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PMMA
Kinds of PMMA Terms modified by PMMA Selected AbstractsHighly efficient capture and enumeration of low abundance prostate cancer cells using prostate-specific membrane antigen aptamers immobilized to a polymeric microfluidic deviceELECTROPHORESIS, Issue 18 2009Udara Dharmasiri Abstract Prostate tumor cells over-express a prostate-specific membrane antigen (PSMA) that can be used as a marker to select these cells from highly heterogeneous clinical samples, even when found in low abundance. Antibodies and aptamers have been developed that specifically bind to PSMA. In this study, anti-PSMA aptamers were immobilized onto the surface of a capture bed poised within a PMMA, microchip, which was fabricated into a high-throughput micro-sampling unit (HTMSU) used for the selective isolation of rare circulating prostate tumor cells resident in a peripheral blood matrix. The HTMSU capture bed consisted of 51 ultra-high-aspect ratio parallel curvilinear channels with a width similar to the prostate cancer cell dimensions. The surface density of the PSMA-specific aptamers on an ultraviolet-modified PMMA microfluidic capture bed surface was determined to be 8.4×1012,molecules/cm2. Using a linear velocity for optimal cell capture in the aptamer-tethered HTMSU (2.5,mm/s), a recovery of 90% of LNCaP cells (prostate cancer cell line; used as a model in this example) was found. Due to the low abundance of these cells, the input volume required was 1,mL and this could be processed in ,29,min using an optimized linear flow rate of 2.5,mm/s. Captured cells were subsequently released intact from the affinity surface using 0.25%,w/w trypsin followed by counting individual cells using a contact conductivity sensor integrated into the HTMSU that provided high detection and sampling efficiency (,100%) and did not require staining of the cells for enumeration. [source] SDS-CGE of proteins in microchannels made of SU-8 filmsELECTROPHORESIS, Issue 18 2006Maria Agirregabiria Abstract This work describes the SDS-CGE of proteins carried out in microchannels made of the negative photoresist EPON SU-8. Embedded electrophoretic microchannels have been fabricated with a multilayer technology based on bonding and releasing steps of stacked SU-8 films. This technology allows the monolithic integration of the electrodes in the device. A high wafer fabrication yield and mass production compatibility guarantees low costs and high reliability. A poly(methyl methacrylate) (PMMA) packaging allows an easy setup and replacement of the device for electrophoresis experiments. In addition, the wire-bonding step is avoided. The electrophoretic mobilities of four proteins have been measured in microchannels filled with polyacrylamide. Different pore sizes have been tested obtaining their Ferguson plots. Finally, a separation of two proteins (20 and 36,kDa) has been carried out confirming that this novel device is suitable for protein separation. A resolution of 2.75 is obtained. This is the first time that this SU-8 microfluidic technology has been validated for SDS-CGE of proteins. This technology offers better separation performance than glass channels, at lower costs and with an easy packaging procedure. [source] Internal electrolyte temperatures for polymer and fused-silica capillaries used in capillary electrophoresisELECTROPHORESIS, Issue 22 2005Christopher J. Evenhuis Abstract Polymers are important as materials for manufacturing microfluidic devices for electrodriven separations, in which Joule heating is an unavoidable phenomenon. Heating effects were investigated in polymer capillaries using a CE setup. This study is the first step toward the longer-term objective of the study of heating effects occurring in polymeric microfluidic devices. The thermal conductivity of polymers is much smaller than that of fused silica (FS), resulting in less efficient dissipation of heat in polymeric capillaries. This study used conductance measurements as a temperature probe to determine the mean electrolyte temperatures in CE capillaries of different materials. Values for mean electrolyte temperatures in capillaries made of New Generation FluoroPolymer (NGFP), poly-(methylmethacrylate) (PMMA), and poly(ether ether ketone) (PEEK) capillaries were compared with those obtained for FS capillaries. Extrapolation of plots of conductance versus power per unit length (P/L) to zero power was used to obtain conductance values free of Joule heating effects. The ratio of the measured conductance values at different power levels to the conductance at zero power was used to determine the mean temperature of the electrolyte. For each type of capillary material, it was found that the average increase in the mean temperature of the electrolyte (,TMean) was directly proportional to P/L and inversely proportional to the thermal conductivity (,) of the capillary material. At 7.5,W/m, values for ,TMean for NGFP, PMMA, and PEEK were determined to be 36.6, 33.8, and 30.7°C, respectively. Under identical conditions, ,TMean for FS capillaries was 20.4°C. [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] A polymeric master replication technology for mass fabrication of poly(dimethylsiloxane) microfluidic devicesELECTROPHORESIS, Issue 9 2005Hai-Fang Li Abstract A protocol of producing multiple polymeric masters from an original glass master mold has been developed, which enables the production of multiple poly(dimethylsiloxane) (PDMS)-based microfluidic devices in a low-cost and efficient manner. Standard wet-etching techniques were used to fabricate an original glass master with negative features, from which more than 50 polymethylmethacrylate (PMMA) positive replica masters were rapidly created using the thermal printing technique. The time to replicate each PMMA master was as short as 20 min. The PMMA replica masters have excellent structural features and could be used to cast PDMS devices for many times. An integration geometry designed for laser-induced fluorescence (LIF) detection, which contains normal deep microfluidic channels and a much deeper optical fiber channel, was successfully transferred into PDMS devices. The positive relief on seven PMMA replica masters is replicated with regard to the negative original glass master, with a depth average variation of 0.89% for 26 ,m deep microfluidic channels and 1.16% for the 90 ,m deep fiber channel. The imprinted positive relief in PMMA from master-to-master is reproducible with relative standard deviations (RSDs) of 1.06% for the maximum width and 0.46% for depth in terms of the separation channel. The PDMS devices fabricated from the PMMA replica masters were characterized and applied to the separation of a fluorescein isothiocyanate (FITC)-labeled epinephrine sample. [source] Intra-articular stabilisation of the equine cricoarytenoid jointEQUINE VETERINARY JOURNAL, Issue 6 2008J. CHEETHAM Summary Reasons for performing study: The success of laryngoplasty is limited by abduction loss in the early post operative period. Objective: To determine the efficacy of polymethylmethacrylate (PMMA) in stabilising the cricoarytenoid joint (CAJ) and reducing the force on the laryngoplasty suture. Hypothesis: Injection into the cricoarytenoid joint resists the forces produced by physiological laryngeal air flows and pressures thereby reducing the force experienced by the laryngoplasty suture. Methods: Ten cadaver larynges were collected at necropsy and PMMA was injected into one CAJ at selected random. Each larynx was subjected to physiological conditions with with constant (static) or cycling (dynamic) flow. The specimens were tested sequentially in each of 4 conditions: 1) bilateral full abduction (Control 1); 2) transection of the suture on the side without PMMA; 3) bilateral abduction achieved by replacing the suture (Control 2); and 4) cutting the suture on the PMMA side. Tracheal pressure and flow and pressure in the flow chamber were recorded using pressure and flow transducers. The strain experienced by each suture during bilateral abduction (Controls 1 and 2) was measured. Statistical comparison of the 4 conditions was performed using a mixed effect model with Tukey's post hoc test for multiple comparisons. The strain gauge data were analysed by paired comparison of the regression slopes. Results: In the static and dynamic states, tracheal pressure increased and tracheal flow decreased when the suture on the non-cement side was cut (P<0.05). There was no significant difference in any outcome measure between PMMA injected into the CAJ and bilaterally abducted specimens (Controls 1 and 2) for either condition. The rate of increase in strain with increasing translaryngeal pressure was significantly less on the suture with PMMA placed in the CAJ (P = 0.03). Conclusions: These data provide strong evidence that injecting PMMA into the CAJ resists the collapsing effect of physiological airflows and pressures in vitro and reduces the force experienced by the laryngoplasty suture during maximal abduction. Potential relevance: Augmentation of prosthetic laryngoplasty with this technique may reduce arytenoid abduction loss in the early post operative period. [source] Powder Metallurgical Near-Net-Shape Fabrication of Porous NiTi Shape Memory Alloys for Use as Long-Term Implants by the Combination of the Metal Injection Molding Process with the Space-Holder Technique,ADVANCED ENGINEERING MATERIALS, Issue 12 2009Manuel Köhl Abstract A new method was developed for producing highly porous NiTi for use as an implant material. The combination of the space-holder technique with the metal injection molding process allows a net-shape fabrication of geometrically complex samples and the possibility of mass production for porous NiTi. Further, the porosity can be easily adjusted with respect to pore size, pore shape, and total porosity. The influence of the surface properties of powder metallurgical NiTi on the biocompatibility was first examined using human mesenchymal stem cells (hMSCs). It was found that pre-alloyed NiTi powders with an average particle size smaller than 45,,m led to the surface properties most suitable for the adhesion and proliferation of hMSCs. For the production of highly porous NiTi, different space-holder materials were investigated regarding low C- and O-impurity contents and the reproducibility of the process. NaCl was the most promising space-holder material compared to PMMA and saccharose and was used in subsequent studies. In these studies, the influence of the total porosity on the mechanical properties of NiTi is investigated in detail. As a result, bone-like mechanical properties were achieved by the choice of Ni-rich NiTi powder and a space-holder content of 50,vol% with a particle size fraction of 355,500,,m. Pseudoelasticity of up to 6% was achieved in compression tests at 37,°C as well as a bone-like loading stiffness of 6.5,GPa, a sufficient plateau stress ,25 of 261,MPa and a value for ,50 of 415,MPa. The first biological tests of the porous NiTi samples produced by this method showed promising results regarding proliferation and ingrowth of mesenchymal stem cells, also in the pores of the implant material. [source] High-Nanofiller-Content Graphene Oxide,Polymer Nanocomposites via Vacuum-Assisted Self-AssemblyADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Karl W. Putz Abstract Highly ordered, homogeneous polymer nanocomposites of layered graphene oxide are prepared using a vacuum-assisted self-assembly (VASA) technique. In VASA, all components (nanofiller and polymer) are pre-mixed prior to assembly under a flow, making it compatible with either hydrophilic poly(vinyl alcohol) (PVA) or hydrophobic poly(methyl methacrylate) (PMMA) for the preparation of composites with over 50 wt% filler. This process is complimentary to layer-by-layer assembly, where the assembling components are required to interact strongly (e.g., via Coulombic attraction). The nanosheets within the VASA-assembled composites exhibit a high degree of order with tunable intersheet spacing, depending on the polymer content. Graphene oxide,PVA nanocomposites, prepared from water, exhibit greatly improved modulus values in comparison to films of either pure PVA or pure graphene oxide. Modulus values for graphene oxide,PMMA nanocomposites, prepared from dimethylformamide, are intermediate to those of the pure components. The differences in structure, modulus, and strength can be attributed to the gallery composition, specifically the hydrogen bonding ability of the intercalating species [source] A Versatile Solvent-Free "One-Pot" Route to Polymer Nanocomposites and the in situ Formation of Calcium Phosphate/Layered Silicate Hybrid NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Hans Weickmann Abstract Poly(methyl methacrylate) (PMMA), polystyrene (PS), and polyurethane (PU) nanocomposites containing well-dispersed calcium phosphate/layered silicate hybrid nanoparticles were prepared in a versatile solvent-free "one-pot" process without requiring separate steps, such as organophilic modification, purification, drying, dispersing, and compounding, typical for many conventional organoclay nanocomposites. In this "one-pot" process, alkyl ammonium phosphates were added as swelling agents to a suspension of calcium/layered silicate in styrene, methyl methacrylate, or polyols prior to polymerization. Alkyl ammonium phosphates were prepared in situ by reacting phosphoric acid with an equivalent amount of alkyl amines such as stearyl amine (SA) or the corresponding ester- and methacrylate-functionalized tertiary alkyl amines, obtained via Michael Addition of SA with methyl acrylate or ethylene 2-methacryloxyethyl acrylate. Upon contact with the calcium bentonite suspension, the cation exchange of Ca2+ in the silicate interlayers for alkyl ammonium cations rendered the bentonite organophilic and enabled effective swelling in the monomer accompanied by intercalation and in situ precipitation of calcium phosphates. According to energy dispersive X-ray analysis, the calcium phosphate precipitated exclusively onto the surfaces of the bentonite nanoplatelets, thus forming easy-to-disperse calcium phosphate/layered silicate hybrid nanoparticles. Incorporation of 5,15,wt% of such hybrid nanoparticles into PMMA, PS, and PU afforded improved stiffness/toughness balances of the polymer nanocomposites. Functionalized alkyl ammonium phosphate addition enabled polymer attachment to the nanoparticle surfaces. Transmission electron microscopy (TEM) analyses of PU and PU-foam nanocomposites, prepared by dispersing hybrid nanoparticles in the polyols prior to isocyanate cure, revealed the formation of fully exfoliated hybrid nanoparticles. [source] Surface temperature measurements on burning materials using an infrared pyrometer: accounting for emissivity and reflection of external radiationFIRE AND MATERIALS, Issue 1 2004Joe Urbas Abstract This paper demonstrates the successful use of an infrared pyrometer, operating in the 8,10 µm wavelength band, to measure the surface temperature of combustible specimens in a heat release calorimeter. The temperature histories of ten different materials were measured in the ICAL (intermediate scale calorimeter). The set of materials comprised four wood products, gypsum board, polyisocyanurate foam, PVC floor tile, PMMA and two non-combustible boards. A small-diameter bare thermocouple was installed on each specimen in order to determine an accurate temperature for comparison. The spectral emissivity and the spectral flux reflected from the surface were measured simultaneously and used to correct the apparent temperature measured by the pyrometer. The spectral emissivity and reflected spectral flux were both constant prior to ignition for all the combustible materials. During the burning phase all the combustible materials had a spectral emissivity very close to unity. The agreement between the temperatures measured with the pyrometer and thermocouple was not affected by the flame. The wood products, the polyisocyanurate foam and the calcium silicate board required no correction for reflected spectral flux over the whole temperature range. Copyright © 2004 John Wiley & Sons, Ltd. [source] Functional Chromium Wheel-Based Hybrid Organic,Inorganic Materials for Dielectric ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Vito Di Noto Abstract The first example of organic,inorganic hybrid materials based on the embedding of a chromium,nickel wheel cluster {[(n-C3H7)2NH2]- [Cr7NiF8(O2C4H5)16]} (Cr7Ni) into poly(methyl methacrylate) (PMMA) and the characterization of the dielectric properties of the obtained material is described. By an optimized copolymerization of the methacrylate-functionalized chromium,nickel wheel with methyl methacrylate in a cluster/monomer 1:200 molar mixture, a homogeneous hybrid material CrNi_MMA200 is obtained. The electrical responses of the non-doped PMMA and of the hybrid material were studied by broadband dielectric spectroscopy (BDS) from 0.01,Hz to 10,MHz and over the temperature range of 5,115,°C. The permittivity profiles reveal two relaxation peaks in the materials, which correspond to the , and , relaxation modes of the PMMA matrix. The position of these modes shifts toward higher frequencies as temperature increases. BDS is a powerful tool revealing the intimate miscibility of the various components of the hybrid material, thus indicating that, on a molecular scale, the material proposed is a homogeneous system. Finally, a value of the dielectric constant of 2.9 at 25,°C and 1,kHz is determined. This value is noticeably lower than the value of 3.2 obtained for pristine PMMA prepared following the same synthesis protocol. Thus, these results classify the hybrid CrNi_MMA200 as an appealing starting material for the development of dielectric polymeric layers for the development of innovative capacitors, transistors, and other microelectronic devices. The vibrational properties of the hybrid materials are investigated by Fourier-transform infrared (FT-IR) and Raman spectroscopy, whereas the thermal behavior is analyzed by thermogravimetric analysis (TGA). Swelling experiments are used to qualitatively evaluate the crosslinking density of the hybrid materials. The integrity of the wheels once embedded in the macromolecular backbone is confirmed by extended X-ray absorption fine structure (EXAFS) and electron spin resonance (EPR) spectroscopic measurements. [source] Modeling Polymer Dielectric/Pentacene Interfaces: On the Role of Electrostatic Energy Disorder on Charge Carrier MobilityADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Nicolas G. Martinelli Abstract Force-field and quantum-chemical calculations are combined to model the packing of pentacene molecules at the atomic level on two polymer dielectric layers (poly(methyl methacrylate) (PMMA) versus polystyrene (PS)) widely used in field-effect transistors and to assess the impact of electrostatic interactions at the interface on the charge mobility values in the pentacene layers. The results show unambiguously that the electrostatic interactions introduce a significant energetic disorder in the pentacene layer in contact with the polymer chains; a drop in the hole mobility by a factor of 5 is predicted with PS chains while a factor of 60 is obtained for PMMA due to the presence of polar carbonyl groups. [source] Battery Drivable Organic Single-Crystalline Transistors Based on Surface Grafting Ultrathin Polymer DielectricADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Liqiang Li Abstract High-performance and battery drivable organic single-crystalline transistors with operational voltages,,,2.0,V are demonstrated using high-quality copper phthalocyanine (CuPc) single-crystalline nanoribbons and ultrathin polymer nanodielectrics. The ultrathin polymer nanodielectric is synthesized by grafting a ca. 10,nm poly(methyl methacrylate) (PMMA) brush on a silicon surface via surface-initiated atom-transfer radical polymerization (SI-ATRP). This surface-grafted nanodielectric exhibits a large capacitance, excellent insulating property, and good compatibility with organic semiconductors. The realization of a low operational voltage for battery driving at high performance, together with the merits of surface grafting of a nanodielectric, as well as the mechanical flexibility of the organic nanoribbon, suggests a bright future for use of these transistors in low-cost and flexible circuits. [source] Printable Ferroelectric PVDF/PMMA Blend Films with Ultralow Roughness for Low Voltage Non-Volatile Polymer MemoryADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Seok Ju Kang Abstract Here, a facile route to fabricate thin ferroelectric poly(vinylidene fluoride) (PVDF)/poly(methylmethacrylate) (PMMA) blend films with very low surface roughness based on spin-coating and subsequent melt-quenching is described. Amorphous PMMA in a blend film effectively retards the rapid crystallization of PVDF upon quenching, giving rise to a thin and flat ferroelectric film with nanometer scale , -type PVDF crystals. The still, flat interfaces of the blend film with metal electrode and/or an organic semi-conducting channel layer enable fabrication of a highly reliable ferroelectric capacitor and transistor memory unit operating at voltages as low as 15,V. For instance, with a TIPS-pentacene single crystal as an active semi-conducting layer, a flexible ferroelectric field effect transistor shows a clockwise I,V hysteresis with a drain current bistability of 103 and data retention time of more than 15,h at ±15,V gate voltage. Furthermore, the robust interfacial homogeneity of the ferroelectric film is highly beneficial for transfer printing in which arrays of metal/ferroelectric/metal micro-capacitors are developed over a large area with well defined edge sharpness. [source] Organic Thin Film Transistors with Polymer Brush Gate Dielectrics Synthesized by Atom Transfer Radical PolymerizationADVANCED FUNCTIONAL MATERIALS, Issue 1 2008C. Pinto Abstract Low operating voltage is an important requirement that must be met for industrial adoption of organic field-effect transistors (OFETs). We report here solution fabricated polymer brush gate insulators with good uniformity, low surface roughness and high capacitance. These ultra thin polymer films, synthesized by atom transfer radical polymerization (ATRP), were used to fabricate low voltage OFETs with both evaporated pentacene and solution deposited poly(3-hexylthiophene). The semiconductor-dielectric interfaces in these systems were studied with a variety of methods including scanning force microscopy, grazing incidence X-ray diffraction and neutron reflectometry. These studies highlighted key differences between the surfaces of brush and spun cast polymethyl methacrylate (PMMA) films. [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] Siloxane Copolymers for Nanoimprint Lithography,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2007P. Choi Abstract Presented here is the novel use of thermoplastic siloxane copolymers as nanoimprint lithography (NIL) resists for 60,nm features. Two of the most critical steps of NIL are mold release and pattern transfer through dry etching. These require that the NIL resist have low surface energy and excellent dry-etching resistance. Homopolymers traditionally used in NIL, such as polystyrene (PS) or poly(methyl methacrylate) (PMMA), generally cannot satisfy all these requirements as they exhibit polymer fracture and delamination during mold release and have poor etch resistance. A number of siloxane copolymers have been investigated for use as NIL resists, including poly(dimethylsiloxane)- block -polystyrene (PDMS- b -PS), poly(dimethylsiloxane)- graft -poly(methyl acrylate)- co -poly(isobornyl acrylate) (PDMS- g -PMA- co -PIA), and PDMS- g -PMMA. The presence of PDMS imparts the materials with many properties that are favorable for NIL, including low surface energy for easy mold release and high silicon content for chemical-etch resistance,in particular, extremely low etch rates (comparable to PDMS) in oxygen plasma, to which organic polymers are quite susceptible. These properties give improved NIL results. [source] CdS-Nanoparticle/Polymer Composite Shells Grown on Silica Nanospheres by Atom-Transfer Radical Polymerization,ADVANCED FUNCTIONAL MATERIALS, Issue 3 2005T. Cui Abstract In this paper we describe the combined use of surface-initiated atom transfer radical polymerization (ATRP) and a gas/solid reaction in the direct preparation of CdS-nanoparticle/block-copolymer composite shells on silica nanospheres. The block copolymer, consisting of poly(cadmium dimethacrylate) (PCDMA) and poly(methyl methacrylate) (PMMA), is obtained by repeatedly performing the surface-initiated ATRP procedures in N,N -dimethylformamide (DMF) solution at room temperature, using cadmium dimethacrylate (CDMA) and methyl methacrylate (MMA) as the monomers. CdS nanoparticles with an average size of about 3,nm are generated in situ by exposing the silica nanospheres coated with block-copolymer shells to H2S gas. These synthetic core,shell nanospheres were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), diffuse reflectance UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD). These composite nanospheres exhibit strong red photoluminescence in the solid state at room temperature. [source] Graphoepitaxial Assembly of Symmetric Block Copolymers on Weakly Preferential SubstratesADVANCED MATERIALS, Issue 38 2010Eungnak Han Weakly preferential substrates were utilized in a single step process to direct the assembly of symmetric PS- b -PMMA. The thickness dependence of domain orientation on weakly preferential substrates was exploited to dictate the lateral ordering of perpendicular lamellae. [source] Semiconductor-Dielectric Blends: A Facile All Solution Route to Flexible All-Organic TransistorsADVANCED MATERIALS, Issue 42 2009Wi Hyoung Lee A one-step process for the production of all-organic, all-solution-processed field-effect transistors (FETs) can be achieved using triethylsilylethynyl anthradithiophene (TES-ADT). TES-ADT has a lower surface energy than poly(methyl methacrylate) (PMMA), which results in a segregation and crystal formation of TES-ADT at the air,film interface after spin-casting and subsequent solvent annealing. The resulting FETs comprise vertically phase-separated semiconducting and dielectric layers and exhibit high performances. [source] Multibit Storage of Organic Thin-Film Field-Effect TransistorsADVANCED MATERIALS, Issue 19 2009Yunlong Guo Organic thin-film field-effect transistor (OTFT) multibit storage devices are fabricated based on pentacene or copper phthalocyaine (CuPc) with normal polymer modifying layers of polystyrene (PS) or polymethylmethacrylate (PMMA). The devices shows excellent multibit storage properties in a single OTFT using electric and light-assisted programs. [source] Surface Selective Deposition of PMMA on Layered Double Hydroxide Nanocrystals Immobilized on Solid Substrates,ADVANCED MATERIALS, Issue 5 2009Jong Hyeon Lee A novel nanostructured hybrid PMMA/MgAl-LDH thin film enables a strong UV-blocking effect, up to 97% below 300,nm, and excellent visible transparency. The graft density of PMMA films can be controlled by adjusting the area coverage of immobilized LDH monolayer with a highly-orientated structure on oxide, metal, and polymer substrates. [source] Numerical finite element formulation of the Schapery non-linear viscoelastic material modelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2004Rami M. Haj-Ali Abstract This study presents a numerical integration method for the non-linear viscoelastic behaviour of isotropic materials and structures. The Schapery's three-dimensional (3D) non-linear viscoelastic material model is integrated within a displacement-based finite element (FE) environment. The deviatoric and volumetric responses are decoupled and the strain vector is decomposed into instantaneous and hereditary parts. The hereditary strains are updated at the end of each time increment using a recursive formulation. The constitutive equations are expressed in an incremental form for each time step, assuming a constant incremental strain rate. A new iterative procedure with predictor,corrector type steps is combined with the recursive integration method. A general polynomial form for the parameters of the non-linear Schapery model is proposed. The consistent algorithmic tangent stiffness matrix is realized and used to enhance convergence and help achieve a correct convergent state. Verifications of the proposed numerical formulation are performed and compared with a previous work using experimental data for a glassy amorphous polymer PMMA. Copyright © 2003 John Wiley & Sons, Ltd. [source] Ceramic,Polymer Ba0.6Sr0.4TiO3/Poly(Methyl Methacrylate) Composites with Different Type Composite Structures for Electronic TechnologyINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2010Hong Wang Ba0.6Sr0.4TiO3 (BST)/poly(methyl methacrylate) (PMMA) composites with 0,3, 1,3, and 2,2 type structures were prepared and studied. The effect of composite type on the dielectric properties of BST/PMMA composites was comprehensively investigated by both theoretical and experimental methods. The 1,3 type composite shows the highest permittivity and dielectric tunability, while the 2,2 and 0,3 type composites show lower permittivity as well as lower dielectric tunabilities. The experimentally measured dielectric properties are in agreement with the theoretically calculated values. The results help in understanding and tailoring the dielectric properties of ceramic,polymer composites by choosing a suitable composite structure. [source] Versatile Use of Vertical-Phase-Separation-Induced Bilayer Structures in Organic Thin-Film Transistors,ADVANCED MATERIALS, Issue 6 2008Longzhen Qiu A semiconductor-top and dielectric-bottom bilayer structure is fabricated by surface-induced vertical phase separation of poly(3-hexylthiophene) (P3HT) and poly(methyl methacrylate) (PMMA) blends (see figure). This structure allows to prepare high-performance, low-semiconductor-content, and low-voltage-driven TFTs in a very effective method, in which the dielectric and semiconductor layers are deposited onto a substrate in a one-step process. [source] Synthesis of Novel Nickel Sulfide Submicrometer Hollow Spheres,ADVANCED MATERIALS, Issue 9 2003Y. Hu Nickel sulfide uniform hollow spheres (see scanning electron microscopy image, Figure) have been successfully synthesized by ,-irradiation of a PMMA,CS2,ethanol aqueous solution that contains NiSO4·6H2O at room temperature. Calculation shows that the diameter of the NiS hollow spheres is 500 nm and the thickness of shell is ,,20 nm. A possible growth mechanism is also presented. [source] X-ray powder diffraction quantitative analysis of an amorphous SiO2,poly(methyl methacrylate) nanocompositeJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2008P. Riello Quantification of individual phases within a multiphase amorphous material has been achieved using a newly developed technique based on X-ray powder diffraction. The quantification method was developed during a study of an amorphous silica,poly(methyl methacrylate) (SiO2,PMMA) hybrid nanocomposite. The efficiency of the method as a quantifying tool for individual phases was demonstrated for samples of SiO2,PMMA prepared either by polymerization of methyl methacrylate in the presence of amorphous SiO2 or by mechanically mixing known quantities of the individual and pre-prepared SiO2 and PMMA materials. The weight percentages of amorphous SiO2 in the nanocomposites as determined by application of the new technique were analogously found to be 29%, a result that was supported by thermogravimetric analysis and helium picnometry measurements. [source] Inhibition of biofilms associated with dentures and toothbrushes by tetrasodium EDTAJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007D.A. Devine Abstract Aims:, We examined the efficacy of tetrasodium EDTA in eradicating biofilms derived from salivary inocula or pure cultures of Candida albicans on discs of polymethyl methacrylate (PMMA) denture base or on toothbrushes that had been used normally for 4,8 weeks. Its efficiency in virus neutralization was also determined. Methods and Results:, Overnight (16 h) treatment with 4% (w/v) tetrasodium EDTA solution reduced salivary and C. albicans biofilm viable counts by ,99%. Biofilm removal was confirmed using confocal laser scanning microscopy. Presence/absence of sucrose during biofilm formation had no effect on killing efficacy. Prolonged treatment of PMMA with tetrasodium EDTA did not influence subsequent formation of C. albicans biofilms or affect surface roughness of the PMMA, but it reduced subsequent biofilm formation from a salivary inoculum. Infectivities of herpes simplex virus and polio virus suspensions were reduced by >99·99% by treatment for 1 and 2 h, respectively. Conclusions:, Tetrasodium EDTA solution efficiently disinfected toothbrushes and PMMA discs, with the detachment of biofilms, and rapidly neutralized both nonenveloped and enveloped viruses. Significance and Impact of the Study:, Dentures and toothbrushes become contaminated by bacterial biofilms and by viruses. There is a need for disinfection methods that are rapidly effective, cost-effective, nontoxic and easily implemented. These studies indicate that tetrasodium EDTA solution has disinfection applications in the oral care field. [source] Influence of processing conditions and physicochemical interactions on morphology and fracture behavior of a clay/thermoplastic/thermosetting ternary blendJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010M. Hernandez Abstract This study provides information on the mechanical behavior of epoxy-poly(methyl methacrylate) (PMMA)-clay ternary composites, which have been prepared using the phase separation phenomenon of PMMA and the introduction of organophilic-modified montmorillonites (MMTs), the continuous matrix being the epoxy network. Two dispersion processing methods are used: a melt processing without any solvent and an ultrasonic technique with solvent and a high-speed stirrer. TEM analysis shows that phase separation between PMMA and the epoxy network was obtained in the shape of spherical nodules in the presence of the clay in both process methods used. Nanoclay particles were finely dispersed inside thermosetting matrix predominantly delaminated when ultrasonic blending was used; whereas micrometer-sized aggregates were formed when melt blending was used. The mechanical behavior of the ternary nanocomposites was characterized using three-point bending test, dynamic mechanical analysis (DMA), and linear elastic fracture mechanics. The corresponding fracture surfaces were examined by scanning electron microscopy to identify the relevant fracture mechanisms involved. It was evidenced that the better dispersion does not give the highest toughness because ternary nanocomposites obtained by melt blending present the highest fracture parameters (KIc). Some remaining disordered clay tactoids seem necessary to promote some specific toughening mechanisms. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Plasma-induced graft polymerization of poly(ethylene glycol) on poly(methyl methacrylate) surfaces for improving antistatic propertyJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2010Yanlin Wei Abstract Ar plasma-induced graft polymerization of poly(ethylene glycol) (PEG) on Ar plasma pretreated poly(methyl methacrylate) (PMMA) surfaces was carried out to improve the antistatic properties. The surface composition and microstructure of the PEG-grafted PMMA surfaces from plasma induction were characterized by attenuated total reflectance Fourier transfer infrared (ATR-FTIR) spectroscopy, water contact angles (CA), and atomic force microscopy (AFM) measurements. The measurements revealed that the antistatic properties can be remarkably improved with the surface resistivity of PEG-grafted PMMA surface decreasing significantly by 3,6 orders of magnitude, with the optimum condition for polymerization grafted onto the Ar plasma pretreated PMMA surface being 40 W for RF power and 3 min for glow discharge time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] | |||||||||||||||||||||||||||||||||||||