Home About us Contact
|
Home About us Contact | ||
|
|
||
Polymer Materials (polymer + material)
Selected AbstractsTransfection of Cells Mediated by Biodegradable Polymer Materials with Surface-Bound PolyethyleneimineBIOTECHNOLOGY PROGRESS, Issue 2 2000Ji Zheng Poly(,-CBZ- L -lysine) can be mixed with biodegradable polymers such as poly(D,L -lactic- co -glycolic acid) or poly(L -lactic acid) and formed into films, foams, or microspheres. Surface amino groups may then be deprotected with acid or lithium/liquid ammonia. The amino groups serve as a method to modify the surface by attachment of other molecules. In the present experiments, we show that these polymer materials, as films or foams, may be surface modified by the attachment of polyethyleneimine (PEI). Plasmid DNA attached to the PEI can transfect cells plated on the surface over several days. Covalent atachment of PEI was required for transfection to be efficient. PEI was also attached to surface-bound collagen on cell culture plates and was shown to mediate transfection. [source] The Relevance of the Collaborative Effect in Determining the Performances of Photorefractive Polymer MaterialsCHEMPHYSCHEM, Issue 2 2010Rocco Angelone Dr. Abstract A derivative of 2-methylindole, 3-[2-(4-nitrophenyl)ethenyl]-1-allyl-2-methylindole, NPEMI-A, is studied for its photoconductivity and photorefractivity behaviour. Its blends with the organic polymer poly-(2,3-dimethyl- N -vinylindole), PVDMI, are also investigated. Due to the expected and devised mutual solubility of the two components of the blends, it is possible to carry out measurements with the weight percent of the chromophore NPEMI-A changing from zero to 100. Films were produced by a squeezing process between two ITO-covered glass sheets. No opacity phenomena, that are so common for many other organic blends due to the segregation of the dissolved chromophore, are observed. The photorefractive optical gain ,2 is obtained as a function of the chromophore content. Differential scanning calorimetry measurements (DSC) are also carried out to obtain the whole change of the glass transition temperature Tg as a function of the amount of chromophore contained in the blends. From the experimental trend of Tg a meaningful quantitative estimate of the value of the electrostatic interactions acting in the studied blends, is obtained. The importance of the value of Tg, and of the electrostatic interactions, in determining the extent of the photorefractivity is clearly evident. The results are compared for NPEMI-A (,2=210 cm,1) and for NPEMI-E (,2 , 2000 cm,1) that has a N-2-ethylhexyl group instead of a N-allyl group. The Pockels and Kerr contributions and,for the first time,a "collaborative effect" of the photorefractivity of NPEMI-A are distinguished and quantitatively evaluated. [source] VISCOELASTICITY OF A SIMULATED POLYMER AND COMPARISON WITH CHICKPEA FLOUR DOUGHSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2006NIDHI YADAV ABSTRACT An integrated approach consisting of compression and stress relaxation is performed with a simulated model system of poly dimethyl siloxane (PDMS), a viscoelastic polymer material when the compressive strain, height of sample and crosshead speed were varied. The parameters derived are the forces at the end of compression and relaxation, energy for compression and the extent of elasticity of the sample based on the ratios of forces as well as the proposed energy values. The results were verified with food doughs undergoing large deformations that show a nonlinear behavior. The proposed extent of elasticity based on the ratios of energy stored and compression can be used as an index for the characterization of viscoelasticity. A nonlinear three-parameter model had also been proposed to predict the stress decay characteristics as a function of time, which was found suitable for the PDMS system, and was better than the two-parameter Peleg model as judged by lower variance values (0.0006,0.018 and 0.002,0.048, respectively). Further, an actual system of food doughs in the form of chickpea (Cicer arietinum L.) flour dough was used to verify the proposed model and viscoelastic index at different moisture contents (27,39%) subjected to compressive strains of 25,75%. The nonlinear relaxation characteristics of the food dough are sensitive to moisture content as well as to strain level. [source] Promising Optoelectronic Materials: Polymers Containing Phosphorescent Iridium(III) ComplexesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 9-10 2010Qiang Zhao Abstract As one of the most promising optoelectronic materials, polymers that contain phosphorescent IrIII complexes have attracted more and more interest in recent years. They are a class of well-known electroluminescent materials with excellent performance. So far, efficient green-, red-, and white-emitting polymer light-emitting diodes based on polymers with on-chain IrIII complexes have been realized successfully. For the realization of this class of polymer material, IrIII complexes (as energy guest) can be introduced into the main-chain or side-chain of polymers (as energy host). In this article, we summarize the design principles, synthetic routes, structure,property relationships, and applications in optoelectronic devices of polymers that contain phosphorescent IrIII complexes. [source] Theoretical Derivation of the Molecular Weight Distribution of End-Capped Linear Condensation PolymersMACROMOLECULAR THEORY AND SIMULATIONS, Issue 1 2009Henk Knoester Abstract End-capped, low molecular weight polymers have found numerous practical applications. By providing the end-capper molecules with specific chemical functionality, the polymer material can be equipped with a desired chemical behavior for product application or polymer processing. Using probabilistic methods, formulas are derived for calculating the target molecular weight distribution and its averages for the case of linear condensation polymerization. The formulas are generally applicable, allowing for arbitrary amounts of monofunctional monomers or end-capper molecules affecting either one or both functional groups involved in the polymerization process. [source] A stochastic flow model for a tubular solution polymerization reactorPOLYMER ENGINEERING & SCIENCE, Issue 11 2007Ardson dos S. Vianna Jr. Residence time distributions were evaluated experimentally for three tubular solution polymerization reactors to analyze aspects of the fluid-dynamic behavior of these reactors. The analysis of the available experimental data indicates that the flow characteristics of these reactors may be subject to stochastic perturbations. A stochastic flow model is then proposed by assuming that a viscous polymer layer is formed in the proximities of the reactor walls and that plugs of polymer material are released at random during the operations. This model is able to represent the available experimental data fairly well for three tubular reactors with different configurations. POLYM. ENG. SCI., 47:1839,1846, 2007. © 2007 Society of Plastics Engineers [source] On the relation between surface texture and gloss of injection-molded pigmented plasticsPOLYMER ENGINEERING & SCIENCE, Issue 10 2005Ingrid Ariño The relation between the surface topography of injection-molded plastic objects with deliberately imposed textures and their gloss, measured by means of a conventional glossmeter at incident angles of 20°, 60°, and 85°, was investigated. A modification of the general scalar Kirchhoff approximation, which accounts for geometrical features of the glossmeter, is used to describe the experimental gloss values of the textured surfaces. The agreement between the measured and the calculated values for incidence angles of 20° and 60° confirms the usefulness of the approach, though several of the textured surfaces used here are too rough for the Kirchhoff theory to be strictly valid. A poorer agreement, however, was noted at higher incidence angles (85° in this case). For very smooth surfaces (without any texture), the classical Bennett-Porteus theory could in many cases describe the gloss level with sufficient accuracy. The influence on the measured gloss of the polymer material (in terms of its refractive index) and the color of the injection-molded object is also discussed. Light beige specimens in three different polymeric materials (acrylonitrile-butadiene-styrene, acrylonitrile-butadiene-styrene/polycarbonate blend, and polypropylene) as well as three acrylonitrile-butadiene-styrene products with different colors were used. The refractive index of the polymer had no major influence on the measured gloss. The gloss level increased slightly with increasing lightness of the specimens, which can be associated with an increased contribution from the bulk scattering. However, the surface texture governed most of the gloss variations. POLYM. ENG. SCI., 45:1343,1356, 2005. © 2005 Society of Plastics Engineers [source] Influence of heat treatment on the space charge within an epoxy resin polymer material,POLYMER INTERNATIONAL, Issue 7 2001Hajer Guermazi Abstract The influence of heat treatment on the appearance and the evolution of the space charge repartition within an epoxy resin polymer material is investigated. The space charge measurements were made using the thermal step method (TSM) and the thermally stimulated depolarization currents (TSDC) method. The results obtained show the behaviour of the space charge density after heat treatment and, in particular, it can be concluded that the charges are stabilized in deep levels. © 2001 Society of Chemical Industry [source] Wine bottle closures: physical characteristics and effect on composition and sensory properties of a Semillon wine 1.AUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2001Performance up to 20 months post-bottling Abstract A Semillon wine was bottled using 14 different closures: a screw-cap type, two grades of conventional natural cork, two ,technical cork' closures (natural cork with a synthetic component), and 9 closures manufactured from synthetic polymer material. Closure performance was evaluated for physical aspects (e.g. extraction force and energy, change in closure diameter, and ease of closure reinsertion), and for wine composition and sensory properties. Wine under the screw cap closure retained the greatest concentration of sulfur dioxide (SO2) and ascorbic acid and had the slowest rate of browning. For other closures the trend of SO2 loss relative to the screw cap closure was apparent from an early stage of testing, and was most evident in the group of synthetic closures, intermediate in the conventional corks, and least evident in the technical cork closures. The loss of SO2 was in general highly correlated with an increase in wine browning (OD420) and the concentration of SO2 in the wine at six months was a strong predictor of future browning in the wine, particularly after eighteen months. Neither the concentration of dissolved oxygen at bottling (0.6,3.1 mg/L), nor the physical closure measures were predictors of future browning. For several closures upright storage tended to accelerate loss of SO2 from the wine, but in many cases this effect was marginal. The closures differed widely in regard to physical characteristics, and in general synthetic corks appeared least ,consumer-friendly' in terms of extraction forces, energies, and ease of closure re-insertion, but there was a trend for natural cork closures to exhibit larger variability in physical characteristics than technical cork and synthetic closures. Sensory analysis indicated large differences in wine flavour properties, with closures which tended to result in the best retention of free SO2 having wine sensory scores for ,citrus' that were generally high whilst scores for the attributes ,developed'/,oxidised' were low. The situation was reversed for wine under closures that performed poorly in the retention of free SO2. It was found that below a critical level of free SO2 remaining in the wine, closures exhibited substantially higher ,oxidised' aroma. Whilst trichloroanisole-type (TCA) taint was a noticeable problem for some cork and technical cork closures, any plastic-type taint appeared not to be a problem with most synthetic closures. [source] Effect of PCBM Concentration on Photoluminescence Properties of Composite MEH-PPV/PCBM Nanoparticles Investigated by a Franck,Condon Analysis of Single-Particle Emission SpectraCHEMPHYSCHEM, Issue 14 2009Daeri Tenery Dr. Abstract The emission of composite conjugated polymer (MEH-PPV)/fullerene (PCBM) nanoparticles is investigated by single particle spectroscopy (SPS), and changes in vibronic structure with nanoparticle composition are evaluated by means of a detailed Franck,Condon analysis. Consistent with previous reports we find that the emission spectra can be modeled as the superposition of two types of emitters, one with aggregate character and one with molecular character. Major findings from the fitting of the SPS data to a Franck,Condon model are that 1) the occurrence of each of the two types of emitters changes with nanoparticle composition to the point that no aggregate emitters are detected (at 50 wt,% PCBM), 2) at the highest PCBM doping levels (75 wt,% PCBM) aggregate emitters reappear due to nanoscale phase separation in the composite nanoparticles, 3) the molecular emitters show small Huang,Rhys factors that increase with PCBM doping, indicative of extensive delocalization and exciton migration that is reduced by the disorder introduced in the polymer material by PCBM doping and 4) the aggregate emitters show large Huang,Rhys factors, indicative of the localized nature of these energy trap sites, with a broad distribution of values of these Huang,Rhys factors. The latter observation suggests a broad heterogeneous distribution of aggregate morphologies in blended conducting polymer materials, which can be attributed to variations in polymer chain folding and stacking at the aggregate sites. The reported results obtained by the SPS approach show how blending conjugated polymers with fullerenes at various doping levels induces changes in interchain interactions and aggregate site density even at length scales below a few tens of nanometers that affect conjugated polymer material properties, an observation that has gone unnoticed in bulk studies of blended conjugated polymer films. [source] Knowledge-Based Approach towards Hydrolytic Degradation of Polymer-Based BiomaterialsADVANCED MATERIALS, Issue 32-33 2009Dieter Hofmann Abstract The concept of hydrolytically degradable biomaterials was developed to enable the design of temporary implants that substitute or fulfill a certain function as long as required to support (wound) healing processes or to control the release of drugs. Examples are surgical implants, e.g., sutures, or implantable drug depots for treatment of cancer. In both cases degradability can help to avoid a second surgical procedure for explanation. Although degradable surgical sutures are established in the clinical practice for more than 30 years, still more than 40% of surgical sutures applied in clinics today are nondegradable.1 A major limitation of the established degradable suture materials is the fact that their degradation behavior cannot reliably be predicted by applying existing experimental methodologies. Similar concerns also apply to other degradable implants. Therefore, a knowledge-based approach is clearly needed to overcome the described problems and to enable the tailored design of biodegradable polymer materials. In this Progress Report we describe two methods (as examples for tools for this fundamental approach): molecular modeling combining atomistic bulk interface models with quantum chemical studies and experimental investigations of macromolecule degradation in monolayers on Langmuir,Blodgett (LB) troughs. Finally, an outlook on related future research strategies is provided. [source] Precisely Defined Heterogeneous Conducting Polymer Nanowire Arrays , Fabrication and Chemical Sensing ApplicationsADVANCED MATERIALS, Issue 20 2009Yixuan Chen Heterogeneous conducting polymer nanostructures are fabricated using a newly developed method. Completely isolated nanowires of several conducting polymer materials can be fabricated side-by-side with perfect registry to each other on a rigid or flexible substrate. Results of a chemical sensing study using PPY and PEDOT nanowires are presented (see figure). [source] Luminescent Conjugated Polymer Nanowire Y-Junctions with On-Branch Molecular AnisotropyADVANCED MATERIALS, Issue 10-11 2009Deirdre O'Carroll Polyfluorene nanowire Y-junctions synthesized by solution-assisted template wetting are shown to exhibit strongly polarized light emission from the branches and stems. It is demonstrated that the Y-junctions can be positioned, and branching angles may be adjusted, by micromanipulation. Nanowire junctions of this type could ultimately facilitate the incorporation of conjugated polymer materials into highly integrated electronic and photonic circuits and systems. [source] Formation of highly oriented biodegradable polybutylene succinate adipate nanocomposites: Effects of cation structures on morphology, free volume, and propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009Katherine M. Dean Abstract Many biodegradable polymer materials have not been found to be suitable replacements for more traditional non-biodegradable polymers owing to their insufficient gas and vapor barrier properties. The use of a series of novel organically modified synthetic fluorohectorites (FHTs) has been explored to produce biodegradable polybutylene succinate adipate (PBSA)-clay nanocomposites with improved barrier. Highly oriented nanoclay structures (clearly showing a tortuous path required to reduce gas and vapor transmission) were observed using transmission electron microscopy (TEM), resulting in a significant reduction in oxygen permeability (up to a 53% decrease). In particular, these oriented structures were observed in the FHTs modified with di poly(oxyethylene) alkyl methyl ammonium and the longer chain dimethyl dialkyl ammonium. Orientation and dispersion were found to be a result of chemical functionality, chain length, and unique aspect ratios of these FHTs. It was concluded that this reduction in permeability was predominantly due to the tortuous path created by oriented platelets and not from any nucleating effects the platelets may have had. Interestingly, the FHTs were shown to disrupt crystallinity and no change in free volume (as measured using positron annihilation life-time spectroscopy) was observed. The excellent clay dispersion and orientation also led to significant increases in other properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Thermal energy transport within porous polymer materials: Effects of fiber characteristicsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Huijun Wu Abstract A theoretical model integrating the radiative and conductive heat transfer is presented and applied to evaluate the thermal energy transport within porous polymer materials. The model was first validated by comparing the computed thermal energy flux with the experimental measurements of two porous polymer materials made of wool and polyester. The model was then used to predict the effects of the polymer fiber characteristics (viz. fiber fractional volume, fiber emissivity, fiber radius, and fiber thermal conductivity) on the thermal energy flux within the porous polymer materials. It was found that decreasing fiber radius would significantly reduce the total thermal energy flux through the porous polymer materials, whereas increasing fibre emissivity or decreasing the thermal conductivity would cause a just slight reduction of the total thermal energy flux. The fiber fractional volume had a significant influence on the thermal energy flux, and thereby the fiber fractional volume can be optimized in view of improving the thermal insulating performance of the porous polymer materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Grafting of poly(N -isopropylacrylamide) onto nylon and polystyrene surfaces by atmospheric plasma treatment followed with free radical graft copolymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Xiaoling Wang Abstract Stimuli-responsive polymer materials (SRPs) have potential uses in drug delivery, tissue engineering, bioreactors, and cell-surface adhesion control. Temperature-responsive surfaces were fabricated by grafting poly(N -isopropylacrylamide) (PNIPAM) onto nylon and polystyrene surfaces via a new procedure, i.e., He atmospheric plasma treatment followed by free radical graft copolymerization. The atmospheric plasma exhibits the activation capability to initiate graft copolymerization. The procedure is suitable for integration into a continuous manufacturing process. To reduce homopolymerization and enhance graft yield, Mohr's salt was added. The graft of PNIPAM was confirmed by Fourier transform infrared spectroscopy and atomic force microscopy. Dramatic water contact angle increase was found for PNIPAM-grafted polymers at about 32°C, indicating the temperature sensitivity of the grafted surface, i.e., the change of surface from hydrophilic to hydrophobic when temperature increases above the lower critical solution temperature (LCST). The addition of Mohr's salt enhances the grafting reaction and the magnitude of temperature sensitivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3614,3621, 2007 [source] Hydrolytic degradation of poly(ethylene terephthalate)JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Seyed Saeid Hosseini Abstract Molecular weight is an important factor in the processing of polymer materials, and it should be well controlled to obtain desired physical properties in final products for end-use applications. Degradation processes of all kinds, including hydrolytic, thermal, and oxidative degradations, cause chain scission in macromolecules and a reduction in molecular weight. The main purpose of this research is to illustrate the importance of degradation in the drying of poly(ethylene terephthalate) (PET) before processing and the loss of weight and mechanical properties in textile materials during washing. Several techniques were used to investigate the hydrolytic degradation of PET and its effect on changes in molecular weight. Hydrolytic conditions were used to expose fiber-grade PET chips in water at 85°C for different periods of time. Solution viscometry and end-group analysis were used as the main methods for determining the extent of degradation. The experimental results show that PET is susceptible to hydrolysis. Also, we that as the time of retention in hydrolytic condition increased, the molecular weight decreases, but the rate of chain cleavage decreased to some extent, at which point there was no more sensible degradation. The obtained moisture content data confirmed the end-group analysis and viscometry results. Predictive analytical relationships for the estimation of the extent of degradation based on solution viscosity and end-group analysis are presented. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2304,2309, 2007 [source] Kinetics of interaction of palm ethyl biodiesel with three different polymer materialsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2008Giselle Lutz Abstract Diesel diffuses into neoprene matrices 10% faster than palm ethyl biodiesel at 20°C. In contrast, the palm biodiesel soaks highly plasticized PVC five times faster than diesel. Phthalate plasticizer leaks from the PVC matrix 14 times faster when biodiesel is the absorbed liquid, relative to petrodiesel. This biodiesel penetrates polybutadiene-styrene resins at rates that depend on the ratio of phenyl to CHCH units in the resins. Copyright © 2008 John Wiley & Sons, Ltd. [source] Resistive switching polymer materials based on poly(aryl ether)s containing triphenylamine and 1,2,4-triazole moietiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2008Kun-Li Wang Abstract A series of poly(aryl ether)s were successfully prepared via aromatic nucleophilic substitution reaction from various bisphenols and a novel bipolar aryl difluoride monomer containing electron-donor triphenylamine and electron-acceptor 1,2,4-triazole moieties. The poly(aryl ether)s exhibited excellent solubility in organic solvents such as dimethylformamide, chloroform, and tetrahydrofuran at room temperature. The poly(aryl ether)s showed high thermal stability with Td10 higher than 500 °C and glass transition temperatures (Tg) higher than 187 °C. The thin films of the poly(aryl ether)s indicated bistable resistive switching behavior with ON/OFF current ratios as high as 103. The switching on and switching off bias voltages of the poly(aryl ether)s were affected by the bisphenol moiety. The good resistive switching behavior of the poly(aryl ether)s made them promising candidates for future nonvolatile memory applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6861,6871, 2008 [source] Influence of Processing Temperature on Microcellular Injection-Moulded Wood,Polypropylene CompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006Andrzej K. Bledzki Abstract Summary: Microcellular wood fibre reinforced polymer materials are significant because of their possibility to reduce the density of automotive components through microcellular structure, process and product part advantages, and as a new development with bio-fibre strengthened plastics. Soft wood fibre reinforced PP composites in box part and panel shape were prepared by an injection moulding process. Polymeric microspheres as a chemical foaming agent (endothermic) were used to produce the microcellular composites. The influence of injection moulding processing temperature on the microcellular structure and properties (tensile and flexural properties, notched charpy impact strength) was investigated by varying the temperature over the 150,170,°C, 160,180,°C and 170,190,°C. A comparative study of cell morphology, weight reduction and mechanical properties was conducted between box part and panel. Microcell morphology, cell size, shape and distribution were investigated using scanning electron micrographs. The results indicated that the lower processing temperature should be below the range of 170,190,°C and processing temperature at 160,180,°C, where the composites showed finer cellular structure compared to other processing temperatures. The mechanical properties did not differ with the variation of processing temperature regardless of composite types (box part or panel). Cellular structure changes in the box part were found considering near or far from injecting point. Microcellular injection-moulded box part (geometry: 150,×,100,×,70 mm3 in size) of soft wood fibre,PP composites. [source] Biomimetic Polymer Nanostructures by Injection MoldingMACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2003Nikolaj Gadegaard Abstract The nanometer scale topography of self-assembling structural protein complexes in animals is believed to induce favorable cell responses. An important example of such nanostructured biological complexes is fibrillar collagen that possesses a cross-striation structure with a periodicity of 69 nm and a peak-to-valley distance of 4,6 nm. Bovine collagen type I was assembled into fibrillar structures in vitro and sedimented onto solid supports. Their structural motif was transferred into a nickel replica by physical vapor deposition of a small-grained metal layer followed by galvanic plating. The resulting inverted nickel structure was found to faithfully present most of the micrometer and nanometer scale topography of the biological original. This nickel replica was used as a die for the injection molding of a range of different thermoplastic polymers. Total injection molding cycle times were in the range of 30,45 seconds. One of the polymer materials investigated, polyethylene, displayed poor replication of the biological nanotopographical motif. However, the majority of the polymers showed very high replication fidelity as witnessed by their ability to replicate the cross-striation features of less than 5 nm height difference. The latter group of materials includes poly(propylene), poly(methyl methacrylate), poly(L -lactic acid), polycaprolactone, and a copolymer of cyclic and linear olefins (COC). This work suggests that the current limiting factor for the injection molding of nanometer scale topography in thermoplastic polymers lies with the grain size of the initial metal coating of the mold rather than the polymers themselves. [source] Polymer Crystallization: A DSC Approach to Building the T-CR-T DiagramMACROMOLECULAR THEORY AND SIMULATIONS, Issue 2-3 2008Rosa Berlanga Abstract T-CR-T diagrams are one of the most reliable ways to predict the thermal behavior of material solidification from the melt. A brief description of solidification accounting for continuous cooling is presented for fast-crystallizing polymers. An isoconversional method is applied to the kinetic analysis of non-isothermal processes. The solidification process of different polymer materials: high density polyethylene based samples and mixtures of PEG with a pharmaceutical drug were analyzed by means of DSC. Several diagrams were constructed and the best agreement between experimental data and the calculated T-CR-T curves corresponds to the use of the isoconversional method. [source] The shock and release behavior of an aerospace-grade cured aromatic amine epoxy resinPOLYMER COMPOSITES, Issue 10 2008P.J. Hazell Knowing the dynamic behavior of polymer materials that are used in the construction of fiber-reinforced composite materials is particularly important for such materials that are subjected to impact. In this work, we have conducted a number of plate-impact experiments on a commercially important aromatic amine epoxy resin that is used in the construction of carbon fiber composite materials. The measured Hugoniot in shock velocity,particle velocity space was Us = 2.65 + 1.55 up (,0 = 1.141 g/cc), and is similar to the measured Hugoniots of other resins presented by different researchers. We have also measured the longitudinal stress in the shocked material and shown, in common with other polymers, that above a threshold stress, an increase in shear strength with impact stress is observed. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Poly(hydroxyether of bisphenol A) -alt -polydimethylsiloxane: a novel thermally crosslinkable alternating block copolymerPOLYMER INTERNATIONAL, Issue 2 2009Lei Wang Abstract BACKGROUND: An important strategy for making polymer materials with combined properties is to prepare block copolymers consisting of well-defined blocks via facile approaches. RESULTS: Poly(hydroxyether of bisphenol A)- block -polydimethylsiloxane alternating block copolymers (PH- alt -PDMS) were synthesized via Mannich polycondensation involving phenolic hydroxyl-terminated poly(hydroxyether of bisphenol A), diaminopropyl-terminated polydimethylsiloxane and formaldehyde. The polymerization was carried out via the formation of benzoxazine ring linkages between poly(hydroxyether of bisphenol A) and polydimethylsiloxane blocks. Differential scanning calorimetry and small-angle X-ray scattering show that the alternating block copolymers are microphase-separated. Compared to poly(hydroxyether of bisphenol A), the copolymers displayed enhanced surface hydrophobicity (dewettability). In addition, subsequent crosslinking can occur upon heating the copolymers to elevated temperatures owing to the existence of benzoxazine linkages in the microdomains of hard segments. CONCLUSION: PH- alt -PDMS alternating block copolymers were successfully obtained. The subsequent self-crosslinking of the PH- alt -PDMS alternating block copolymers could lead to these polymer materials having potential applications. Copyright © 2008 Society of Chemical Industry [source] Understanding surfaces and buried interfaces of polymer materials at the molecular level using sum frequency generation vibrational spectroscopyPOLYMER INTERNATIONAL, Issue 5 2007Zhan Chen Abstract This paper reviews recent progress in the studies on polymer surfaces/interfaces using sum frequency generation (SFG) vibrational spectroscopy. SFG theory, technique, and some experimental details have been presented. The review is focused on the SFG studies on buried interfaces involving polymer materials, such as polymer,water interfaces and polymer,polymer interfaces. Molecular interactions between polymer surfaces and adhesion promoters as well as biological molecules such as proteins and peptides have also been elucidated using SFG. This review demonstrates that SFG is a powerful technique to characterize molecular level structural information of complicated polymer surfaces and interfaces in situ. Copyright © 2006 Society of Chemical Industry [source] Preparation and characterization of microcapsulated red phosphorus and its flame-retardant mechanism in halogen-free flame retardant polyolefinsPOLYMER INTERNATIONAL, Issue 8 2003Qiang Wu Abstract Microcapsulated red phosphorus (MRP), with a melamine,formaldehyde resin coating layer, was prepared by two-step coating processes. The physical and chemical properties of MRP were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) and other measurements. The flame retardant action and mechanism of MRP in the halogen-free flame retardant (HFFR) polyolefins (PO) blends have been studied using cone calorimeter, limiting oxygen index (LOI), thermogravimetric analysis (TGA) and dynamic FTIR spectroscopy. The results show that the MRP, which is coated with melamine,formaldehyde resin, has a higher ignition point, a considerably lower amount of phosphine evolution and of water absorption compared with red phosphorus (RP) itself. The data observed by cone calorimeter, LOI and TGA measurements from the PO/HFFR blends demonstrated that the MRP can decrease the heat release rate and effective heat of combustion, and increase the thermostability and LOI values of PO materials. The dynamic FTIR results revealed the flame-retardant mechanism that RP can promote the formation of charred layers with the P,O and P,C complexes in the condensed phase during burning of polymer materials. Copyright © 2003 Society of Chemical Industry [source] Depth profiling of polymer films with grazing-incidence small-angle X-ray scatteringACTA CRYSTALLOGRAPHICA SECTION A, Issue 3 2009Marsha A. Singh A model-free method of reconstructing depth-specific lateral scattering from incident-angle-resolved grazing-incidence small-angle X-ray scattering (GISAXS) data is proposed. The information on the material which is available through variation of the X-ray penetration depth with incident angle is accessed through reference to the reflected branch of the GISAXS process. Reconstruction of the scattering from lateral density fluctuations is achieved by solving the resulting Fredholm integral equation with minimal a priori information about the experimental system. Results from simulated data generated for hypothetical multilayer polymer systems with constant absorption coefficient are used to verify that the method can be applied to cases with large X-ray penetration depths, as typically seen with polymer materials. Experimental tests on a spin-coated thick film of a blend of diblock copolymers demonstrate that the approach is capable of reconstruction of the scattering from a multilayer structure with the identification of lateral scattering profiles as a function of sample depth. [source] Ultrasonically enhanced delivery and degradation of PAHs in a polymer,liquid partitioning system by a microbial consortiumBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Pedro A. Isaza Abstract The current study examined the effects of ultrasonic irradiation on mass transfer and degradation of PAHs, by an enriched consortium, when delivered from polymeric matrices. Rates of release into methanol under sonicated conditions, relative to unmixed cases, for phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene were increased approximately fivefold, when delivered from Desmopan 9370 A (polyurethane). Similar effects were observed in Hytrel and Kraton® D4150 K polymers as well as recycled Bridgestone tires. Enhancements were also displayed as shifts to higher release equilibria under sonicated conditions, relative to non-sonicated cases, agreeing with current knowledge in sonochemistry and attributed to cavitation. Ultrasonic effects on microbial activity were also investigated and cell damage was found to be non- permanent with consortium re-growth being observed after sonic deactivation. Finally, the lumped effect of sonication on degradation of phenanthrene delivered from Desmopan was examined under the absence and presence of sonication. Rates of degradation were found to be increased by a factor of four demonstrating the possibility of using ultrasonic irradiation for improved mass transport in solid,liquid systems. Cellular inactivation effects were not evident, and this was attributed to the attenuation of sonic energy arising from the presence of solid polymer materials in the medium. The findings of the study demonstrate that sonication can be used to improve mass transport of poorly soluble compounds in microbial degradations, and alleviate limiting steps of soil remediation processes proposed in previous research. Biotechnol. Bioeng. 2009; 104: 91,101 © 2009 Wiley Periodicals, Inc. [source] Transfection of Cells Mediated by Biodegradable Polymer Materials with Surface-Bound PolyethyleneimineBIOTECHNOLOGY PROGRESS, Issue 2 2000Ji Zheng Poly(,-CBZ- L -lysine) can be mixed with biodegradable polymers such as poly(D,L -lactic- co -glycolic acid) or poly(L -lactic acid) and formed into films, foams, or microspheres. Surface amino groups may then be deprotected with acid or lithium/liquid ammonia. The amino groups serve as a method to modify the surface by attachment of other molecules. In the present experiments, we show that these polymer materials, as films or foams, may be surface modified by the attachment of polyethyleneimine (PEI). Plasmid DNA attached to the PEI can transfect cells plated on the surface over several days. Covalent atachment of PEI was required for transfection to be efficient. PEI was also attached to surface-bound collagen on cell culture plates and was shown to mediate transfection. [source] Semiconducting Neutral Microstructures Fabricated by Coordinative Self-Assembly of Intramolecular Charge-Transfer Tetrathiafulvalene DerivativesCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2009Yan Geng Dr. Abstract A new class of tetrathiafulvalene-based microstructures fabricated by coordinative self-assembly has been prepared by a solution process. Upon incorporation of Pb2+ and Zn2+ ions, 1D wirelike microstructures and spherical polymer particles were achieved, respectively (see picture). The neutral coordination polymers are conductive and magnetic at room temperature without external manipulation. A new class of tetrathiafulvalene(TTF)-based microstructures fabricated by coordinative self-assembly has been successfully prepared by a solution process. The morphology of the TTF coordination polymers is readily tuned by the variation of metal ions. Upon incorporation of Pb2+ and Zn2+ ions, one-dimensional (1D) wirelike microstructures and spherical polymer particles were achieved, respectively. These results indicate that the coordinative approach pursued in this work, in which the building blocks of 1 are linked in a coordination polymer chain by association with metal ions, is an efficient and versatile approach to produce more mechanically robust micro- and nanometer-sized coordination polymer materials. More interestingly, the neutral coordination polymers are conductive and magnetic at room temperature without external manipulation. Such conductivity is reminiscent of the behavior of the neutral conductive TTF in single crystals. [source] | ||||||||||||||||