SiO2 PMMA-GMA亚微米复合粒子的制备及其对环氧树脂的改性

用溶胶-凝胶法制备了表面含可聚合官能团的亚微米SiO₂粒子,利用在其表面的乳液聚合成功制备了具有核-壳结构的SiO₂-聚甲基丙烯酸甲酯(PMMA)-甲基丙烯酸缩水甘油酯(GMA)复合粒子,通过TEM、FTIR和TGA对其结构进行了表征;然后制备了SiO₂-PMMA-GMA/环氧树脂复合材料,利用SEM观察其断裂形貌,并分析了复合粒子增韧环氧树脂的机制。结果表明: SiO₂为复合粒子的内核,粒径约为180 nm,其表面被PMMA-GMA聚合物包覆,厚度约为20 nm;PMMA-GMA聚合物与SiO₂的质量比为87.4%,PMMA-GMA聚合物对SiO₂的接枝率及PMMA-GMA聚合物的有效接枝率分别为77.0%和88.1%;当SiO₂-PMMA-GMA复合粒子在环氧树脂中的含量为4wt%时,其固化后的冲击强度可由19.2 kJ/m²增加到42.0 kJ/m²。     

N-channel thin-film transistors based on 1,4,5,8-naphthalene tetracarboxylic dianhydride with ultrathin polymer gate buffer layer

N-channel operation of thin-film transistors based on 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTCDA) with a 9-nm-thick poly(methyl methacrylate) (PMMA) gate buffer layer was examined. The uniform coverage of the ultrathin PMMA layer on an SiO₂ gate insulator, verified by X-ray reflectivity measurement, caused the increase of electron field-effect mobility because of the suppression of electron traps existing on the SiO₂ surface. In addition, air stability for n-channel operation of the NTCDA transistor was also improved by the PMMA layer which possibly prevented the adsorption of ambient water molecules onto the SiO₂ surface.     

Facile synthesis and anti-icing performance of superhydrophobic flower-like OTS-SiO2 with tunable size

The superhydrophobic flower-like OTS-SiO₂ particles with tunable size were synthesized for application in anti-icing technology, in which the nanosilica fibers were grown on surface of SiO₂ sphere. Furthermore, the anti-icing process of flower-like OTS-SiO₂ particles was investigated by a high speed video and thermal infrared imaging equipment. It was found that the flower-like OTS-SiO₂ particles with a diameter of 300.0 nm showed best anti-icing ability, in which the frozen time of water droplets could be prolonged to 564.0 s at −25.0℃. The good anti-icing ability was attributed to micro-nano hierarchical structure and surface modification of flower-like OTS-SiO₂ particles. The work has an important guiding implication for the subsequent design and preparation of superhydrophobic particles for application in anti-icing technology.     

Effect of grafted polymer species on particle monolayer structure at the air-water interface

We have studied poly(methyl methacrylate)-grafted(PMMA) particle monolayer systems at the air-water interface. In previous papers, we reported that PMMA chains grafted from particles (silica particle and polystyrene latex) were extended on water surfaces. Through observing deposited particle monolayers on substrates using SEM, we have confirmed that PMMA of large molecular weights were either dispersed or arrayed in structure with long inter-particle distances approximately 500 nm. In contrast, low molecular weight PMMA were observed to aggregate upon deposition. We speculated that the difference in morphology in deposited particle monolayers would be attributed to the affinity between the grafted polymer and the substrate. To examine the effect of this affinity three new polymer-grafted silica particles were synthesized with a fairly high graft density of about 0.14 approximately 0.43 nm(-2). As well as PMMA-grafted silica particles (SiO2-PMMA), poly(2-hydroxyethyl methacrylate) and poly(t-butyl methacrylate)--grafted silica particles (SiO2-PHEMA and SiO2-PtBuMA) were also prepared and subjected to pi-A isotherm measurements and SEM observations. These pi-A isotherms indicated that polymer-grafted silica formed monolayer at the air-water interface, and the onset area of increasing surface pressure suggests that the polymer chains are extended on a water surface. However, the morphology of the deposited monolayer is highly dependent on polymer species: SiO2-PHEMA showed that the dispersed particle monolayer structure was independent of grafted molecular weight while SiO2-tBuMA showed an aggregated structure that was also independent of grafted moleculer weight. SiO2-PMMA showed intermediate tendencies: dispersed structure was observed with high grafted molecular weight and aggregated structure was observed with low grafted molecule weight. The morphology on glass substrate would be explaiened by hydrophilic interaction between grafted polymer and hydrophilic glass substrate.     

Preparation and characterization of polyimide/silica nanocomposite spheres

Silica (SiO₂) nanocomposite spherical particles coated with polyimide had been synthesized by a dispersion polymerization method. The chemical structure of polyimide/silica (PI/SiO₂) nanocomposite spherical particles was investigated by using FT-IR, and the surface morphology characterization was performed with SEM. The TEM showed that SiO₂ core was surface-coated with a multilayer composite and the multilayer thickness was about 20 nm. Moreover, the particles were homogeneously distributed and interconnected very fine. Basing the results, it was found that the PI/SiO₂ nanocomposite particles were core–shell structure.     

Synthesis and characterization of <Emphasis Type="Italic">in situ</Emphasis> prepared poly (methyl methacrylate) nanocomposites

Hybrid materials, which consist of organic-inorganic materials, are of profound interest owing to their unexpected synergistically derived properties. These hybrid materials replaced the pristine polymers due to their higher strength and stiffness in the recent years. In the present work, studies concerning the preparation of poly (methyl methacrylate) (PMMA), PMMA/SiO₂, and PMMA/TiO₂ nanocomposites are reported. These nanocomposite polymers were synthesized by means of free radical polymerization of methyl methacrylate using benzoyl peroxide as an initiator in a water medium. Further ‘sol-gel’ transformation based hydrolysis and condensation of Ti and Si alkoxides were used to prepare the inorganic phase during the polymerization process of MMA. Paper presented at the Indo-Singapore symposium on ‘Advanced Functional Materials’, IIT Mumbai, 2006.     

Control of the Surface Morphology of Ceramic/Polymer Composite Inks for Inkjet Printing

The use of organic/inorganic composite inks in the Drop on Demand inkjet printing technology is a promising as well as demanding approach for the fabrication of composite thick films. Therefore, a versatile ceramic/polymer composite ink system for inkjet printing is developed in this study, containing Ba_0.6Sr_0.4TiO₃ (BST) and poly(methyl methacrylate) (PMMA). When developing such inks suitable for a one‐step fabrication, the major challenge is to fulfill the requirements of the inkjet printing technology and to obtain homogeneous surface morphologies after drying. Thus, possible influencing factors like the solvent composition, the solids content, and the ratio of ceramic to polymer are investigated to obtain a detailed knowledge for the general ink development. The fluid mechanical properties, viscosity, density, and surface tension are characterized. The main focus of this study lies on the drying behavior of the different inks, with the interactions of the ceramic particles, and the dissolved polymer molecules being highlighted. Furthermore, the drying behavior depending on the ink composition is shown. This study provides new insights into the possibility of using composite inks for the inkjet printing process and the fabrication of printed composite thick films in a single process step.

     

Characterization of SiO2/Ag composite particles synthesized by in situ reduction and its application in electrically conductive adhesives

In the study, SiO₂/Ag composite particles with silver coating onto the surface of silica have been successfully prepared via a novel and facile approach (Oxidation–Reduction Method). In this approach, the SiO₂ particles were first modified with 3-ammoniatriethoxysilane (APTES) and glyoxalic acid (GA) through two-step reaction, the aldehyde group (CHO) were anchored onto the surfaces of silica spheres via electrostatic attraction, these [Ag(TEA)₂]⁺ ions in the solution were then reduced by the CHO and coated onto the surface of silica to obtain SiO₂/Ag composite particles. The effects of the reaction conditions on silver content and synthetic mechanism had also been discussed. The structure, morphology and optical properties of the SiO₂/Ag composite particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–vis spectroscopy. The results showed the surface of SiO₂ was surrounded by pure silver nanoparticles, and the silver nanoparticles had face-centered-cubic structure, the SiO₂/Ag composite particles with core–shell morphology and special optical properties. And the small content SiO₂/Ag composite particles applied in electrically conductive adhesives (ECAs) improved the electrical bulk resistivity and tensile shear strength.     

Poly(vinylidene fluoride)/poly(methyl methacrylate)/TiO2 blown films: preparation and surface study

Blown films of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) blends and PVDF/PMMA/TiO₂ composites were prepared by melting-extrusion for the first time. The crystalline structure and surface morphology PVDF/PMMA (DFMA) blown films were investigated using differential scanning calorimeter (DSC), atomic force microscope (AFM), and X-ray diffractometry (XRD). PVDF/PMMA/TiO₂ blown films were further prepared and underwent surface treatment. The results show that PVDF/PMMA/TiO₂ blown films present good mechanical properties, and acrylic acid surface-grafted films exhibit good adhesion capability and long-lasting hydrophilicity, making them attractive as encapsulation materials.     

Synthesis and electrorheological properties of polyaniline/silicon dioxide composites

This study was to synthesize the inherently conductive polymer polyaniline using an optimized process to prepare polyaniline/silicon dioxide (PANI/SiO₂) composites by in situ polymerization and ex situ solution mixing. PANI and PANI/SiO₂ composite films were prepared by drop-by-drop and spin-coating methods. The morphology of particles and films were examined by a scanning electron microscope (SEM). SEM measurements indicated that the SiO₂ were well-dispersed and isolated in composite films. The electrorheological (ER), characteristics of the PANI/SiO₂ composites were investigated. A volume fraction series (φ = 5–25 %) of the PANI/SiO₂/silicone oil dispersions were prepared and sedimentation stabilities were determined. An ER activity was observed from the samples, when subjected to external electric field strength thus, they were classified as smart materials. Some parameters affecting the ER properties of the dispersions such as volume fraction, shear rate, electric field strength, frequency, and temperature were investigated.     

Synthesis and photo activity of flower-like anatase TiO2 with {001} facets exposed

Developing photocatalysts with specific morphology promises good opportunities to discover the geometry-dependent properties. Herein, flower-like anatase TiO₂ assemblies with dominant {001} facets exposed were successfully synthesized via a simple, economical hydrothermal route with titanium sulfate and hydrofluoric acid. Their surface morphology and structure were investigated by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, and Brunauer-Emmet-Teller N₂ gas adsorption-desorption isotherms. The optical property and the photo-induced charge carriers of the flower-like TiO₂ were studied by UV-vis diffuse reflectance spectroscopy and transient photovoltage technique. The flower-like TiO₂ particles exhibited a good photocatalytic activity in degrading rhodamine B.     

Surface functionalization of BiFeO<Subscript>3</Subscript>: A pathway for the enhancement of dielectric and electrical properties of poly(methyl methacrylate)–BiFeO<Subscript>3</Subscript> composite films

A novel two-phase composite film is prepared by the solvent casting method employing poly(methyl methacrylate) (PMMA) as polymer matrix and bismuth ferrite (BFO) as ceramic filler. The surfaces of BFO are functionalized by proper hydroxylating agents to activate their chemical nature. The structural analysis of the composite films confirms that the composites made up of functionalized BFO (BFO-OH) have a distorted rhombohedral structure. The morphological analysis shows that BFO-OH particles are equally distributed over the polymer matrix. The -OH functionality of BFO-OH is confirmed by FTIR. The dielectric and electrical studies at a frequency range from 100 Hz to 1 MHz reveal that PMMA-(BFO-OH) composites have enhanced dielectric constant as well as electrical conductivities, much higher than that of unmodified composites. According to the ferroelectric measurement result, the hydroxylated composite film shows a superior ferroelectric behavior than that of the unmodified one, with a remanent polarization (2P_r) of 2.764 μC/cm².     

Synthesis and characterization of monodispersed polymer/polydiacetylene nanocrystal composite particles

Monodispersed polymer/polydiacetylenecomposite particles were synthesized by soap-free seeded emulsion polymerization of styrene andmethyl methacrylate; the products were characterized by XRD, SEM, TEM, UV-visible spectroscopy, and single particle scattering spectroscopy. In the synthesis process, polydiacetylene nanocrystals were found to act as inhibitor, and consequently a relatively low concentration was necessary. Different monomers lead to the differences in reaction condition and particle morphology; the PMMA composite particles were simpler in preparation than polystyrene particles, but the latter havebetter spherical morphology. The composite particles were composed of polymer shells and polydiacetylene cores, which kept their crystal structure and optical properties. A high percentage of cored particles could be achieved with optimized reaction conditions where the amount of seed was sufficient and the oily oligomer by-product was suppressed.     

A study incorporating nano-sized silica into PVC-blend-based polymer electrolytes for lithium batteries

Blends of poly(vinyl chloride)-poly(methyl methacrylate) (PVC/PMMA) and poly(vinyl chloride)-poly(ethylene oxide) (PVC/PEO) with lithium triflate (LiCF₃SO₃) as salt, ethylene carbonate (EC), and dibuthyl phthalate (DBP) as plasticizers and nano-sized silica (SiO₂) as filler, the first of its kind in such a study, were prepared using the solution-cast technique. This study affirmed that SiO₂ added PVC-PMMA and PVC-PEO-blend-based polymer electrolytes have the ability to retain their ionic conductivity and integrity even after 60 days of storage time at room temperature. The reduction of ionic conductivity values in PVC-PMMA-LiCF₃SO₃-DBP-EC:SiO₂-based and SiO₂-free membranes are 9 and 30%, respectively. When PVC-PEO-blend was used, the reduction of ionic conductivity values in PVC-PEO-LiCF₃SO₃-DBP-EC:SiO₂-based and SiO₂-free system was 16 and 40%, respectively, after 60 days of storage also at room temperature. The SiO₂-based complexes were also found to maintain their conductivity at higher temperatures of 60 °C and 90 °C with progressive storage times. This clearly shows that the SiO₂-induced stabilizing effect is maintained even at higher temperatures. Silica has brought the conductivity of polymer electrolytes into the useful realm for materials in lithium polymer battery applications.     

Optical properties of titanium dioxide nanoparticles/3-(2-benzothiazolyl)-7-N,N-diethylaminocoumarin/polymethyl methacrylate composite films

3-(2-benzothiazolyl)-7-N,N-diethylaminocoumarin organic laser dye-polymethyl methacrylate (PMMA) composite films doped with inorganic titanium dioxide (TiO₂) particles are fabricated by spin-coating technique. TiO₂ nanoparticles exhibit a strong influence on optical properties of the organic laser dye/PMMA composite films. The refractive index and absorbance (absorption intensity) of organic laser dye/PMMA composite film with micro- and nanoparticles of TiO₂ are reduced, compared to those without TiO₂ particles. The organic laser dye/PMMA composite film with TiO₂ nanoparticles has the lowest refractive index and absorbance values. Photoluminescence intensities of all systems exhibit a maximum peak around the excitation wavelength, close to that of the organic laser dye, at 450 nm and the minimum around the excitation wavelength of 350 nm. Photoluminescence intensity of the organic laser dye/PMMA composite film with TiO₂ microparticles is always the lowest at all excitation wavelengths. However, the photoluminescence intensity of the organic laser dye/PMMA composite film with TiO₂ nanoparticles has the highest value at excitation wavelengths of 330 and 380 nm, while the photoluminescence intensity of composite film without TiO₂ particles is more than that with nanoparticles at other excitation wavelengths.     

Surface morphology and structural analysis of fluorocarbon nano-rings formation through EBL and SiO2 plasma etching

This paper reports the formation of nano-scale ring-shaped fluorocarbon macromolecules during silicon dioxide SiO₂ reactive ion etching (RIE). This nanostructure was created on a SiO₂ substrate with poly methyl methacrylate (PMMA) mask during the RIE process, using trifluoromethane (CHF₃) and oxygen etchants. Variation in etching time results in the creation of square, double concentric, and flower-shaped nano-rings around SiO₂ micro-pits. In addition, increasing the etching times leads to an increase in ring width. The formation of these nano-rings is shown by a deposition of passivation layer, consisting of silicon oxide, Si_xO_y and fluorocarbon, C_xF_y, on sidewalls during SiO₂ etching in fluorocarbon plasma. Field Emission Scanning Electron Microscopy (FESEM) and Energy-dispersive X-ray (EDX) were utilized to investigate the morphology and the structure of the nano-rings. Results show that the flower-shaped nano-rings were created on the surface of silicon for 8 min of etching time. These fluorocarbon nano-rings could be used as nano-scale templates.     

Sub-glassy relaxation modes in PMMA and PMMA + SiO<Subscript>2</Subscript> hosts of non-polar perylene derivatives

The dielectric response of poly(methyl methacrylate) (PMMA) in solid solutions of perylene derivative laser dyes in PMMA and PMMA + SiO₂ has been studied by means of the thermally stimulated depolarization currents (TSDC) technique, with the aim to isolate molecular and phase interactions in the dye blends. The changes in characteristics of the β-relaxation mode of PMMA are interpreted with respect to the dissimilar local environments of the polar carboxy-methyl pendant groups of PMMA. An important "chemical" effect on the β relaxation mechanism recorded in the organic-inorganic composites, is the formation of hydrogen bonds between the acidic pore surfaces of SiO₂ and the acetate side-groups. Several "physical" effects produced by the chromophores and the geometrical confinement, like the modification of the monomer-to-polymer conversion rates, the polymer's free volume and the extent of the PMMA-SiO₂ interaction, are discussed.     

原位聚合制备P（AN-MMA）/TiO2复合聚合物电解质

以丙烯腈(AN)和甲基丙烯酸甲酯(MMA)为单体,在钛酸丁酯水解生成的TiO2粒子表面乳液聚合制备复合聚合物P(AN-MMA)/TiO2,并以此聚合物制备了多孔复合聚合物膜。采用核磁共振(NMR)、红外光谱(FT-IR)、差热分析(DSC)、扫描电镜(SEM)等对聚合物膜进行了表征,并测试了所得聚合物电解质的交流阻抗谱。结果表明,AN和MMA通过打开各自的C=C双键形成共聚物,TiO2在基体中分散均匀。当TiO2添加量为10.8%时,复合聚合物电解质的室温离子电导率达到1.12×10-3S/cm。     

Core/shell structured sSiO2/mSiO2 composite particles: The effect of the core size on oxide chemical mechanical polishing

In a typical chemical mechanical polishing (CMP) process, the type, morphology, structure, mechanical, and surface characteristics of abrasive particles play an important role in influencing the material removal process. The novel abrasive particles with special mechanical and/or tribochemical properties have been introduced into CMP processes for the improvement of surface quality and finishing efficiency. In this work, the composite particles containing solid silica (sSiO₂) cores and mesoporous silica (mSiO₂) shells were prepared via a developed Stöber method using cetyltrimethylammonium bromide as a structure-templating surfactant. The as-synthesized core/shell structured sSiO₂/mSiO₂ composite particles were characterized by powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen sorption–desorption measurements. The effect of the sSiO₂ core size of the composite particles on oxide CMP performance was evaluated in terms of surface roughness and material removal rate (MRR). The root-mean-square surface roughness (0.15–0.31 nm) of the polished substrates slightly increased with increasing of the sSiO₂ core size (168–353 nm) of the composites with a comparable mSiO₂ shell thickness (16–18 nm). The sSiO₂/mSiO₂ composite particles with a relatively smaller or larger core presented a relatively high MRR for silicon oxide films. These oxide CMP results could be rationalized according to the contact area mechanism and indentation-based mechanism, incorporating the total contact area and chemical reactivity between particles and wafers, and the indentation depth of an abrasive particle onto the substrate surface.     

Effect of C<Subscript>60</Subscript> fullerene additives on the thermal conductivity of poly(methyl methacrylate) films

The thermal conductivity of a composite comprising C₆₀ fullerene particles dispersed in a poly(methyl methacrylate) (PMMA) matrix exhibits a significant decrease, even at small concentrations of the fullerene. It is concluded that the main factor that determines this behavior is a decrease in the mean free-path length of phonons, which is caused by increasing inhomogeneity of the material and growing number of the scattering centers.