101
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Goel V, Pietrasik J, Dong H, Sharma J, Matyjaszewski K, Krishnamoorti R. Structure of Polymer Tethered Highly Grafted Nanoparticles. Macromolecules 2011. [DOI: 10.1021/ma200621r] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Vivek Goel
- Department of Chemical Engineering, University of Houston, Houston, Texas 77204, United States
| | - Joanna Pietrasik
- Department of Chemistry, Institute of Polymer and Dye Technology, Technical University of Lodz, 90 924 Lodz, Poland
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Hongchen Dong
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Jitendra Sharma
- Department of Chemical Engineering, University of Houston, Houston, Texas 77204, United States
| | - Krzysztof Matyjaszewski
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Ramanan Krishnamoorti
- Department of Chemical Engineering, University of Houston, Houston, Texas 77204, United States
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102
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Schöpe HJ, Wette P. Seed- and wall-induced heterogeneous nucleation in charged colloidal model systems under microgravity. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 83:051405. [PMID: 21728532 DOI: 10.1103/physreve.83.051405] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 03/19/2011] [Indexed: 05/31/2023]
Abstract
Understanding the process that drives an undercooled fluid to the crystal state is still a challenging issue for condensed matter physics and plays a key role in designing new materials. The crystallization kinetics and the resulting polycrystalline morphology are given by a complex interplay of crystal nucleation, growth, and ripening. A great deal of progress has been made in recent years using colloidal suspensions as model systems in the study of crystallization. Close analogies to atomic systems are observed which can be exploited to address questions not accessible in atomic solidification. Here we present systematic measurements of the crystallization kinetics of a charged colloidal model system adding small amounts of seeds using time resolved scattering techniques. Large seeds show strong sedimentation under gravity even on the time scale of the crystallization process. To avoid this problem we performed our measurements under microgravity during parabolic flights. We report how the seed size and structure affect crystal nucleation and growth as functions of metastability giving the possibility to modify the crystallization process and the resulting microstructure of the polycrystal.
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103
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Bartlett AP, Agarwal AK, Yethiraj A. Dynamic templating of colloidal patterns in three dimensions with nonuniform electric fields. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:4313-4318. [PMID: 21417342 DOI: 10.1021/la200179c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Order-disorder transitions in colloidal systems are an attractive option for making switchable materials. Electric-field-driven order-disorder transitions are especially attractive for this purpose because the tuning parameter is easily and externally controllable. However, precise positional control of 3D structure is immensely challenging. Using patterned electrodes, we demonstrate that ac electric fields-dominantly dielectrophoresis (DEP) coupled with an electrohydrodynamic mechanism consisting of induced-charge electro-osmosis (ICEO)-can be used to template colloidal order dynamically in three dimensions. We find that the electric field geometry dictates the location, size, and shape of colloidal patterns and can produce patterns with surprising complexity.
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Affiliation(s)
- Andrew P Bartlett
- Department of Physics and Physical Oceanography, Memorial University, St. John's, Newfoundland and Labrador, Canada A1B 3X7
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104
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Pichumani M, Giuliani M, González-Viñas W. One-dimensional cluster array at the three-phase contact line in diluted colloids subjected to ac electric fields. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 83:047301. [PMID: 21599340 DOI: 10.1103/physreve.83.047301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Indexed: 05/30/2023]
Abstract
Colloidal particles provide an efficient means of building multiple scale structured materials from colloidal dispersions. In this Brief Report we account for experimental evidence on the formation of a colloidal cluster array at a three-phase contact line. We study the influence of low frequency external alternating electric fields on a diluted colloidal dispersion opened to the air. We focus on the cluster formation and their evolution in the meniscus by measuring characteristic times and lengths. We observe that the clusters are separated by a well-defined length and that, in our experimental conditions, they survive between 5 and 15 min. These new results could be of technological relevance in building tailored colloidal structures in nonpatterned substrates.
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Affiliation(s)
- M Pichumani
- Department of Physics and Applied Mathematics, University of Navarra, Irunlarrea s/n, E-31080 Pamplona, Spain
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105
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Jeong KU, Jang JH, Kim DY, Nah C, Lee JH, Lee MH, Sun HJ, Wang CL, Cheng SZD, Thomas EL. Three-dimensional actuators transformed from the programmed two-dimensional structures via bending, twisting and folding mechanisms. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c0jm03631e] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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106
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Dutta N, Green D. Impact of solvent quality on nanoparticle dispersion in semidilute and concentrated polymer solutions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:16737-16744. [PMID: 20973521 DOI: 10.1021/la102401w] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We investigated how solvent quality affects the stability of polymer-grafted nanoparticles in semidilute and concentrated polymer solutions, which extends our previous studies on these types of dispersions in good solvents [Langmuir 2008, 24, 5260-5269]. As discussed in the current article, dynamic light scattering (DLS) was used to quantify the diffusion of polydimethylsiloxane-grafted silica nanoparticles, or PDMS-g-silica, in bromocyclohexane as well as in PDMS/bromocyclohexane solutions. We established that bromocyclohexane is a theta solvent for PDMS by varying the temperature of the solutions with PDMS-g-silica nanoparticles and detecting their aggregation at a theta temperature of T(Θ) = 19.6 °C. Using this temperature as a benchmark for the transition between good and bad solvent conditions, further stability tests were carried out in semidilute and concentrated polymer solutions of PDMS in bromocyclohexane at T = 10-60 °C. Irrespective of temperature, i.e., solvent quality, we found that the nanoparticles dispersed uniformly when molecular weight of the graft polymer was greater than that of the free polymer. However, when the free polymer molecular weight was greater than that of the graft polymer, the nanoparticles aggregated. Visual studies were also used to confirm the correspondence between nanoparticle stability and graft and free polymer molecular weights in a wide range of marginally poor solvents with PDMS. Further, the correspondence between nanoparticle stability and instability with graft and free polymer molecular weight and solvent quality was also supported with self-consistent mean-field calculations. Thus, by relating experiment and theory, our results indicate that nanoparticle stability in semidilute and concentrated polymer solutions is governed by interactions between the graft and free polymers under conditions of variable solvency.
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Affiliation(s)
- Nupur Dutta
- Department of Chemical Engineering, University of Virginia, 102 Engineers Way, Charlottesville, Virginia 22904, United States
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107
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Li F, Josephson DP, Stein A. Colloidal Assembly: The Road from Particles to Colloidal Molecules and Crystals. Angew Chem Int Ed Engl 2010; 50:360-88. [PMID: 21038335 DOI: 10.1002/anie.201001451] [Citation(s) in RCA: 472] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Fan Li
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN 55455, USA
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108
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Li F, Josephson DP, Stein A. Kolloidale Organisation: der Weg vom Partikel zu kolloidalen Molekülen und Kristallen. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201001451] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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109
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Bohn JJ, Tikhonov A, Asher SA. Colloidal crystal growth monitored by Bragg diffraction interference fringes. J Colloid Interface Sci 2010; 350:381-6. [PMID: 20542277 PMCID: PMC2926244 DOI: 10.1016/j.jcis.2010.04.072] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 04/15/2010] [Accepted: 04/26/2010] [Indexed: 11/18/2022]
Abstract
We monitored the crystal growth kinetics of crystallization of a shear melted crystalline colloidal array (CCA). The fcc CCA heterogeneously nucleates at the flow cell wall surface. We examined the evolution of the (1 1 1) Bragg diffraction peak, and, for the first time, quantitatively monitored growth by measuring the temporal evolution of the Bragg diffraction interference fringes. Modeling of the evolution of the fringe patterns exposes the time dependence of the increasing crystal thickness. The initial diffusion-driven linear growth is followed by ripening-driven growth. Between 80 and 90 microM NaCl concentrations the fcc crystals first linearly grow at rates between 1.9 and 4.2 microm/s until they contact homogeneously nucleated crystals in the bulk. At lower salt concentrations interference fringes are not visible because the strong electrostatic interactions between particles result in high activation barriers, preventing defect annealing and leading to a lower crystal quality. The fcc crystals melt to a liquid phase at >90 microM NaCl concentrations. Increasing NaCl concentrations slow the fcc CCA growth rate consistent with the expectation of the classical Wilson-Frenkel growth theory. The final thickness of wall-nucleated CCA, that is determined by the competition between growth of heterogeneously and homogenously nucleated CCA, increases with higher NaCl concentrations.
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Affiliation(s)
- Justin J. Bohn
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, USA
| | - Alexander Tikhonov
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, USA
| | - Sanford A. Asher
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, USA
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110
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Stipp A, Schöpe HJ, Palberg T, Eckert T, Biehl R, Bartsch E. Optical experiments on a crystallizing hard-sphere-polymer mixture at coexistence. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:051401. [PMID: 20866224 DOI: 10.1103/physreve.81.051401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Indexed: 05/29/2023]
Abstract
We report on the crystallization kinetics in an entropically attractive colloidal system using a combination of time resolved scattering methods and microscopy. Hard sphere particles are polystyrene microgels swollen in a good solvent (radius a=380 nm, starting volume fraction 0.534) with the short ranged attractions induced by the presence of short polymer chains (radius of gyration r g=3 nm, starting volume fraction 0.0224). After crystallization, stacking faulted face centered cubic crystals coexist with about 5% of melt remaining in the grain boundaries. From the Bragg scattering signal we infer the amount of crystalline material, the average crystallite size and the number density of crystals as a function of time. This allows to discriminate an early stage of conversion, followed by an extended coarsening stage. The small angle scattering (SALS) appears only long after completed conversion and exhibits Furukawa scaling for all times. Additional microscopic experiments reveal that the grain boundaries have a reduced Bragg scattering power but possess an increased refractive index. Fits of the Furukawa function indicate that the dimensionality of the scatterers decreases from 2.25 at short times to 1.65 at late times and the characteristic length scale is slightly larger than the average crystallite size. Together this suggests the SALS signal is due scattering from a foam like grain boundary network as a whole.
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Affiliation(s)
- Andreas Stipp
- Institut für Physik, Johannes Gutenberg Universität, Staudingerweg 7, D-55128 Mainz, Germany
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111
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Wette P, Klassen I, Holland-Moritz D, Herlach DM, Schöpe HJ, Lorenz N, Reiber H, Palberg T, Roth SV. Communications: Complete description of re-entrant phase behavior in a charge variable colloidal model system. J Chem Phys 2010; 132:131102. [DOI: 10.1063/1.3380823] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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112
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Lorenz NJ, Schöpe HJ, Reiber H, Palberg T, Wette P, Klassen I, Holland-Moritz D, Herlach D, Okubo T. Phase behaviour of deionized binary mixtures of charged colloidal spheres. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:464116. [PMID: 21715880 DOI: 10.1088/0953-8984/21/46/464116] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We review recent work on the phase behaviour of binary charged sphere mixtures as a function of particle concentration and composition. Both size ratios Γ and charge ratios Λ are varied over a wide range. Unlike the case for hard spheres, the long-ranged Coulomb interaction stabilizes the crystal phase at low particle concentrations and shifts the occurrence of amorphous solids to particle concentrations considerably larger than the freezing concentration. Depending on Γ and Λ, we observe upper azeotrope, spindle, lower azeotrope and eutectic types of phase diagrams, all known well from metal systems. Most solids are of body centred cubic structure. Occasionally stoichiometric compounds are formed at large particle concentrations. For very low Γ, entropic effects dominate and induce a fluid-fluid phase separation. Since for charged spheres the charge ratio Λ is also decisive for the type of phase diagram, future experiments with charge variable silica spheres are suggested.
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Affiliation(s)
- Nina J Lorenz
- Institut für Physik, Johannes Gutenberg Universität Mainz, Staudinger Weg 7, D-55128 Mainz, Germany
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113
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Wette P, Engelbrecht A, Salh R, Klassen I, Menke D, Herlach DM, Roth SV, Schöpe HJ. Competition between heterogeneous and homogeneous nucleation near a flat wall. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:464115. [PMID: 21715879 DOI: 10.1088/0953-8984/21/46/464115] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We studied the competition between heterogeneous and homogeneous nucleation of an aqueous suspension of charged colloidal spheres close to the container walls. Samples of equilibrium crystalline structure were shear-melted and the metastable melt left to solidify after the cessation of shear. The crystallization kinetics was monitored using time-resolved scattering techniques: at low particle number densities n we applied an improved static light scattering method while at large particle concentrations ultra-small-angle x-ray scattering was applied for the first time. Our results show some unexpected behavior: the heterogeneous nucleation at the container walls is delayed in comparison to the homogeneous bulk nucleation and its rate density appears surprisingly slightly smaller, demonstrating the complexity of the observed crystallization process.
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Affiliation(s)
- Patrick Wette
- Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), D-51170 Köln, Germany
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114
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Agarwal AK, Yethiraj A. Low-density ordered phase in brownian dipolar colloidal suspensions. PHYSICAL REVIEW LETTERS 2009; 102:198301. [PMID: 19519002 DOI: 10.1103/physrevlett.102.198301] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Revised: 12/11/2008] [Indexed: 05/27/2023]
Abstract
We study the low volume fraction and electric field phase behavior of a Brownian colloidal suspension. On the application of a uniform ac field, we find a novel phase where chains of particles aggregate to form a well defined cellular network, consisting of particle-free "voids" surrounded by a percolating network of particle-rich walls. This cellular structure is stable to very long times, indicative of an equilibrium thermodynamic phase. The cell-cell spacing is not sensitive to the concentration of the sample but scales with sample thickness. Any self-consistent mechanism for the existence of this void phase must consist of long-ranged repulsions and shorter-ranged attractions.
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Affiliation(s)
- Amit K Agarwal
- Department of Physics and Physical Oceanography, Memorial University, St. John's, Newfoundland and Labrador, A1B 3X7, Canada.
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115
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Zhang J, Sun Z, Yang B. Self-assembly of photonic crystals from polymer colloids. Curr Opin Colloid Interface Sci 2009. [DOI: 10.1016/j.cocis.2008.09.001] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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116
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Palberg T, Stipp A, Bartsch E. Unusual crystallization kinetics in a hard sphere colloid-polymer mixture. PHYSICAL REVIEW LETTERS 2009; 102:038302. [PMID: 19257401 DOI: 10.1103/physrevlett.102.038302] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Indexed: 05/27/2023]
Abstract
We investigated the crystallization kinetics of a hard sphere colloid-polymer mixture at conditions where about 95% of solid coexists with about 5% of fluid. From time resolved Bragg and small angle light scattering, we find that the crystallite size increases with a power law of exponent alpha approximately 1/3 during both the conversion and the coarsening stage. This observation points to a single conserved order parameter for both stages and cannot be explained if the mixture is regarded as an effective one-component system. We alternatively suggest that--based on local geometric demixing--the polymer density takes the role of the conserved order parameter.
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Affiliation(s)
- Thomas Palberg
- Johannes Gutenberg Universität, Institut für Physik, Staudingerweg 7, D-55128 Mainz, Germany
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117
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Haro-Pérez C, Rojas-Ochoa LF, Castañeda-Priego R, Quesada-Pérez M, Callejas-Fernández J, Hidalgo-Alvarez R, Trappe V. Dynamic arrest in charged colloidal systems exhibiting large-scale structural heterogeneities. PHYSICAL REVIEW LETTERS 2009; 102:018301. [PMID: 19257245 DOI: 10.1103/physrevlett.102.018301] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2008] [Revised: 09/09/2008] [Indexed: 05/27/2023]
Abstract
Suspensions of charged liposomes are found to exhibit typical features of strongly repulsive fluid systems at short length scales, while exhibiting structural heterogeneities at larger length scales that are characteristic of attractive systems. We model the static structure factor of these systems using effective pair interaction potentials composed of a long-range attraction and a shorter range repulsion. Our modeling of the static structure yields conditions for dynamically arrested states at larger volume fractions, which we find to agree with the experimentally observed dynamics.
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Affiliation(s)
- C Haro-Pérez
- Grupo de Física de Fluidos y Biocoloides, Departamento de Física Aplicada, Universidad de Granada, 18071 Granada, Spain
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118
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Jeong KU, Jang JH, Koh CY, Graham MJ, Jin KY, Park SJ, Nah C, Lee MH, Cheng SZD, Thomas EL. Colour-tunable spiral photonic actuators. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b822980p] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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119
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Wette P, Klassen I, Holland-Moritz D, Palberg T, Roth SV, Herlach DM. Colloids as model systems for liquid undercooled metals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:010501. [PMID: 19256992 DOI: 10.1103/physreve.79.010501] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Indexed: 05/27/2023]
Abstract
Charged colloidal particles interact via a hard core Yukawa potential, while isotropic Lennard-Jones-like potentials are frequently used as pair potentials in metals. We present measurements of the structure factor of shear molten monodisperse colloids and molten metals using ultrasmall-angle x-ray scattering and elastic neutron scattering, respectively. In both systems data analysis gives evidence of fivefold-symmetric short-range order becoming more pronounced with increasing deviations from equilibrium. The experiments demonstrate that in both systems topological effects control ordering in the melt state.
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Affiliation(s)
- Patrick Wette
- Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, 51170 Köln, Germany
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120
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Schmiedeberg M, Stark H. Colloidal ordering on a 2D quasicrystalline substrate. PHYSICAL REVIEW LETTERS 2008; 101:218302. [PMID: 19113456 DOI: 10.1103/physrevlett.101.218302] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Indexed: 05/27/2023]
Abstract
By using Monte Carlo simulations, we study the complex phase behavior of charged-stabilized colloidal particles in a two-dimensional substrate potential with quasicrystalline decagonal symmetry. In the regime where the strengths of the substrate and colloidal pair potential are comparable, we identify a novel and unexpected quasicrystalline phase with pure 20-fold bond order and a disordered structure without any apparent rotational symmetry. Furthermore, we demonstrate how phasonic displacements in the substrate potential induce phasonic flips in the colloidal monolayer.
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Affiliation(s)
- Michael Schmiedeberg
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany
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121
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Mohanty PS, Richtering W. Structural Ordering and Phase Behavior of Charged Microgels. J Phys Chem B 2008; 112:14692-7. [DOI: 10.1021/jp808203d] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- P. S. Mohanty
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany
| | - W. Richtering
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany
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122
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Archimedean-like tiling on decagonal quasicrystalline surfaces. Nature 2008; 454:501-4. [PMID: 18650921 DOI: 10.1038/nature07074] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Accepted: 05/06/2008] [Indexed: 11/08/2022]
Abstract
Monolayers on crystalline surfaces often form complex structures with physical and chemical properties that differ strongly from those of their bulk phases. Such hetero-epitactic overlayers are currently used in nanotechnology and understanding their growth mechanism is important for the development of new materials and devices. In comparison with crystals, quasicrystalline surfaces exhibit much larger structural and chemical complexity leading, for example, to unusual frictional, catalytical or optical properties. Deposition of thin films on such substrates can lead to structures that may have typical quasicrystalline properties. Recent experiments have indeed showed 5-fold symmetries in the diffraction pattern of metallic layers adsorbed on quasicrystals. Here we report a real-space investigation of the phase behaviour of a colloidal monolayer interacting with a quasicrystalline decagonal substrate created by interfering five laser beams. We find a pseudomorphic phase that shows both crystalline and quasicrystalline structural properties. It can be described by an archimedean-like tiling consisting of alternating rows of square and triangular tiles. The calculated diffraction pattern of this phase is in agreement with recent observations of copper adsorbed on icosahedral Al(70)Pd(21)Mn(9) surfaces. In addition to establishing a link between archimedean tilings and quasicrystals, our experiments allow us to investigate in real space how single-element monolayers can form commensurate structures on quasicrystalline surfaces.
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123
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Cerdà JJ, Sintes T, Holm C, Sorensen CM, Chakrabarti A. Shear effects on crystal nucleation in colloidal suspensions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:031403. [PMID: 18851034 DOI: 10.1103/physreve.78.031403] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2008] [Indexed: 05/26/2023]
Abstract
Extensive two-dimensional Langevin dynamics simulations are used to determine the effect of steady shear flows on the crystal nucleation kinetics of charge stabilized colloids and colloids whose pair potential possess an attractive shallow well of a few k_{B}T 's (attractive colloids). Results show that in both types of systems small amounts of shear speeds up the crystallization process and enhances the quality of the growing crystal significantly. Moderate shear rates, on the other hand, destroy the ordering in the system. The very high shear rate regime where a reentering transition to the ordered state could exist is not considered in this work. In addition to the crystal nucleation phenomena, the analysis of the transport properties and the characterization of the steady state regime under shear are performed.
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Affiliation(s)
- Juan J Cerdà
- Frankfurt Institute for Advanced Studies, J. W. Goethe-Universität, Ruth-Moufang-Strasse 1, D-60438, Frankfurt am Main, Germany
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124
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Mittal M, Lele PP, Kaler EW, Furst EM. Polarization and interactions of colloidal particles in ac electric fields. J Chem Phys 2008; 129:064513. [DOI: 10.1063/1.2969103] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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125
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Arcos C, Kumar K, González-Viñas W, Sirera R, Poduska KM, Yethiraj A. Orientationally correlated colloidal polycrystals without long-range positional order. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:050402. [PMID: 18643013 DOI: 10.1103/physreve.77.050402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Revised: 03/31/2008] [Indexed: 05/08/2023]
Abstract
We probe the local and global structure of spin-coated colloidal crystals via laser diffraction measurements and scanning electron and atomic force microscopies, and find that they are unique three-dimensional orientationally correlated polycrystals, exhibiting short-range positional order but long-range radial orientational correlations, reminiscent of-but distinct from-two-dimensional colloidal hexatic phases. Thickness and symmetries are controllable by solvent choice and spin speed. While the polycrystallinity of these colloidal films limits their applicability to photonics, we demonstrate their feasibility as templates to make crack-free magnetic patterns.
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Affiliation(s)
- Cristina Arcos
- Department of Physics and Physical Oceanography, Memorial University, St. John's, NL, Canada A1B 3X7
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Palit S, Yethiraj A. A new model system for diffusion NMR studies of concentrated monodisperse and bidisperse colloids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:3747-3751. [PMID: 18302433 DOI: 10.1021/la703402b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A method to prepare monodisperse and simultaneously NMR-visible and fluorescent colloidal particles is described, and a systematic approach to obtain spectrally resolved diffusion coefficient for every component in a monodisperse colloidal suspension is presented. We also prepared bidisperse colloidal suspensions, where each colloid component has a distinct NMR spectral signature, and obtained the diffusion coefficients of both colloid species simultaneously in concentrated colloidal suspensions, with volume fractions between 20 and 50%. The colloidal model system developed in this work enables the study of colloidal phase behavior in binary mixtures for different number and size ratios.
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Affiliation(s)
- Swomitra Palit
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, NL, Canada
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