerical investigations, mainly focusing on static structure and equilibrium dynamics, the authors explore the out-of-equilibrium aging dynamics. They analyze the wave vector and waiting time dependence of the dynamics, focusing on the single-particle and collective density fluctuations (intermediate scattering functions), the mean-squared displacement, and the rotational dynamics. Their findings confirm the complexity of the out-of-equilibrium dynamical behavior of this class of colloidal suspensions and suggest that an arrested disordered state driven by a repulsive Yukawa potential, i.e., a Wigner glass, can be observed in this model.
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Affiliation(s)
- S Mossa
- European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble, France
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36
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Bier M, Harnau L, Dietrich S. Surface properties of fluids of charged platelike colloids. J Chem Phys 2006; 125:184704. [PMID: 17115776 DOI: 10.1063/1.2360939] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Surface properties of mixtures of charged platelike colloids and salt in contact with a charged planar wall are studied within density functional theory. The particles are modeled by hard cuboids with their edges constrained to be parallel to the Cartesian axes corresponding to the Zwanzig model [J. Chem. Phys. 39, 1714 (1963)] and the charges of the particles are concentrated at their centers. The density functional applied is an extension of a recently introduced functional for charged platelike colloids. It provides a qualitative approach because it does not determine the relation between the actual and the effective charges entering into the model. Technically motivated approximations, such as using the Zwanzig model, are expected not to influence the results qualitatively. Analytically and numerically calculated bulk and surface phase diagrams exhibit first-order wetting for sufficiently small macroion charges and isotropic bulk order as well as first-order drying for sufficiently large macroion charges and nematic bulk order. The asymptotic wetting and drying behaviors are investigated by means of effective interface potentials which turn out to be asymptotically the same as for a suitable neutral system governed by isotropic nonretarded dispersion forces. Wetting and drying points as well as predrying lines and the corresponding critical points have been located numerically. A crossover from monotonic to nonmonotonic electrostatic potential profiles upon varying the surface charge density has been observed. Nonmonotonic electrostatic potential profiles are equivalent to the occurrence of charge inversion. Due to the presence of both the Coulomb interactions and the hard-core repulsions, the surface potential and the surface charge do not vanish simultaneously, i.e., the point of zero charge and the isoelectric point of the surface do not coincide.
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Affiliation(s)
- Markus Bier
- Max-Planck-Institut für Metallforschung, Heisenbergstrasse 3, 70569 Stuttgart, Germany.
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37
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Zhou S. Formalism for calculation of polymer-solvent-mediated potential. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 74:011402. [PMID: 16907091 DOI: 10.1103/physreve.74.011402] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2005] [Indexed: 05/11/2023]
Abstract
A simple theoretical approach is proposed for calculation of a solvent-mediated potential (SMP) between two colloid particles immersed in a polymer solvent bath in which the polymer is modeled as a chain with intramolecular degrees of freedom. The present recipe is only concerned with the estimation of the density profile of a polymer site around a single solute colloid particle instead of two solute colloid particles separated by a varying distance as done in existing calculational methods for polymer-SMP. Therefore the present recipe is far simpler for numerical implementation than the existing methods. The resultant predictions for the polymer-SMP and polymer solvent-mediated mean force (polymer-SMMF) are in very good agreement with available simulation data. With the present recipe, change tendencies of the contact value and second virial coefficiency of the SMP as a function of size ratio between the colloid particle and polymer site, the number of sites per chain, and the polymer concentration are investigated in detail. The metastable critical polymer concentration as a function of size ratio and the number of sites per chain is also reported for the first time. To yield the numerical solution of the present recipe at less than on a personal computer, a rapid and accurate algorithm for the numerical solution of the classical density functional theory is proposed to supply rapid and accurate estimation of the density profile of the polymer site as an input into the present formalism.
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Affiliation(s)
- Shiqi Zhou
- Institute of Modern Statistical Mechanics, Hunan University of Technology, Wenhua Road, Zhuzhou City, 412008, People's Republic of China.
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38
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Delville A. Electrostatic stability of a large collection of charged anisotropic nanoparticles: a monte carlo study exploiting a hierarchical approach. J Phys Chem B 2006; 110:11950-7. [PMID: 16800500 DOI: 10.1021/jp0612883] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have performed Monte Carlo simulations of the self-organization of large collections of charged disks of various electric charges to probe the influence of electrostatic coupling on the structure and the mechanical stability of aqueous dispersions of charged anisotropic nanoparticles in the presence of salt. A hierarchical approach of the long-range Coulombic potential was used to perform such Monte Carlo simulations of a large number of charged species. By analyzing the influence of the net electric charge of the disks on their self-organization, we detected a negative contribution to the mean force potential resulting from their electrostatic coupling. In addition, it has been shown that the same electrostatic coupling restricts the spatial extend of locally ordered microdomains within dilute dispersions of charged anisotropic colloids.
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Affiliation(s)
- A Delville
- CRMD, CNRS, 1B rue de la Férollerie, 45071 Orléans Cedex 02, France.
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39
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Ruzicka B, Zulian L, Ruocco G. More on the phase diagram of Laponite. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:1106-11. [PMID: 16430272 DOI: 10.1021/la0524418] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The phase diagram of a charged colloidal system (Laponite) has been investigated by dynamic light scattering in a previously unexplored range of salt and clay concentrations. Specifically, the clay weight and salt molar concentrations have been varied in the ranges C(w) = 0.004 divided by 0.025 and C(s) = (1 x 10(-3) divided by 5 x 10(-3)) M, respectively. As in the case of free salt water samples (C(s) approximately = 1 x 10(-4) M), an aging dynamics toward two different arrested phases is found in the whole examined C(w) and C(s) range. Moreover a transition between these two different regimes is found. It is clear from these measurements that a revision of the phase diagram is necessary and a new "transition" line between two different arrested states is drawn.
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Affiliation(s)
- B Ruzicka
- Dipartimento di Fisica, Universitá di Roma La Sapienza, P.zle A. Moro 2, I-00185 Roma, Italy
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