Poly Methyl Methacrylate Matrix Research Articles

Polymeric electrooptic composite based on Disperse Red and its derivatives for use in photonics

Electrooptic polymers based on the chromophore Disperse Red and its derivatives in a matrix of polymethyl methacrylate and polyacrylate have been studied, and the limiting concentration of the chromophore has been determined. The optimum conditions have been found for creating anisotropy of the active layer by the method of polarization in a corona discharge. The degree of orientation of the chromophore and the temporal stability of the induced anisotropy have been investigated by measuring the optical absorption and the second-harmonic generation. Using the nanoimprint process, microstrip structures have been fabricated with a strip width of 5-50μm.

AC Electrical and Structural Properties of Polymethylmethacrylate/Aluminum Composites

Different concentrations (i.e., 10, 20, 30, and 40 wt%) of Al metal are dispersed in polymethylmethacrylate (PMMA) matrix and the composite films are prepared by solution casting method. The frequency and temperature dependence of dielectric constant, dielectric loss, and conductivity of pure polymer and polymer composites filled with Al-metal filler are studied in the broad frequency range from 100 Hz to 10 MHz and in the temperature range 25—80°C. It is observed that the dielectric constant, dielectric loss, and electrical conductivity gradually increase with filler concentration and also with temperature and is explained in terms of hopping conduction mechanism. The electrical conductivity of the composites obeys universal power law model (i.e., σ = Af n), where n is power exponent. A comparison of dielectric constant values of PMMA/Al composites is made with predictions of theoretical models and it is observed that an empirical power equation gives a better fit to our results. Structural property of the composites is studied by means of X-ray diffraction. The results show that the crystallinity and crystalline size increase with increasing concentration of aluminum filler. Average surface roughness is observed to change with filler concentration as obtained from atomic force microscopy and scanning electron microscopy analysis.

PREPARATION AND CHARACTERISTIC OF POLY(METHYL METHACRYLATE) PIGMENT POWDERY COATING FOR PAPER IN SUPERCRITICAL CARBON DIOXIDE

Powdery coating particles mingled polymethyl methacrylate(PMMA) and calcium carbonate inorganic pigment were obtained under water-free conditions in supercritical carbon dioxide(sc-CO2).The formation was confirmed by FTIR and GPC method.The effects of monomer,initiator,stabilizer concentration and the reaction temperature and time on the polymerization conversion rate and molecular weight of the polymer were discussed and the experimental results indicated that the molecular weight and the molecular weight distribution of the PMMA could be controlled within a suitable range when the reaction pressure was 10 MPa,reaction temperature was 75℃,reaction time was 8 h,monomer concentration was 0.10 g/mL,initiator concentration was 0.10 × 10-2 g/mL and stabilizer concentration was 0.06 × 10-2 g/mL.From SEM observation,it was found that the pigment granules were able to evenly disperse and embedded in the PMMA matrix and didn't show conglomeration.

Luminescence recognition behavior concerning different anions by lanthanide complex equipped with electron-withdraw groups and in PMMA matrix

Lanthanide tris(2-thenoyltrifluoroacetonate) complex based on 2-(3,5-difluorophenyl)imidazo [4,5-f]-1,10-phenanthroline ( 1) with red luminescence acted as effective receptors for F − and AcO − anions. Spectroscopic studies of UV–vis, fluorescence and NMR present that the sensor exhibits striking emission changes to fluoride (green) and acetate anions (yellow-red to green) respectively due to hydrogen binding interactions. More importantly, transparent hybrid thick films composed by europium complex and poly-methyl methacrylate (PMMA) matrix were successfully prepared. All the films exhibit intense red emissions of europium ions and the optimized composing concentration of luminescent species is 0.5 mg/5 ml MMA. The derived film could give rise to luminescence change in fluoride anion containing DMSO solution. The micro-structure and size of the hybrid films were characterized by dynamic light scattering (DLS), the results reflect that granule size has the average diameter of 300 nm.

ZnS:Cu Polymer Nanocomposites for Thin Film Electroluminescent Devices

Copper-doped zinc sulphide nanoparticles with varying copper content were synthesized via a coprecepitation method and embedded in polymer thin films by phase transfer technique to examine direct current electroluminescence (DC-EL) properties. A single layer structure (ITO/ZnS:Cu@ polymer/Al) was chosen to examine the influence of film thickness, copper content and polymeric matrix. Two types of devices were investigated based either on an insulating polymethylmethacrylate (PMMA) matrix or a semiconducting poly(9-vinylcarbazole) (PVK) matrix. The resulting DC-EL differs in spectral characteristics showing a broad EL emission over the whole visible range for PMMA based devices and EL with narrow full width at half-maxima values (FWHM) and maxima positions close to those observed in photoluminescence (PL) spectra of particle dispersions.

Enhancement of hydrogen gas permeability in electrically aligned MWCNT-PMMA composite membranes

The multi-walled carbon nanotube (MWCNT) dispersed polymethylmethacrylate (PMMA) composite membranes have been prepared for hydrogen gas permeation application. Composite membranes are characterized by Raman spectroscopy, optical microscopy, X-ray diffraction, electrical measurements and gas permeability measurements. The effect of electric field alignment of MWCNT in PMMA matrix on gas permeation has been studied for hydrogen gas. The permeability measurements indicated that the electrically aligned MWCNT in PMMA has shown almost 2 times higher permeability for hydrogen gas as compare to randomly dispersed MWCNT in PMMA. The enhancement in permeability is explained on the basis of well aligned easy channel provided by MWCNT in electrically aligned sample. The effect of thickness of membrane on the gas permeability also studied and thickness of about 30 μm found to be optimum thickness for fast hydrogen gas permeates.

WE‐E‐204B‐02: Release Kinetics of Radio‐Sensitizers from Nanoporous Coatings on Gold Fiducials: Biological In‐Situ Dose‐Painting for IGRT

Purpose: Image‐guided radiation treatments routinely utilize radio‐opaque implantable devices, such as fiducials or brachytherapy spacers, for improved spatial accuracy. We study the hypothesis that the therapeutic efficiency of IGRT can be enhanced through simultaneous in‐situ delivery of radiosensitizers, contained within nanoparticles and nanoporous polymer matrices coating gold fiducial markers or spacers implanted in the tumor (BIS‐IGRT, Biological In‐Situ Image‐Guided Radiation Therapy). Methods and Materials: Biocompatible polymers loaded with model molecules were coated as a thin film on gold fiducials. The nanoporous morphology of the polymer coatings allowed controlled release of molecules and nanoparticles. Two experimental approaches were studied: (i) a free drug release system, (Doxorubicin, a hydrophilic drug in Poly(methyl methacrylate (PMMA) coating) and (ii) Poly(D,L‐lactic‐co‐glycolic acid) (PLGA) nanoparticles loaded with Coumarin‐6, a fluorescent model for a hydrophobic drug, in a chitosan matrix applied as gold fiducial coating. Measurements of temporal release kinetics in buffer and spatial release profiles in agarose were carried out using fluorescence spectroscopy. Results: For gold fiducials coated with Doxorubicin in PMMA matrix an initial release of Dox within the first few hours was followed by a sustained release over the course of next 3 months. Release of Dox from within PMMA matrix is dependent on the concentration of Dox, ratio of PMMA/Dox, thickness of PMMA/Dox coating on gold surface. The release profile of coumarin‐6 loaded nanoparticles from chitosan film on gold fiducials showed that (63±10)% of NPs were released in twenty days, and after that, the release became slower and additional 37% of release was observed after additional twenty‐days. Spatial release profiles in an agarose phantom were also measured and compared with release kinetics models. Conclusions: The results show that dosage and rate of release of these radiosenstizers can be precisely tailored to achieve the desired release profile for BIS‐IGRT.

Temperature effects on emission of quantum dots embedded in polymethylmethacrylate

We successfully used CdSe/ZnS quantum dots (QDs) as a dopant within a polymethylmethacrylate (PMMA) matrix. This doped material was used in the fabrication of a microstructured polymer optical fiber whose photoluminescence was characterized. A detailed analysis of the emission properties of the QDs as a function of temperature is presented, with the temperature dependence of this emission broken into components to show contributions from the thermo-optic effect of the PMMA and the temperature-dependence of the bandgap of the QDs.

Metastable phases in Gallium–Indium eutectic alloy particles and their size dependence

In this paper, submicrometer-sized Ga–In eutectic alloy particles were dispersed into polymethylmethacrylate (PMMA) matrix by ultrasonic vibration and sedimentation method. The solidification and melting processes of Ga–In eutectic alloy particles were studied by differential scanning calorimeter (DSC). Four endothermal peaks with the onset temperature located at 16, −11, −22, and −27 °C were observed in DSC heating curves, which corresponded to the melting process of the stable Ga–In phase α-Ga(In) and three metastable phases of β-Ga(In), δ-Ga(In) and γ-Ga(In), respectively. The stable phase α-Ga(In) can only be formed when the size of alloy particle was larger than 0.58 μm. Conversely, metastable phases β-Ga(In), δ-Ga(In) and γ-Ga(In) are mainly formed. The result shows that phase structures in Ga–In eutectic alloy are size dependent.

Fracture toughness and creep performance of PMMA composites containing micro and nanosized carbon filaments

Chopped carbon fiber (CCF), multiwall carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs) were introduced to polymethylmethacrylate (PMMA) via melt compounding. Fracture toughness and creep performance of these composites are presented. A constant volume concentration of 1 vol.% was used. Dispersion was evaluated on both micro- and nano-scales. Flexural modulus was also measured. Composite behavior was found to differ both between fillers and studied property; fracture toughness or creep resistance. While MWCNTs and CNFs did not increase fracture toughness, they did improve creep resistance. Here, MWCNTs had a more significant effect. CCFs were the only fillers that improved fracture toughness. Their effect on creep was less significant than MWCNTs. Analysis of the data in this study suggests that carbon nanofilaments function mainly to resist crack initiation rather than propagation in the PMMA matrix.

Photochromism and Thermochromism of some Spirooxazines and Naphthopyrans in the Solid State and in Polymeric Film

In this work the photochromic behaviors of four Reversacol compounds from James Robinson Ltd., previously investigated in solution, have been studied in a microcrystalline solid phase and embedded in a poly(methyl methacrylate) matrix (PMMA). The compounds studied belong to the classes of spirooxazines and naphthopyrans. In solution, they showed photocoloration and thermocoloration. Embedded into polymeric films, as well as in the microcrystalline phase, they have maintained their photochromic and thermochromic behavior. The photocoloration quantum yields in PMMA were determined and found to be fairly high. Compared to solution, the kinetic and thermodynamic activation parameters of thermal bleaching significantly changed. The solid environment has the effect of slowing down the bleaching rates in films as well in the pure crystalline phase and introduces multiexponential terms in the photocoloration and thermal bleaching kinetics. Activation enthalpy and entropy decrease, compared to solution, leaving the activation free energy substantially unchanged. Thermochromism was characterized through the equilibrium constant and the thermodynamic standard parameters, ΔH0, ΔS0, and ΔG0, of the thermal reactions. Time-dependent processes were also analyzed according to the maximum entropy method (MEM). Based on the data from the least-squares and MEM treatments, the occurrence of multiexponential kinetics in polymers was attributed to the effects of the inhomogeneous distribution of free volume in the matrix.

Electrical and thermal properties of carbon nanotubes/PMMA composites induced by low magnetic fields

Ni particles supported on carbon nanotubes (CNTs) were dispersed in a polymethyl methacrylate (PMMA) matrix by solution blending and then cast onto an electrode to get composite films under low magnetic fields. The orientation of CNTs in the films was characterised by scanning electron microscope and optical microscope. Multimeter and high resistance meter were used to study the electrical behaviour of the nanocomposites. The glass transition temperature Tg of PMMA was determined by differential scanning calorimetry. The results show that the alignment of the CNTs dispersed in the PMMA was achieved under a low magnetic strength below 0·5 T. Because of the ferromagnetism of Ni particles, the magnetic alignment of CNTs susceptibly changed. The magnetic alignment units in this work were rod-like CNTs aggregates instead of single CNTs, which took part in the buildup of a specific CNTs network structure in PMMA matrix. The network structure played a key role in significantly improving electrical conductivity and Tg of the nanocomposites.

Influence of surface layer conditions of multiwall carbon nanotubes on their electrophysical properties

We have investigated temperature σ( T) and magnetic field σ( B) dependences of the conductivity of multiwalled carbon nanotubes (MWNTs) with different average outer diameter d̄ and composite materials on the bases of these MWNTs in dielectric polymethyl methacrylate matrix (PMMA). It was shown that the percolation threshold of the electrical conductance for MWNT/PMMA composites lies in the range of concentration of MWNTs lower than 0.5 wt.%. From the joint analysis of σ( T) and σ( H) we have found that quantum corrections to the conductivity for interaction electrons is dominated in MWNTs with average outer diameters d̄ ∼ 23 nm and MWNT/PMMA composite materials. We determined the constant of electron–electron interaction λ from quantum correction to σ( T) and σ( H). In the result we have found that λ depends on the concentration of MWNTs in MWNT/PMMA materials. This fact demonstrates that the interaction of the dielectric material of PMMA with surface atoms of MWNTs leads to the change of the λ in MWNTs. For MWNTs with average outer diameters d̄ ≤ 13 nm and for composite on the base of these MWNTs we have observed the domination of one dimensional variable range hopping conductivity (VRHC) at a temperature below 20 K. From the data of VRHC we estimated the density of localized states at the Fermi level N( E F) and demonstrated that N( E F) is decreasing in composite materials.

Electrospinning Preparation of Uniaxially Aligned Ternary Terbium Complex/Polymer Composite Fibers and Considerably Improved Photostability

In order to improve photoluminescence properties, terbium complex Tb(acac)3phen (acacacetylacetone, phen-1,10-phenanthroline) was incorporated into polystyrene (PS), polyvinylpyrrolidone (PVP), and polymethylmethacrylate (PMMA) matrixes and electrospun into various aligned composite fibers. Their morphology, structure and photoluminescence properties were systematically characterized and studied. The results demonstrated that under the ultraviolet (UV) light exposure, the emission intensity for 5D4 --> 7F(J) of Tb3+ in the composite fibers considerably increased, while it was greatly quenched in the pure complex, implying remarkably improved photostability in the composites. The composite fibers also demonstrated much better temperature stability of photoluminescence over the pure complex.

Preparation and properties of carbon fiber/ hydroxyapatite‐poly(methyl methacrylate) biocomposites

AbstractAn in situ polymerization with a later solution co‐mixing approach was used in the preparation of polymethyl methacrylate (PMMA) matrix composites using hydroxyapatite (HA) nanoparticles and short carbon fibers(C(f)) as reinforcing materials. The microstructures and fracture surface morphologies of the prepared C(f)/HA‐PMMA composite were characterized using XRD, FTIR, SEM, EDS, and FESEM analyses. The mechanical properties of the composites were tested by a universal testing machine. Results show that the surface of nitric acid‐oxidized carbon fibers and lecithin‐treated HA contain new functional groups. Uniform dispersion of short fibers and HA nanoparticles in PMMA matrix is successfully achieved and the mechanical properties of the composites are obviously improved. The flexural strength, flexural modulus, and Young's modulus of the composites reach the maximum value 128.12 MPa, 1.150 GPa, and 4.572 GPa when carbon fiber and HA mass fraction arrive to 4% and 8%, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Investigations on drop penetration and wetting characteristics of powder-liquid systems in relation to the mixing of acrylic bone cement

This study investigated methyl methacrylate – polymethyl methacrylate powder bed interactions through droplet analyses, using model fluids and commercially available bone cement. The effects of storage temperature of liquid monomer and powder packing configuration on drop penetration time were investigated. Methyl methacrylate showed much more rapid imbibition than caprolactone due to decrease in both contact angle and fluid viscosity. Drop penetration of caprolactone through polymethyl methacrylate increased with decrease in bed macro-voids and increase in bulk density as predicted by the modified constant drawing area penetration model and confirmed by drop penetration images. Linear relationships were found between droplet mass and drawing area with imbibition time. Further experiments showed gravimetric analysis of the polymerised methyl methacrylate – polymethyl methacrylate matrix under various storage temperatures correlated with Reynolds number and Washburn analyses. These observations have direct implications for the design of mixing and delivery systems for acrylic bone cements used in orthopaedic surgery.

Preparation of a Superparamagnetic Nanocomposite with a High Content of Magnetic Iron Oxide in a PMMA Matrix by Precipitation Polymerization

We have prepared nanocomposites containing large amounts of superparamagnetic nanoparticles dispersed in a polymethyl methacrylate matrix. The preparation was divided into three steps. In the first step, maghemite nanoparticles were synthesized using coprecipitation from aqueous solutions, followed by coating with oleic acid (OA). In the second step, the OA-coated nanoparticles were dispersed in n-decane to prepare a stable, concentrated suspension. Finally, methyl methacrylate was added to the suspension and in situ polymerization was carried out at elevated temperatures. The content of nanoparticles was controlled by varying the nanoparticles/monomer ratio. The main focus was on controlling the nanocomposite's homogeneity. The nanocomposites were characterized using X-ray powder diffractometry, TEM, SEM, thermogravimetry, FT-IR, NMR and magnetic measurements. The TEM analysis showed that the nanoparticles were well dispersed in the polymer matrix. They retained their superparamagnetic nature even when encapsulated by polymer with concentrations up to 48 wt%. The high loading of magnetic nanoparticles resulted in relatively high saturation magnetizations of the nanocomposites, up to 31 emu/g.

Numerical investigation of the (1+1)D self-trapping of laser beams in polymeric films based on polymethylmethacrylate and phenanthrenequinone

An analytical description connected with a numerical calculation of the propagation of self-trapped laser beams in a polymethylmethacrylate matrix containing phenanthrenequinone molecules is presented. A theoretical model for the spatial distribution of boundary optical waves is developed in dependence on characteristic beam parameters.

Influence of bin time and excitation intensity on fluorescence lifetime distribution and blinking statistics of single quantum dots

In this study of single CdSe/ZnS quantum dots in a polymethyl methacrylate (PMMA) matrix, we report narrowing of fluorescence lifetime distribution with increased bin time or excitation intensity mostly due to statistical variance of photon counts per bin and Auger relaxation. We also observed saturation for the excitation intensity dependence of the exponential bending rate for the blinking statistics for quantum dots in PMMA but not on glass.

Incorporation of multiwalled carbon nanotubes to acrylic based bone cements: Effects on mechanical and thermal properties

Polymethyl methacrylate (PMMA) bone cement–multiwalled carbon nanotube (MWCNT) nanocomposites with a weight loading of 0.1% were prepared using 3 different methods of MWCNT incorporation. The mechanical and thermal properties of the resultant nanocomposite cements were characterised in accordance with the international standard for acrylic resin cements. The mechanical properties of the resultant nanocomposite cements were influenced by the type of MWCNT and method of incorporation used. The exothermic polymerisation reaction for the PMMA bone cement was significantly reduced when thermally conductive functionalised MWCNTs were added. This reduction in exotherm translated in a decrease in thermal necrosis index value of the respective nanocomposite cements, which potentially could reduce the hyperthermia experienced in vivo. The morphology and degree of dispersion of the MWCNTs in the PMMA matrix at different scales were analysed using scanning electron microscopy. Improvements in mechanical properties were attributed to the MWCNTs arresting/retarding crack propagation through the cement by providing a bridging effect into the wake of the crack, normal to the direction of crack growth. MWCNT agglomerations were evident within the cement microstructure, the degree of these agglomerations was dependent on the method used to incorporate the MWCNTs into the cement.