101
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Xu Z, Zhang Y, Li P, Gao C. Strong, conductive, lightweight, neat graphene aerogel fibers with aligned pores. ACS NANO 2012; 6:7103-13. [PMID: 22799441 DOI: 10.1021/nn3021772] [Citation(s) in RCA: 287] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Liquid crystals of anisotropic colloids are of great significance in the preparation of their ordered macroscopic materials, for example, in the cases of carbon nanotubes and graphene. Here, we report a facile and scalable spinning process to prepare neat "core-shell" structured graphene aerogel fibers and three-dimensional cylinders with aligned pores from the flowing liquid crystalline graphene oxide (GO) gels. The uniform alignment of graphene sheets, inheriting the lamellar orders from GO liquid crystals, offers the porous fibers high specific tensile strength (188 kN m kg(-1)) and the porous cylinders high compression modulus (3.3 MPa). The porous graphene fibers have high specific surface area up to 884 m(2) g(-1) due to their interconnected pores and exhibit fine electrical conductivity (2.6 × 10(3) to 4.9 × 10(3) S m(-1)) in the wide temperature range of 5-300 K. The decreasing conductivity with decreasing temperature illustrates a typical semiconducting behavior, and the 3D interconnected network of 2D graphene sheets determines a dual 2D and 3D hopping conduction mechanism. The strong mechanical strength, high porosity, and fine electrical conductivity enable this novel material of ordered graphene aerogels to be greatly useful in versatile catalysts, supercapacitors, flexible batteries and cells, lightweight conductive fibers, and functional textiles.
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Affiliation(s)
- Zhen Xu
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, People's Republic of China
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102
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Paineau E, Dozov I, Bihannic I, Baravian C, Krapf MEM, Philippe AM, Rouzière S, Michot LJ, Davidson P. Tailoring highly oriented and micropatterned clay/polymer nanocomposites by applying an a.c. electric field. ACS APPLIED MATERIALS & INTERFACES 2012; 4:4296-4301. [PMID: 22833688 DOI: 10.1021/am300980r] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Clay/polymer nanocomposites have recently raised much interest because of their widespread industrial applications. Nevertheless, controlling both clay platelet exfoliation and orientation during polymerization still remains challenging. Herein, we report the elaboration of clay/polymer nanocomposite hydrogels from aqueous suspensions of natural swelling clays submitted to high-frequency a.c. electric fields. X-ray scattering experiments have confirmed the complete exfoliation of the clay sheets in the polymer matrix, even after polymerization. Moreover, polarized light microscopy shows that the clay platelets were perfectly oriented by the electric field and that this field-induced alignment was frozen in by in situ photopolymerization. This procedure allowed us to not only produce uniformly aligned samples but also pattern platelet orientation, at length scales down to 20 μm. This straightforward and cheap nanocomposite patterning technique can be easily extended to a wide range of natural or synthetic inorganic anisotropic particles.
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Affiliation(s)
- Erwan Paineau
- Laboratoire de Physique des Solides, UMR 8502, Paris-Sud University, Bâtiment 510, 91405 Orsay Cedex, France.
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103
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Chang YW, Mejia AF, Cheng Z, Di X, McKenna GB. Gelation via ion exchange in discotic suspensions. PHYSICAL REVIEW LETTERS 2012; 108:247802. [PMID: 23004332 DOI: 10.1103/physrevlett.108.247802] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 04/30/2012] [Indexed: 06/01/2023]
Abstract
The phase behavior of charged disk suspensions displays a strong dependence on ionic strengths, as the interplay between excluded volume and electrostatic interactions determines the formation of glasses, gels, and liquid crystal states. The various ions in natural soil or brine, however, could present additional effects, especially considering that most platelet structures bear a momentous ion-exchange capacity. Here we observed how ion exchange modulates and controls the interaction between individual disks and leads to unconventional phase transitions from isotropic gel to nematic gel and finally to nematic liquid crystals.
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Affiliation(s)
- Ya-Wen Chang
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843, USA
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104
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Delhorme M, Labbez C, Jönsson B. Liquid Crystal Phases in Suspensions of Charged Plate-Like Particles. J Phys Chem Lett 2012; 3:1315-20. [PMID: 26286776 DOI: 10.1021/jz300380n] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Anisotropic interactions in colloidal suspensions have recently emerged as a route for the design of new soft materials. Nonisotropic particles can form nematic, smectic, hexatic, and columnar liquid crystals. Although the formation of these phases is well rationalized when excluded volume is solely at play, the role of electrostatic interactions still remains unclear and even less so when particles present a charge heterogeneity, for example, clays. Here, we use Monte Carlo simulations of concentrated suspensions of charged disk-like particles to reveal the role of Coulomb interactions and charge anisotropy underlying liquid crystal formation and structures. We observe a vast zoo of exotic structures, going from hexatic to columnar phases, which are shown to be controlled by the charge anisotropy. The particle volume fraction at which these phases start to form is found to decrease with increasing Coulomb interactions and charge anisotropy, which suggests a route to tune the structure of aqueous liquid crystals.
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Affiliation(s)
- Maxime Delhorme
- †Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Université de Bourgogne, 21078 Dijon Cedex, France
| | - Christophe Labbez
- †Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Université de Bourgogne, 21078 Dijon Cedex, France
| | - Bo Jönsson
- ‡Department of Theoretical Chemistry, Chemical Center, POB 124, S-221 00 Lund, Sweden
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105
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Morales-Anda L, Wensink HH, Galindo A, Gil-Villegas A. Anomalous columnar order of charged colloidal platelets. J Chem Phys 2012; 136:034901. [PMID: 22280777 DOI: 10.1063/1.3673877] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Monte Carlo computer simulations are carried out for a model system of like-charged colloidal platelets in the isothermal-isobaric ensemble (NpT). The aim is to elucidate the role of electrostatic interactions on the structure of synthetic clay systems at high particle densities. Short-range repulsions between particles are described by a suitable hard-core model representing a discotic particle. This potential is supplemented with an electrostatic potential based on a Yukawa model for the screened Coulombic potential between infinitely thin disklike macro-ions. The particle aspect-ratio and electrostatic parameters were chosen to mimic an aqueous dispersion of thin, like-charged, rigid colloidal platelets at finite salt concentration. An examination of the fluid phase diagram reveals a marked shift in the isotropic-nematic transition compared to the hard cut-sphere reference system. Several statistical functions, such as the pair correlation function for the center-of-mass coordinates and structure factor, are obtained to characterize the structural organization of the platelets phases. At low salinity and high osmotic pressure we observe anomalous hexagonal columnar structures characterized by interpenetrating columns with a typical intercolumnar distance corresponding to about half of that of a regular columnar phase. Increasing the ionic strength leads to the formation of glassy, disordered structures consisting of compact clusters of platelets stacked into finite-sized columns. These so-called "nematic columnar" structures have been recently observed in systems of charge-stabilized gibbsite platelets. Our findings are corroborated by an analysis of the static structure factor from a simple density functional theory.
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Affiliation(s)
- L Morales-Anda
- Departamento de Ingeniería Física, División de Ciencias e Ingenierías Campus León, Universidad de Guanajuato, Colonia Lomas del Campestre, León 37150, México
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106
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Shahin A, Joshi YM. Hyper-aging dynamics of nanoclay suspension. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:5826-5833. [PMID: 22414339 DOI: 10.1021/la205153b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Aqueous suspension of nanoclay Laponite undergoes structural evolution as a function of time, which enhances its elasticity and relaxation time. In this work, we employ an effective time approach to investigate long-term relaxation dynamics by carrying out creep experiments. Typically, we observe that the monotonic evolution of elastic modulus shifts to lower aging times, while maxima in viscous moduli get progressively broader for experiments carried out on a later date after preparation (idle time) of the nanoclay suspension. Application of effective time theory produces a superposition of all the creep curves irrespective of their initial state. The resulting dependence of the relaxation time on aging time shows very strong hyper-aging dynamics at short idle times, which progressively weakens to demonstrate a linear dependence in the limit of very long idle times. Remarkably, this behavior of nanoclay suspensions is akin to that observed for polymeric glasses. Consideration of aging as a first-order process suggests that continued hyper-aging dynamics causes cessation of aging. The dependence of relaxation time on aging time, therefore, must attenuate eventually producing linear or weaker dependence on time in order to approach a progressively low-energy state in the limit of very long times as observed experimentally. We also develop a simple scaling model based on a concept of aging of an energy well, which qualitatively captures various experimental observations very well, leading to profound insight into the hyper-aging dynamics of nanoclay suspensions.
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Affiliation(s)
- A Shahin
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur, India
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107
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Kleshchanok D, Holmqvist P, Meijer JM, Lekkerkerker HNW. Lyotropic Smectic B Phase Formed in Suspensions of Charged Colloidal Platelets. J Am Chem Soc 2012; 134:5985-90. [DOI: 10.1021/ja300527w] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dzina Kleshchanok
- Van’t
Hoff Laboratory,
Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands
| | - Peter Holmqvist
- Soft
Condensed Matter Group,
Institute of Complex Systems (ICS-3), Forschungszentrum Juelich, Germany
| | - Janne-Mieke Meijer
- Van’t
Hoff Laboratory,
Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands
| | - Henk N. W. Lekkerkerker
- Van’t
Hoff Laboratory,
Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands
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108
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Turesson M, Jönsson B, Labbez C. Coarse-graining intermolecular interactions in dispersions of highly charged colloids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:4926-4930. [PMID: 22404737 DOI: 10.1021/la3005008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Effective pair potentials between charged colloids, obtained from Monte Carlo simulations of two single colloids in a closed cell at the primitive model level, are shown to reproduce accurately the structure of aqueous salt-free colloidal dispersions, as determined from full primitive model simulations by Linse et al. (Linse, P.; Lobaskin, V. Electrostatic Attraction and Phase Separation in Solutions of Like-Charged Colloidal Particles. Phys. Rev. Lett.1999, 83, 4208). Excellent agreement is obtained even when ion-ion correlations are important and is in principle not limited to spherical particles, providing a potential route to coarse-grained colloidal interactions in more complex systems.
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109
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Xu Z, Gao C. Graphene chiral liquid crystals and macroscopic assembled fibres. Nat Commun 2011; 2:571. [PMID: 22146390 PMCID: PMC3247827 DOI: 10.1038/ncomms1583] [Citation(s) in RCA: 454] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 11/02/2011] [Indexed: 12/22/2022] Open
Abstract
Chirality and liquid crystals are both widely expressed in nature and biology. Helical assembly of mesophasic molecules and colloids may produce intriguing chiral liquid crystals. To date, chiral liquid crystals of 2D colloids have not been explored. As a typical 2D colloid, graphene is now receiving unprecedented attention. However, making macroscopic graphene fibres is hindered by the poor dispersibility of graphene and by the lack of an assembly method. Here we report that soluble, chemically oxidized graphene or graphene oxide sheets can form chiral liquid crystals in a twist-grain-boundary phase-like model with simultaneous lamellar ordering and long-range helical frustrations. Aqueous graphene oxide liquid crystals were continuously spun into metres of macroscopic graphene oxide fibres; subsequent chemical reduction gave the first macroscopic neat graphene fibres with high conductivity and good mechanical performance. The flexible, strong graphene fibres were knitted into designed patterns and into directionally conductive textiles.
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Affiliation(s)
- Zhen Xu
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, PR China
| | - Chao Gao
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, PR China
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110
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Shahin A, Joshi YM, Ramakrishna SA. Interface-induced anisotropy and the nematic glass/gel state in jammed aqueous Laponite suspensions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:14045-14052. [PMID: 21995523 DOI: 10.1021/la202398v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Aqueous suspensions of Laponite, a system composed of disklike nanoparticles, are found to develop optical birefringence over several days, well after the suspensions solidified because of jamming. The optical anisotropy is particularly enhanced near the air-Laponite suspension interface over length scales of several millimeters, which is beyond 5 orders of magnitude larger than the particle length scale, suggestive of large-scale ordering influenced by the interface. The orientational order increases with time and is always greater for higher concentration of salt, higher concentration of Laponite, and higher temperatures of the suspension. Although weakly birefringent, Laponite suspensions covered by paraffin oil do not show any enhancement in optical anisotropy near the interface compared to that in the bulk. We suggest that the expedited structure formation near the air interface propagating progressively inside the sample is responsible for the observed behavior. We discuss the observed nematic ordering in the context of glass-like and gel-like microstructure associated with aqueous Laponite suspensions.
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Affiliation(s)
- A Shahin
- Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016, India
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111
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Miyamoto N, Yamamoto S, Shimasaki K, Harada K, Yamauchi Y. Exfoliated Nanosheets of Layered Perovskite KCa2Nb3O10 as an Inorganic Liquid Crystal. Chem Asian J 2011; 6:2936-9. [DOI: 10.1002/asia.201100279] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Indexed: 11/10/2022]
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112
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Paineau E, Michot LJ, Bihannic I, Baravian C. Aqueous suspensions of natural swelling clay minerals. 2. Rheological characterization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:7806-7819. [PMID: 21591697 DOI: 10.1021/la2001267] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report in this article a comprehensive investigation of the viscoelastic behavior of different natural colloidal clay minerals in aqueous solution. Rheological experiments were carried out under both dynamic and steady-state conditions, allowing us to derive the elasticity and yield stress. Both parameters can be renormalized for all sizes, ionic strength, and type of clay using in a first approach only the volume of the particles. However, applying such a treatment to various clays of similar shapes and sizes yields differences that can be linked to the repulsion strength and charge location in the swelling clays. The stronger the repulsive interactions, the better the orientation of clay particles in flows. In addition, a master linear relationship between the elasticity and yield stress whose value corresponds to a critical deformation of 0.1 was evidenced. Such a relationship may be general for any colloidal suspension of anisometric particles as revealed by the analysis of various experimental data obtained on either disk-shaped or lath- and rod-shaped particles. The particle size dependence of the sol-gel transition was also investigated in detail. To understand why suspensions of larger particles gel at a higher volume fraction, we propose a very simplified view based on the statistical hydrodynamic trapping of a particle by an another one in its neighborhood upon translation and during a short period of time. We show that the key parameter describing this hydrodynamic trapping varies as the cube of the average diameter and captures most features of the sol-gel transition. Finally, we pointed out that in the high shear limit the suspension viscosity is still closely related to electrostatic interactions and follows the same trends as the viscoelastic properties.
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Affiliation(s)
- Erwan Paineau
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL, UMR 7569, BP40 54501 Vandœuvre, Cedex France.
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113
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Dozov I, Paineau E, Davidson P, Antonova K, Baravian C, Bihannic I, Michot LJ. Electric-Field-Induced Perfect Anti-Nematic Order in Isotropic Aqueous Suspensions of a Natural Beidellite Clay. J Phys Chem B 2011; 115:7751-65. [DOI: 10.1021/jp201201x] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- I. Dozov
- Laboratoire de Physique des Solides, UMR 8502 CNRS−Université Paris-Sud, Bât. 510, 91405 Orsay Cedex, France
| | - E. Paineau
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40, 54501 Vandœuvre Cedex, France
| | - P. Davidson
- Laboratoire de Physique des Solides, UMR 8502 CNRS−Université Paris-Sud, Bât. 510, 91405 Orsay Cedex, France
| | - K. Antonova
- Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, 1784 Sofia, Bulgaria
| | - C. Baravian
- Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France
| | - I. Bihannic
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40, 54501 Vandœuvre Cedex, France
| | - L. J. Michot
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40, 54501 Vandœuvre Cedex, France
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114
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Pujala RK, Pawar N, Bohidar HB. Landau theory description of observed isotropic to anisotropic phase transition in mixed clay gels. J Chem Phys 2011; 134:194904. [PMID: 21599085 DOI: 10.1063/1.3590028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A characteristic new cooperative dehydration transition, in 1:1 Laponite-MMT cogel, was observed at T(c) ≈ 60 °C, a temperature at which the storage modulus (G(')) and depolarization ratio (D(p)) showed sharp increase, and the isotropic cogel turned into an anisotropic one. The dehydration dynamics could be described through power-law relations: G(') ∼ (T(c)-T)(-γ) and D(p) ∼ (T(c)-T)(-β) with γ ≈ β = 0.40 ± 0.05. The x-ray diffraction data revealed that the crystallite size decreased from 17 nm (at 20 °C) to 10 nm (at 80 °C) implying loss of free and inter-planar water. When this cogel was spontaneously cooled below T(c), it exhibited much larger storage modulii values which implied the existence of several metastable states in this system. This phase transition could be modeled through Landau theory, where the depolarization ratio was used as experimental order parameter (ψ). This parameter was found to scale with temperature, as ψ ∼ (T(c)-T)(-α), with power-law exponent α = 0.40 ± 0.05; interestingly, we found α ≈ β ≈ γ.
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Affiliation(s)
- Ravi Kumar Pujala
- Nanomaterials and Nanocomposite Laboratory, School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067, India
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115
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Phillips J, Schmidt M. Phase behaviour of binary mixtures of diamagnetic colloidal platelets in an external magnetic field. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:194111. [PMID: 21525550 DOI: 10.1088/0953-8984/23/19/194111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Using fundamental measure density functional theory we investigate paranematic-nematic and nematic-nematic phase coexistence in binary mixtures of circular platelets with vanishing thicknesses. An external magnetic field induces uniaxial alignment and acts on the platelets with a strength that is taken to scale with the platelet area. At particle diameter ratio λ = 1.5 the system displays paranematic-nematic coexistence. For λ = 2, demixing into two nematic states with different compositions also occurs, between an upper critical point and a paranematic-nematic-nematic triple point. Increasing the field strength leads to shrinking of the coexistence regions. At high enough field strength a closed loop of immiscibility is induced and phase coexistence vanishes at a double critical point above which the system is homogeneously nematic. For λ = 2.5, besides paranematic-nematic coexistence, there is nematic-nematic coexistence which persists and hence does not end in a critical point. The partial orientational order parameters along the binodals vary strongly with composition and connect smoothly for each species when closed loops of immiscibility are present in the corresponding phase diagram.
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Affiliation(s)
- Jonathan Phillips
- H H Wills Physics Laboratory, University of Bristol, Royal Fort, Bristol, UK
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116
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Philippe AM, Baravian C, Imperor-Clerc M, De Silva J, Paineau E, Bihannic I, Davidson P, Meneau F, Levitz P, Michot LJ. Rheo-SAXS investigation of shear-thinning behaviour of very anisometric repulsive disc-like clay suspensions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:194112. [PMID: 21525562 DOI: 10.1088/0953-8984/23/19/194112] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Aqueous suspensions of swelling clay minerals exhibit a rich and complex rheological behaviour. In particular, these repulsive systems display strong shear-thinning at very low volume fractions in both the isotropic and gel states. In this paper, we investigate the evolution with shear of the orientational distribution of aqueous clay suspensions by synchrotron-based rheo-SAXS experiments using a Couette device. Measurements in radial and tangential configurations were carried out for two swelling clay minerals of similar morphology and size, Wyoming montmorillonite and Idaho beidellite. The shear evolution of the small angle x-ray scattering (SAXS) patterns displays significantly different features for these two minerals. The detailed analysis of the angular dependence of the SAXS patterns in both directions provides the average Euler angles of the statistical effective particle in the shear plane. We show that for both samples, the average orientation is fully controlled by the local shear stress around the particle. We then apply an effective approach to take into account multiple hydrodynamic interactions in the system. Using such an approach, it is possible to calculate the evolution of viscosity as a function of shear rate from the knowledge of the average orientation of the particles. The viscosity thus recalculated almost perfectly matches the measured values as long as collective effects are not too important in the system.
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Affiliation(s)
- A M Philippe
- Laboratoire d'Energétique et de Mécanique Théorique et Appliquée, Nancy University-CNRS, UMR 7563, Vandœuvre Lès Nancy, France.
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117
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Doshi N, Cinacchi G, van Duijneveldt JS, Cosgrove T, Prescott SW, Grillo I, Phipps J, Gittins DI. Structure of colloidal sphere-plate mixtures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:194109. [PMID: 21525556 DOI: 10.1088/0953-8984/23/19/194109] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In addition to containing spherical pigment particles, coatings usually contain plate-like clay particles. It is thought that these improve the opacity of the paint film by providing an efficient spacing of the pigment particles. This observation is counterintuitive, as suspensions of particles of different shapes and sizes tend to phase separate on increase of concentration. In order to clarify this matter a model colloidal system is studied here, with a sphere-plate diameter ratio similar to that found in paints. For dilute suspensions, small angle neutron scattering revealed that the addition of plates leads to enhanced density fluctuations of the spheres, in agreement with new theoretical predictions. On increasing the total colloid concentration the plates and spheres phase separate due to the disparity in their shape. This is in agreement with previous theoretical and experimental work on colloidal sphere-plate mixtures, where one particle acts as a depleting agent. The fact that no large scale phase separation is observed in coatings is ascribed to dynamic arrest in intimately mixed, or possibly micro-phase separated structures, at elevated concentration.
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Affiliation(s)
- N Doshi
- School of Chemistry, University of Bristol, Bristol, UK
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118
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Leferink Op Reinink ABGM, Meijer JM, Kleshchanok D, Byelov DV, Vroege GJ, Petukhov AV, Lekkerkerker HNW. 3D structure of nematic and columnar phases of hard colloidal platelets. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:194110. [PMID: 21525552 DOI: 10.1088/0953-8984/23/19/194110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present small angle x-ray scattering data of single-domain nematic and columnar liquid crystal phases in suspensions of sterically stabilized gibbsite platelets. The measurements are performed with different sample orientations to obtain information about the three-dimensional structure of the liquid crystalline phases. With the x-ray beam incident along the director of the nematic phase a strong correlation peak is observed corresponding to the side-to-side interparticle correlations, which suggests a columnar nematic structure. Upon sample rotation this side-to-side correlation peak of the nematic shifts to higher Q-values, suggesting the presence of strong fluctuations of small stacks of particles with different orientations, while the overall particle orientation is constant. In the hexagonal columnar phase, clear Bragg intercolumnar reflections are observed. Upon rotation, the Q-value of these reflections remains constant while their intensity monotonically decreases upon rotation. This indicates that the column orientation fluctuates together with the particle director in the columnar phase. This difference between the behaviour of the columnar and the nematic reflections upon sample rotation is used to assign the liquid crystal phase of a suspension consisting of larger platelets, where identification can be ambiguous due to resolution limitations.
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119
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Paineau E, Bihannic I, Baravian C, Philippe AM, Davidson P, Levitz P, Funari SS, Rochas C, Michot LJ. Aqueous suspensions of natural swelling clay minerals. 1. Structure and electrostatic interactions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:5562-5573. [PMID: 21476528 DOI: 10.1021/la2001255] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this article, we present a general overview of the organization of colloidal charged clay particles in aqueous suspension by studying different natural samples with different structural charges and charge locations. Small-angle X-ray scattering experiments (SAXS) are first used to derive swelling laws that demonstrate the almost perfect exfoliation of clay sheets in suspension. Using a simple approach based on geometrical constraints, we show that these swelling laws can be fully modeled on the basis of morphological parameters only. The validity of this approach was further extended to other clay data from the literature, in particular, synthetic Laponite. For all of the investigated samples, experimental osmotic pressures can be properly described by a Poisson-Boltzmann approach for ionic strength up to 10(-3) M, which reveals that these systems are dominated by repulsive electrostatic interactions. However, a detailed analysis of the Poisson-Boltzmann treatment shows differences in the repulsive potential strength that are not directly linked to the structural charge of the minerals but rather to the charge location in the structure for tetrahedrally charged clays (beidellite and nontronites) undergoing stronger electrostatic repulsions than octahedrally charged samples (montmorillonites, laponite). Only minerals subjected to the strongest electrostatic repulsions present a true isotropic to nematic phase transition in their phase diagrams. The influence of ionic repulsions on the local order of clay platelets was then analyzed through a detailed investigation of the structure factors of the various clay samples. It appears that stronger electrostatic repulsions improve the liquidlike positional local order.
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Affiliation(s)
- Erwan Paineau
- Laboratoire Environnement et Minéralurgie, Nancy Université-CNRS, UMR 7569, BP40 54501 Vandœuvre Cedex, France.
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120
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Pujala RK, Pawar N, Bohidar HB. Universal sol state behavior and gelation kinetics in mixed clay dispersions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:5193-5203. [PMID: 21466239 DOI: 10.1021/la1048453] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Sol and gel state behavior, in aqueous salt free dispersions, of clays Laponite (L) and Na montmorillonite (MMT) was studied at various mixing ratios (L:MMT = r = 1:0.5, 1:1, and 1:2). In the sol state, the zeta potential and gelation concentration of L-MMT obeyed the universal relation, X(L-MMT) = (rX(L) + X(MMT))/(1 + r), where X is zeta potential or gelation concentration (c(g)), implying that these properties are linear combinations of the same of their individual components. The low frequency storage modulus (G(0)'), relative viscosity (η(r)), and apparent cluster size (R) could be universally described by the power-law, G(0)' ∼ ((c/c(g)) - 1)(t) (c > c(g)), and η(r), R ∼ (1 - (c/c(g)))(-k,ν) (c < c(g)), with t = 1.5, k = 1.1, and υ = 0.8 close to the gelation concentration, for r = 1:1 cogel, consistent with the percolation model description of gelation. Interestingly, the hyperscaling relation δ = t/(k + t) yielded δ = 0.56 not too different from the predicted value ∼0.7, while the experimental value of δ obtained from G''(ω) ∼ ω(δ) close to c ≈ c(g) yielded δ = 1.5, which was at variance with the hyperscaling result. The experimental data, on hand, mostly supported percolation type gelation mechanism. As the cogels were slowly heated, at a characteristic temperature, T(g), a sharp increase in G' value was noticed, implying a transition to gel hardening (a new phase state). The temperature-dependent behavior followed the power-law description, G' ∼ (T(g) - T)(-γ) (T < T(g)), with γ = 0.40 ± 0.05 invariant of composition of the cogel, whereas for MMT and Laponite, γ = 0.25 and 0.55, respectively. It has been shown that the cogel has significantly enhanced mechanical (G(0) increased by 10 times for r = 1:1 cogel) and thermal properties (T(g) increased by 13 °C for 1:1 cogel) that can be exploited to design customized soft materials.
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Affiliation(s)
- Ravi Kumar Pujala
- Nanomaterials and Nanocomposite Laboratory School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067, India
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Abstract
The formation of liquid crystals (LCs) is the most viable approach to produce macroscopic, periodic self-assembled materials from oriented graphene sheets. Herein, we have discovered that well-soluble and single-layered graphene oxide (GO) sheets can exhibit nematic liquid crystallinity in water and first established their isotropic-nematic solid phase diagram versus mass fraction and salt concentration. The zeta potential of GO dispersion is around -64 mV, and its absolute value decreases with increasing salt concentration, implying that the electrostatic repulsive force between negatively charged GO sheets is the dominant interaction in the system of GOLCs and also explaining the salt-dependent phase behavior. For single-layer GO sheets with average diameter of 2.1 μm and polydispersity index of 83%, the isotropic-nematic phase transition occurs at a mass concentration of ∼0.025%, and a stable nematic phase forms at ∼0.5%. Rheological measurements showed that GO aqueous dispersions performed as typical shear flows and confirmed the isotropic-nematic transition. The ordering of GO sheets in aqueous dispersions and the solid state is demonstrated by the characterizations of polarized-light optical microscopy, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The direct, real-time fluorescent inspections by confocal laser microscopy further reveal that the individually dispersed fluorescent GO sheets align with orientational directions along their long axes. These novel findings shed light on the phase behaviors of diversely topological graphenes and lay the foundation for fabrication of long-range, ordered nano-objects and macroscopically assembled graphene-based functional materials.
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Affiliation(s)
- Zhen Xu
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, People's Republic of China
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Jiang C, Wang Z, Huang H, He T. Large-scale and highly oriented liquid crystal phase in suspensions of polystyrene-block-poly(L-lactide) single crystals. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:4351-4357. [PMID: 21405072 DOI: 10.1021/la200314t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A large number of lozenge-shaped and sandwiched polystyrene-block-poly(L-lactide) (PS-b-PLLA) single crystals were prepared by the self-seeding technique. The single crystals were nearly monodispersed in both thickness and diameter. They are well-dispersed because of the steric stabilization offered by tethered PS in p-xylene, which is a good solvent for PS. The suspensions were observed to separate into a transparent upper phase and a turbid lower phase. The lower phase showed uniform iridescent stripes extending over the whole tube between crossed polarizers. The birefringence demonstrates the liquid crystal order, and the uniform stripes reveal that the phase is a well-oriented single domain. The phase-transition concentration is rather low. Polarizing light microscopy (PLM) images show Schlieren texture and thread-like texture. Small-angle X-ray scattering (SAXS) results showed that the single crystals in the liquid crystal phase oriented horizontally with a vertical repeat distance of about 70 nm. Additionally, the possible structure of the liquid crystal phase is being discussed. The novel disclike colloidal particle might be useful for anisotropic photonic materials.
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Affiliation(s)
- Chunbo Jiang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China
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123
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Stamatoiu O, Mirzaei J, Feng X, Hegmann T. Nanoparticles in liquid crystals and liquid crystalline nanoparticles. Top Curr Chem (Cham) 2011; 318:331-93. [PMID: 21928012 DOI: 10.1007/128_2011_233] [Citation(s) in RCA: 138] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Combinations of liquid crystals and materials with unique features as well as properties at the nanoscale are reviewed. Particular attention is paid to recent developments, i.e., since 2007, in areas ranging from liquid crystal-nanoparticle dispersions to nanomaterials forming liquid crystalline phases after surface modification with mesogenic or promesogenic moieties. Experimental and synthetic approaches are summarized, design strategies compared, and potential as well as existing applications discussed. Finally, a critical outlook into the future of this fascinating field of liquid crystal research is provided.
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Affiliation(s)
- Oana Stamatoiu
- Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada, R3T 2N2
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124
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Mourad MCD, Petukhov AV, Vroege GJ, Lekkerkerker HNW. Lyotropic hexagonal columnar liquid crystals of large colloidal gibbsite platelets. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:14182-14187. [PMID: 20712370 DOI: 10.1021/la100797x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We report the formation of hexagonal columnar liquid crystal phases in suspensions of large (570 nm diameter), sterically stabilized, colloidal gibbsite platelets in organic solvent. In thin cells these systems display strong iridescence originating from hexagonally arranged columns that are predominantly aligned perpendicularly to the cell walls. Small angle X-ray scattering and polarization microscopy indicate the presence of orientational fluctuations in the hexagonal columnar liquid crystal phase. The presence of decoupling of the average platelet orientation and the column axis as well as column undulations leading to a decrease of the effective column diameter are discussed. The fact that these phenomena are particularly pronounced in the vertical direction and are enhanced toward the bottom part of the system points to the role of gravitational compaction on the structure.
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Affiliation(s)
- Maurice C D Mourad
- Van 't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands.
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125
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Porion P, Faugère AM, Michot LJ, Paineau E, Delville A. Orientational microdynamics and magnetic-field-induced ordering of clay platelets detected by 2H NMR spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:7035-7044. [PMID: 20047274 DOI: 10.1021/la904298d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The orientation of montmorillonite clays induced by a static magnetic field is quantified by using (2)H NMR spectroscopy. Indeed, the residual quadrupolar splitting of the (2)H resonance line measured for heavy water is a direct consequence of the specific orientation of the clay platelets in the static magnetic field. In the dilute regime, this residual splitting increases linearly with clay concentration, which confirms that the clay/clay electrostatic repulsions remain negligible by comparison with the diamagnetic coupling of these anisotropic platelets. At higher concentration, the electrostatic repulsion between clay particles markedly enhances the detected splitting. Such enhancement is well predicted by numerical simulations. By varying the size of the clay platelets and the strength of the static magnetic field, it is possible to evaluate the order of magnitude of the diamagnetic susceptibility of these anisotropic colloids.
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Affiliation(s)
- Patrice Porion
- Centre de Recherche sur la Matière Divisée, CNRS-Université d'Orléans, UMR6619, 45071 Orléans Cedex 02, France.
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126
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Byelov DV, Mourad MCD, Snigireva I, Snigirev A, Petukhov AV, Lekkerkerker HNW. Experimental observation of fractionated crystallization in polydisperse platelike colloids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:6898-6901. [PMID: 20392119 DOI: 10.1021/la100993k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We have discovered that the long-term aging of the hexagonal columnar liquid-crystal phase of polydisperse gibbsite platelets leads to fractionated crystallization, that is, to the formation of coexisting columnar crystals with different periods. This process was revealed by microradian X-ray diffraction demonstrating the splitting of the Bragg intercolumnar reflections into sequences of sharper reflections. The fractionated crystallization was observed in a number of samples of sterically stabilized as well as charge-stabilized polydisperse gibbsite platelets.
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Affiliation(s)
- D V Byelov
- Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands.
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127
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Miyamoto N, Iijima H, Ohkubo H, Yamauchi Y. Liquid crystal phases in the aqueous colloids of size-controlled fluorinated layered clay mineral nanosheets. Chem Commun (Camb) 2010; 46:4166-8. [PMID: 20454743 DOI: 10.1039/b927335b] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Size-controlled nanosheet colloids of fluorohectorite and fluortetrasilicic mica were prepared in high yield and their transitions to fluid liquid crystal (LC) phases with highly ordered lamellar structures were identified over a wide concentration range, which is a rare case for clay mineral systems.
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Affiliation(s)
- Nobuyoshi Miyamoto
- Department of Life, Environment and Materials Science, Fukuoka Institute of Technology, 3-30-1 Wajiro-Higashi, Higashi-ku, Fukuoka 811-0295, Japan.
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128
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Ringdal NI, Fonseca DM, Hansen EL, Hemmen H, Fossum JO. Nematic textures in colloidal dispersions of Na-fluorohectorite synthetic clay. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:041702. [PMID: 20481735 DOI: 10.1103/physreve.81.041702] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Indexed: 05/22/2023]
Abstract
We have studied stable strata of gravity-induced phase separation in suspensions of synthetic Na-fluorohectorite clay in saline solutions. We have observed how the strata depend on clay concentration as well as on salt content. The mass distribution and density variation at the isotropic-nematic interface indicate that existing models and assumptions in existing simulations are able to relatively well account for the observed behavior. We suggest that discrepancies could be due to the high polydispersity and the irregular shape of our Na-fluorohectorite particles, as well as diffusive double-layer effects, which could result in a competition between nematic ordering and gelation. The dependence on ionic strength displays three main regimes irrespective of clay concentration. At low ionic strength (approximately 0.1-5 mM NaCl), the Debye screening length is longer than the van der Waals force range. In this regime, the particles repel each other electrostatically and entropy-driven Onsager-type nematic ordering may occur, although gelation effects could also play a role. For ionic strengths above about 5 mM, we believe that the van der Waals force comes into play and that particles attract each other locally according to the classical Derjaguin, Landau, Verwey, and Overbeek (DLVO) model of colloid interactions, resulting in a small-domain regime of attractive nematiclike ordering. In the third regime, for ionic strengths above approximately 10 mM, the clay particles aggregate into larger assemblies, due to the dominant van der Waals force, and the observed birefringency is reduced. We have studied the nematic phase in detail between crossed polarizers and have found textures showing nematic Schlieren patterns. By rotating the polarizers as well as the samples, we have observed examples of disclinations of strengths -1, -1/2, and +1.
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Affiliation(s)
- N I Ringdal
- Department of Physics, Norwegian University of Science and Technology, Hoegskoleringen 5, N-7491 Trondheim, Norway
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129
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Kinsela AS, Tjitradjaja A, Collins RN, Waite TD, Payne TE, Macdonald BC, White I. Influence of calcium and silica on hydraulic properties of sodium montmorillonite assemblages under alkaline conditions. J Colloid Interface Sci 2010; 343:366-73. [DOI: 10.1016/j.jcis.2009.10.044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Revised: 10/17/2009] [Accepted: 10/20/2009] [Indexed: 10/20/2022]
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130
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Mourad MCD, Byelov DV, Petukhov AV, Matthijs de Winter DA, Verkleij AJ, Lekkerkerker HNW. Sol-gel transitions and liquid crystal phase transitions in concentrated aqueous suspensions of colloidal gibbsite platelets. J Phys Chem B 2010; 113:11604-13. [PMID: 19655775 DOI: 10.1021/jp903783b] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this paper, we present a comprehensive study of the sol-gel transitions and liquid crystal phase transitions in aqueous suspensions of positively charged colloidal gibbsite platelets at pH 4-5 over a wide range of particle concentrations (50-600 g/L) and salt concentrations (10(-4)-10(-1) M NaCl). A detailed sol-gel diagram was established by oscillatory rheological experiments. These demonstrate the presence of kinetically arrested states both at high and at low salt concentrations, enclosing a sol region. Birefringence and iridescence show that in the sol state nematic and hexagonal columnar liquid crystal phases are formed. The gel and liquid crystal structures are studied in further detail using small-angle X-ray scattering (SAXS) and cryo-focused ion beam/scanning electron microscopy (cryo-FIB-SEM). The gel formed at high salt concentration shows signatures of a sponge-like structure and does not display birefringence. In the sol region, by lowering the salt concentration and/or increasing the gibbsite concentration, the nematic phase gradually transforms from the discotic nematic (ND) into the columnar nematic (NC) with much stronger side-to-side interparticle correlations. Subsequently, this NC structure can be either transformed into the hexagonal columnar phase or arrested into a birefringent repulsive gel state with NC structure.
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Affiliation(s)
- Maurice C D Mourad
- van 't Hoff Laboratory for Physical and Colloid Chemistry, Faculty of Sciences, Utrecht University, P.O. Box 80.056, 3508 TB Utrecht, The Netherlands.
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131
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Mourad MCD, Verhoeff AA, Byelov DV, Petukhov AV, Lekkerkerker HNW. Devitrification of the glassy state in suspensions of charged platelets. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:474218. [PMID: 21832497 DOI: 10.1088/0953-8984/21/47/474218] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Colloidal suspensions of charged gibbsite platelets at salt concentrations of 10(-2) M and below and with a sufficiently high particle concentration form a kinetically arrested, glassy state. We study the evolution of the glassy state in suspensions of three different gibbsite systems. Despite differences in size and polydispersity, we observe small, iridescent grains of the hexagonal columnar phase, for all these systems after periods of months to years. The connections between this devitrification phenomenon and the structure of the glassy state are discussed.
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Affiliation(s)
- M C D Mourad
- Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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132
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Paineau E, Antonova K, Baravian C, Bihannic I, Davidson P, Dozov I, Impéror-Clerc M, Levitz P, Madsen A, Meneau F, Michot LJ. Liquid-Crystalline Nematic Phase in Aqueous Suspensions of a Disk-Shaped Natural Beidellite Clay. J Phys Chem B 2009; 113:15858-69. [DOI: 10.1021/jp908326y] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- E. Paineau
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - K. Antonova
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - C. Baravian
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - I. Bihannic
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - P. Davidson
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - I. Dozov
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - M. Impéror-Clerc
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - P. Levitz
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - A. Madsen
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - F. Meneau
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
| | - L. J. Michot
- Laboratoire Environnement et Minéralurgie, Nancy University CNRS-INPL UMR 7569, BP40 54501 Vandœuvre Cedex France, Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chaussee 72, Sofia, 1784, Bulgaria, Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University UMR 7563 CNRS-INPL-UHP, 2, Avenue de la Forêt de Haye, BP160 54504 Vandœuvre Cedex, France, Laboratoire de Physique des Solides, UMR 8502 CNRS-Université Paris-Sud Bât 510 91405 Orsay
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Hemmen H, Ringdal NI, De Azevedo EN, Engelsberg M, Hansen EL, Méheust Y, Fossum JO, Knudsen KD. The isotropic-nematic interface in suspensions of Na-fluorohectorite synthetic clay. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:12507-12515. [PMID: 19856989 DOI: 10.1021/la901784k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Colloidal suspensions of Na-fluorohectorite synthetic clay platelets in saline water exhibit coexisting isotropic and nematic phases, due to gravitational separation of the polydisperse particles. We study the ordering of the platelets at the interfaces between various coexisting phases. Four different experimental techniques are employed: visual observation of birefringence, synchrotron wide angle and small-angle X-ray scattering, and magnetic resonance imaging. We find that at the narrow isotropic sol-nematic sol interface the platelets are lying horizontally, i.e. with their mean platelet normal along the vertical direction. The experiments indicate that the platelets align homeotropically both at the isotropic sol-nematic sol interface and at the nematic sol-wall interface. We further investigate the complex alignment effect of a horizontally applied magnetic field in the nematic sol, and we compare it with the adjacent nematic gel.
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Affiliation(s)
- Henrik Hemmen
- Department of Physics, Norwegian University of Science and Technology, Hoegskoleringen 5, N-7491, Trondheim, Norway.
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134
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Shukla A, Joshi YM. Ageing under oscillatory stress: Role of energy barrier distribution in thixotropic materials. Chem Eng Sci 2009. [DOI: 10.1016/j.ces.2009.03.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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135
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Nakato T, Miyamoto N. Liquid Crystalline Behavior and Related Properties of Colloidal Systems of Inorganic Oxide Nanosheets. MATERIALS 2009. [PMCID: PMC5525201 DOI: 10.3390/ma2041734] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Inorganic layered crystals exemplified by clay minerals can be exfoliated in solvents to form colloidal dispersions of extremely thin inorganic layers that are called nanosheets. The obtained “nanosheet colloids” form lyotropic liquid crystals because of the highly anisotropic shape of the nanosheets. This system is a rare example of liquid crystals consisting of inorganic crystalline mesogens. Nanosheet colloids of photocatalytically active semiconducting oxides can exhibit unusual photoresponses that are not observed for organic liquid crystals. This review summarizes experimental work on the phase behavior of the nanosheet colloids as well as photochemical reactions observed in the clay and semiconducting nanosheets system.
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Affiliation(s)
- Teruyuki Nakato
- Division of Bio-Applications and Systems Engineering (BASE), Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, Tokyo 184-8588, Japan
- Author to whom correspondence should be addressed; E-Mail: ; Tel./Fax: +81-42-388-7344
| | - Nobuyoshi Miyamoto
- Department of Life, Environment, and Materials Science, Faculty of Engineering, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka-shi, Fukuoka 811-0295, Japan; E-Mail:
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136
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Verhoeff AA, Wensink HH, Vis M, Jackson G, Lekkerkerker HNW. Liquid Crystal Phase Transitions in Systems of Colloidal Platelets with Bimodal Shape Distribution. J Phys Chem B 2009; 113:13476-84. [DOI: 10.1021/jp902858k] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- A. A. Verhoeff
- Van’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, and Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - H. H. Wensink
- Van’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, and Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - M. Vis
- Van’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, and Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - G. Jackson
- Van’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, and Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - H. N. W. Lekkerkerker
- Van’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, and Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
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137
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Porion P, Delville A. Multinuclear NMR study of the structure and micro-dynamics of counterions and water molecules within clay colloids. Curr Opin Colloid Interface Sci 2009. [DOI: 10.1016/j.cocis.2008.08.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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138
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Uniform discotic wax particles via electrospray emulsification. J Colloid Interface Sci 2009; 334:22-8. [DOI: 10.1016/j.jcis.2009.02.044] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2008] [Revised: 02/25/2009] [Accepted: 02/27/2009] [Indexed: 11/19/2022]
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139
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Zhang Z, Krishna N, Lettinga MP, Vermant J, Grelet E. Reversible gelation of rod-like viruses grafted with thermoresponsive polymers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:2437-42. [PMID: 19166277 DOI: 10.1021/la8029903] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The synthesis and selected macroscopic properties of a new model system consisting of poly(N-isopropylacrylamide) (PNIPAM)-coated rod-like fd virus particles are presented. The sticky rod-like colloids can be used to study effect of particle shape on gelation transition, the structure and viscoelasticity of isotropic and nematic gels, and to make both open isotropic as well as ordered nematic particle networks. This model system of rod-like colloids, for which the strength of attraction between the particles is tunable, is obtained by chemically grafting highly monodisperse rod-like fd virus particles with thermoresponsive polymers, e.g. PNIPAM. At room temperature, suspensions of the resulting hybrid PNIPAM-fd are fluid sols which are in isotropic or liquid crystalline phases, depending on the particle concentration and ionic strength. During heating/cooling, the suspensions change reversibly between sol and gel state near a critical temperature of approximately 32 degrees C, close to the lower critical solution temperature of free PNIPAM. The so-called nematic gel, which exhibits a cholesteric feature, can therefore be easily obtained. The gelation behavior of PNIPAM-fd system and the structure of the nematic gel have been characterized by rheology, optical microscopy and small-angle X-ray scattering.
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Affiliation(s)
- Zhenkun Zhang
- IFF, Institut Weiche Materie, Forschungszentrum Julich, D-52425 Julich, Germany
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140
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Chung I, Song JH, Jang JI, Freeman AJ, Ketterson JB, Kanatzidis MG. Flexible Polar Nanowires of Cs5BiP4Se12 from Weak Interactions between Coordination Complexes: Strong Nonlinear Optical Second Harmonic Generation. J Am Chem Soc 2009; 131:2647-56. [DOI: 10.1021/ja808242g] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- In Chung
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Chemistry and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208
| | - Jung-Hwan Song
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Chemistry and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208
| | - Joon I. Jang
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Chemistry and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208
| | - Arthur J. Freeman
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Chemistry and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208
| | - John B. Ketterson
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Chemistry and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208
| | - Mercouri G. Kanatzidis
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Chemistry and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208
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141
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de Azevedo EN, Engelsberg M. Strongly damped dynamics of nematically ordered colloidal clay platelets in a magnetic field. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1175-1180. [PMID: 19072575 DOI: 10.1021/la803110f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The anisotropy of the diffusivity of water molecules, probed via (1)H nuclear magnetic resonance imaging techniques, is used to study the extremely slow dynamics in the nematic phase of synthetic Na-fluorhectorite platelets in aqueous suspension. The anisotropy of the diamagnetic susceptibility of the platelets Deltachi, and the torque experienced in an applied magnetic field, permit one to monitor the time evolution starting from two different initial conditions. The dynamics of the ordered platelets can be modeled by a one-dimensional Fokker-Planck equation, which permits a satisfactory description of the experimental results. From the torque-free evolution, one concludes that the process is diffusive with an extremely slow rotational diffusivity D(phi) = 9.9 x 10(- 3) rad(2)/h. The forced evolution requires a numerical solution of the full Fokker-Planck equation and yields an effective, per platelet, diamagnetic susceptibility anisotropy Deltachi = - 1.63 x 10(- 20) J/T(2).
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Affiliation(s)
- Eduardo N de Azevedo
- Programa de Pos-Graduacao em Ciencia de Materiais, Universidade Federal de Pernambuco, Cidade Universitaria, 50670-901, Recife, Pernambuco, Brazil
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142
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Nakato T, Yamada Y, Miyamoto N. Photoinduced Charge Separation in a Colloidal System of Exfoliated Layered Semiconductor Controlled by Coexisting Aluminosilicate Clay. J Phys Chem B 2009; 113:1323-31. [DOI: 10.1021/jp807214w] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Teruyuki Nakato
- Division of Bio-Applications and Systems Engineering (BASE), Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, Tokyo 184-8588, Japan, and Department of Life, Environment, and Materials Science, Faculty of Engineering, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka-shi, Fukuoka 811-0295, Japan
| | - Yoshimi Yamada
- Division of Bio-Applications and Systems Engineering (BASE), Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, Tokyo 184-8588, Japan, and Department of Life, Environment, and Materials Science, Faculty of Engineering, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka-shi, Fukuoka 811-0295, Japan
| | - Nobuyoshi Miyamoto
- Division of Bio-Applications and Systems Engineering (BASE), Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, Tokyo 184-8588, Japan, and Department of Life, Environment, and Materials Science, Faculty of Engineering, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka-shi, Fukuoka 811-0295, Japan
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143
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Michot LJ, Baravian C, Bihannic I, Maddi S, Moyne C, Duval JFL, Levitz P, Davidson P. Sol-gel and isotropic/nematic transitions in aqueous suspensions of natural nontronite clay. Influence of particle anisotropy. 2. Gel structure and mechanical properties. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:127-139. [PMID: 19067578 DOI: 10.1021/la801894a] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
After size-selection, the phase behavior of aqueous suspensions of nontronite clay was analyzed by osmotic pressure measurements, rheological experiments, and small-angle X-ray scattering. All the measurements confirm that for ionic strength < or =10(-3) M/L, the system is purely repulsive. By combining results from osmotic pressure measurements and X-ray scattering, it appears that the pressure of the system can be well-described using a simple Poisson-Boltzmann treatment based on the interaction between charged infinite parallel planes. In terms of rheological properties, even if the status of the sol/gel transition remains partially unclear as the number density of particles at the sol-gel transition exhibits a -2 power dependence with average particle size, the yield stress and elasticity of the gels can be easily renormalized for all particle sizes on the basis of the volume of the particles. Furthermore, rheological modeling of the flow curves shows that for all the particles, an approach based on excluded volume effects captures most features of nontronite suspensions. Still, the high shear flow properties of the suspensions that reveal a strong orientation of particles in the flow are affected by electrostatic interactions. This study then shows that the rich phase behavior of clay minerals, notably the fact that some clay minerals display an isotropic/nematic transition while others exhibit a sol-gel transition, requires a full understanding of all the interactions in the system that can only be achieved by working on well-characterized size-selected samples.
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Affiliation(s)
- Laurent J Michot
- Laboratoire Environnement et Mineralurgie, Nancy University, CNRS-INPL UMR 7569 BP40 54501 Vandaeuvre Cedex, France.
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144
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145
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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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146
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Cousin F, Cabuil V, Grillo I, Levitz P. Competition between entropy and electrostatic interactions in a binary colloidal mixture of spheres and platelets. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:11422-11430. [PMID: 18781779 DOI: 10.1021/la8015595] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We describe the phase behavior of an aqueous mixture of discotic nanoparticles of laponite and spherical magnetic nanoparticles of maghemite. To obtain stable mixtures from a chemical point of view, the maghemite nanoparticles are first coated by a thin layer of silica in order to adapt their surface chemistry to that of laponite nanoparticles: this enables one to raise volume fractions of maghemite Phi mag in the laponite suspensions up to several percent. Although the system is out of equilibrium, a "fluid-solid" state diagram was established showing that the mixtures undergo a fluid-solid transition, similar to that of pure suspensions of laponite, over a given volume fraction of laponite Phi lap and over a given Phi mag. An increase in Phi mag shifts Phi lap toward the lower values. When a solid sample is just above Phi lap, the application of an external magnetic field gradient induces a solid-to-liquid transition if the sample is located not too far from Phi lap on the state diagram. The structure of the mixtures, determined either at small scale by small-angle neutron scattering (SANS) or at intermediate scales by optical microscopy, shows that the solid samples are phase separated at a local scale: they are made of densely connected domains of laponite nanoparticles surrounding liquid pockets of maghemite nanoparticles. The size of the pockets grows with time. The magnetic liquid pockets are responsible for the rupture of the solid samples when an external magnetic field gradient is applied since their deformation induces local mechanical stress, internally damaging the network formed by the solid domains of laponite. The microscopic phase separation is the result of two opposite effects: (i) entropic effects that tend to phase separate the system macroscopically when the packing entropy overcomes the orientational entropy and (ii) long-range electrostatic repulsions that freeze the system.
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Affiliation(s)
- Fabrice Cousin
- Laboratoire Leon Brillouin, CEA-CNRS, CEA-Saclay, 91191 Gif-sur-Yvette, France.
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147
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Mourad MCD, Devid EJ, van Schooneveld MM, Vonk C, Lekkerkerker HNW. Formation of nematic liquid crystals of sterically stabilized layered double hydroxide platelets. J Phys Chem B 2008; 112:10142-52. [PMID: 18651762 DOI: 10.1021/jp803114v] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Colloidal platelets of hydrotalcite, a layered double hydroxide, have been prepared by coprecipitation at pH 11-12 of magnesium nitrate and aluminum nitrate at two different magnesium to aluminum ratios. Changing the temperature and ionic strength during hydrothermal treatment, the platelets were tailored to different sizes and aspect ratios. Amino-modified polyisobutylene molecules were grafted onto the platelets following a convenient new route involving freeze-drying. Organic dispersions in toluene were prepared of the particles with the largest size and highest aspect ratio. The colloidal dispersions prepared in this way showed isotropic-nematic phase transitions above a limiting concentration in a matter of days. The number density at the transition and the width of the biphasic region were determined and compared to theory. The orientation of the platelets in nematic droplets (tactoids) and at the isotropic-nematic interface were analyzed by polarization microscopy. It was observed that sedimentation induces a nematic layer in samples that are below the limiting concentration for isotropic-nematic phase separation. No nematic phase was observed in the initial aqueous suspensions of the ungrafted particles.
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Affiliation(s)
- Maurice C D Mourad
- van't Hoff Laboratory for Physical and Colloid Chemistry, Utrecht University, Utrecht, The Netherlands.
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148
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Engelsberg M, de Azevedo EN. Diamagnetic Orientation of a Fluid of Hard Thin Disks and Anisotropy of the Water Diffusivity in the Nematic Phase of a Suspension of Clay Platelets. J Phys Chem B 2008; 112:7045-50. [DOI: 10.1021/jp710615v] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- M. Engelsberg
- Departamento de Física, Universidade Federal de Pernambuco, and Programa de Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, 50670-901 Recife, Pernambuco, Brazil
| | - E. N. de Azevedo
- Departamento de Física, Universidade Federal de Pernambuco, and Programa de Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, 50670-901 Recife, Pernambuco, Brazil
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149
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Page MG, Zemb T, Dubois M, Cölfen H. Osmotic Pressure and Phase Boundary Determination of Multiphase Systems by Analytical Ultracentrifugation. Chemphyschem 2008; 9:882-90. [DOI: 10.1002/cphc.200700668] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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150
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Santiwong S, Chang S, Waite T. Determination of hydraulic and depth-dependent properties of nematically ordered montmorillonite assemblages during microfiltration. J Memb Sci 2008. [DOI: 10.1016/j.memsci.2008.01.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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