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1.
The mechanism of silica particle formation in monomer microemulsions is studied using dynamic light scattering (DLS), atomic
force microscopy, small-angle X-ray scattering (SAXS), and conductivity measurements. The hydrolysis of tetraethylorthosilicate
(TEOS) in methylmethacrylate (MMA) microemulsions (MMA = methylmethacrylate) is compared with the formation of SiO2 particles in heptane microemulsions. Stable microemulsions without cosurfactant were found for MMA, the nonionic surfactant
Marlophen NP10, and aqueous ammonia (0.75 wt%). In the one-phase region of the ternary phase diagram, the water/surfactant
ratio (R
w) could be varied from 6 to 18. The DLS and SAXS measurements show that reverse micelles form in these water-in-oil (w/o)
microemulsions. The minimum water-to-surfactant molar ratio required for micelle formation was determined. Particle formation
is achieved from the base-catalyzed hydrolysis of TEOS. According to atomic force microscopy measurements of particles isolated
from the emulsion, the particle size can be effectively tailored in between 20 and 60 nm by varying R
w from 2–6 in heptane w/o microemulsions. For MMA-based microemulsions, the particle diameter ranges from 25 to 50 nm, but
the polydispersity is higher. Tailoring of the particle size is not achieved with R
w, but adjusting the particle growth period produces particles between 10 and 70 nm. 相似文献
2.
通过溶胶-凝胶法与半连续种子乳液聚合法相结合,以正硅酸乙酯(TEOS)制备的纳米SiO2为核,以甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)和甲基丙烯酸三氟乙酯(3FMA)的共聚物P(MMA/BA/3FMA)为壳,合成了SiO2@P(MMA/BA/3FMA)核-壳结构纳米复合粒子.为防止纳米SiO2的团聚,提高其与共聚物的结合力,用乙烯基三甲氧基硅烷(VTMS)对纳米SiO2进行改性.通过红外光谱、透射电子显微镜、动态激光散射粒度仪、静态接触角测试仪、X射线光电子能谱分析和热重分析等表征了乳液结构及膜性能.结果表明,获得的复合纳米粒子呈现粒径分布为40~50 nm的核-壳结构球型颗粒.由于含氟官能团的迁移使得氟元素在膜-空气界面富集,有效降低了膜的表面自由能.当3FMA质量分数达到25%时,膜表面自由能达到最低值(23.13 mN/m).随着3FMA含量的增加,共聚物初始热分解温度由350℃提高到390℃. 相似文献
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反相微乳液法制备纳米SiO2的研究 总被引:10,自引:0,他引:10
在壬基酚聚氧乙烯5醚(NP-5)/环己烷/氨水的反相微乳液体系中,进行正硅酸乙酯(TEOS)的水解、缩合反应,得到粒径在30~50 nm的单分散纳米SiO2胶体。红外光谱法(FTIR)及透射电子显微镜(TEM)观察证明了纳米SiO2粒子的生成。反相微乳液体系相图的研究表明,水相为氨水比纯水有较窄的W/O型微乳区。氨水微乳液是碱催化TEOS水解、缩合制备纳米SiO2粒子的适宜体系。当体系中TEOS的浓度增大时,粒子的粒径随之增大。降低NP-5 相似文献
5.
Yifei Yuan 《Journal of solid state chemistry》2011,184(12):3364-3367
Modified LaB6 particles with sizes ranging from 50 nm to 400 nm were added into polymethyl methacrylate (PMMA) matrix in order to investigate the effect of added LaB6 particles on optical properties of LaB6/PMMA composites. Method of in-situ polymerization was applied to prepare PMMA from raw material—methyl methacrylate (MMA), a process during which LaB6 particles were dispersed in MMA. Ultraviolet-visible-near infrared (UV-vis-NIR) absorption spectrum was used to study optical properties of the as-prepared materials. The difference in particle size could apparently affect the composites' absorption of visible light around wavelength of 600 nm. Added LaB6 particles with size of about 70 nm resulted in the best optical properties among these groups of composites. 相似文献
6.
PMMA/SiO2透明块体材料的热性能分析与微观结构表征 总被引:1,自引:0,他引:1
以正硅酸乙酯为前驱体,采用无溶剂水解技术,制备出了均一、稳定、透明的二氧化硅溶胶,通过透射电镜分析,粒径在100nm左右;在溶胶中加入甲基丙烯酸甲酯(MMA)和偶氮二异丁腈(AIBN),采用热固化的方式制备出透明的块体PMMA/SiO2杂化材料,通过差热分析、热重和透射电镜表征杂化材料的热性能和微观结构,实验结果表明:当体系中的SiO2含量超过20%时,杂化材料无明显的玻璃化转变温度;无机相均匀分散在有机相中,两相之间没有明显的相分离现象,制备出均一的杂化材料。 相似文献
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微乳法制备纳米TiO2 /SiO2的结构及光催化研究 总被引:1,自引:0,他引:1
Nanosized TiO2 and TiO2/SiO2 particles were prepared by hydrolysis of tetrabutyl titanate (TBOT) and tetraethyl orthosilicate (TEOS) in the TX-100 reverse microemulsion. These particles were characterized by TG-DSC, XRD, FTIR, TEM,N2 adsorption-desorption. Their photocatalytic activity was tested by degradation of methyl orange. The result shows that TiO2/SiO2 nanoparticles are with a monodispersed spherical phase and a uniform size distribution,and TiO2 particles are dispersed on the surface of SiO2. The band for Ti-O-Si vibration in FTIR was observed, the Ti-O-Si bond increased the stability of anatase TiO2, suppressed the phase transformation of titania from anatase to rutile. And due to the addition of SiO2, the average size of titania decreased from 38 nm in pure TiO2 to 5 nm in TiO2/SiO2. It was found, under UV light irradiation, TiO2/SiO2 particles showed higher activity than pure TiO2, and TiO2/SiO2(1/1) particles showed the highest photocatalytic activity on the photocatalytic decomposition of methyl orange, which was influenced by crystal structure, particle size, crystallinity and Surface area Characteristics. 相似文献
9.
S. Y. Park E. J. Park M. Y. Lee C. Park H. G. Kim E. D. Jeong K. T. Lim 《先进技术聚合物》2008,19(12):1803-1808
Al(OH)3/PMMA nanocomposites were prepared by the emulsion polymerization of methyl methacrylate (MMA) in the presence of surface‐functionalized Al(OH)3 particles. Nanosized Al(OH)3 particles were previously functionalized with a silane coupling agent, 3‐(trimethoxysilyl) propyl methacrylate (γ‐MPS), which was confirmed by FT‐IR and XRF analysis. The average size of seed particles was around 70 nm, and the density of the coupling agent on the particles was calculated to be 8.9 µmol m?2. The emulsion polymerization was attempted at relatively high solid content of 40–46 wt%. The ratio of the seed particles to MMA had a strong influence on the stability of latex as well as the morphology of composites. Nanocomposites where several PMMA nodules were attached on the surface of Al(OH)3 core were produced with stable latex emulsion when the weight percents of Al(OH)3 to MMA were below 20. In the case of higher ratio of 30%, however, the latexes became unstable with an aggregation, and the product morphology was in the shape of large composite. Thermogravimetric analysis showed an improved thermal stability of PMMA composites with the incorporation of Al(OH)3 nanoparticles. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
10.
Ying Huang Xinlong Wang Xiaoxun Jin Tongwen Wang 《Journal of Thermal Analysis and Calorimetry》2014,117(2):755-763
Graphene oxide (GO) is used as a stabilizer in the Pickering emulsion polymerization of methyl methacrylate (MMA) to prepare PMMA/GO nanocomposites. Transmission electron microscope studies of the emulsion polymerization products showed that the average diameter of nanocomposite particles was about 150 nm, the transparent GO flakes covered the surface of the particles, and were well dispersed in polymer matrix. The influence of GO on the thermal stability of PMMA was investigated by thermogravimetry analysis and differential scanning calorimetry. The results showed that the thermal stability and the glass transition temperature (T g) of PMMA/GO nanocomposites were improved obviously compared with PMMA. The apparent activation energy (E a) for the degradation process of PMMA/GO nanocomposites was evaluated by Kissinger method, which indicated that their E a s were much higher than those of PMMA both in nitrogen and air atmosphere. 相似文献
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Hybrid materials based on silicic acid and polymethyl methacrylate (PMMA) were prepared by in situ bulk polymerization of a silicic acid sol and MMA mixture. Silicic acid sol was obtained by tetrahydrofuran (THF) extraction of silicic acid from water. Silicic acid was prepared by hydrolysis and condensation of sodium silicate in the presence of 3.6 M HCl. As a comparative study, PMMA composites filled by silica particles, which were derived from calcining the silicic acid gel, were prepared by a comparable in situ polymerization. Each set of PMMA/silica composites was subjected to thermal and mechanical studies. Residual THF in PMMA/silicic acid composites impacted the properties of the polymer composites. With increase in silica content, the PMMA composites filled with silica particles showed improved thermal and mechanical properties, whereas a decrease in thermal stability and mechanical strength was found for PMMA composites filled with silicic acid dissolved in THF. With a better compatibility with polymer matrix, silicic acid sol shows better reinforcement than silica particles in PMMA films prepared via blending of the corresponding THF solutions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
13.
Summary: We previously discovered that structurally well-defined polymer/inorganic composite particles, i.e., poly(methyl methacrylate) (PMMA)/CaCO3/SiO2 three-component composite particles, can be achieved via reverse atom transfer radical polymerization (ATRP), using 2,2′-azo-bis-isobutyronitrile as initiator and CuII bromide as catalyst. In the present study, the influence of the mass ratio of CaCO3/SiO2 two-component composite particles to methyl methacrylate (MMA) on the rate and behavior of the polymerization was studied in detail. The results illustrate that increasing the mass ratio of CaCO3/SiO2 two-component composite particles will decrease the overall rate of polymerization of MMA under standard reverse ATRP conditions. Thermal properties of the obtained well-defined particles were characterized and determined by thermogravimetric analysis (TGA). The results indicate that well-defined PMMA chains grafted on the surface of CaCO3/SiO2 particles were only degraded by random chain scission of C C linkages within the PMMA chain, which is different from the degradation of PMMA chains prepared via traditional radical polymerization. This difference is reasonably ascribed to the difference between the end groups of PMMA prepared via reverse ATRP and that via traditional radical polymerization, which has been confirmed by end group analysis measured by 1H–NMR spectroscopy. 相似文献
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Water-in-oil (w/o) microemulsions of methyl methacrylate (MMA), acrylic acid (AA), sodium acrylamidostearate (NaAAS), and water were investigated. MMA, AA, and NaAAS could be terpolymerized in these microemulsions. For a composition of 54% MMA, 34% AA, 2% NaAAS, and 10% H2O, polymers of high molecular weights of about 1,000,000 were obtained between 3.5 to 24% polymer conversion. The system became a transparent gel when conversion exceeded 36%. Transparent solid terpolymer containing water up to 16% were also obtained after fully polymerizations of certain compositions. 相似文献
16.
Zgheib N Putaux JL Thill A D'Agosto F Lansalot M Bourgeat-Lami E 《Langmuir : the ACS journal of surfaces and colloids》2012,28(14):6163-6174
Stable methyl methacrylate (MMA) miniemulsions were successfully prepared using for the first time cerium oxide (CeO(2)) nanoparticles as solid stabilizers in the absence of any molecular surfactant. The interaction between MMA droplets and CeO(2) nanoparticles was induced by the use of methacrylic acid (MAA) as a comonomer. Both MAA and CeO(2) contents played a key role on the diameter and the stability of the droplets formed during the emulsification step. Cryo-transmission electron microscopy (TEM) images of the suspensions formed with 35 wt % of CeO(2) showed the presence of polydisperse 50-150 nm spherical droplets. More surprisingly, some nonspherical (likely discoidal) objects that could be the result of the sonication step were also observed. The subsequent polymerization of these Pickering miniemulsion droplets led to the formation of composite PMMA latex particles armored with CeO(2). In all cases, the conversion was limited to ca. 85%, concomitant with a loss of stability of the latex for CeO(2) contents lower than 35 wt %. This stability issues were likely related to the screening of the cationic charges present on CeO(2) nanoparticles upon polymerization. TEM images showed mostly spherical particles with a diameter ranging from 100 to 400 nm and homogeneously covered with CeO(2). Besides, for particles typically larger than 200 nm, a buckled morphology was observed supporting the presence of residual monomer at the end of the polymerization and consistent with the limited conversion. The versatility of these systems was further demonstrated using 35 wt % of CeO(2) and replacing MMA by n-butyl acrylate (BA) either alone or in combination with MMA. Stable monomer emulsions were always obtained, with the droplet size increasing with the hydrophobicity of the oil phase, pointing out the key influence of the wettability of the solid stabilizer. The polymerization of Pickering miniemulsion stabilized by CeO(2) nanoparticles proved to be an efficient strategy to form armored composite latex particles which may find applications in coating technology. 相似文献
17.
在位分散聚合聚甲基丙烯酸甲酯/二氧化硅纳米复合材料研究 总被引:70,自引:0,他引:70
应用在位分散聚合方法制备了分散相粒径介于130nm左右的聚甲基丙烯酸甲酯/二氧化硅PMMA/SiO2纳米复合材料,并利用SEM,DMA,TGA等手段研究了该体系的性能.结果表明,经表面处理的SiO2无机填料在复合材料基体中分散均匀,界面粘结好.SiO2填充粒子的用量对基体的热稳定性,动态力学行为,光学行为以及拉伸强度,弹性模量,断裂伸长率等力学性能都有较大影响 相似文献
18.
用甲基丙烯酸甲酯(MMA)作油相,反相胶束微乳液作为模板,制备了纳米氯化银(AgCl)粒子,再进行原位聚合制备了纳米氯化银/聚甲基丙烯酸甲酯(AgCl/PMMA)复合材料.透射电镜(TEM)分析表明,纳米AgCl的尺寸为20~80 nm.扫描电镜(SEM)测试表明纳米AgCl粒子均匀地存在于PMMA基材中.红外分析证明,胶束中水和表面活性剂AOT的羰基在MMA聚合后微观环境发生变化,纳米粒子同聚合物之间有吸附行为.动态力学(DMTA)分析复合材料,发现纳米AgCl粒子与聚合物之间存在强烈相互作用,形成了中间相层(interphase layer),改变了聚合物的动态力学性能. 相似文献
19.
The design and fabrication of novel poly(N-benzophenoyl methacrylamide-co-N-hydroxyethyl acrylamide)@SiO(2) composites are reported herein. These core-shell composites demonstrate orthogonal functionality, composed of photoreactive cores, containing a benzophenone (BPh) moiety and silica (SiO(2)) shells, enabling the utilization of the free hydroxyl groups via silane-based chemistry. The co-polymer cores, which are 1.28μm in diameter, are first obtained by dispersion polymerization of photoreactive (N-benzophenoyl methacrylamide) (polyBPMA) and N-Hydroxyethyl acrylamide (HEAA). Next, silica seeds with a 42nm diameter are deposited onto the surfaces as a result of the hydrolysis and the condensation of tetraethyl orthosilicate (TEOS) in a basic condition. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), FT-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), UV-spectrophotometry, X-ray photoelectron spectroscopy (XPS), and ζ-potential measurements were used to characterize the composites. The morphology and surface smoothness of the deposited silica nanoparticles (NPs) were found to strongly depend on a number of parameters such as the pH value of the medium, TEOS concentration, and the temperature. 相似文献
20.
An environmentally friendly one-pot synthetic method based on green chemistry was developed to prepare thermodynamically partially compatible poly(2,6-dimethyl-1,4-phenylene oxide)/poly(methylmethacrylate) (PPO/PMMA) alloy in water. The oxidative polymerization of 2,6-dimethylphenol in alkaline aqueous solution was firstly conducted and then methyl methacrylate (MMA) was added into the reactor before the end of polymerization. MMA could penetrate into PPO particles and then in situ reverse atom transfer radical polymerization (RATRP) of methyl methacrylate was initiated by 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride after the oxidative polymerization. Both the oxidative polymerization of 2,6-dimethylphenol and RATRP of methyl methacrylate were catalyzed by the complex of CuCl2 and 4-dimethylaminopyridine. Finally, thermodynamically partially compatible PPO/PMMA alloy was successfully prepared which possessed a multi-layer core-shell structure with two polymers embedded in each other. 相似文献