Effect of solvents on the dynamic viscoelastic behavior of poly(methyl methacrylate) film prepared by solvent casting

Poly(methyl methacrylate) films were prepared by dissolving the polymer in chloroform, toluene and tetrahydrofuran, with identical concentrations of 200 mg/mL, and drop casting the solutions on Teflon surface at room temperature. The thermal, thermomechanical and structural properties have been investigated by differential scanning calorimetry, dynamic mechanical analyzer, and Fourier transform infrared spectroscopy, respectively. The dynamic mechanical behavior of the films has been measured over a temperature range of 30–150 °C, using sinusoidal stress with a frequency of 2 Hz. The samples prepared from tetrahydrofuran showed the highest storage modulus, indicating a higher polymer chain entanglement in that solvent, whereas the samples prepared from chloroform showed the lowest storage modulus. The samples prepared from chloroform, which showed the weakest mechanical properties, also showed the lowest glass transition temperature, which is evidence of the plasticization and solvent retention mechanism of chloroform. The spectroscopic analysis confirmed the solvent-polymer interactions giving rise to the above mentioned effects.     

Improved thermal properties of graphene oxide-incorporated poly(methyl methacrylate) microspheres

Graphene, a single layer of carbon atoms in a two-dimensional lattice, has attracted considerable attention owing to its unique physical, chemical and mechanical properties. In particular, because of its excellent thermal properties such as high thermal conductivity and good thermal stability, graphene has been regarded as a one of the promising candidates for the reinforcing fillers on the polymer composites field. In this study, we prepared the poly(methyl methacrylate) (PMMA)/graphene oxide (GO) nanocomposite by a simple solution mixing process, and examined the thermal reinforcing effects of GO on a PMMA matrix. Using thermogravimetric analysis, differential scanning calorimeter, and thermal conductivity meter, we investigated the effects of GO on the thermal properties of PMMA/GO nanocomposites. With 3 wt% of GO loading, the glass transition temperature (Tg) of the PMMA/GO nanocomposite were increased by more than 7 degrees C and the thermal conductivity of which also improved 1.8 times compared to pure PMMA.     

Modification on crystallization of poly(vinylidene fluoride) (PVDF) by solvent extraction of poly(methyl methacrylate) (PMMA) in PVDF/PMMA blends

The crystallization modification of poly(vinylidene fluoride) (PVDF) was investigated for the blend films of PVDF and poly(methyl methacrylate) (PMMA). The mass crystallinity (χ_c) and further, the β-phase content (F_(β)) of PVDF, were studied for the as-prepared blend films with different mass ratios. In addition, the variations of χ_c and F_(β) were systematically probed once the PMMA component was removed from the related blend systems. DSC, FTIR and XRD measurements all indicated that 1) χ_c, F_(β) and even the content of α-phase (F_(α)) decreased with the addition of PMMA; 2) with the extraction of PMMA, both χ_c and F_(β) increased while F_(α) decreased. It is worth noting that the increase of χ_c and F_(β) depended on the relative amount of extracted PMMA (E_PMMA), i.e., the more PMMA was removed, the more χ_c and F_(β) increased. These results reveal the hindrance effect from the PMMA constituent to the crystallization of PVDF, and consequently, this restriction would be released when the PMMA was extracted.     

Characterization and properties of in situ emulsion polymerized poly(methyl methacrylate)/graphene nanocomposites

Poly(methyl methacrylate) (PMMA)/graphene nanocomposites were prepared by in situ emulsion polymerization. Raman and Fourier transform infrared spectra showed that PMMA polymer contained partially reduced graphite oxide. Dynamic mechanical analysis and differential scanning calorimetry analysis showed that graphene in the PMMA matrix acted as reinforcing filler; it enhanced the storage moduli and glass transition temperatures of the nanocomposites. Thermogravimetric analysis showed that the thermal stability of the nanocomposites increased by ca. 35 °C. The electrical conductivity of nanocomposite with 3 wt.% graphite oxide was 1.5 S m⁻¹ at room temperature.     

The influence of solvent quality on the mechanical properties of thin cast isotactic poly(methyl methacrylate) coatings

Thin coatings of isotactic poly(methyl methacrylate) were cast on glass from solvents of different quality, which was expected to result in different molecular morphologies. The elastic moduli and hardness of the coatings were measured using a nanoindenter. The aim was to examine the viability of this technique for assessing the influence of the morphology on the mechanical properties. The interpretation of the data was complicated by both the influence of the hard substrate and possibly by the plasticising effect of retained solvent in the bulk. Nevertheless, it was reasonable to conclude that a coating cast from a good solvent was stiffer and harder than that from a poor solvent. This is consistent with previous frictional and spectroscopic studies.     

Porous nanocomposites prepared from layered clay and PMMA [poly(methyl methacrylate)]

The aim of the present work is the preparation of PMMA based porous nanocomposites that contain clay (montmorillonite, MMT) platelets as reinforcements within the cell walls of the porous structure. To render the clay layers organophilic, MMT was surface treated by an ion exchange reaction between interlayer cations of the clay and ammonium ions of a surfactant. Clay/PMMA based porous nanocomposites were prepared by polymerization of water-in-oil emulsions with and without clay addition. The microstructure and compressive mechanical behavior of the nanocomposites were investigated. The results of mechanical tests showed that the porous systems with the addition of 1 wt.% of organoclay (OMMT) exhibited a 90% and 50% increase of collapse stress and elastic modulus values, respectively, as compared to neat porous PMMA.     

Spectroscopic analysis of poly(methyl methacrylate)/alumina polymer nanocomposites prepared by in situ (bulk) polymerization

Poly(methyl methacrylate) polymer nanocomposites were prepared by in situ bulk free radical polymerization. To ensure high-quality dispersion of the oxide nanoparticles, some composites were prepared from nanoparticles predispersed in propylene glycol methyl ether acetate (PGMEA). The degree to which this additional dispersing medium interacted with the aluminum oxide nanoparticle was studied by attenuated total reflectance (ATR-FTIR), which confirmed secondary bonding and ionic interaction across the particle/dispersing medium interface. Additionally, the effect of the dispersing medium and the nanoparticles on the degree of monomer conversion was determined by Raman spectroscopy. In the presence of oxide nanoparticles alone, the active surface of the nanoparticles traps propagating radicals which significantly reduces monomer conversion. Conversely, the degree of monomer conversion is enhanced in composites containing predispersing nanoparticles, apparently by passivation/functionalization of the oxide surface by the PGMEA.     

Processing and properties of poly(methyl methacrylate)/carbon nanofiber composites

Single wall carbon nanotubes, multiwall carbon nanotubes, as well as carbon nanofibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nanofibers used was 5 and 10% by weight, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using the small-scale melt processing fiber spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNFs. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. CNF reinforcement efficiency has been analyzed using the modified Cox model.     

Morphological and physicochemical properties of spin-coated poly(3-octylthiophene)/polystyrene composite thin films

Poly(3-octylthiophene) (P3OT) was synthesized by direct oxidation of 3-octylthiophene with FeCl₃ as oxidant. Molecular weight of P3OT polymer was measured by size exclusion chromatography. Homogeneous poly(3-octylthiophene) (P3OT) and polystyrene (PS) composite films have been synthesized by spin-coating technique from toluene with different polymer concentrations. The doped films were obtained by immersion for 30 s in a 0.3 M ferric chloride (FeCl₃) solution in nitromethane. A classical percolation phenomenon was observed in the electrical properties of these blends, it was smaller than 5% of P3OT in the blend. Surface topographical changes were studied by atomic force microscopy (AFM). AFM images of the composite films revealed surface morphology variation as a function of different P3OT concentration in PS, phase segregation was observed, and PS is shown to segregate to the surface of the films. The higher PS solubility, in comparison with the P3OT solubility, in toluene resulted in PS/P3OT bilayers. The films exhibited pit and island like topography, the pit size changed with the polymer concentration. Optical absorption properties of the polymeric films were analyzed in pristine and doped state. In doped state, the bipolaronic bands at 0.5 and 1.6 eV are shown in a 4% conductive polymer in the PS/P3OT film. Finally thermogravimetric analysis was also made on the simple and composite polymers.     

聚甲基丙烯酸甲酯掺杂剂对7,7,8,8-四氰基苯醌二甲烷薄膜特性的影响

采用旋涂法制备了7,7,8,8-四氰基苯醌二甲烷(TCNQ)及聚甲基丙烯酸甲酯(PMMA)掺杂后的TCNQ敏感薄膜,探讨了PMMA掺杂剂及不同转速对薄膜性能的影响.结果表明,TCNQ/PMMA复合薄膜中TCNQ颗粒变得更细小和均匀,但对NH3的响应不稳定;纯TCNQ薄膜对NH3具有相当高的灵敏度,但响应和恢复时间较长.     

Optoelectronic properties of graphene thin films prepared by thermal reduction of graphene oxide

Graphene thin films have been prepared by thermal reduction of graphene oxide. Raising the reduction temperature results in a red-shift of the G peak in Raman spectra. The reduction temperature turns out to strongly affect the morphology of the prepared graphene film. Photoluminescence (PL) results show that the band gap of graphene can be tuned by varying the reduction temperature. The thermal reduction process has been optimized in an effort to minimize the formation of wrinkles/folds on the graphene surface leading to enhanced PL and Raman peak intensities and reduced electrical sheet resistance.     

Processing and properties of poly(methyl methacrylate)/carbon nano fiber composites

Single wall carbon nanotubes, multi-wall carbon nanotubes, as well as carbon nano fibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nano fibers used was 5 and 10 wt%, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using small-scale melt spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNF. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. The CNF reinforcement efficiency has been analyzed using the modified Cox model.     

Thermal and optical properties of poly(methyl methacrylate)/calcium carbonate nanocomposite

The study deals with thermal and optical properties of poly(methyl methacrylate) (PMMA) containing 2wt% calcium carbonate (CaCO₃) nanofiller. It was found that the thermal conductivity increases with increasing temperatures, due to thermal activation of the phonons in the PMMA/CaCO₃ nanocomposite. This enhancement in the thermal conduction is mainly attributed to the heat transferred by lattice vibrations as major contributors and electrons as minor contributors during thermal conduction. The optical properties were investigated as a function of wavelength and photon energy of UV radiation. The optical results obtained were analysed in terms of absorption formula for noncrystalline materials. It was found that the measured optical energy gap for the pure PMMA is greater than the PMMA/CaCO₃ nanocomposite. The width of the energy tails of the localised states was calculated. Adding CaCO₃ nanofiller into PMMA matrix may cause the localised states of different colour centres to overlap and extend in the mobility gap. This overlap may give an evidence for decreasing energy gap when adding CaCO₃ nanofiller in the polymer matrix.     

Anti-reflective properties of nano-structured alumina thin films on poly(methyl methacrylate) substrates by the sol-gel process with hot water treatment

Alumina gel films were coated on poly(methyl methacrylate) (PMMA) substrates using the sol-gel process, and pseudo-boehmite nanocrystals of several tens of nanometers were precipitated on the surface of the alumina gel films through immersion in hot water. It was found that the PMMA substrates, which were coated with the pseudo-boehmite nanocrystals precipitated alumina, exhibited very slight incident-angle dependence in transmittance up to 60°. The reflectance of PMMA substrates coated with the nanocrystal-precipitated alumina was less than 0.8% in the visible light region.     

Silver nano-structures prepared by oriented evaporation on laser-patterned poly(methyl methacrylate)

Preparation of ordered arrays of silver nanostructures with defined shape and symmetry on patterned polymer surface is described. Laser irradiation of porphyrine-doped poly(methyl methacrylate) leads to a material flow driven by temperature gradient and to creation of regular surface pattern. Subsequent shadow silver evaporation results in selective silver deposition and creation of ordered system of silver arcs. Structures produced in this way are examined using AFM, SEM, XPS, and FIB–SEM methods.     

Electrospinning preparation and photoluminescence properties of poly (methyl methacrylate)/Eu3+ ions composite nanofibers and nanoribbons

Nanofibers and nanoribbons of poly (methyl methacrylate) (PMMA)/Eu³⁺ ions composites with different concentration of Eu³⁺ ions were successfully prepared by using a simple electrospinning technique. From the results of scanning electron microscopy and energy-dispersive X-ray spectroscopy, we found that the morphology of the as-electrospun PMMA/Eu³⁺ ions composites could be changed from fiber to ribbon structure by adjusting the concentration of Eu³⁺ ions in the electrospun precursor solution. The coordination between the Eu³⁺ ions and PMMA molecules were investigated by Fourier transform infrared spectroscopy and differential thermal analysis. The photoluminescence (PL) properties of the as-electrospun PMMA/Eu³⁺ ions composites were studied in comparison to those of the Eu(NO₃)₃ powder. It was showed that the ⁵D₀–⁷F_J (J = 0, 1, 2, 3, 4) emission appeared in the PL spectra of the as-electrospun PMMA/Eu³⁺ ions composites, whereas the ⁵D₀–⁷F₀ emission was completely absent in the PL spectra of Eu(NO₃)₃ powder due to the different local environments surrounding Eu³⁺ ions. It was interesting to note that the intensity ratios of the electric–dipole and magnetic–dipole transitions for the PMMA/Eu³⁺ ions composites could be enhanced significantly by increasing electrospinning voltage.     

Holographic characterization of azo-dye doped poly (methyl methacrylate) films

Many holographic techniques have been developed for non-destructive studies and characterization of materials. In this paper, discussion will be made about the employed holographic technique to characterize the poly(methyl methacrylate) (PMMA) matrices doped with azo-dyes. In this manner we were able to study the effect of the thickness of the samples, the effect of concentration of the azo-dyes and of PMMA and the effect of aging (storage time) on the holographic efficiency (diffraction efficiency) of these materials. Auto-erasable holographic gratings have been successfully recorded on azo-dye doped PMMA films and the dynamic diffraction efficiency was monitored with light different from that used for the recording.     

Mechanical properties of polycarbonate and poly(methyl methacrylate) films reinforced with surface-functionalized nanodiamonds

Polymer nanocomposites (PNCs) possess highly versatile characteristics, depending on the nanofiller properties such as its chemical composition, particle size, dimension, polydispersity, concentration, or surface functional groups. In comparison with micron-sized materials, the nanofiller having a large surface area facilitates stronger interaction with the matrix. In this work, various surface-functionalized nanodiamonds (sf-NDs) having hydroxyl, carboxyl, amino, and amide group were prepared, and dispersed into polycarbonate (PC) and poly(methyl methacrylate) (PMMA) polymers. The polymer nanocomposites (PNCs) which contain the ND content of 5 wt% were subjected to the measurements of mechanical properties such as hardness and Young's modulus by atomic force microscopy (AFM) nanoindentation. It was observed that the hardness and Young's modulus of the polymer nanocomposites depend on strongly the nature of functional groups. The amine or amide functionalization gives the high mechanical properties for both polymers. The interfacial interaction between sf-NDs and polymer matrices is an important factor determining the mechanical properties of the PNCs.