Poly Methyl Methacrylate Matrix Research Articles

Influence of dyes doped in solid state polymeric matrices as spectral converters on efficiency of a flash-lamp pumped Nd:YAG laser

Organic dye materials doped in poly-methyl methacrylate matrix were used as spectral converters to increase the energy efficiency of a flash-lamp pumped Nd:YAG laser. In this process, the useless part of emitted spectrum from the pumping lamp is absorbed by dye molecules and, subsequently, re-emitted at longer wavelengths where the narrow absorption line of neodymium ion at about 580nm can be used more efficiently. As a result, approximately 40% enhancement in energy efficiency was achieved.

Interactions in organic rectorite composite gel polymer electrolyte

AbstractRectorite (REC) was modified with dodecyl benzyl dimethyl ammonium chloride (1227) to form an organic-modified rectorite, termed OREC. The OREC was used as a filler additive to modify gel polymer electrolytes (GPEs) which consisted of polymethyl methacrylate (PMMA), propylene carbonate (PC) and LiClO4. Studies of ionic conductivity and viscosity of liquid electrolytes and pure PC, respectively, clearly showed that these properties are greatly influenced by temperature and the amount of OREC added; a consequence of the interactions between the components of CPEs. The Fourier transform infrared (FTIR) spectroscopy results indicated that there were two kinds of interaction: namely (1) a strong hydrogen bond between Si–OH and C=O of PC and (2) a weak interaction between Li+ and C=O. Inverse gas chromatography (IGC) research supported the FTIR interpretation, indicating that the two interactions exist and that the H bond is the stronger of the two. In CPEs, the polymer matrix of PMMA merely supports the active components and does not influence the interactions between them. The OREC greatly increased the crucial plasticizer maintenance property when the amount of clay added was optimum.

Photoinduced enhancement of luminescence from (dibenzoylmethanato)boron difluoride in polymethyl methacrylate

The photochemical behavior of (dibenzoylmethanato)boron difluoride in the polymethyl methacrylate matrix was studied. Photoinduced luminescence enhancement was observed, and a mechanism of the process related to the aggregation of high-polarity luminophore molecules under irradiation was suggested.

Superparamagnetic nanocomposites of iron oxide in a polymethyl methacrylate matrix synthesized by in situ 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.

Dielectric relaxation of (N(C2H5)4)2CoCl2Br2 nanocrystallites incorporated into the PMMA matrix

The dielectric properties of tetraethylammonium dibromo-dichloro-cobaltate (N(C2H5)4)2CoCl2Br2 (TEA-CBC) nanocrystallites incorporated into the polymethylmethacrylate (PMMA) matrix were investigated within the spectral range of 3×105–3×109Hz in the temperature range of 90–300K. The considerable difference of the dielectric spectra of the nanocomposite compared to the TEA-CBC crystal and to the pure PMMA matrix was observed. The phenomenon of the ‘negative capacity’ has been found in the considered material. Its dependence on the NC content was investigated. Temperature investigations of the dielectric permittivity for the TEA-CBC NC incorporated into the polymer PMMA matrices have shown the sharp-like resonance dependences of the imaginary part of the dielectric permittivity near 1.2GHz. The intensity of the corresponding resonance peaks increase sub-linearly with increasing NC content. Taking into account the substantial growth of the imaginary part of the permittivity with increasing NC concentration, one can assume that the main contribution to the effect is given by the interface NC-PMMA regions. Additional experiments were performed to eliminate the influence of ‘geometry factor’.

Optical switching of a photochromic bis-phenylazo compound in PMMA films

We present our results on a newly synthesized bis-phenylazo derivative, namely bisperfluoroalkylsulfonylamino- arylazomethylene-triphenyl-phosphorane (BAM-TPP). Thin films of BAM-TPP in polymethylmethacrylate (PMMA) matrix were prepared. The films (thickness, d < 60 μm) were exposed to UV-vis light with variable intensity in order to stimulate the photochromic reaction of BAM-TPP. The resulting absorption changes of the BAM-TPP/PMMA films were investigated by spectrophotometry. The absorption spectra reveal that BAM-TPP molecules in PMMA undergo photoisomerization with resulting decrease of absorbance in the range 500–700 nm. Finally, the time response of film transmittance at 514 nm under increasing CW light intensity was recorded, showing that the reverse photochromic process brings the absorbance back to its pristine value. The obtained films thus proved to be suitable for optical switching applications.

A novel glucose biosensor based on immobilization of glucose oxidase into multiwall carbon nanotubes–polyelectrolyte-loaded electrospun nanofibrous membrane

Nanofibrous glucose electrodes were fabricated by the immobilization of glucose oxidase (GOx) into an electrospun composite membrane consisting of polymethylmethacrylate (PMMA) dispersed with multiwall carbon nanotubes (MWCNTs) wrapped by a cationic polymer (poly(diallyldimethylammonium chloride) (PDDA)) and this nanofibrous electrode (NFE) is abbreviated as PMMA–MWCNT(PDDA)/GOx–NFE. The NFE was characterized for morphology and electroactivity by using electron microscopy and cyclic voltammetry, respectively. Field emission transmission electron microscopy (FETEM) image reveals the dispersion of MWCNT(PDDA) within the matrix of PMMA. Cyclic voltammetry informs that NFE is suitable for performing surface-confined electrochemical reactions. PMMA–MWCNT(PDDA)/GOx–NFE exhibits excellent electrocatalytic activity towards hydrogen peroxide (H 2O 2) with a pronounced oxidation current at +100 mV. Glucose is amperometrically detected at +100 mV (vs. Ag/AgCl) in 0.1 M phosphate buffer solution (PBS, pH 7). The linear response for glucose detection is in the range of 20 μM to 15 mM with a detection limit of 1 μM and a shorter response time of ∼4 s. The superior performance of PMMA–MWCNT(PDDA)/GOx–NFE is due to the wrapping of PDDA over MWCNTs that binds GOx through electrostatic interactions. As a result, an effective electron mediation is achieved. A layer of nafion is made over PMMA–MWCNT(PDDA)/GOx–NFE that significantly suppressed the electrochemical interference from ascorbic acid or uric acid. In all, PMMA–MWCNT(PDDA)/GOx–nafion–NFE has exhibited excellent properties for the sensitive determination of glucose like high selectivity, good reproducibility, remarkable stability and without interference from other co-existing electroactive species.

Controllable synthesis of ZnS/PMMA nanocomposite hybrids generated from functionalized ZnS quantum dots nanocrystals

We reported controllable synthesis of ZnS nanocrystal-polymer transparent hybrids by using polymethylmethacrylate (PMMA) as a polymer matrix. In a typical run, the appropriate amounts of zinc chloride (ZnCl2) and sodium sulfide (Na2S) in the presence of 2-mercaptoethanol (ME) as the organic ligand were well dispersed in H2O/dimethylformamide solution without any aggregation. In addition, the Mn-doped ZnS nanocrystals (NCs) were synthesized with similar method. Then, ZnS-PMMA hybrids were obtained via free radical polymerization in situ by using ZnS NCs functionalized with methacryloxypropyltrimethoxysilane (MPS). FT-IR characterization indicates the formation of robust bonding between ZnS NCs and the organic ligand. The TEM images show that ZnS NCs are well dispersed in PMMA matrix, and particle size of as-prepared ZnS NCs is about 2.6 nm, in agreement with the computing results of Brus’s model and Debye–Scherrer formula. The photoluminescence measurements present that ZnS NCs, Mn-doped ZnS NCs, and ZnS/PMMA hybrid show good optical properties.

Giant magnetoresistance of Fe3O4-polymethylmethacrylate nanocomposite aligned fibers via electrospinning

This paper describes the results of investigations on giant negative magnetoresistance (GMR) in nanocomposite aligned fibers prepared using electrospinning. The nanocomposite contains polymethylmethacrylate (PMMA) matrix and the nanoparticles of polymer (PMMA) grafted magnetite, Fe3O4 (PGM). Even for the low magnetic field (1T) a GMR of about 50% was observed for low loading (5wt%) of PGM at room temperature. The fibers were characterized using scanning electron microscope and high resolution transmission electron microscope. X-ray diffraction (XRD) patterns were recorded for clean PMMA fibers, PMMA granules, and PGM nanoparticles. The dc conductivity was calculated from the I-V characteristics for the fibers at room temperature.

An image processing algorithm for single-photon fluorescent tomography under conditions of strong scattering

An algorithm for digital processing of images recorded by means of scanning laser fluorescent tomography is developed. Images of the test object fabricated from a polymethylmethacrylate matrix with rhodamin 6G put in water solution of dry milk modeling a brain tissue are processed. The algorithm allows not only the contours of the object distorted because of strong scattering in biological tissues but also a finer object structure to be reconstructed. In addition, the algorithm enables three-dimensional object structure to be reconstructed for the known distribution of dye concentration in the object, which is also demonstrated in the present paper.

Nanocarbon-poly(methyl methacrylate) composite materials

Nanocarbon-poly(methyl methacrylate) sols were prepared by pulsed laser ablation at the interface of target submerged in flowing liquid (PLA-IT/SFL) method, and the corresponding composite films were prepared by solution-casting. Spectra results indicated that there existed interactions between nanocarbon and the polymethyl methacrylate (PMMA) matrix, which was consistent with the decrease in glass transition temperature of the composites with increase of carbon content. TEM images revealed that a carbon encapsulated core/shell structure was formed in the composites, which could ensure good dispersion of carbon nanoparticles within the PMMA matrix. The decomposition of the composites was less influenced by the introduction of nanocarbon particles.

Behavior of particle-filled polymer composite under static and dynamic loading

Experimental results of quasi-static and dynamic fracture of particle-filled polymer composite (PFPCM) “ALTUGLAS EI CH25” with a matrix of polymethylmethacrylate (PMMA) are reported in this paper. PMMA matrix is filled with rubber particles, as result a shock-resistant transparent composite is produced. The main task was to investigate experimentally and theoretically the fracture toughness of this composite under static and dynamic loading. A high-rate loading has been created by impulse magnetic field. Analysis of fracture process and its relation with the load parameters and material microstructure have been established. Application of the original testing method enabled determination of fracture toughness at very short loading times and comparison of the results with material dynamic properties. Theoretical analyses are based in general on the notion of delayed fracture. More specifically, the theoretical analysis is based on experimental results and on the hypothesis of fracture incubation time, or delay time.

Enhanced luminescence observed in polyaniline–polymethylmethacrylate composites

Polyaniline (PANI) is one of the highly pursued conducting polymers owing to its high electrical conductivity, interesting optical properties and excellent environmental stability. Recently, it is also being used extensively as hole-injecting electrodes in polymer LEDs. Inspite of its excellent electrical properties, the mechanical strength and processibility are not very attractive. It is reported that making composites of PANI with conventional polymers such as polymethylmethacrylate (PMMA), significantly improves the mechanical strength and processibility. Recently, we have observed that the DC electrical conductivity of HCl doped PANI can be further enhanced by making composites with PMMA. PMMA has been reported to have excellent optical properties such as very good transparency in the visible region and fairly good photoluminescence emission. This prompted us to carry out investigations on the optical properties of this composite, especially the photoluminescence characteristics. In the present work, we have synthesized PANI–PMMA composites using bulk polymerized PMMA. The FTIR spectrum reveals that PANI has been dispersed as an interpenetrating network in the PMMA matrix. The change in the photoluminescence (PL) behaviour of PANI–PMMA composites with different aniline to PMMA feed ratios has been investigated. It is observed that the photoluminescence intensity increases with increase in the PMMA content in the composite, possibly due to greater chances of exciton formation and subsequent radiative decay to the ground state. The PL spectrum of PMMA is also taken for comparison. The enhancement in the PL intensity of the composites with increase in the aniline to PMMA feed ratio is quite comparable with the enhancement in the DC electrical conductivity of these composites.

Influences of compositions and ligands on photoluminescent properties of Eu(III) ions in composite europium complex/PMMA systems

Three kinds of europium complexes; Eu(phen) 2Cl 3(H 2O) 2, Eu(DN-bpy)phenCl 3(H 2O) 2 and Eu(DB-bpy)phenCl 3(H 2O) 2 (phen: 1,10-phenanthroline, DN-bpy: 4,4′-Dinonyl-2,2′-dipyridyl, DB-bpy: 4,4′-Di- tert-butyl-2,2′-dipyridyl) were prepared and then incorporated into polymethyl methacrylate (PMMA) matrix with different molar ratios of C O groups/Eu 3+ ions. The final solid composites were formed by a self-assembly process among Eu 3+ ion, the ligands and PMMA during the solvent evaporation process, and then the ligands re-coordinate to Eu(III). It was found that the ligands affect not only the emission properties of the pure complexes, but also the miscibility of the complexes and PMMA. More than one kind of symmetric sites of Eu 3+ ions were formed in the composites due to the coordination of C O in PMMA to Eu 3+ ions. The micro-environments of Eu(III) in the composites were changed with the compositions and the ligands, leading to the change in the crystalline structure, and consequently, the emission characteristics.

Light transmitting electromagnetic wave shielding composite materials using electromagnetic wave polarizing effect

Light transmitting and electromagnetic wave shielding material using a cross-polarizing effect of unidirectionally aligned electrically conductive fiber-dielectric composite has been developed. Two-electrically isolated unidirectionally aligned continuous electrically conductive fiber layers were incorporated into an optically transparent polymethylmethacrylate (PMMA) matrix. Electromagnetic wave shielding by the polarizing effect of the composite was examined by the free-space method in a frequency range from 18to24GHz. The composite shields electromagnetic wave with a small expense of light transmittance of the PMMA matrix. Effect of fiber spacing, angle of fiber axis direction, and polarizing mode of incident electromagnetic wave are discussed based on experimental results. It is concluded that the use of the polarizing effect is an effective way to obtain an optically transparent electromagnetic shielding material.

Fabrication of Fe3O4 nanoparticle arrays via patterned template assisted self-assembly

Magnetic nanoparticle arrays have been fabricated by combining chemically synthesizedFe3O4 nanoparticles with a diblock copolymer template substrate consisting of self-assembled polystyrene(PS) dots in a polymethylmethacrylate (PMMA) matrix. The influence of the volume fraction of theFe3O4 suspending solution and the withdrawal speed of the template on the formation of arraystructures was investigated. A small volume fraction of the nanoparticles and lowwithdrawal speed play an important role in the fabrication of the patterned arrays ofnanoparticles via template assisted self-assembly. Below a withdrawal speed of0.5 mm s−1 and a nanoparticle volume fraction below 0.05 vol% (in particular, at extremely highdilutions of less than 0.01 vol%), the selective deposition of one to several nanoparticles onevery single PS dot becomes possible.

Complete UV emission of ZnO nanoparticles in a PMMA matrix

Preparation and photoluminescence (PL) properties of zinc oxide (ZnO) nanoparticles embedded in a lipophilic polymethyl methacrylate (PMMA) matrix are reported in detail with an unbalanced sol–gel route. A high-resolution transmission electron microscope (HRTEM) indicates that ZnO particles are highly crystallized, with a size of 5–6 nm and hexagonal wurtzite structure. During the sol–gel reaction, partial ester groups of R-COOCH3 in PMMA are hydrolyzed to form carboxylic ion groups, which chemisorb on the surface of ZnO nanoparticles to eliminate the defects; thus ZnO nanoparticles in the PMMA matrix exhibit complete ultraviolet (UV) emissions, while emissions in the visible region are fully quenched.

Nanocomposite polymeric electrolytes to record electrophysiological brain signals in prolonged, unconventional or extreme conditions

Chemically stable nanocomposite iono-conducting polymeric membranes (based on lithium salts and nanocrystalline oxide powders dispersed in a polymethyl methacrylate matrix) performed successfully in the recording of human brain responses to visual stimulation. Impedance was higher than that of conventional electrodes. However, the electrophysiological signals recorded by acid Al2O3 and neutral Al2O3 5wt.% and 10wt.% nanocomposite gel electrolytes were comparable to those obtained with standard electrodes, even without preliminary skin cleaning and in the absence of gel electrolytes allowing better contact with and skin–electrode ionic conductance. The electrochemical and mechanical characteristics of these membranes make them fit for human and animal research, for clinical application (specifically in emergencies, prolonged electrophysiological recordings), or in unconventional or extreme conditions when fluid electrolytes are unsuitable (e.g., biomedical space research).

Microdeformation mechanisms in rubber toughened PMMA and PMMA-based copolymers

The classical method of toughening polymethylmethacrylate (PMMA) is to incorporate composite rubber particles into the homopolymer matrix. This approach has been extended in the present work by (i) combining rubber toughening with chemical modification of the matrix or (ii) introduction of the rubber modifier via PMMA– b-polybutylacrylate (PBA)– b-PMMA triblock copolymers. Significant improvements in fracture toughness at low speeds were observed in notched compact tension tests when the ductility of the rubber toughened PMMA matrix was improved by copolymerization, and comparable levels of toughness were achieved in the block copolymers. However, both types of material showed a transition to more brittle behavior at impact speeds, associated with increased localization of the crack tip deformation. Physical interpretations for this behavior and the scope for further optimization of the fracture response are discussed.

Multiscale approach to the behaviour and damage of the heterogeneous elastic–viscoplastic materials

Both natural and man-made materials, often exhibit heterogeneous structure, depending on the scale of observation. This heterogeneous aspect acts as an important factor on their macroscopic mechanical behaviour response. One of the most reliable ways to obtain a quantitative relation between different scales is the use of the homogenisation methods. The fundamental assumption in these methods is the existence of a unit cell that is representative for the microstructure of the material under consideration, the so-called representative volume element (RVE). Modelling the mechanical behaviour of heterogeneous elastic–viscoplastic solids under finite strains framework, by using numerical homogenisation methodology is the main goal purchased in this work. Generally, the macroscopic quantities are formulated as average values of the corresponding microscopic state variables. The average of a quantity is taken over the region occupied by the unit cell [R. Hill, Elastic properties of reinforced solids: some theoretical principles, J. Mech. Phys. Solids 11 (1963) 357–372]. The method which is proposed here, has been validated by comparing results of F.E. simulations with the experimental results. The composite elements consist of a polymeric continuous matrix of polymethylmethacrylate filled with rubber particles, to obtain the so-called RT-PMMA (rubber toughened PMMA). An hyper-elastic–viscoplastic description was developed to account for both finite strains and time and history dependence mechanical behaviour that exhibits most of polymers. With regard to the influence of the damage in such kinds of composites materials, the evolution of the cavitation mechanism, identified as one of the possible damage process, is also examined.