Characterization and human gingival fibroblasts biocompatibility of hydroxyapatite/PMMA nanocomposites for provisional dental implant restoration

The aim of this study was to determine nHA/PMMA composites (H/P) in an optimal ratio with improved cytocompatibility as well as valid physical properties for provisional dental implant restoration. 20 wt.%, 30 wt.%, 40 wt.% and 50 wt.% H/P were developed and characterized using XPS, bending strength test and SEM. Human gingival fibroblasts cultured in extracts or directly on sample discs were investigated by fluorescent staining and MTT assay. Chemical integration in nHA/PMMA interface was indicated by XPS. Typical fusiform cells with adhesion spots were detected on H/P discs. MTT results also indicated higher cell viability in 30 wt.% and 40 wt.% H/P discs (P < 0.05). We conclude that nHA addition to PMMA enhances cytocompatibility and the optimal nHA/PMMA ratio for provisional fixed crowns (PFC) is 0.4:1.     

Conductivity and thermal stability of proton-conducting electrolytes at confined geometry of polymeric gel

The proton-conducting gel electrolytes based on poly(methyl methacrylate) (PMMA) doped by acid solutions in aprotic solvents were synthesized and discussed in this work. The gel conductivity as a function on concentrations of acid and polymer as well as of molecular mass of PMMA has been analyzed. The thermal stability of electrolytes was estimated and discussed. Extreme dependence of the conductivity on concentration is found to be for the gel (at a concentration of PMMA from 5 to 15 wt.%). The increase of electrical conductivity in the concentration range from 5 to 10 wt.% of PMMA with an increase in viscosity of the system is discussed as an indication of an involvement of the polymer matrix in increasing the mobility of the charge carriers in frame of Grotthuss mechanism.     

Photochemical kinetics for holographic grating formation in phenanthrenequinone doped poly (methyl methacrylate) photopolymer

The photochemical kinetics of phenanthrenequinone (PQ) doped poly (methyl methacrylate) photopolymer in holographic recording was studied theoretically and experimentally. The diffusion of PQ molecules during holographic recording was negligible because of its small diffusion coefficient at room temperature. A photochemical reaction kinetics model of PQ/PMMA was established. The analytical expressions for the temporal variations of transmittance and diffraction efficiency were derived. By fitting the experimental curves, some parameters related with the polymer components were obtained by the proposed model, which can be used to analyze the photochemical process and will be helpful to the optimization of material preparation.     

Adhesion,morphology, and heat resistance properties of polyurethane coated poly(methyl methacrylate)/fullerene-C60 composite films

Novel polyurethane (PU) adhesive was prepared and coated on poly(methyl methacrylate) (PMMA) and poly(methyl methacrylate)/fullerene (PMMA/Full-C₆₀) composite. Dip-coating technique was employed as facile and cost-effective procedure to coat polyurethane on film substrate. The properties of PU/PMMA and PU/PMMA/Full-C₆₀ composite were studied using Fourier transform infrared spectroscopy, Field Emission Scanning Electron Microscopy, tensile, adhesion, thermal and flammability measurement. Testing polyurethane-coated PMMA exhibited crumpled surface while fullerene addition formed unique pattern of dispersed spherical structures. Fullerene nanofiller loading improved the adhesion and mechanical properties of composite films due to polymer–carbon interaction. In PU/PMMA/Full-C₆₀ 0.5 composite with 0.5 wt.% nanofiller, tensile strength (71.4 MPa) was increased by 18.6% while tensile modulus was increased by 143.85% compared with PU/PMMA. In PU/PMMA/Full-C₆₀ 0.5, T₀ of 473 °C and T_max of 655 °C were observed. Increasing the fullerene content up to 0.5 wt.% decreased the peak heat release rate to 131 kW/m². Novel polyurethane-coated PMMA/Full-C₆₀ composite have potential applications as adhesive coatings in electronic and automotive appliances.     

Study on the mechanism of dark enhancement in phenanthrenequinone-doped poly(methyl methacrylate) photopolymer for holographic recording

The dark enhancements with various exposure energies are studied in thick PQ/PMMA photopolymer. Considered the weak molecules diffusion of PQ component and the grating detuning, a new mechanism of dark reaction is proposed to explain the dark enhancement. Moreover, the influences of dark reaction on Bragg angular selectivity and grating recording are analyzed. The results are beneficial to the practical holography application.     

Electrical,structural, and optical characterization of coal ash–PEO/PMMA blend composites

In the present work, indigenous coal ash taken from Sharigh, Balochistan, Pakistan was used to prepare polymer electrolyte films with PEO/PMMA/LiClO₄. Coal ash was first characterized by various techniques like Surface and Porosity Analysis, SEM/energy dispersive X-ray analysis (EDX), transmission electron microscopy, Fourier transform infrared (FTIR), and XRD. Chemical composition of ash was confirmed by EDX. Then, the utility of coal ash towards fabricating PEO/PMMA/LiClO₄/coal ash composites was studied in order to explore its use as an additive for polymeric blend composites. The ash incorporation into the polymeric blend composites was studied by X-ray diffraction and UV/Visible spectroscopy, while ionic conductivity measurements were undertaken by Impedance spectroscopy. Room temperature conductivity of polymeric blend composites was found to increase sharply with ash content and reached maximum at 3.3 wt.% of ash. Both direct and indirect band gap energies of polymeric blend decreased with coal ash incorporation. The decrease was at peak at 3.3 wt.% of ash. Coal ash has found to improve the performance of polymeric blends.     

Fabrication of Ni Nanoparticles Loaded on β-Cyclodextrin/Polymethyl Methacrylate Composite Nanofibers via Electrospinning,Immersion, and Chemical Reduction

In recent years, nickel based nanomaterials have attracted much attraction owing to their low cost and the unique catalytic properties in some special reactions. Uniform diameter polymethyl methacrylate (PMMA) nanofibers and β-cyclodextrin (β-CD) functionalized PMMA nanofibers were obtained through electrospinning. Nickel-loaded nanofibers (Ni/β-CD/PMMA) were prepared by a reductive impregnation method. With increasing addition of β-CD, the diameter of the composite nanofibers became larger. The images by scanning electron microscopy (SEM) suggested that the morphology for different β-CD loadings of the β-CD/PMMA nanofibers was uniform until the loading of β-CD was 8 wt.%; the morphology of the nanofibers then became nonuniform and nodes appeared. Energy dispersive spectrometry (EDS) revealed that the Ni nanoparticles were loaded on the surface of nanofibers successfully.     

Eu3+配合物掺杂聚合物的制备与光谱性能研究

以噻吩甲酰三氟丙酮(2-thenoyltrifluoroacetone , TTFA), 六氟乙酰丙酮(hexafluoro- acetylacetone, HFA)和甲基联苯甲酰(dibenzoylmethide, DBM) 分别为配体合成了Eu3+的三种β-二酮类配合物Eu(TTFA)3、Eu(HFA)3和 Eu(DBM)3,以及掺杂这三种配合物的聚合物（聚甲基丙烯酸甲酯,PMMA）,并用分光光度计对它们的荧光光谱特性进行了分析研究.结果表明,三种配合物中Eu(TTFA)3荧光强度最强,并分析了其原因,发现能级匹配、配体取代基、配体结构对称性等均对配合物发光效率有重要的影响.通过比对,证明了TTFA是Eu3+发红色荧光的优良配体.进一步研究还发现,Eu(TTFA)3掺杂PMMA中稀土离子的荧光强度和荧光寿命均随掺杂浓度（质量分数为0.08～0.5）的增加而增大.     

Coating zinc oxide submicron crystals on poly(methyl methacrylate) chips and spheres via ultrasound irradiation

Ultrasound irradiation is used for anchoring zinc oxide submicron crystals with a main diameter and length of 280 nm and 470 nm, respectively, onto the surface of poly(methyl methacrylate) PMMA chips (2 mm diameter), and zinc oxide crystals with a mean diameter and length of 150 nm and 230 nm, respectively, onto the surface of the PMMA spheres (1–10 μm). The zinc oxide crystals were obtained by sonochemical irradiation of a mixture containing the PMMA, zinc (II) acetate dihydrate, ethanol, water, and 24 wt.% aqueous ammonia for 2 h, yielding a PMMA–zinc oxide composite. By controlling the atmosphere and reaction conditions, we could achieve well-adhered zinc oxide crystals on the surface of poly(methyl methacrylate). The resulting zinc oxide–PMMA composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis (EDX), high-resolution scanning electron microscopy (HRSEM), and photoluminescence (PL) spectroscopy. The zinc oxide-deposited PMMA chips (loaded with 0.03–1.0 wt.% ZnO) were successfully homogenized in melt by extrusion and then injection molded into small, disc-shaped samples. These samples were analyzed with respect to their directional spectral optical properties in UV, Vis and IR spectroscopy.     

Glass transition temperature and thermal stability of ZnS/PMMA nanocomposites

In this article, ZnS nanoparticles were prepared by wet chemical precipitation method using zinc sulphate (ZnSO₄), sodium sulphide (Na₂S) and thio-glycerol. These nanoparticles were characterized through X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The solution-based processing was used to prepare Poly methyl methacrylate (PMMA) nanocomposites with different weight percents (0, 2, 4, 6 and 8) of ZnS nanoparticles. The obtained ZnS/PMMA nanocomposites were characterized through XRD, scanning electron microscope and TEM measurements. The dynamic mechanical analyzer was used to obtain the storage modulus and glass transition temperature (T _g) of the nanocomposites. The apparent activation energy of the glass transition region was also determined using the Vogel–Fulcher–Tammann equation. The results indicated that the thermal stability of ZnS/PMMA nanocomposites was higher than PMMA and 6 wt. % of ZnS nanoparticles in PMMA matrix showed the maximum activation energy, which indicated that this nanocomposite had higher thermal stability than other composites.     

Effect of rare earth elements on the structural and optical properties of PMMA for possible uses in polymer optical communications

Rare-earth elements (REEs) as Tm⁺³, Er⁺³, Yb⁺³ and Nd⁺³ have a significant optical photon emission. Therefore, Films of PMMA doped with 5?wt.% of NdCl₃, TmCl₃, ErCl₃ or YbCl₃ were prepared using the casting technique. FTIR of the prepared films has been studied. The optical and dispersion behavior of all doped samples have been investigated. The reflectance (R) and the transmittance (T) were measured in the wavelength range of 200–2500?nm. FTIR of all PMMA reveals that, REEs addition to PMMA samples creates new transmission peaks C=O groups and a decrease in the intensity of the absorption band of C–O groups has been obtained. The results showed the dependency of the refractive index and energy gap on the REE electronic transitions nature. The obtained results suggest strongly the applicability of these PMMA derivatives in improving the performance of the polymer optical fiber (POF).     

Clustering study in Eu(DBM)3Phen-doped polymer optical fibers by optical properties and near-field scanning microscopy

The clusters of Eu3+ ion in Eu(DBM)3Phen-doped polymethyl methacrylate (PMMA) have been studied by three means. The relative fluorescence intensity ratio of the 5D0 → 7F2 to 5D0 → 7F1 transitions with different concentrations of Eu3+ in Eu(DBM)3Phen-doped PMMA and metastable-state (5D0) lifetime dependence on Eu3+ concentration are analyzed. The analysis indicates that there are no clustering effects in Eu3+ ions of Eu(DBM)3Phen-doped PMMA when the Eu3+ doping concentration is up to 1.0 wt.-%. At the same time, the clustering effect has not been observed by the scanning near-field optical microscopy (SNOM) in Eu(DBM)3Phen-doped PMMA with 1.0 wt.-% of Eu3+ ions. The analysis reveals that a high concentration of Eu3+ can be incorporated into polymer optical fiber (POF) without clustering effect.OCIS codes: 180.5810, 300.6280, 250.5460, 160.5690.     

Effect of PMMA on crystallization behavior and hydrophilicity of poly(vinylidene fluoride)/poly(methyl methacrylate) blend prepared in semi-dilute solutions

Films of poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend were derived from a special procedure of casting semi-dilute solutions. Hydrophilic character and crystallization of PVDF were optimized by variation of PMMA concentration in PVDF/PMMA blends. It was found that a PVDF/PMMA blend containing 70 wt% PMMA has a good performance for the potential application of hydrophilic membranes via thermally induced phase separation. The films presented β crystalline phase regardless of PMMA content existed in the blends. Thermal analysis of the blends showed a promotion of crystallization of PVDF with small addition of PMMA which induced larger lamellar thickness of PVDF, leading to the largest spherulitic crystal of PVDF (10 wt% PMMA) is about 8 μm. SEM micrographs illustrated no phase separation occurred in blends, due to the high compatibility between PVDF and PMMA.     

The influence of γ-irradiation on some physical properties of chlorophyll/PMMA films

Films of poly(methylmethacrylate) PMMA doped with different concentrations of chlorophyll, from 2.5 up to 12.5 wt.%, have been prepared by casting method. Studies were carried out utilizing FT-IR, UV/vis, fluorescence, TGA and DC electrical conduction to characterize the structural, optical and thermal properties of the films before and after irradiation. Results revealed that the structural and chemical characterizations of PMMA films are affected by the addition of chlorophyll and increasing dose of γ-irradiation. FT-IR analysis revealed that the hydroxyl and carbonyl groups were responsible for the decrease of the bands intensities with increasing the dose rate up to 100 kGy. The change in these groups was attributed to competitive processes: decomposition with ester group abstraction and oxidation with formation of new oxidized carbonyls in the polymeric chains. The values of optical energy gap for the samples were decreased upon irradiation; this indicates that there is a charge transfer complexes arise between PMMA and chlorophyll. TGA analysis shows that the addition of chlorophyll to PMMA films enhances their thermal stability. The electric conduction data were interpreted on the basis of an intrachain one-dimensional interpolaron hopping model of Kuivalainen.     

ABS ternary blends: Morphology,surface gloss,and mechanical properties

ABS/PMMA/PC (acrylonitrile-butadiene-styrene)/poly(methyl methacrylate)/bisphenol A polycarbonate) and ABS/PMMA/phenoxy ternary blends were prepared using a corotating twin-screw extruder, where the ABS content was fixed at 60% by weight, and the other ingredients varied 0 ～ 40%. Tensile modulus, yield strength, elongation at break, and notched impact strength varied linearly with compositions in ABS/PMMA/phenoxy blends, whereas positive synergisms of these properties were generally obtained with ABS/PMMA/PC blends. The results were interpreted in terms of interpositions of PMMA between ABS and PC, which were seen from the TEM micrographs and predicted from the spreading coefficient. Surface gloss of ABS increased in ABS/ PMMA(60/40) blend but decreased in ternary blends, and this phenomenon was possibly explained by the pearl gloss mechanism.     

Fabrication and characterization of poly(methyl methacrylate) photopolymer doped with 9,10-phenanthrenequinone (PQ) based derivatives for volume holographic data storage

We present our studies on the photopolymer of poly(methyl methacrylate) (PMMA) doped with 9,10-phenanthrenequinone based derivatives for volume holographic storage. By introducing different functional groups on the side-chain of 9,10-phenanthrenequinone molecule, the holographic characteristics of the material can be modified. The photoreaction involved with the holographic recording in the samples was investigated by measuring UV-Vis absorption spectrum and mass spectrum. The experimental results show that the similar behaviors were exhibited in these photopolymers. It is found that phase hologram recording in our PQ derivatives doped PMMA photopolymer involves a structure change of the quinone based molecule, which induces a strong change of the refractive index. Experimental characterizations on holographic data storage, including material sensitivity, dynamic range (M#) and bit-error-rate have been performed. We found that, by selecting appropriate functional groups, an improvement in sensitivity and M# for holographic data storage can be achieved.     

Role of salt concentration on conductivity optimization and structural phase separation in a solid polymer electrolyte based on PMMA-LiClO4

Although a large number of ionic conductors based on poly(methyl-methacrylate) (PMMA) are reported in literature, an optimization of salt concentration with respect to conductivity and stability properties remains by and large neglected. We report, perhaps for the first time, such an optimization of salt (LiClO₄) concentration on structural, morphological, electrical, and ion–polymer interaction in PMMA-based solid polymer films. The active coordination site for the cation (Li⁺), out of the two possible electron donating functional groups (i.e. C=Ö and Ö–CH₃) in PMMA, has been ascertained on the basis of evidences recorded in Fourier transform infrared spectrum. The results suggested C=Ö as the only possible site in PMMA matrix for coordination with Li⁺ cation. The X-ray diffraction results have clearly indicated an optimum limit of salt dissolution in PMMA matrix corresponding to O/Li = 4 (i.e., ~21wt.%) above which “phase-separation” occurs distinctly. The effect of salt concentration on amorphous → crystalline phase changes in PMMA and its correlation to morphology have been clearly observed in terms of their impact on electrical properties. An optimum electrical conductivity of ~7.2 × 10^?5S cm^?1 has been recorded at 100°C (~PMMA glass transition). The temperature dependence of conductivity follows typical Vogel–Tamman–Fulcher behavior.     

Holographic storage stability in PQ-PMMA bulk photopolymer

Holographic storage stability is investigated experimentally in phenanthrenequinone (PQ) doped poly-(methyl methacrylate) (PMMA) photopolymer with high thickness and rigid polymer matrix. It is demonstrated that the stability consists of two continuous processes, dark enhancement and decay of holograms, which are corresponding to the diffusion of PQ and its photoproduct molecules, respectively. During dark enhancement the Bragg detuning of angle selectivity is observed. Therefore it is necessary to obtain steady holograms quality by adjusting the readout angle. After reaching steady state, the long-term stability of holograms is determined by the diffusion of photoproducts. Temperature is a most significant parameter for long-term stability, which can bring sufficient energy to increase the diffusion of photoproducts and reduce the stability. Finally low temperature and uniform exposure as alternative methods are proposed to optimize the storage stability after dark enhancement. Moreover the influence of humidity on the storage stability is neglectable.     

涂覆聚甲基丙酸甲酯的磁性膜外磁场作用下的往复滑动摩擦行为研究

磁性材料被广泛应用于磁记录和磁润滑等领域,聚甲基丙烯酸甲酯因其良好的介电性,能够用作磁性材料的表面涂层.本文对外磁场作用下,外加载荷和磁场强度对往复滑动的聚甲基丙烯酸甲酯/磁性薄膜双膜系摩擦性能的影响开展了研究.实验结果表明:聚甲基丙烯酸甲酯/磁性双膜体系的摩擦性能随载荷和磁场强度改变而变化;但在干摩擦和硅油润滑两种模式下,磁场对其摩擦学性能的影响规律不同.理论分析了磁场作用下磁场诱发的磁性力与摩擦副物理性质变化对摩擦力和摩擦系数的影响,与实验结果符合良好.研究结果为磁性薄膜的界面介质设计与控制提供了依据.     

旋涂速度对制备P3HT有机场效应晶体管性能的影响

采用溶液化的方法制备了以PMMA为绝缘层、P3HT为有源层的有机场效应晶体管.研究了P3HT有源层和PMMA绝缘层的旋涂速度对器件性能的影响.实验结果表明,当P3HT和PMMA的旋涂速度均为2 000 r/min时,器件的性能最佳.峰值场效应迁移率为6.84×10^-2 cm²·V^－1·s^－1.结果表明,选择适当的旋涂速度是一种有效提高溶液化制备有机场效应晶体管性能的方法.