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Parreño O, Ramos PM, Karayiannis NC, Laso M. Self-Avoiding Random Walks as a Model to Study Athermal Linear Polymers under Extreme Plate Confinement. Polymers (Basel) 2020; 12:E799. [PMID: 32260075 PMCID: PMC7240602 DOI: 10.3390/polym12040799] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 03/24/2020] [Accepted: 03/25/2020] [Indexed: 02/04/2023] Open
Abstract
Monte Carlo (MC) simulations, built around chain-connectivity-altering moves and a wall-displacement algorithm, allow us to simulate freely-jointed chains of tangent hard spheres of uniform size under extreme confinement. The latter is realized through the presence of two impenetrable, flat, and parallel plates. Extreme conditions correspond to the case where the distance between the plates approaches the monomer size. An analysis of the local structure, based on the characteristic crystallographic element (CCE) norm, detects crystal nucleation and growth at packing densities well below the ones observed in bulk analogs. In a second step, we map the confined polymer chains into self-avoiding random walks (SAWs) on restricted lattices. We study all realizations of the cubic crystal system: simple, body centered, and face centered cubic crystals. For a given chain size (SAW length), lattice type, origin of SAW, and level of confinement, we enumerate all possible SAWs (equivalently all chain conformations) and calculate the size distribution. Results for intermediate SAW lengths are used to predict the behavior of long, fully entangled chains through growth formulas. The SAW analysis will allow us to determine the corresponding configurational entropy, as it is the driving force for the observed phase transition and the determining factor for the thermodynamic stability of the corresponding crystal morphologies.
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Key Words
- confinement, crystallization, entropy, hard sphere, polymer, random walk, Monte Carlo, phase transition, lattice model, cubic crystal system, direct enumeration
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Affiliation(s)
| | | | - Nikos Ch. Karayiannis
- Institute for Optoelectronic Systems and Microtechnology (ISOM) and Escuela Técnica Superior de Ingenieros Industriales (ETSII), Universidad Politecnica de Madrid (UPM), José Gutierrez Abascal 2, 28006 Madrid, Spain; (O.P.); (P.M.R.); (M.L.)
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2
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PVB/ATO Nanocomposites for Glass Coating Applications: Effects of Nanoparticles on the PVB Matrix. COATINGS 2019. [DOI: 10.3390/coatings9040247] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Films made of poly(vinyl butyral) (PVB) and antimony-doped tin oxide (ATO) nanoparticles (NPs), both uncoated and surface-modified with an alkoxysilane, were prepared by solution casting at filler volume fractions ranging from 0.08% to 4.5%. The films were characterized by standard techniques including transmission electron microscopy, thermogravimetric analysis and differential scanning calorimetry (DSC). In the polymeric matrix, the primary NPs (diameter ~10 nm) aggregate exhibiting different morphologies depending on the presence of the surface coating. Coated ATO NPs form spherical particles (with a diameter of 300–500 nm), whereas more elongated fractal structures (with a thickness of ~250 nm and length of tens of micrometers) are formed by uncoated NPs. The fraction of the polymer interacting with the NPs is always negligible. In agreement with this finding, DSC data did not reveal any rigid interface and 1H time domain nuclear magnetic resonance (NMR) and fast field-cycling NMR did not show significant differences in polymer dynamics among the different samples. The ultraviolet-visible-near infrared (UV-Vis-NIR) transmittance of the films decreased compared to pure PVB, especially in the NIR range. The solar direct transmittance and the light transmittance were extracted from the spectra according to CEN EN 410/2011 in order to test the performance of our films as plastic layers in laminated glass for glazing.
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Papacharalambous M, Karvounis G, Kenanakis G, Gupta A, Rubinsky B. The Effect of Textiles Impregnated with Particles of High Emissivity in the Far Infrared, on the Temperature of the Cold Hand. J Biomech Eng 2018; 141:2716676. [PMID: 30458507 DOI: 10.1115/1.4042044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Indexed: 11/08/2022]
Abstract
In engineering and medicine, there is a growing interest in using textiles made of composites with enhanced thermal properties. One such type of textile is fabric impregnated with ceramics and mineral particles. This material has high emissivity in the infrared range and may have therapeutic benefits for treatments of diseases, like Raynaud's syndrome. While there is significant clinical and commercial interest, there is an evident lack of fundamental studies on the heat transfer aspects of these fabrics. The goal of this technical brief is to presents results from a fundamental study examining the thermal effects of fabric with ceramics and minerals (produced by Nanobionic Inc.) on the temperatures of the hands. With a confidence level of 90%, the results show that the textile with ceramics and minerals has an enhanced thermal effect on warming a cold hand in comparison to a placebo fabric without ceramics or minerals. Much more research is needed to increase the level of confidence and develop a fundamental understanding of the mechanism.
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Affiliation(s)
- Michael Papacharalambous
- Chief of Internal Medicine, Orthobiotiki Medical Center, 3-5 Sorou, Marousi, 15125, Athens, Greece
| | - Georgia Karvounis
- Orthobiotiki Medical Center, 3-5 Sorou, Marousi, 15125, Athens, Greece
| | - George Kenanakis
- Foundation for Research & Technology - Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), N. Plastira 100, Vasilika Vouton, Heraklion, Crete, GR - 700 13, Greece
| | - Anshal Gupta
- Department of Mechanical Engineering, University of California Berkeley, Berkeley CA 94720 USA
| | - Boris Rubinsky
- Fellow ASME, Department of Mechanical Engineering, University of California Berkeley, Berkeley CA 94720 USA
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Schulz M, Keddie JL. A critical and quantitative review of the stratification of particles during the drying of colloidal films. SOFT MATTER 2018; 14:6181-6197. [PMID: 30024010 DOI: 10.1039/c8sm01025k] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
For a wide range of applications, films are deposited from colloidal particles suspended in a volatile liquid. There is burgeoning interest in stratifying colloidal particles into separate layers within the final dry film to impart properties at the surface different to the interior. Here, we outline the mechanisms by which colloidal mixtures can stratify during the drying process. The problem is considered here as a three-way competition between evaporation of the continuous liquid, sedimentation of particles, and their Brownian diffusion. In particle mixtures, the sedimentation of larger or denser particles offers one means of stratification. When the rate of evaporation is fast relative to diffusion, binary mixtures of large and small particles can stratify with small particles on the top, according to physical models and computer simulations. We compare experimental results found in the scientific literature to the predictions of several recent models in a quantitative way. Although there is not perfect agreement between them, some general trends emerge in the experiments, simulations and models. The stratification of small particles on the top of a film is favoured when the colloidal suspension is dilute but when both the concentration of the small particles and the solvent evaporation rate are sufficiently high. A higher particle size ratio also favours stratification by size. This review points to ways that microstructures can be designed and controlled in colloidal materials to achieve desired properties.
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Affiliation(s)
- M Schulz
- Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, England, UK.
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Lee J, Lee SJ, Ahn KH, Lee SJ. Bimodal colloid gels of highly size-asymmetric particles. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:012313. [PMID: 26274168 DOI: 10.1103/physreve.92.012313] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Indexed: 06/04/2023]
Abstract
We report a type of colloidal gel, induced by a minute incremental addition of mutually attractive small particles (size ∼12 nm) to a suspension of highly charged large particles (size ∼500 nm). The gel's morphological behavior does not follow the typical power-law scaling for fractal clusters. Its unique scaling behavior has two distinct power-law indices, based on particle volume fraction. We show the unique scaling behavior arises when nonfractal networks of large particles are bridged by small-particle clusters, which occurs between a lower and upper critical boundary of small particle volume fraction.
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Affiliation(s)
- Jooyoung Lee
- School of Chemical and Biological Engineering, Institute of Chemical Process, Seoul National University, Seoul, 151-744 Korea
| | - Seong Jae Lee
- Department of Polymer Engineering, The University of Suwon, Gyeonggi, 445-743 Korea
| | - Kyung Hyun Ahn
- School of Chemical and Biological Engineering, Institute of Chemical Process, Seoul National University, Seoul, 151-744 Korea
| | - Seung Jong Lee
- School of Chemical and Biological Engineering, Institute of Chemical Process, Seoul National University, Seoul, 151-744 Korea
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Blattmann CO, Sotiriou GA, Pratsinis SE. Rapid synthesis of flexible conductive polymer nanocomposite films. NANOTECHNOLOGY 2015; 26:125601. [PMID: 25736387 DOI: 10.1088/0957-4484/26/12/125601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Polymer nanocomposite films with nanoparticle-specific properties are sought out in novel functional materials and miniaturized devices for electronic and biomedical applications. Sensors, capacitors, actuators, displays, circuit boards, solar cells, electromagnetic shields and medical electrodes rely on flexible, electrically conductive layers or films. Scalable synthesis of such nanocomposite films, however, remains a challenge. Here, flame aerosol deposition of metallic nanosliver onto bare or polymer-coated glass substrates followed by polymer spin-coating on them leads to rapid synthesis of flexible, free-standing, electrically conductive nanocomposite films. Their electrical conductivity is determined during their preparation and depends on substrate composition and nanosilver deposition duration. Accordingly, thin (<500 nm) and flexible nanocomposite films are made having conductivity equivalent to metals (e.g. 5 × 10(4) S cm(-1)), even during repetitive bending.
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Affiliation(s)
- C O Blattmann
- Particle Technology Laboratory, Institute of Process Engineering, Department of Mechanical and Process Engineering, ETH Zürich, Sonneggstrasse 3, 8092 Zürich, Switzerland
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Sung S, Kim DS. UV-curing and mechanical properties of polyester-acrylate nanocomposites films with silane-modified antimony doped tin oxide nanoparticles. J Appl Polym Sci 2012. [DOI: 10.1002/app.38824] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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8
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Influence of polymer particle size on the percolation threshold of electrically conductive latex-based composites. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/polb.22344] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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9
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Using analytical centrifugation to characterize the dispersibility and particle size distributions of organic/inorganic composite coatings. JOURNAL OF POLYMER RESEARCH 2011. [DOI: 10.1007/s10965-011-9563-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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10
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Wei P, Xiaowei H, Yan C. Preparation and Characterization of Poly (vinyl alcohol)/Antimony-Doped Tin Oxide Nanocomposites. INT J POLYM MATER PO 2010. [DOI: 10.1080/00914037.2010.504172] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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11
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Hakimelahi HR, Hu L, Rupp BB, Coleman MR. Synthesis and characterization of transparent alumina reinforced polycarbonate nanocomposite. POLYMER 2010. [DOI: 10.1016/j.polymer.2010.04.023] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Photocatalysed (Meth)acrylate Polymerization by (Antimony-Doped) Tin Oxide Nanoparticles and Photoconduction of Their Crosslinked Polymer Nanoparticle Composites. JOURNAL OF NANOTECHNOLOGY 2010. [DOI: 10.1155/2010/579708] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the absence of another (photo)radical initiator Sb:SnO2nanoparticles (0≤Sb≤13at %) photocatalyze during irradiation with UV light the radical polymerization of (meth)acrylate monomers. When cured hard and transparent (>98%) films with a low haze (<1%) are required, when these particles are grafted in advance with 3-methacryloxypropyltrimethoxysilane (MPS) and doped with Sb. Public knowledge about the photocatalytic properties of Sb:SnO2nanoparticles is hardly available. Therefore, the influence of particle concentration, surface groups, and Sb doping on the rate of C=C (meth)acrylate bond polymerization was determined with aid of real-time FT-IR spectroscopy. By using a wavelength of irradiation with a narrow bandgab (315±5 nm) the influence of these factors on the quantum yield (Φ) and on polymer and particle network structure formation was determined. It is shown that Sb doping and MPS grafting of the particles lowers Φ. MPS grafting of the particles also influences the structure of the polymer network formed. Without Sb doping of these particles unwanted, photocatalytic side reactions occur. It is also shown that cured MPS-Sb:SnO2/(meth)acrylate nanocomposites have photoconduction properties even when the particle concentration is as low as 1 vol.%. The results suggest that the Sb:SnO2(Sb>0at %) nanoparticles can be attractive fillers for other photocatalytic applications photorefractive materials, optoelectronic devices and sensors.
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Miriyala SM, Kim YS, Liu L, Grunlan JC. Segregated Networks of Carbon Black in Poly(vinyl acetate) Latex: Influence of Clay on the Electrical and Mechanical Behavior. MACROMOL CHEM PHYS 2008. [DOI: 10.1002/macp.200800384] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Luo H, Cardinal CM, Scriven LE, Francis LF. Ceramic nanoparticle/monodisperse latex coatings. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:5552-5561. [PMID: 18416565 DOI: 10.1021/la800050u] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Ceramic nanoparticle/monodisperse latex coatings with a nanoparticle-rich surface and a latex-rich body were created by depositing aqueous dispersions of monodisperse latex, approximately 550 nm in diameter, and nanosized ceramic particles onto substrates and drying. On the top surface of the dried coating, the latex particles are closely packed with nanoparticles uniformly occupying the interstitial spaces, and along the cross section, nanoparticles fill the spaces between the latex particles in the near surface region; a compacted latex structure, nearly devoid of nanoparticles, lies beneath. Cryogenic scanning electron microscopy images of partially dried coatings at successive drying stages reveal two important steps in forming this structure: top-down consolidation of latex particles and accumulation of nanoparticles in interstitial spaces among latex particles near the surface. A systematic study of the effect of processing conditions, including nanoparticle concentration, nanoparticle size, latex glass transition temperature, and drying conditions, on the final microstructure was carried out. The unique microstructure described above forms when the monodisperse latex is large enough to create pore channels for the transport of nanosized particles and the drying conditions favor "top-down" as opposed to "edge-in" drying.
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Affiliation(s)
- Hui Luo
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Luo H, Scriven LE, Francis LF. Cryo-SEM studies of latex/ceramic nanoparticle coating microstructure development. J Colloid Interface Sci 2007; 316:500-9. [PMID: 17854820 DOI: 10.1016/j.jcis.2007.07.047] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 07/07/2007] [Accepted: 07/10/2007] [Indexed: 10/23/2022]
Abstract
Cryogenic scanning electron microscopy (cryo-SEM) was used to investigate microstructure development of composite coatings prepared from dispersions of antimony-doped tin oxide (ATO) nanoparticles (approximately 30 nm) or indium tin oxide (ITO) nanoparticles (approximately 40 nm) and latex particles (polydisperse, D(v): approximately 300 nm). Cryo-SEM images of ATO/latex dispersions as-frozen show small clusters of ATO and individual latex particles homogeneously distribute in a frozen water matrix. In contrast, cryo-SEM images of ITO/latex dispersions as-frozen show ITO particles adsorb onto latex particle surfaces. Electrostatic repulsion between negatively charged ATO and negatively charged latex particles stabilizes the ATO/latex dispersion, whereas in ITO/latex dispersion, positively charged ITO particles are attracted onto surfaces of negatively charged latex particles. These results are consistent with calculations of interaction potentials from past research. Cryo-SEM images of frozen and fractured coatings reveal that both ceramic nanoparticles and latex become more concentrated as drying proceeds; larger latex particles consolidate with ceramic nanoparticles in the interstitial spaces. With more drying, compaction flattens the latex-latex particle contacts and shrinks the voids between them. Thus, ceramic nanoparticles are forced to pack closely in the interstitial spaces, forming an interconnected network. Finally, latex particles partially coalesce at their flattened contacts, thereby yielding a coherent coating. The research reveals how nanoparticles segregate and interconnect among latex particles during drying.
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Affiliation(s)
- Hui Luo
- Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave. SE, Minneapolis, MN 55455, USA
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17
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Novák I, Florián Š, Pollák V. Behavior of Pressure-Sensitive Adhesives Filled with Metallized Inorganic Particles. INT J POLYM MATER PO 2007. [DOI: 10.1080/00914030701307870] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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18
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Harris DJ, Hu H, Conrad JC, Lewis JA. Patterning colloidal films via evaporative lithography. PHYSICAL REVIEW LETTERS 2007; 98:148301. [PMID: 17501317 DOI: 10.1103/physrevlett.98.148301] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Indexed: 05/15/2023]
Abstract
We investigate evaporative lithography as a route for patterning colloidal films. Films are dried beneath a mask that induces periodic variations between regions of free and hindered evaporation. Direct imaging reveals that particles segregate laterally within the film, as fluid and entrained particles migrate towards regions of higher evaporative flux. The films exhibit remarkable pattern formation that can be regulated by tuning the initial suspension composition, separation distance between the mask and underlying film, and mask geometry.
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Affiliation(s)
- Daniel J Harris
- Department of Materials Science and Engineering and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Posthumus W, Laven J, de With G, van der Linde R. Control of the electrical conductivity of composites of antimony doped tin oxide (ATO) nanoparticles and acrylate by grafting of 3-methacryloxypropyltrimethoxysilane (MPS). J Colloid Interface Sci 2006; 304:394-401. [PMID: 17010985 DOI: 10.1016/j.jcis.2006.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Revised: 07/12/2006] [Accepted: 09/01/2006] [Indexed: 11/17/2022]
Abstract
The effect of the addition of antimony doped tin oxide (ATO) nanoparticles on the electrical conductivity of acrylate films is described. To enable dispersing of ATO in acrylate matrices, 3-methacryloxypropyltrimethoxysilane (MPS) was grafted on the surface of the filler. The amount of MPS used for this surface modification was found to strongly affect the electrical conductivity. Surface modification with a large amount of MPS resulted in colloidally stable dispersions of ATO, leading to a homogeneous distribution. Surface modification with small amounts of MPS led to instable ATO dispersions and aggregation of ATO into a fractal type network, which gives a much higher conductivity especially at low-volume fractions. For composites with a fractal type ATO network a second effect was found. Decreasing the amount of on ATO grafted MPS resulted in an increase of the electrical conduction between the ATO particles.
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Affiliation(s)
- Willem Posthumus
- Laboratory of Materials and Interface Chemistry (SMG), Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
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Uğur S, Pehlivan E, Tepehan F, Pekcan O. Ceramic encapsulated latex composites. J Colloid Interface Sci 2006; 295:457-63. [PMID: 16188272 DOI: 10.1016/j.jcis.2005.08.053] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2004] [Revised: 07/21/2004] [Indexed: 11/17/2022]
Abstract
This work reports the encapsulation of latex particles in Al2O3-polystyrene (PS) composite films. These films were prepared from PS particles in Al2O3 dispersion at room temperature in various latex contents. Composite films were annealed at elevated temperatures in 10 min time interval above the glass transition temperature (Tg) of polystyrene. Transmitted photon intensities, I(tr) were monitored after each annealing step. AFM micrographs were also used to observe the physical changes of the composite films during annealing. It was observed that latex particles are encapsulated above a critical Al2O3 content of 33 wt% which corresponds to the critical occupation probability of p(c) = 0.33 at which the film obey the site-percolation model with a critical exponent of 0.45. Below p(c), it was seen that complete latex film formation process took place, where transparency of the film was increased by annealing.
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Affiliation(s)
- S Uğur
- Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
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Sun J, Francis LF, Gerberich WW. Mechanical properties of polymer-ceramic nanocomposite coatings by depth-sensing indentation. POLYM ENG SCI 2005. [DOI: 10.1002/pen.20271] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Sun J, Velamakanni BV, Gerberich WW, Francis LF. Aqueous latex/ceramic nanoparticle dispersions: colloidal stability and coating properties. J Colloid Interface Sci 2004; 280:387-99. [PMID: 15533412 DOI: 10.1016/j.jcis.2004.08.014] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2004] [Accepted: 08/04/2004] [Indexed: 11/29/2022]
Abstract
The effect of pH on the colloidal stability of aqueous dispersions containing antimony-doped tin oxide (ATO) or indium tin oxide (ITO) nanoparticles and poly(vinyl acetate-acrylic) copolymer (PVAc-co-acrylic) latex particles was investigated using experimental observations and Derjiaguin, Landau, Verwey and Overbeek (DLVO) theory. The microstructure, electrical properties and optical properties of composite coatings prepared from various dispersions were also studied. Zeta potential measurements revealed that the isoelectric point (IEP) of ATO nanoparticles was below pH 2.0, that of ITO nanoparticles was at pH approximately 6.0 and that of PVAc-co-acrylic latex was at pH approximately 2.0. ATO/PVAc-co-acrylic dispersions prepared at pH 3 were stable, but those prepared at pH 1.5 formed aggregates, which settled quickly with time. DLVO theory predictions are in accord with these results. Stable ITO/PVAc-co-acrylic dispersions are obtained at a pH of 3.0 and 11.0, but dispersions are not stable at a pH of 6.0, the IEP of ITO. At a pH of 3.0, DLVO results predict attraction between ITO particles and latex particles. Dispersion pH affected the microstructures and properties of ATO (or ITO)/PVAc-co-acrylic coatings. Suspensions that formed aggregates produced coatings with lower percolation thresholds and lower transparencies than those produced from stable suspensions.
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Affiliation(s)
- Jiakuan Sun
- Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Avenue SE, Minneapolis, MN 55455, USA
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Greene ME, Kinser CR, Kramer DE, Pingree LSC, Hersam MC. Application of scanning probe microscopy to the characterization and fabrication of hybrid nanomaterials. Microsc Res Tech 2004; 64:415-34. [PMID: 15549695 DOI: 10.1002/jemt.20100] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Scanning probe microscopy (SPM) is a widely used experimental technique for characterizing and fabricating nanostructures on surfaces. In particular, due to its ability to spatially map variations in materials properties with nanometer spatial resolution, SPM is particularly well suited to probe the subcomponents and interfaces of hybrid nanomaterials, i.e., materials that are made up of distinct nanometer scale components with distinguishable properties. In addition, the interaction of the SPM tip with materials can be intentionally tuned such that local surface modification is achieved. In this manner, hybrid nanostructures can also be fabricated on solid substrates using SPM. This report reviews recent developments in the characterization and fabrication of hybrid nanomaterials with SPM. Specific attention is given to nanomaterials that consist of both organic and inorganic components including individual biomolecules mounted on inorganic substrates. SPM techniques that are particularly well suited for characterizing the mechanical and electrical properties of such hybrid systems in atmospheric pressure environments are highlighted, and specific illustrative examples are provided. This review concludes with a brief discussion of the remaining challenges and promising future prospects for this field.
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Affiliation(s)
- Mark E Greene
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, USA
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