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2964 KiB

Open AccessArticle

Comparison of the Nanostructure and Mechanical Performance of Highly Exfoliated Epoxy-Clay Nanocomposites Prepared by Three Different Protocols

by Fatemeh Shiravand, John M. Hutchinson, Yolanda Calventus and Francesc Ferrando

Materials 2014, 7(6), 4196-4223; https://doi.org/10.3390/ma7064196 - 30 May 2014

Cited by 9 | Viewed by 6271

Abstract

Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para-amino phenol (TGAP), have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2 [...] Read more.

Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para-amino phenol (TGAP), have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2 wt% and 5 wt% of organically modified montmorillonite (MMT), and are: isothermal cure at selected temperatures; pre-conditioning of the resin-clay mixture before isothermal cure; incorporation of an initiator of cationic homopolymerisation, a boron tri-fluoride methyl amine complex, BF₃·MEA, within the clay galleries. It was found that features of the cure kinetics and of the nanostructure correlate with the measured impact strength of the cured nanocomposites, which increases as the degree of exfoliation of the MMT is improved. The best protocol for toughening the TGAP/MMT nanocomposites is by the incorporation of 1 wt% BF₃·MEA into the clay galleries of nanocomposites containing 2 wt% MMT. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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649 KiB

Open AccessArticle

Antimicrobial Activity of Chitosan-Carbon Nanotube Hydrogels

by Jayachandran Venkatesan, Rangasamy Jayakumar, Annapoorna Mohandas, Ira Bhatnagar and Se-Kwon Kim

Materials 2014, 7(5), 3946-3955; https://doi.org/10.3390/ma7053946 - 19 May 2014

Cited by 103 | Viewed by 9984

Abstract

In the present study, we have prepared chitosan-carbon nanotube (Chitosan-CNT) hydrogels by the freeze-lyophilization method and examined their antimicrobial activity. Different concentrations of CNT were used in the preparation of Chitosan-CNT hydrogels. These differently concentrated CNT hydrogels were chemically characterized using Fourier Transform-Infrared [...] Read more.

In the present study, we have prepared chitosan-carbon nanotube (Chitosan-CNT) hydrogels by the freeze-lyophilization method and examined their antimicrobial activity. Different concentrations of CNT were used in the preparation of Chitosan-CNT hydrogels. These differently concentrated CNT hydrogels were chemically characterized using Fourier Transform-Infrared Spectroscopy, Scanning Electron Microscopy and Optical microscopy. The porosity of the hydrogels were found to be >94%. Dispersion of chitosan was observed in the CNT matrix by normal photography and optical microscopy. The addition of CNT in the composite scaffold significantly reduced the water uptake ability. In order to evaluate antimicrobial activity, the serial dilution method was used towards Staphylococcus aureus, Escherichia coli and Candida tropicalis. The composite Chitosan-CNT hydrogel showed greater antimicrobial activity with increasing CNT concentration, suggesting that Chitosan-CNT hydrogel scaffold will be a promising biomaterial in biomedical applications. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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633 KiB

Open AccessArticle

Tunneling Conductivity and Piezoresistivity of Composites Containing Randomly Dispersed Conductive Nano-Platelets

by Amirhossein Biabangard Oskouyi, Uttandaraman Sundararaj and Pierre Mertiny

Materials 2014, 7(4), 2501-2521; https://doi.org/10.3390/ma7042501 - 28 Mar 2014

Cited by 114 | Viewed by 9526

Abstract

In this study, a three-dimensional continuum percolation model was developed based on a Monte Carlo simulation approach to investigate the percolation behavior of an electrically insulating matrix reinforced with conductive nano-platelet fillers. The conductivity behavior of composites rendered conductive by randomly dispersed conductive [...] Read more.

In this study, a three-dimensional continuum percolation model was developed based on a Monte Carlo simulation approach to investigate the percolation behavior of an electrically insulating matrix reinforced with conductive nano-platelet fillers. The conductivity behavior of composites rendered conductive by randomly dispersed conductive platelets was modeled by developing a three-dimensional finite element resistor network. Parameters related to the percolation threshold and a power-low describing the conductivity behavior were determined. The piezoresistivity behavior of conductive composites was studied employing a reoriented resistor network emulating a conductive composite subjected to mechanical strain. The effects of the governing parameters, i.e., electron tunneling distance, conductive particle aspect ratio and size effects on conductivity behavior were examined. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1016 KiB

Open AccessArticle

Metallocene Based Polyolefin Nanocomposites

by Walter Kaminsky

Materials 2014, 7(3), 1995-2013; https://doi.org/10.3390/ma7031995 - 10 Mar 2014

Cited by 20 | Viewed by 7586

Abstract

One of the most efficient and versatile ways to synthesize polyolefin nanocomposites is the in-situ polymerization of olefins in the presence of nano particles by metallocene catalysts. Metallocene/methylaluminoxane (MAO) catalysts are soluble in hydrocarbons and therefore they can be absorbed perfectly in solution [...] Read more.

One of the most efficient and versatile ways to synthesize polyolefin nanocomposites is the in-situ polymerization of olefins in the presence of nano particles by metallocene catalysts. Metallocene/methylaluminoxane (MAO) catalysts are soluble in hydrocarbons and therefore they can be absorbed perfectly in solution onto the surface of particles or fibers and after addition of ethene or propene they can then catalyze a polyolefin film on the surface. Metallocene/MAO and other single site catalysts allow the synthesis of polymers with a precisely defined microstructure, tacticity, and stereoregularity as well as new copolymers with superior properties such as film clarity, high tensile strength and lower content of extractables. The polymer properties can be enlarged by the incorporation of nanofillers. The resulting polyethylene or polypropylene nanocomposites give a tremendous boost to the physical and chemical properties such as dramatically improved stiffness, high gas barrier properties, significant flame retardancy, and high crystallization rates. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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538 KiB

Open AccessArticle

Nanocomposites Polarizing by Absorption: Dichroism in the Near-Infrared Region (NIR)

by Lorenz Bonderer, Dirk I. Uhlenhaut, Paul Smith and Walter Caseri

Materials 2014, 7(3), 1899-1911; https://doi.org/10.3390/ma7031899 - 05 Mar 2014

Cited by 5 | Viewed by 6450

Abstract

We describe the preparation of nanocomposites which exhibit dichroism in the near infrared region (NIR). These materials consist of crosslinked poly(dimethylsiloxane) (PDMS) and gold nanoparticles, coated with 1-dodecanethiol or tert-tetradecanethiol. The alkanethiols improve dispersibility of the gold particles, and accordingly composites were [...] Read more.

We describe the preparation of nanocomposites which exhibit dichroism in the near infrared region (NIR). These materials consist of crosslinked poly(dimethylsiloxane) (PDMS) and gold nanoparticles, coated with 1-dodecanethiol or tert-tetradecanethiol. The alkanethiols improve dispersibility of the gold particles, and accordingly composites were manufactured by diffusion of the particles into swollen self-supporting PDMS elastomer films. After drying, the films were exposed to solvents for one minute, stretched in wet state, dried again and annealed. This procedure led to formation of oriented linear gold particle assemblies within stretched polymer. If the aspect ratio of the particle assemblies is high, the absorption of polarized light in the NIR region is expected to depend on the angle between the polarization plane and the orientation direction of the particle assemblies, and this was observed to be the case. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1932 KiB

Open AccessArticle

A New Epoxy-Based Layered Silicate Nanocomposite Using a Hyperbranched Polymer: Study of the Curing Reaction and Nanostructure Development

by Pilar Cortés, Iria Fraga, Yolanda Calventus, Frida Román, John M. Hutchinson and Francesc Ferrando

Materials 2014, 7(3), 1830-1849; https://doi.org/10.3390/ma7031830 - 04 Mar 2014

Cited by 16 | Viewed by 7700

Abstract

Polymer layered silicate (PLS) nanocomposites have been prepared with diglycidyl ether of bisphenol-A (DGEBA) epoxy resin as the matrix and organically modified montmorillonite (MMT) as the clay nanofiller. Resin-clay mixtures with different clay contents (zero, two, five and 10 wt%) were cured, both [...] Read more.

Polymer layered silicate (PLS) nanocomposites have been prepared with diglycidyl ether of bisphenol-A (DGEBA) epoxy resin as the matrix and organically modified montmorillonite (MMT) as the clay nanofiller. Resin-clay mixtures with different clay contents (zero, two, five and 10 wt%) were cured, both isothermally and non-isothermally, using a poly(ethyleneimine) hyperbranched polymer (HBP), the cure kinetics being monitored by differential scanning calorimetry (DSC). The nanostructure of the cured nanocomposites was characterized by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), and their mechanical properties were determined by dynamic mechanical analysis (DMA) and impact testing. The results are compared with an earlier study of the structure and properties of the same DGEBA-MMT system cured with a polyoxypropylene diamine, Jeffamine. There are very few examples of the use of HBP as a curing agent in epoxy PLS nanocomposites; here, it is found to enhance significantly the degree of exfoliation of these nanocomposites compared with those cured with Jeffamine, with a corresponding enhancement in the impact energy for nanocomposites with the low clay content of 2 wt%. These changes are attributed to the different cure kinetics with the HBP, in which the intra-gallery homopolymerization reaction is accelerated, such that it occurs before the bulk cross-linking reaction. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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516 KiB

Open AccessArticle

Electrophoretic Deposition of Chitosan/h-BN and Chitosan/h-BN/TiO₂ Composite Coatings on Stainless Steel (316L) Substrates

by Namir S. Raddaha, Luis Cordero-Arias, Sandra Cabanas-Polo, Sannakaisa Virtanen, Judith A. Roether and Aldo R. Boccaccini

Materials 2014, 7(3), 1814-1829; https://doi.org/10.3390/ma7031814 - 04 Mar 2014

Cited by 63 | Viewed by 10281

Abstract

This article presents the results of an experimental investigation designed to deposit chitosan/hexagonal boron nitride (h-BN) and chitosan/h-BN/titania (TiO₂) composites on SS316L substrates using electrophoretic deposition (EPD) for potential antibacterial applications. The influence of EPD parameters (voltage and deposition time) and [...] Read more.

This article presents the results of an experimental investigation designed to deposit chitosan/hexagonal boron nitride (h-BN) and chitosan/h-BN/titania (TiO₂) composites on SS316L substrates using electrophoretic deposition (EPD) for potential antibacterial applications. The influence of EPD parameters (voltage and deposition time) and relative concentrations of chitosan, h-BN and TiO₂ in suspension on deposition yield was studied. The composition and structure of deposited coatings were investigated by FTIR, XRD and SEM. It was observed that h-BN and TiO₂ particles were dispersed in the chitosan matrix through simultaneous deposition. The adhesion between the electrophoretic coatings and the stainless steel substrates was tested by using tape test technique, and the results showed that the adhesion strength corresponded to 3B and 4B classes. Corrosion resistance was evaluated by electrochemical polarization curves, indicating enhanced corrosion resistance of the chitosan/h-BN/TiO₂ and chitosan/h-BN coatings compared to the bare stainless steel substrate. In order to investigate the in-vitro inorganic bioactivity, coatings were immersed in simulated body fluid (SBF) for 28 days. FTIR and XRD results showed no formation of hydroxyapatite on the surface of chitosan/h-BN/TiO₂ and chitosan/h-BN coatings, which are therefore non bioactive but potentially useful as antibacterial coatings. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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583 KiB

Open AccessArticle

Uptake of Eudragit Retard L (Eudragit^® RL) Nanoparticles by Human THP-1 Cell Line and Its Effects on Hematology and Erythrocyte Damage in Rats

by Mosaad A. Abdel-Wahhab, Khaled G. Abdel-Wahhab, Fathia A. Mannaa, Nabila S. Hassan, Ramia Safar, Roudayna Diab, Bernard Foliguet, Luc Ferrari and Bertrand H. Rihn

Materials 2014, 7(3), 1555-1572; https://doi.org/10.3390/ma7031555 - 28 Feb 2014

Cited by 12 | Viewed by 7256

Abstract

The aim of this study was to prepare Eudragit Retard L (Eudragit RL) nanoparticles (ENPs) and to determine their properties, their uptake by the human THP-1 cell line in vitro and their effect on the hematological parameters and erythrocyte damage in rats. ENPs [...] Read more.

The aim of this study was to prepare Eudragit Retard L (Eudragit RL) nanoparticles (ENPs) and to determine their properties, their uptake by the human THP-1 cell line in vitro and their effect on the hematological parameters and erythrocyte damage in rats. ENPs showed an average size of 329.0 ± 18.5 nm, a positive zeta potential value of +57.5 ± 5.47 mV and nearly spherical shape with a smooth surface. THP-1 cell lines could phagocyte ENPs after 2 h of incubation. In the in vivo study, male Sprague-Dawley rats were exposed orally or intraperitoneally (IP) with a single dose of ENP (50 mg/kg body weight). Blood samples were collected after 4 h, 48 h, one week and three weeks for hematological and erythrocytes analysis. ENPs induced significant hematological disturbances in platelets, red blood cell (RBC) total and differential counts of white blood cells (WBCs) after 4 h, 48 h and one week. ENP increased met-Hb and Co-Hb derivatives and decreased met-Hb reductase activity. These parameters were comparable to the control after three weeks when administrated orally. It could be concluded that the route of administration has a major effect on the induction of hematological disturbances and should be considered when ENPs are applied for drug delivery systems. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1772 KiB

Open AccessArticle

Structural Characterization of Polymer-Clay Nanocomposites Prepared by Co-Precipitation Using EPR Techniques

by Udo Kielmann, Gunnar Jeschke and Inés García-Rubio

Materials 2014, 7(2), 1384-1408; https://doi.org/10.3390/ma7021384 - 21 Feb 2014

Cited by 9 | Viewed by 6600

Abstract

Polymer-clay nanocomposites (PCNCs) containing either a rubber or an acrylate polymer were prepared by drying or co-precipitating polymer latex and nanolayered clay (synthetic and natural) suspensions. The interface between the polymer and the clay nanoparticles was studied by electron paramagnetic resonance (EPR) techniques [...] Read more.

Polymer-clay nanocomposites (PCNCs) containing either a rubber or an acrylate polymer were prepared by drying or co-precipitating polymer latex and nanolayered clay (synthetic and natural) suspensions. The interface between the polymer and the clay nanoparticles was studied by electron paramagnetic resonance (EPR) techniques by selectively addressing spin probes either to the surfactant layer (labeled stearic acid) or the clay surface (labeled catamine). Continuous-wave (CW) EPR studies of the surfactant dynamics allow to define a transition temperature T* which was tentatively assigned to the order-disorder transition of the surfactant layer. CW EPR studies of PCNC showed that completely exfoliated nanoparticles coexist with agglomerates. HYSCORE spectroscopy in PCNCs showed couplings within the probe −assigned with DFT computations− and couplings with nuclei of the environment, ¹H and ²³Na for the surfactant layer probe, and ²⁹Si, ⁷Li, ¹⁹F and ²³Na for the clay surface probe. Analysis of these couplings indicates that the integrity of the surfactant layer is conserved and that there are sizeable ionic regions containing sodium ions directly beyond the surfactant layer. Simulations of the very weak couplings demonstrated that the HYSCORE spectra are sensitive to the composition of the clay and whether or not clay platelets stack. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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320 KiB

Open AccessArticle

Synthesis and Characterization of Holmium-Doped Iron Oxide Nanoparticles

by Maarten Bloemen, Stefaan Vandendriessche, Vincent Goovaerts, Ward Brullot, Maarten Vanbel, Sophie Carron, Nick Geukens, Tatjana Parac-Vogt and Thierry Verbiest

Materials 2014, 7(2), 1155-1164; https://doi.org/10.3390/ma7021155 - 12 Feb 2014

Cited by 32 | Viewed by 7734

Abstract

Rare earth atoms exhibit several interesting properties, for example, large magnetic moments and luminescence. Introducing these atoms into a different matrix can lead to a material that shows multiple interesting effects. Holmium atoms were incorporated into an iron oxide nanoparticle and the concentration [...] Read more.

Rare earth atoms exhibit several interesting properties, for example, large magnetic moments and luminescence. Introducing these atoms into a different matrix can lead to a material that shows multiple interesting effects. Holmium atoms were incorporated into an iron oxide nanoparticle and the concentration of the dopant atom was changed in order to determine its influence on the host crystal. Its magnetic and magneto-optical properties were investigated by vibrating sample magnetometry and Faraday rotation measurements. The luminescent characteristics of the material, in solution and incorporated in a polymer thin film, were probed by fluorescence experiments. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1549 KiB

Open AccessArticle

Effective Optical Properties of Plasmonic Nanocomposites

by Christoph Etrich, Stephan Fahr, Mehdi Keshavarz Hedayati, Franz Faupel, Mady Elbahri and Carsten Rockstuhl

Materials 2014, 7(2), 727-741; https://doi.org/10.3390/ma7020727 - 27 Jan 2014

Cited by 46 | Viewed by 10740

Abstract

Plasmonic nanocomposites find many applications, such as nanometric coatings in emerging fields, such as optotronics, photovoltaics or integrated optics. To make use of their ability to affect light propagation in an unprecedented manner, plasmonic nanocomposites should consist of densely packed metallic nanoparticles. This [...] Read more.

Plasmonic nanocomposites find many applications, such as nanometric coatings in emerging fields, such as optotronics, photovoltaics or integrated optics. To make use of their ability to affect light propagation in an unprecedented manner, plasmonic nanocomposites should consist of densely packed metallic nanoparticles. This causes a major challenge for their theoretical description, since the reliable assignment of effective optical properties with established effective medium theories is no longer possible. Established theories, e.g., the Maxwell-Garnett formalism, are only applicable for strongly diluted nanocomposites. This effective description, however, is a prerequisite to consider plasmonic nanocomposites in the design of optical devices. Here, we mitigate this problem and use full wave optical simulations to assign effective properties to plasmonic nanocomposites with filling fractions close to the percolation threshold. We show that these effective properties can be used to properly predict the optical action of functional devices that contain nanocomposites in their design. With this contribution we pave the way to consider plasmonic nanocomposites comparably to ordinary materials in the design of optical elements. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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847 KiB

Open AccessArticle

Nanocomposites Based on Luminescent Colloidal Nanocrystals and Polymeric Ionic Liquids towards Optoelectronic Applications

by Annamaria Panniello, Chiara Ingrosso, Paul Coupillaud, Michela Tamborra, Enrico Binetti, Maria Lucia Curri, Angela Agostiano, Daniel Taton and Marinella Striccoli

Materials 2014, 7(1), 591-610; https://doi.org/10.3390/ma7010591 - 21 Jan 2014

Cited by 6 | Viewed by 8248

Abstract

Polymeric ionic liquids (PILs) are an interesting class of polyelectrolytes, merging peculiar physical-chemical features of ionic liquids with the flexibility, mechanical stability and processability typical of polymers. The combination of PILs with colloidal semiconducting nanocrystals leads to novel nanocomposite materials with high potential [...] Read more.

Polymeric ionic liquids (PILs) are an interesting class of polyelectrolytes, merging peculiar physical-chemical features of ionic liquids with the flexibility, mechanical stability and processability typical of polymers. The combination of PILs with colloidal semiconducting nanocrystals leads to novel nanocomposite materials with high potential for batteries and solar cells. We report the synthesis and properties of a hybrid nanocomposite made of colloidal luminescent CdSe nanocrystals incorporated in a novel ex situ synthesized imidazolium-based PIL, namely, either a poly(N-vinyl-3-butylimidazolium hexafluorophosphate) or a homologous PIL functionalized with a thiol end-group exhibiting a chemical affinity with the nanocrystal surface. A capping exchange procedure has been implemented for replacing the pristine organic capping molecules of the colloidal CdSe nanocrystals with inorganic chalcogenide ions, aiming to disperse the nano-objects in the PILs, by using a common polar solvent. The as-prepared nanocomposites have been studied by TEM investigation, UV-Vis, steady-state and time resolved photoluminescence spectroscopy for elucidating the effects of the PIL functionalization on the morphological and optical properties of the nanocomposites. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1030 KiB

Open AccessArticle

High-Voltage Insulation Organic-Inorganic Nanocomposites by Plasma Polymerization

by Wei Yan, Zhao Jun Han, B. Toan Phung, Franz Faupel and Kostya Ostrikov

Materials 2014, 7(1), 563-575; https://doi.org/10.3390/ma7010563 - 20 Jan 2014

Cited by 20 | Viewed by 7920

Abstract

In organic-inorganic nanocomposites, interfacial regions are primarily influenced by the dispersion uniformity of nanoparticles and the strength of interfacial bonds between the nanoparticles and the polymer matrix. The insulating performance of organic-inorganic dielectric nanocomposites is highly influenced by the characteristics of interfacial regions. [...] Read more.

In organic-inorganic nanocomposites, interfacial regions are primarily influenced by the dispersion uniformity of nanoparticles and the strength of interfacial bonds between the nanoparticles and the polymer matrix. The insulating performance of organic-inorganic dielectric nanocomposites is highly influenced by the characteristics of interfacial regions. In this study, we prepare polyethylene oxide (PEO)-like functional layers on silica nanoparticles through plasma polymerization. Epoxy resin/silica nanocomposites are subsequently synthesized with these plasma-polymerized nanoparticles. It is found that plasma at a low power (i.e., 10 W) can significantly increase the concentration of C–O bonds on the surface of silica nanoparticles. This plasma polymerized thin layer can not only improve the dispersion uniformity by increasing the hydrophilicity of the nanoparticles, but also provide anchoring sites to enable the formation of covalent bonds between the organic and inorganic phases. Furthermore, electrical tests reveal improved electrical treeing resistance and decreased dielectric constant of the synthesized nanocomposites, while the dielectric loss of the nanocomposites remains unchanged as compared to the pure epoxy resin. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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395 KiB

Open AccessArticle

Visible Light Curable Restorative Composites for Dental Applications Based on Epoxy Monomer

by Alessandra Vitale, Marco Sangermano, Roberta Bongiovanni, Peter Burtscher and Norbert Moszner

Materials 2014, 7(1), 554-562; https://doi.org/10.3390/ma7010554 - 20 Jan 2014

Cited by 56 | Viewed by 8257

Abstract

A cationic photo-curable cycloaliphatic epoxy resin has been investigated as reactive monomer in blue light crosslinking process. We have demonstrated that camphorquinone is able to abstract labile hydrogen from the epoxy monomer, giving rise to the formation of carbon-centered radicals that are oxidized [...] Read more.

A cationic photo-curable cycloaliphatic epoxy resin has been investigated as reactive monomer in blue light crosslinking process. We have demonstrated that camphorquinone is able to abstract labile hydrogen from the epoxy monomer, giving rise to the formation of carbon-centered radicals that are oxidized by the onium salt; a complete epoxy group conversion was reached after 50 s of irradiation. The presence of water up to 1 wt% was tolerated without any important detrimental effect on the kinetics of light-curing. The presence of the inorganic filler up to 65 wt% did not significantly influence the curing process. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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645 KiB

Open AccessArticle

Luminescent Properties of Surface Functionalized BaTiO₃ Embedded in Poly(methyl methacrylate)

by Sebastian Requena, Srijan Lacoul and Yuri M. Strzhemechny

Materials 2014, 7(1), 471-483; https://doi.org/10.3390/ma7010471 - 16 Jan 2014

Cited by 23 | Viewed by 7346

Abstract

As-received BaTiO₃ nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyl)triethoxysilane (APTES) and mixed with poly(methyl methacrylate)/toluene solution. The nanocomposite solution was spin coated on Si substrates to form thin films. The photoluminescence spectrum of the pure [...] Read more.

As-received BaTiO₃ nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyl)triethoxysilane (APTES) and mixed with poly(methyl methacrylate)/toluene solution. The nanocomposite solution was spin coated on Si substrates to form thin films. The photoluminescence spectrum of the pure powder was composed of a bandgap emission at 3.0 eV and multiple bands centered about 2.5 eV. Surface functionalization of the BaTiO₃ powder via APTES increases overall luminescence at room temperature while only enhancing bandgap emission at low-temperature. Polymer coating of the functionalized nanoparticles significantly enhances bandgap emissions while decreasing emissions associated with near-surface lattice distortions at 2.5 eV. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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433 KiB

Open AccessCommunication

Thermo-Plasmonics for Localized Graphitization and Welding of Polymeric Nanofibers

by Ahnaf Usman Zillohu, Nisreen Alissawi, Ramzy Abdelaziz and Mady Elbahri

Materials 2014, 7(1), 323-332; https://doi.org/10.3390/ma7010323 - 13 Jan 2014

Cited by 8 | Viewed by 7196

Abstract

There is a growing interest in modulating the temperature under the illumination of light. As a heat source, metal nanoparticles (NPs) have played an important role to pave the way for a new branch of plasmonics, i.e., thermo-plasmonics. While thermo-plasmonics have been [...] Read more.

There is a growing interest in modulating the temperature under the illumination of light. As a heat source, metal nanoparticles (NPs) have played an important role to pave the way for a new branch of plasmonics, i.e., thermo-plasmonics. While thermo-plasmonics have been well established in photo-thermal therapy, it has received comparatively less attention in materials science and chemistry. Here, we demonstrate the first proof of concept experiment of local chemistry and graphitization of metalized polymeric nanofibers through thermo-plasmonic effect. In particular, by tuning the plasmonic absorption of the nanohybrid through a change in the thickness of the deposited silver film on the fibers, the thermo-plasmonic effect can be adjusted in such a way that high enough temperature is generated enabling local welding and graphitization of the polymeric nanofibers. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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611 KiB

Open AccessArticle

Preparation of Fe₃O₄-Embedded Poly(styrene)/Poly(thiophene) Core/Shell Nanoparticles and Their Hydrogel Patterns for Sensor Applications

by Yong Seok Kim, Hyun Jong Lee, Patakamuri Govindaiah, Woohyun Son, Won-Gun Koh, In Woo Cheong and Jung Hyun Kim

Materials 2014, 7(1), 195-205; https://doi.org/10.3390/ma7010195 - 02 Jan 2014

Cited by 13 | Viewed by 9462

Abstract

This research describes the preparation and sensor applications of multifunctional monodisperse, Fe₃O₄ nanoparticles-embedded poly(styrene)/poly(thiophene) (Fe₃O₄-PSt/PTh), core/shell nanoparticles. Monodisperse Fe₃O₄-PSt/PTh nanoparticles were prepared by free-radical combination (mini-emulsion/emulsion) polymerization for Fe₃O₄ [...] Read more.

This research describes the preparation and sensor applications of multifunctional monodisperse, Fe₃O₄ nanoparticles-embedded poly(styrene)/poly(thiophene) (Fe₃O₄-PSt/PTh), core/shell nanoparticles. Monodisperse Fe₃O₄-PSt/PTh nanoparticles were prepared by free-radical combination (mini-emulsion/emulsion) polymerization for Fe₃O₄-PSt core and oxidative seeded emulsion polymerization for PTh shell in the presence of FeCl₃/H₂O₂ as a redox catalyst, respectively. For applicability of Fe₃O₄-PSt/PTh as sensors, Fe₃O₄-PSt/PTh-immobilized poly(ethylene glycol) (PEG)-based hydrogels were fabricated by photolithography. The hydrogel patterns showed a good sensing performance under different H₂O₂ concentrations. They also showed a quenching sensitivity of 1 µg/mL for the Pd²⁺ metal ion within 1 min. The hydrogel micropatterns not only provide a fast water uptake property but also suggest the feasibility of both H₂O₂ and Pd²⁺ detection. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1692 KiB

Open AccessArticle

Preparation of “Cauliflower-Like” ZnO Micron-Sized Particles

by Tamar Gordon, Judith Grinblat and Shlomo Margel

Materials 2013, 6(11), 5234-5246; https://doi.org/10.3390/ma6115234 - 14 Nov 2013

Cited by 5 | Viewed by 6345

Abstract

Porous polydivinyl benzene (PDVB) microspheres of narrow size distribution were formed by a single-step swelling process of template uniform polystyrene microspheres with divinyl benzene (DVB), followed by polymerization of the DVB within the swollen template microspheres. The PDVB porous particles were then formed [...] Read more.

Porous polydivinyl benzene (PDVB) microspheres of narrow size distribution were formed by a single-step swelling process of template uniform polystyrene microspheres with divinyl benzene (DVB), followed by polymerization of the DVB within the swollen template microspheres. The PDVB porous particles were then formed by dissolution of the template polystyrene polymer. Unique “cauliflower-like” ZnO microparticles were prepared by the entrapping of the ZnO precursor ZnCl₂ in the PDVB porous microspheres under vacuum, followed by calcination of the obtained ZnCl₂-PDVB microspheres in an air atmosphere. The morphology, crystallinity and fluorescence properties of those ZnO microparticles were characterized. This “cauliflower-like” shape ZnO particles is in contrast to a previous study demonstrated the preparation of spherical shaped porous ZnO and C-ZnO microparticles by a similar method, using zinc acetate (ZnAc) as a precursor. Two diverted synthesis mechanisms for those two different ZnO microparticles structures are proposed, based on studies of the distribution of each of the ZnO precursors within the PDVB microspheres. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1054 KiB

Open AccessArticle

Preparation and Characterization of Guar-Montmorillonite Nanocomposites

by Rola Mansa and Christian Detellier

Materials 2013, 6(11), 5199-5216; https://doi.org/10.3390/ma6115199 - 13 Nov 2013

Cited by 32 | Viewed by 7027

Abstract

Polymer-clay nanocomposites are highly sought-after materials, mainly due to their applicability in a variety of avenues. From the standpoint of the preparation of these nanocomposites, however, organic compatibility with clay and adherence to “green chemistry” concepts and principles can be limiting factors. As [...] Read more.

Polymer-clay nanocomposites are highly sought-after materials, mainly due to their applicability in a variety of avenues. From the standpoint of the preparation of these nanocomposites, however, organic compatibility with clay and adherence to “green chemistry” concepts and principles can be limiting factors. As such, the objective was to prepare a biopolymer-modified clay nanocomposite using a simple and environmentally friendly method of preparation, whereby pre-treatment of the clay for organic compatibility was bypassed. Novel montmorillonite nanocomposites were prepared using neutral guar gum and cationic guar gum. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of intercalated structures. A monolayer configuration of cationic guar within the interlayer space was indicated by XRD results, while treatment with neutral guar gum resulted in the observance of both monolayer and bilayer configurations. Additionally, TEM results indicated partial exfoliation. Results attributed from ¹³C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy (CP/MAS NMR) of the nanocomposites indicated peaks corresponding to the guar constituent, confirming the adsorption of the biopolymer. Inductively coupled plasma emission spectrometry (ICP-ES) results indicated the exchange of cations present in neutral guar gum with the sodium cations of montmorillonite, in the case of the neutral guar nanocomposites. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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837 KiB

Open AccessArticle

Microgel Modified UV-Cured Methacrylic-Silica Hybrid: Synthesis and Characterization

by Carola Esposito Corcione, Raffaella Striani and Mariaenrica Frigione

Materials 2013, 6(9), 3805-3825; https://doi.org/10.3390/ma6093805 - 06 Sep 2013

Cited by 18 | Viewed by 6778

Abstract

An innovative photopolymerizable microgel modified UV-cured acrylic-silica hybrid formulation was developed and characterized for possible use as protective coating for different substrates. A deep investigation, aiming at providing a strong scientific basis for the production of organic-inorganic (O-I) hybrids exhibiting phase co-continuity, was [...] Read more.

An innovative photopolymerizable microgel modified UV-cured acrylic-silica hybrid formulation was developed and characterized for possible use as protective coating for different substrates. A deep investigation, aiming at providing a strong scientific basis for the production of organic-inorganic (O-I) hybrids exhibiting phase co-continuity, was firstly carried out. The O-I hybrid first proposed in this study was obtained from organic precursors with a high siloxane content, which are mixed with tetraethoxysilane (TEOS) in such a way to produce co-continuous silica nanodomains dispersed within the crosslinked organic phase, as a result of the sol-gel process. The first part of the research deals with the selection and optimization of suitable systems through appropriate chemical modifications, in order to ensure that curing reactions can be carried out at room temperature and in the presence of UV radiation. Firstly, the silica domains are formed, followed by crosslinking reactions of the acrylic groups in the oligomer via a free radical polymerization. The crosslinking reaction was controlled with the use of a suitable photoinitiator. Most of the experimental work was devoted to understanding the morphology of the hybrid system, both in uncured and cured states, and to assess its final thermal and optical properties, using different experiential techniques. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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Review

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Open AccessReview

Functional Films from Silica/Polymer Nanoparticles

by Tânia Ribeiro, Carlos Baleizão and José Paulo S. Farinha

Materials 2014, 7(5), 3881-3900; https://doi.org/10.3390/ma7053881 - 15 May 2014

Cited by 86 | Viewed by 17906

Abstract

High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs) in the polymeric matrices, it is possible to [...] Read more.

High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs) in the polymeric matrices, it is possible to obtain hybrid polymer films with increased tensile strength and impact resistance, without decreasing the flexural properties of the polymer matrix. The SiNPs can further be used as carriers to impart other functionalities (optical, etc.) to the hybrid films. By using polymer-coated SiNPs, it is possible to reduce particle aggregation in the films and, thus, achieve more homogeneous distributions of the inorganic components and, therefore, better properties. On the other hand, by coating polymer particles with silica, one can create hierarchically structured materials, for example to obtain superhydrophobic coatings. In this review, we will cover the latest developments in films prepared from hybrid polymer/silica functional systems. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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749 KiB

Open AccessReview

Smart Polymer/Carbon Nanotube Nanocomposites and Their Electrorheological Response

by Ke Zhang and Hyoung Jin Choi

Materials 2014, 7(5), 3399-3414; https://doi.org/10.3390/ma7053399 - 30 Apr 2014

Cited by 12 | Viewed by 8314

Abstract

This review article summarizes the preparation of polymer/carbon nanotube (CNT) nanocomposites and their applications as electrorheological (ER) fluids. These ER fluids exhibited a controllable electro-response under an applied electric field due to the presence of well-dispersed CNTs. The background, morphology, preparations, and characteristics [...] Read more.

This review article summarizes the preparation of polymer/carbon nanotube (CNT) nanocomposites and their applications as electrorheological (ER) fluids. These ER fluids exhibited a controllable electro-response under an applied electric field due to the presence of well-dispersed CNTs. The background, morphology, preparations, and characteristics of these materials are discussed, specifically focusing on the various approaches in the preparation of polymer/CNT nanocomposites, morphology, and their effects on the ER characteristics. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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Hybrid Organic/Inorganic Nanocomposites for Photovoltaic Cells

by Ruchuan Liu

Materials 2014, 7(4), 2747-2771; https://doi.org/10.3390/ma7042747 - 02 Apr 2014

Cited by 128 | Viewed by 13758

Abstract

Inorganic/organic hybrid solar cells have attracted a lot of interest due to their potential in combining the advantages of both components. To understand the key issues in association with photoinduced charge separation/transportation processes and to improve overall power conversion efficiency, various combinations with [...] Read more.

Inorganic/organic hybrid solar cells have attracted a lot of interest due to their potential in combining the advantages of both components. To understand the key issues in association with photoinduced charge separation/transportation processes and to improve overall power conversion efficiency, various combinations with nanostructures of hybrid systems have been investigated. Here, we briefly review the structures of hybrid nanocomposites studied so far, and attempt to associate the power conversion efficiency with these nanostructures. Subsequently, we are then able to summarize the factors for optimizing the performance of inorganic/organic hybrid solar cells. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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Open AccessReview

Advanced Ceramics from Preceramic Polymers Modified at the Nano-Scale: A Review

by Enrico Bernardo, Laura Fiocco, Giulio Parcianello, Enrico Storti and Paolo Colombo

Materials 2014, 7(3), 1927-1956; https://doi.org/10.3390/ma7031927 - 06 Mar 2014

Cited by 139 | Viewed by 14699

Abstract

Preceramic polymers, i.e., polymers that are converted into ceramics upon heat treatment, have been successfully used for almost 40 years to give advanced ceramics, especially belonging to the ternary SiCO and SiCN systems or to the quaternary SiBCN system. One of their [...] Read more.

Preceramic polymers, i.e., polymers that are converted into ceramics upon heat treatment, have been successfully used for almost 40 years to give advanced ceramics, especially belonging to the ternary SiCO and SiCN systems or to the quaternary SiBCN system. One of their main advantages is the possibility of combining the shaping and synthesis of ceramics: components can be shaped at the precursor stage by conventional plastic-forming techniques, such as spinning, blowing, injection molding, warm pressing and resin transfer molding, and then converted into ceramics by treatments typically above 800 °C. The extension of the approach to a wider range of ceramic compositions and applications, both structural and thermo-structural (refractory components, thermal barrier coatings) or functional (bioactive ceramics, luminescent materials), mainly relies on modifications of the polymers at the nano-scale, i.e., on the introduction of nano-sized fillers and/or chemical additives, leading to nano-structured ceramic components upon thermal conversion. Fillers and additives may react with the main ceramic residue of the polymer, leading to ceramics of significant engineering interest (such as silicates and SiAlONs), or cause the formation of secondary phases, significantly affecting the functionalities of the polymer-derived matrix. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1069 KiB

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Review of Plasmonic Nanocomposite Metamaterial Absorber

by Mehdi Keshavarz Hedayati, Franz Faupel and Mady Elbahri

Materials 2014, 7(2), 1221-1248; https://doi.org/10.3390/ma7021221 - 14 Feb 2014

Cited by 158 | Viewed by 19946

Abstract

Plasmonic metamaterials are artificial materials typically composed of noble metals in which the features of photonics and electronics are linked by coupling photons to conduction electrons of metal (known as surface plasmon). These rationally designed structures have spurred interest noticeably since they demonstrate [...] Read more.

Plasmonic metamaterials are artificial materials typically composed of noble metals in which the features of photonics and electronics are linked by coupling photons to conduction electrons of metal (known as surface plasmon). These rationally designed structures have spurred interest noticeably since they demonstrate some fascinating properties which are unattainable with naturally occurring materials. Complete absorption of light is one of the recent exotic properties of plasmonic metamaterials which has broadened its application area considerably. This is realized by designing a medium whose impedance matches that of free space while being opaque. If such a medium is filled with some lossy medium, the resulting structure can absorb light totally in a sharp or broad frequency range. Although several types of metamaterials perfect absorber have been demonstrated so far, in the current paper we overview (and focus on) perfect absorbers based on nanocomposites where the total thickness is a few tens of nanometer and the absorption band is broad, tunable and insensitive to the angle of incidence. The nanocomposites consist of metal nanoparticles embedded in a dielectric matrix with a high filling factor close to the percolation threshold. The filling factor can be tailored by the vapor phase co-deposition of the metallic and dielectric components. In addition, novel wet chemical approaches are discussed which are bio-inspired or involve synthesis within levitating Leidenfrost drops, for instance. Moreover, theoretical considerations, optical properties, and potential application of perfect absorbers will be presented. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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Nanocomposite Electrospun Nanofiber Membranes for Environmental Remediation

by Shahin Homaeigohar and Mady Elbahri

Materials 2014, 7(2), 1017-1045; https://doi.org/10.3390/ma7021017 - 10 Feb 2014

Cited by 199 | Viewed by 17235

Abstract

Rapid worldwide industrialization and population growth is going to lead to an extensive environmental pollution. Therefore, so many people are currently suffering from the water shortage induced by the respective pollution, as well as poor air quality and a huge fund is wasted [...] Read more.

Rapid worldwide industrialization and population growth is going to lead to an extensive environmental pollution. Therefore, so many people are currently suffering from the water shortage induced by the respective pollution, as well as poor air quality and a huge fund is wasted in the world each year due to the relevant problems. Environmental remediation necessitates implementation of novel materials and technologies, which are cost and energy efficient. Nanomaterials, with their unique chemical and physical properties, are an optimum solution. Accordingly, there is a strong motivation in seeking nano-based approaches for alleviation of environmental problems in an energy efficient, thereby, inexpensive manner. Thanks to a high porosity and surface area presenting an extraordinary permeability (thereby an energy efficiency) and selectivity, respectively, nanofibrous membranes are a desirable candidate. Their functionality and applicability is even promoted when adopting a nanocomposite strategy. In this case, specific nanofillers, such as metal oxides, carbon nanotubes, precious metals, and smart biological agents, are incorporated either during electrospinning or in the post-processing. Moreover, to meet operational requirements, e.g., to enhance mechanical stability, decrease of pressure drop, etc., nanofibrous membranes are backed by a microfibrous non-woven forming a hybrid membrane. The novel generation of nanocomposite/hybrid nanofibrous membranes can perform extraordinarily well in environmental remediation and control. This reality justifies authoring of this review paper. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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Recent Progress in Advanced Nanobiological Materials for Energy and Environmental Applications

by Hyo-Jick Choi and Carlo D. Montemagno

Materials 2013, 6(12), 5821-5856; https://doi.org/10.3390/ma6125821 - 11 Dec 2013

Cited by 15 | Viewed by 8556

Abstract

In this review, we briefly introduce our efforts to reconstruct cellular life processes by mimicking natural systems and the applications of these systems to energy and environmental problems. Functional units of in vitro cellular life processes are based on the fabrication of artificial [...] Read more.

In this review, we briefly introduce our efforts to reconstruct cellular life processes by mimicking natural systems and the applications of these systems to energy and environmental problems. Functional units of in vitro cellular life processes are based on the fabrication of artificial organelles using protein-incorporated polymersomes and the creation of bioreactors. This concept of an artificial organelle originates from the first synthesis of poly(siloxane)-poly(alkyloxazoline) block copolymers three decades ago and the first demonstration of protein activity in the polymer membrane a decade ago. The increased value of biomimetic polymers results from many research efforts to find new applications such as functionally active membranes and a biochemical-producing polymersome. At the same time, foam research has advanced to the point that biomolecules can be efficiently produced in the aqueous channels of foam. Ongoing research includes replication of complex biological processes, such as an artificial Calvin cycle for application in biofuel and specialty chemical production, and carbon dioxide sequestration. We believe that the development of optimally designed biomimetic polymers and stable/biocompatible bioreactors would contribute to the realization of the benefits of biomimetic systems. Thus, this paper seeks to review previous research efforts, examine current knowledge/key technical parameters, and identify technical challenges ahead. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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