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Polymeric Materials (polymeric + material)
Kinds of Polymeric Materials Selected AbstractsTopical Issue: "Biotechnical Functionalization of Renewable Polymeric Materials"ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2008Georg M. Guebitz No abstract is available for this article. [source] Polymeric Materials for Gene Delivery and DNA VaccinationADVANCED MATERIALS, Issue 8 2009David N. Nguyen Abstract Gene delivery holds great potential for the treatment of many different diseases. Vaccination with DNA holds particular promise, and may provide a solution to many technical challenges that hinder traditional vaccine systems including rapid development and production and induction of robust cell-mediated immune responses. However, few candidate DNA vaccines have progressed past preclinical development and none have been approved for human use. This Review focuses on the recent progress and challenges facing materials design for nonviral DNA vaccine drug delivery systems. In particular, we highlight work on new polymeric materials and their effects on protective immune activation, gene delivery, and current efforts to optimize polymeric delivery systems for DNA vaccination. [source] New Polymeric Materials with Interferential Optical PropertiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 13 2007Leïla Ghannam Abstract Nature provides a wide pallet of colors but also a wide number of fascinating optical phenomena such as nacre or interferential effects, which can be observed in insect wings and shellfish. The origin of such effects is attributed to the presence of highly ordered arrangements in Nature's materials. The aim of this paper is to focus some new approaches and advances for creating interferential optical phenomena as observed in nature by tuning or modeling the polymer architectures or organization. A relatively simple method is described to prepare organic/inorganic hybrid pigments constituted of mica platelets and adsorbed polymer layers. It is shown that the color of mica is changed upon polymer adsorption, and when one of the copolymer sequences includes a dye, its color is influenced by the chemical properties of the mica surface. Moreover, a new facile route is presented to obtain highly ordered surfaces using ionomer macromolecular designs synthesized in one step by controlled radical polymerization. The preparation of films with very regular pore size and spatial organization is successfully realized by using ionomer solutions. An original property of these films with an iridescent color obtained by light diffraction as a result of the optical interferences of sunlight with the periodic honeycomb structures is presented. All these new materials based on polymeric controlled structures can reproduce nature by creating an optical interferential and iridescent material, which offers new fascinating applications as original bio-mimetic materials on inorganic surfaces. [source] Quality Concepts for the Improved Use of Recycled Polymeric Materials: A ReviewMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2008Francisco Vilaplana Abstract Polymeric waste materials should be considered resources for the manufacture of new products through recycling processes, with a similar status to virgin fossil-based plastics and biopolymers from renewable resources. Several efforts can be made to achieve this qualitative quantum leap in plastics recycling, and consequently introduce recycled products, with competitive performance, to the market. Scientific knowledge about the degradation processes during the life cycle and the development of fast and reliable analytical methods for the quality assessment of recycled plastics are fundamental to guarantee their performance in new applications. Different strategies,restabilisation, rebuilding, compatibilisation, and addition of elastomers and fillers,can be used to upgrade the structure and properties of polymeric waste streams. This review discusses recent developments in the mechanical recycling of plastics, focusing on how to produce quality materials from waste streams and, thus, contribute to a sustainable management of resources and energy. [source] Thermoreversible Poly(vinylidene fluoride) Gels: A Precursor to Multiporous Polymeric MaterialsMACROMOLECULAR SYMPOSIA, Issue 1 2008D. Dasgupta Abstract Summary: The thermodynamics of gelation of poly(vinylidene fluoride)(PVF2) with camphor (CP) and ethylene carbonate (EC) suggest polymer-solvent compound formation. The presence of solvent molecules in the polymer crystalline phase of the gel is accordingly shown by wide angle X-ray diffraction studies. The dried gels exhibit porous network morphology. Thermoreversible gel of PVF2 in diethyl azelate is also exploited to create multiporous polymer foam. Porosity measurements with the dried PVF2 gels using Mercury intrusion porosimetry and nitrogen sorption ensure the presence of macro and mesopores in the same matrix although the mesoporosity in dried PVF2 -CP gels strongly depend on method of drying. [source] Innentitelbild: Mechanical Nanosensor Based on FRET within a Thermosome: Damage-Reporting Polymeric Materials (Angew. Chem.ANGEWANDTE CHEMIE, Issue 31 200931/2009) Eine hybride Proteinanordnung die in einem Polymergitter eingebettet ist, spricht auf die strukturelle Deformation der Polymermatrix an. In ihrer Zuschrift auf S.,5776,ff. berichten D.,S. Clark und Mitarbeiter über die Einbindung eines FRET-Paars von fluoreszierenden Proteinen in ein Chaperonin. Das mit der Polymermatrix kombinierte Proteinhybrid reagiert auf mechanische Spannungen und zeigt so Schädigungen der Struktur durch Änderung des Fluoreszenzsignals an. [source] Mechanical Nanosensor Based on FRET within a Thermosome: Damage-Reporting Polymeric Materials,ANGEWANDTE CHEMIE, Issue 31 2009Nico Bruns Dr. Unter Spannung: Ändert sich in einem Protein-Polymer-Hybridmaterial die mechanische Spannung der Polymermatrix, so löst dies eine Konformationsänderung des Proteinkomplexes aus: Das Material ,meldet" eine strukturelle Schädigung (siehe Bild). Die Reporterkomponente ist ein Chaperonin, das ein Paar fluoreszierender Proteine kovalent bindet. Wird das Chaperonin deformiert, ändert sich der Abstand zwischen den Fluorophoren und folglich auch das FRET-Signal. [source] Terahertz Photonic Crystals Based on Barium Titanate/Polymer Nanocomposites,ADVANCED MATERIALS, Issue 19 2008Joseph Lott Polymeric materials with engineered refractive indices for applications in the THz regime can be fabricated and processed by conventional melt-processing of inorganic nanomaterials and conventional host polymers. The approach opens up new opportunities for the creation of optical elements to manipulate the technologically relevant THz radiation, for example photonic crystals. [source] Poly(glycoamidoamine)s: Cationic glycopolymers for DNA deliveryJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2006Theresa M. Reineke Abstract Polymer science is playing an exciting role in inspiring and advancing novel discoveries in the area of genetic drug delivery. Polymeric materials can be synthesized and chemically tailored to bind and compact nucleic acids into viral-like nanoparticles termed polyplexes that can deliver genetic materials into cells. This article highlights our work in this area to synthesize and study a novel class of cationic glycopolymers that we have termed poly(glycoamidoamine)s (PGAAs). The design of these materials has been inspired by many previous works in the literature. Carbohydrate comonomers have been incorporated into these structures to lower the toxicity of the delivery vehicle, and oligoamine moieties have been added to yield a cationic backbone that facilitates strong DNA binding, compaction, cellular uptake, and delivery of genetic material. PGAAs have been designed to vary in the carbohydrate size, the hydroxyl number and stereochemistry, the amine number, and the presence or absence of heterocyclic groups. Through structure,bioactivity studies, we have discovered that these materials are highly biocompatible, and each specific feature plays a large role in the observed delivery efficacy. Such structure,property studies are important for increasing our understanding of how the polymer chemistry affects the biological activity for the clinical development of polymer-based therapeutics. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6895,6908, 2006 [source] Poly(methylmethacrylate) and Topas capillary electrophoresis microchip performance with electrochemical detectionELECTROPHORESIS, Issue 16 2005Mario Castaño-Álvarez Abstract A capillary electrophoresis (CE) microchip made of a new and promising polymeric material: Topas (thermoplastic olefin polymer of amorphous structure), a cyclic olefin copolymer with high chemical resistance, has been tested for the first time with analytical purposes, employing an electrochemical detection. A simple end-channel platinum amperometric detector has been designed, checked, and optimized in a poly-(methylmethacrylate) (PMMA) CE microchip. The end-channel design is based on a platinum wire manually aligned at the exit of the separation channel. This is a simple and durable detection in which the working electrode is not pretreated. H2O2 was employed as model analyte to study the performance of the PMMA microchip and the detector. Factors influencing migration and detection processes were examined and optimized. Separation of H2O2 and L -ascorbic acid (AsA) was developed in order to evaluate the efficiency of microchips using different buffer systems. This detection has been checked for the first time with a microchip made of Topas, obtaining a good linear relationship for mixtures of H2O2 and AsA in different buffers. [source] Annealing of Biodegradable Polymer Induced by Femtosecond Laser Micromachining,ADVANCED ENGINEERING MATERIALS, Issue 4 2010Wai Yee Yeong Abstract Femtosecond laser is a potential tool for net shape processing of biodegradable polymers. However, laser processing of polymeric material is still a challenge and the effects induced by laser ablation needs to be investigated. Poly(, -caprolactone) was micromachined at high fluence and the heat affected zone was characterized. Two different phases of microstructure, namely the annealed spherulite zone and the amorphous zone, are found. [source] Applying SEM-Based X-ray Microtomography to Observe Self-Healing in Solvent Encapsulated Thermoplastic Materials,ADVANCED ENGINEERING MATERIALS, Issue 3 2010Steven D. Mookhoek In this work X-ray microtomography was used to observe fracture and healing processes in a liquid-based self-healing thermoplastic material. The method was able to produce data of sufficient resolution (<10,,m) to observe ,60,,m microcapsules containing solvent within a polymeric material and in particular their behavior around a crack zone after fracture and healing. The reconstructed data showed the distribution of filled and several empty microcapsules within the matrix material. Additional color segmentation and 3D rendering of the data unambiguously demonstrated a large concentration of ruptured microcapsules near the fracture surfaces, covering ,75,,m span on both sides of the crack. A close investigation of the crack area confirmed the presence of healed and non-healed regions. Further analysis of the segmented data allowed a quantitative determination of the release of the encapsulated solvent. [source] Influence of TiO2 Nanoparticles Incorporated into Elastomeric Polyesters on their Biocompatibility In Vitro and In VivoADVANCED ENGINEERING MATERIALS, Issue 11 2009Miroslawa El-Fray Abstract Fibroblasts proliferation and apoptosis as well as tissue response after implantation of elastomers containing nanocrystalline TiO2 were investigated in the present in vitro and in vivo study. Materials investigated were soft poly(aliphatic/aromatic-ester) multiblock thermoplastic elastomers with poly(ethylene terephthalate) (PET) hard segments and dimerized linoleic acid (DLA) soft segments, respectively, containing 0.2,wt% TiO2 nanoparticles. An investigation of the influence of TiO2 nanoparticles incorporated into polymeric material on in vitro biocompatibility revealed enhanced cell proliferation and diminished number of necrotic and apoptotic cells as compared to nanoparticles-free polymer. Implantation tests indicated that the observed tissue changes were similar to those observed with medical-grade silicone elastomer, no evidence of contact necrosis being observed. The unchanged morphology of rat liver hepatocytes and the lack of parenchymal necrosis also indicated that exposure to the material containing TiO2 nanoparticles, did not cause any cytotoxic reactions. The present study, thus, showed that elastomeric polyester containing TiO2 nanoparticles are interesting biomimetic constructs for improved tissue regeneration. [source] Preparation and sorption studies of ,-cyclodextrin/epichlorohydrin copolymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Dawn Y. Pratt Abstract ,-Cyclodextrin (,-CD) copolymer materials were synthesized by reacting different mole ratios (1 : 15, 1 : 25 and 1 : 35) of ,-CD with epichlorohydrin (EP). The products were characterized using N2 porosimetry, Fourier Transform Infrared spectroscopy, 13C CP-MAS NMR spectroscopy, thermogravimetry analysis, elemental (C and H) analysis, and scanning electron microscopy. The sorption properties in aqueous solution were studied using p-nitrophenol (PNP) with UV,Vis spectrophotometry. Sorption isotherms were obtained at pH 4.6 and three temperatures (22, 35, and 45°C) and at pH 10.3 at 22°C. The isotherms were analyzed using the BET isotherm model and the sorption parameters provided estimates of the surface area, sorption capacity, and isosteric heats of sorption for each polymeric material. The estimated surface areas are as follows: 58.2, 52.1, and 90.1 m2/g at pH 4.6. At pH 10.3, the estimated surface areas are 44.2, 40.5, and 58.5 m2/g, respectively. The removal efficiency of PNP by the polymeric materials ranged between 4.5 and 58% for the conditions investigated whereas the isosteric heats ranged between ,24.5 and ,13.6 kJ/mol. Removal efficiencies were concluded to strongly depend on the sorption conditions such as pH, temperature, and the relative amounts of sorbent and dye in aqueous solution. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Polymerization at the gas/solution interface: Preparation of polymer microstructures with gas bubbles as templatesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Maciej Mazur Abstract We report on the chemical polymerization of 2-methoxyaniline at the interface between an aqueous solution and air. The polymer is formed in the interfacial region, whereas the soluble trimer is yielded in the bulk of the polymerization solution. The preferential polymerization of 2-methoxyaniline is discussed in terms of monomer and oligomer accumulation at the interface, which influences the reactivity of these species and allows further polymerization. The phenomenon of polymer growth is employed to selectively deposit polymeric material onto glass slides decorated with gas microbubbles. Because of preferential polymerization at the bubble/solution interface, hemispherical features are produced on the surface of glass. When some polymeric material is mechanically removed, microrings or microholes are obtained. The anomalous polymerization of 2-methoxyaniline is compared to that of 2-methylaniline. This monomer polymerizes uniformly within the entire volume of the reaction mixture; thus, no preferential polymer formation at the gas/solution interface is observed. As a result, deposition on microbubble-decorated glass slides produces polymeric films containing a number of microholes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] CHROMATOGRAPHIC SEPARATION AT A PREPARATIVE SCALE OF EGG WHITE OVALBUMIN AND ITS APPLICATION IN THE ELABORATION OF YOGURT MOUSSEJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2006B. PAREDES ABSTRACT Egg white contains high-quality proteins. Some processes using eggs produce egg white as by-product. These egg white proteins may be recovered for use as additive in food products. In the first part of this study, a new polymeric material was developed and used in the chromatographic separation of ovalbumin at preparative scale. Ovalbumin is the major component of egg white and thus, it has the greatest weight in terms of its functional effects. An application of the purified ovalbumin was subsequently studied in the elaboration of yogurt mousse. The results obtained showed that the poly(glycidil methacrylate-co-ethylene dimethacrylate) resin that was manufactured enabled the separation of ovalbumin with good efficiency. This study also showed that the formulation obtained from the yogurt mousse with ovalbumin had a greater yield in volume than the commercial product used as a benchmark, improving the majority of its organoleptic qualities without appreciably affecting its stability and organoleptic properties. [source] Synergistic profiles of chain-breaking antioxidants with phosphites and hindered amine light stabilizers in styrene,ethylene,butadiene,styrene (SEBS) block copolymerJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 1 2006Cristina Luengo The photostabilization of poly(styrene- b -ethylene- co -butylene- b -styrene) (SEBS) by phosphite/p -hydroxybenzoate antioxidants and hindered phenol/hindered amine light stabilizers (HALS) was studied by using a variety of spectroscopic methods, including FTIR, UV, and luminescence spectroscopy coupled with crosslinking and hydroperoxide analysis. The results were compared with those obtained for hindered phenols and their combinations with phosphite antioxidants. All the stabilizing packages stabilized the SEBS in terms of the inhibition of discoloration and the formation of hydroperoxides, acetophenone, and oxidation products, as well as chain scission and disaggregation of the styrene units. Although phosphite/p -hydroxybenzoate combinations appeared to reduce the formation of oxidation products, they did not show any remarkable enhancement in long-term stabilization with respect to phenolic/phosphite antioxidants. On the other hand, strong synergistic profiles were found with the HALS. Mobility and diffusion impediments in the polymeric material appeared to play an important role in the stabilizing activity of the HALS. J. VINYL. ADDIT. TECHNOL. 12:8,13, 2006. © 2006 Society of Plastics Engineers [source] Use of Nitrogen as a Blowing Agent for the Production of Fine-Celled High-Density Polyethylene Foams,MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006John W. S. Lee Abstract Summary: While many experiments have been performed to examine the effects of administering CO2 as a blowing agent in the foaming process, very few studies have investigated the use of N2 for this purpose. In this study, foaming experiments were conducted in extrusion using HDPE as a polymeric material and N2 as a blowing agent. Talc was used as a nucleating agent, and three different pressure-drop rates were applied to study the effects of pressure-drop rates on HDPE foams. The experimental results revealed that the void fraction of high-density foams blown with N2 was not affected by the die temperature, contrasting the situation in low-density foams. Surprisingly, it was the cell density which determined the void fraction of high-density foams. It was also found that the use of talc significantly increased the cell density and the void fraction of the foams and minimized the role played by the pressure-drop rate in cell nucleation. Effect of N2 content on the cell density of HDPE foams. [source] Mesoscopic Morphology of Proton-Conducting Polyelectrolyte Membranes of Nafion® Type: A Self-Consistent Mean Field SimulationMACROMOLECULAR THEORY AND SIMULATIONS, Issue 2 2006Dmitry Y. Galperin Abstract Summary: A SCMF simulation is presented for a coarse-grained model of Nafion®. Based on a number of simplifying assumptions, this study predicts distinct morphological changes in the material upon alteration of temperature and water content. We found that the hydration level corresponding to the microphase segregation depends on the temperature of the system. Spherical clusters constituting the hydrophilic microphase of the membrane at relatively low water content (but above the transition point) grow in size, coalesce and form a network of channels responsible for the ionic transport at higher hydration levels. This hydrophilic phase is shielded from the hydrophobic matrix by the sidechains of Nafion®, their end-groups being turned towards the water clusters. The results obtained are similar to those reported from dissipative particle dynamics studies and support the "cluster-network" model for the low hydration levels and the "sponge" model at higher hydration levels. The simulation approach chosen proved to be effective for the mesoscopic structure analysis of the heterogeneous polymeric material. Schematic representation of the structure of Nafion®-water blends. [source] Hysteretic magnetoresistance in polymeric diodesPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7-8 2009Sayani Majumdar Abstract We report on hysteretic organic magnetoresistance (OMAR) in polymeric diodes. We found that magnitude and lineshape of OMAR depend strongly on the scan speed of the magnetic field and on the time delay between two successive measurements. The time-dependent OMAR phenomenon is universal for diodes made with various polymers. However, the width and magnitude of OMAR varied with the polymeric material. The suggestive reason for this hysteretic behavior is trapped carriers, which in presence of a magnetic field change the ferromagnetic ground-state of the polymer leading to a long spin relaxation time. These experimental observations are significant for clarification of the OMAR phenomenon. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fiber-forming blend polypropylene-polyvinyl alcoholPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 8 2001Anton Marcin Abstract The preparation of a fiber-forming blend consisting of polypropylene and polyvinyl alcohol mixed with glycerol and with polypropylene grafted with maleic anhydride were studied. The physical and mechanical properties of blend fibers were also studied. The rheological measurements for semiquantitative evaluation of technological compatibility of the components and for processing the polymeric material in extruding and spinning process were carried out. The experimental results revealed the technological compatibility of the polypropylene-polyvinyl alcohol blend in the presence of glycerol and polypropylene grafted with maleic anhydride. The colloidal structure of interface layer is assumed to be in a three- or four-component system. The mixture of polyvinyl alcohol with glycerol allows for the preparation of well spun fiber-forming polypropylene blends. Polypropylene-polyvinyl alcohol blend fibers consisting of up to 20% polyvinyl alcohol with sufficient mechanical properties, higher porosity and significantly higher sorption of water than polypropylene fibers alone were prepared. Copyright © 2001 John Wiley & Sons, Ltd. [source] Underivatized cyclic olefin copolymer as substrate material and stationary phase for capillary and microchip electrochromatographyELECTROPHORESIS, Issue 15 2008Omar Gustafsson Abstract We report, for the first time, the use of underivatized cyclic olefin copolymer (COC, more specifically: Topas) as the substrate material and the stationary phase for capillary and microchip electrochromatography (CEC), and demonstrate chromatographic separations without the need of coating procedures. Electroosmotic mobility measurements in a 25,,m id Topas capillary showed a significant cathodic EOF that is pH-dependent. The magnitude of the electroosmotic mobility is comparable to that found in glass substrates and other polymeric materials. Open-tubular CEC was employed to baseline-separate three neutral compounds in an underivatized Topas capillary with plate heights ranging from 5.3 to 12.7,,m. The analytes were detected using UV absorbance at 254,nm, thus taking advantage of the optical transparency of Topas at short wavelengths. The fabrication of a Topas-based electrochromatography microchip by nanoimprint lithography is also presented. The microchip has an array of pillars in the separation column to increase the surface area. The smallest features that were successfully imprinted were around 2,,m wide and 5,,m high. No plasma treatment was used during the bonding, thus keeping the surface properties of the native material. An RP microchip electrochromatography separation of three fluorescently labeled amines is demonstrated on the underivatized microchip with plate heights ranging from 3.4 to 22,,m. [source] Recent progress in the use of soluble ionic polymers as pseudostationary phases for electrokinetic chromatographyELECTROPHORESIS, Issue 23-24 2004Christopher P. Palmer Abstract This review concerns the development, characterization, and application of soluble ionic polymeric materials as pseudostationary phases for electrokinetic chromatography since 2002. Cationic polymers, anionic siloxanes, polymerized surfactants (micelle polymers), and chiral polymers are considered. The use of stable suspensions of polymer nanoparticles in electrokinetic chromatography is also reviewed. [source] Recent progress in the development, characterization and application of polymeric pseudophases for electrokinetic chromatographyELECTROPHORESIS, Issue 22-23 2002Christopher P. Palmer Abstract This review article details the development, characterization and application of polymeric materials as pseudostationary phases for electrokinetic chromatography over the past two years. Recent developments in cationic polymers and anionic siloxane, acrylamide and polymerized surfactants (micelle polymers) are reviewed. Also reviewed is recent progress in the development and characterization of chiral polymeric phases for chiral separations by electrokinetic chromatography, and application of a polymeric pseudophase with electrospray ionization mass spectrometric detection. [source] Towards Higher Laccase Activities Produced by Aquatic Ascomycetous Fungi Through Combination of Elicitors and an Alternative SubstrateENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2008C. Junghanns Abstract Laccases are versatile biocatalysts with various potential biotechnological applications, e.g. the treatment of industrial waste waters, the detoxification of environmental pollutants, or the functionalization of renewable polymeric materials. Central composition experimental design and response surface methodology was applied to optimize the production of laccase by the aquatic ascomycetous fungi, Phoma sp. UHH 5-1-03 and Coniothyrium sp.,Kl-S5, in shake flasks. A complex plant-based medium (tomato juice) and two elicitors (Remazol Brilliant Blue R [RBBR] and CuSO4) were tested in combination at three concentrations. The highest laccase activity of 6322,±,403,U/L was achieved on day,9 for Phoma sp. Coniothyrium sp. exerted a maximum laccase activity of 3035,±,111 U/L on day,4. Optimal conditions were 30,% tomato juice and 450,mg/L RBBR for both strains. A concentration of 250,,M CuSO4 led to highest laccase activities in cultures of Coniothyrium sp., and 50,,M CuSO4 was most effective for Phoma sp. A remarkable synergistic effect of tomato juice and RBBR on laccase production was observed for both strains. The upscaling potential of the optimal induction conditions was demonstrated in a lab-scale fermenter which resulted in maximum activities of 11030,±,177,U/L on day,6 for Phoma sp. and 11530,±,161,U/L on day,9 for Coniothyrium sp. This study therefore presents a promising alternative for laccase production in ascomycetes based on a cheap complex substrate in combination with two elicitors. [source] Physicochemical evaluation of silica-glass fiber reinforced polymers for prosthodontic applicationsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2005Gökçe Meriç This investigation was designed to formulate silica-glass fiber reinforced polymeric materials. Fused silica-glass fibers were chosen for the study. They were heat-treated at various temperatures (500°C, 800°C and 1100°C), silanized, sized and incorporated in two modified resin mixtures (A and B). The flexural properties in dry and wet conditions were tested and statistically analyzed, and the content of residual methyl methacrylate (MMA) monomer, dimensional changes with temperature, water sorption and solubility were determined. Woven fibers [36.9% (wt/wt)], heat-treated at 500°C, gave the highest strength values for the polymeric composites (an ultimate transverse strength of 200 Mpa and a flexural modulus of 10 GPa) compared with the fibers heat-treated at other temperatures. There was no statistically significant difference in the measured flexural properties between resins A and B regarding fiber treatment and water storage time. These fiber composites had a small quantity of residual MMA content [0.37 ± 0.007% (wt/wt)] and very low water solubility, indicating good biocompatibility. It was suggested that silica-glass fibers could be used for reinforcement as a result of their anticipated good qualities in aqueous environments, such as the oral environment. [source] Copper-Free Clickable CoatingsADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Luiz A. Canalle Abstract The copper-catalyzed azide,alkyne 1,3-dipolar cycloaddition (CuAAC) is extensively used for the functionalization of well-defined polymeric materials. However, the necessity for copper, which is inherently toxic, limits the potential applications of these materials in the area of biology and biomedicine. Therefore, the first entirely copper-free procedure for the synthesis of clickable coatings for the immobilization of functional molecules is reported. In the first step, azide-functional coatings are prepared by thermal crosslinking of side-chain azide-functional polymers and dialkyne linkers. In a second step, three copper-free click reactions (i.e., the Staudinger ligation, the dibenzocyclooctyne-based strain-promoted azide,alkyne [3+2] cycloaddition, and the methyl-oxanorbornadiene-based tandem cycloaddition,retro-Diels,Alder (crDA) reaction) are used to functionalize the azide-containing surfaces with fluorescent probes, allowing qualitative comparison with the traditional CuAAC. [source] Self-Healing Materials: A Facile Strategy for Preparing Self-Healing Polymer Composites by Incorporation of Cationic Catalyst-Loaded Vegetable Fibers (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Mater. Discontinuous sisal fibers carrying extremely active (C2H5)2O·BF3 are embedded in epoxy matrix together with epoxy monomer-loaded microcapsules to fabricate self-healing composite based on the healing mechanism of cationic chain polymerization. This approach, described by D. S. Xiao et al. on page 2289, skips the encapsulation of high activity chemicals, reducing the risk of their deactivation during handling. It provides a facile strategy for making extrinsic self-healing polymeric materials. [source] Formation and Properties of Responsive Siloxane-Based Polymeric Surfaces with Tunable Surface Reconstruction KineticsADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Julie Ann Crowe-Willoughby Abstract Here, the formation of responsive polymeric materials with tunable response time is reported. These structures are fabricated by chemically modifying poly(vinylmethyl siloxane) (PVMS) networks with alkanethiols bearing a hydrophilic end-group (COOH or OH). The response time is facilitated by the liquid nature of the PVMS backbone and increases with increase in length of the methylene spacer (CH2)n in the alkanethiol pendent group. While for n,=,2 and 6, the surface reconstructs almost instantaneously, specimens with n,=,11 resist reconstruction because of strong van der Waals forces, leading to the formation of semi-crystalline regions. It is demonstrated that the responsive nature of PVMSS(CH2)11OH can be fine-tuned by varying the temperature; it possesses a faster response at temperatures above the melting point of the S(CH2)11OH moiety. [source] Structural Changes in the BODIPY Dye PM567 Enhancing the Laser Action in Liquid and Solid Media,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007I. García-Moreno Abstract In the search for more efficient and photostable solid-state dye lasers, newly synthesized analogs of the borondipyrromethene (BODIPY) dye PM567, bearing the polymerizable methacryloyloxypropyl group at position 2 (PMoMA) or at positions 2 and 6 (PDiMA), have been studied in the form of solid copolymers with methyl methacrylate (MMA). The parent dye PM567, as well as the model analogs bearing the acetoxypropyl group in the same positions, PMoAc and PDiAc, respectively, have been also studied both in liquid solvents and in solid poly(MMA) (PMMA) solution. Although in liquid solution PMoAc and PDiAc have the same photophysical properties as PM567, PDiAc exhibited a photostability up to 10 times higher than that of PM567 in ethanol under 310,nm-irradiation. The possible stabilization factors of PDiAc have been analyzed and discussed on the basis of the redox potentials, the ability for singlet molecular oxygen [O2(1,g)] generation, the reactivity with O2(1,g), and quantum mechanical calculations. Both PMoAc and PDiAc, pumped transversally at 532,nm, lased in liquid solution with a high (up to 58,%), near solvent-independent efficiency. This enhanced photostabilization has been also observed in solid polymeric and copolymeric media. While the solid solution of the model dye PDiAc in PMMA showed a lasing efficiency of 33,%, with a decrease in the laser output of ca.,50,% after 60,000 pump pulses (10,Hz repetition rate) in the same position of the sample, the solid copolymer with the double bonded chromophore, COP(PDiMA-MMA), showed lasing efficiencies of up to 37,%, and no sign of degradation in the laser output after 100,000 similar pump pulses. Even under the more demanding repetition rate of 30,Hz, the laser emission from this material remained at 67,% of its initial laser output after 400,000 pump pulses, which is the highest laser photostability achieved to date for solid-state lasers based on organic polymeric materials doped with laser dyes. This result indicates that the double covalent linkage of the BODIPY chromophore to a PMMA polymeric matrix is even more efficient than the simple linkage, for its photostabilization under laser operation. [source] | ||||||||||||||||||||||||||||||||||