Preparation of hydrophobic organic-silicanano composites

In this paper, we use silica nanoparticles modified by methacryloxy propyl trimethoxylsilane (KH570) as the core material, and employ polymers including hexafluorobutyl methacrylate (HFMA), dodecafluoroheptyl methacrylate (DFMA) and acrylic ester as the shell materials to prepare the hydrophobic inorganic–organic hybrid nanocomposites with a seed emulsion polymerization strategy. The size, morphologyandproperties of the core-shell structured nanoparticles are investigated by TEM and SEM. The results showthat the polymer nanocomposite has three concentric layers with silica nanoparticles in the center, acrylic polymer as the internal shell and fluorosilicone polymer as the outmost shell. By controlling the ratio of the silica nanoparticles and monomers, we can achieve each composite particle has the core-shell structure with silica nanoparticles as the core and the thin layer of fluorosilicone polymer as the shell. Compared with the traditional polymer film, the nanocomposite film shows a hydrophobic property with a contact angle of up to 100 degree. Therefore, it is feasible to prepare hydrophobic organic–inorganic nanocomposites using the method proposed here.     

Grafting polymers to titania nanoparticles by radical polymerization initiated by diazonium salt

The grafting of biocompatible poly(hydroxyethyl) methacrylate (PHEMA) by a very simple method onto titanium dioxide nanoparticles is reported. The selected grafting process is based on the chemical reduction of diazonium salts by reducing agents in presence of the vinylic monomer. As previously demonstrated on flat surfaces, it leads to strongly grafted and stable polymer films and has many advantages residing in a short one-step reaction occurring at atmospheric pressure, ambient air and room temperature in water. TiO₂ nanoparticles were synthesized by laser pyrolysis, giving nanoparticles with controlled size and composition. The coating, the composition, the chemical structure, and the grafted PHEMA quantities of the resulting products were investigated by Transmission electron microscopy, Infrared-attenuated total reflection, X-ray photoelectron spectroscopy, and Thermogravimetric analysis. It was demonstrated that the PHEMA shell was successfully chemically grafted onto the surface of the TiO₂ core without any significant influence on the morphology of the nanoparticles.     

Thermal stabilities of vermiculites/polystyrene (VMTs/PS) naonocomposites via in-situ bulk polymerization

Serials of vermiculites/polystyrene (VMTs/PS) nanocomposites with different contents of organo-modified vermiculites (organo-VMTs) were successfully prepared by the in-situ bulk polymerization of styrene with the organo-VMTs as macromonomers. The thermogravimetric analysis TGA results showed that the thermal stabilities of the VMTs/PS nanocomposites prepared via the bulk polymerization were better than the pure polystyrene. And the maximum thermal degradation temperature of the nanocomposites increased with the increasing of the amount of the VMTs fillers added. The polymer grafted nanoparticles had lower thermal stabilities than the pure polystyrene because of the lower molecular weight of the grafted polymers. This also showed that the crosslink reactions occurred in the grafted polystyrene chains.     

Surface-initiated atom transfer radical polymerization of methyl methacrylate from magnetite nanoparticles at ambient temperature

The synthesis of methyl methacrylate (MMA) brush from the surface of magnetite nanoparticles (core-shell structure), from initiator moieties anchored covalently to the nanoparticles, via room temperature atom transfer radical polymerization (ATRP) is described. The surface-initiated polymerization was carried out from a surface-confined initiator containing a 2-bromoisobutyrate moiety with Cu(I)Br/PMDETA catalytic system. The initiator moiety was covalently anchored to the nanoparticles via a two step modification reaction scheme. Controlled polymerization was observed if ethyl-2-bromoisobutyrate (2-EiBrB) was added as a free/sacrificial initiator. A linear increase of molecular weight and a narrow molecular weight distribution of the PMMA formed in solution, provide evidence for a controlled surface-initiated polymerization, leading to surface-attached polymer brushes under mild conditions. The grafted PMMA provides good stability and dispersibility for the nanoparticles in organic solvents.     

Preparation of poly(methyl methacrylate) grafted titanate nanotubes by in situ atom transfer radical polymerization

This paper reports the successful preparation of core-shell hybrid nanocomposites by a 'grafting from' approach based on in?situ atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from titanate nanotubes (TNTs). Transmission electron microscope (TEM) images of the products provide direct evidence for the formation of a core-shell structure, possessing a hard core of TNTs and a soft shell of poly-MMA (PMMA). Fourier-transform infrared spectroscopy (FT-IR), hydrogen nuclear magnetic resonance ((1)H NMR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used to determine the chemical structure, morphology, and the grafted PMMA quantities of the resulting products. The grafted PMMA content was well controlled and increased with increasing monomer/initiator ratio. Further copolymerization of hydroxyethyl methacrylate (HEMA) with PMMA-coated TNTs as initiators was realized, illustrating the 'living' characteristics of the ATRP method used in this paper.     

Growth of Ag nanoparticles using plasma-modified multi-walled carbon nanotubes

This study presents a novel method for preparing multi-walled carbon nanotubes (MWNTs) grafted with a poly(2-hydroxyethyl methacrylate) (HEMA)-silver complex (CNTs-HEMA-Ag complex) through plasma-induced grafting polymerization. The characteristics of the MWNTs after being grafted with HEMA polymer are monitored by Fourier transform infrared (FT-IR) spectroscopy. The chelating groups in the HEMA polymer grafted on the surface of the CNTs-HEMA are the coordination sites for chelating silver ions, and are further used as nanotemplates for the growing of Ag nanoparticles (quantum dots). Transmission electron microscopy (TEM) reveals that the particle size of Ag nanoparticles on the CNT surfaces increases with the Ag(+) chelating concentration, reaction time, and reaction temperature. Moreover, the crystalline phase of Ag nanoparticles is identified by using x-ray diffraction (XRD). In addition, high-resolution x-ray photoelectron spectroscopy (XPS) is used to characterize the functional groups on the surface of the MWNTs after chemical modification through plasma treatment; it demonstrates that the growing amount of the Ag nanoparticles on the nanotubes increases with the Ag(+) chelating concentration due to the blocking effect of the Ag particles forming on the MWNTs.     

Fabrication of silicon/polymer composite nanopost arrays and their sensing applications

A novel technique is reported for fabricating silicon/polymer composite nanopost arrays by combining colloidal lithography and surface-initiated atom-transfer radical polymerization. The composite nanopost arrays possess a core/shell nanoarchitecture, with shells of poly(2-hydroxyethyl methacrylate) and cores of silicon nanoposts. The polymer brush possesses quasi-3D homogeneous nanoarchitectures due to the controllable polymerization process using the surface-initiated atom-transfer radical polymerization technique. The composite nanopost arrays are durable due to the particular nanoarchitectures. The backbone templates of the composites are silicon nanopost arrays directly etched from silicon substrates, and the polymer shell is covalently grafted from the arrays. The composite nanopost arrays exhibit vivid colors. Moreover, the colors of the composite nanopost arrays can be tuned from green to red by changing the thickness of fi lm. Specifically, the composite nanopost arrays can be used as sensors to rapidly detect water vapors with high stability and reproducibility. Many different functional surfaces could be prepared through this technique using other functional monomers.     

Structure characterization of Ag-Ga/poly(methyl methacrylate) nanoparticles

The Ag-Ga/poly(methyl methacrylate) nanoparticles were prepared in-situ by emulsion polymerization method under ultrasonic irradiation without any initiators or metal reductant. HRTEM, EDS and XRD experiments were performed to characterize the nanoparticles. The results indicated that the nanocomposite particles possessed core-shell structure with diameters of 80-200 nm, as well as excellent monodispersity. The phenomenon that the polymer forms the shell via layer-by-layer self-assembly was found. XRD proved the existence of Ag0.72Ga0.28 and the probability of new Ag-Ga alloy because of two unknown diffraction peaks.     

Polymer brushes on carbon nanotubes by thiol-lactam initiated radical polymerization of 2-hydroxyethyl methacrylate

Water-soluble polymer brushes with multi-walled carbon nanotubes (MWNTs) as backbones were synthesized by grafting 2-hydroxyethyl methacrylate (HEMA) from surface functionalized MWNTs via in situ surface thiol-lactam initiated radical polymerization. MWNTs were functionalized with 2-mercaptoethanol and used as initiators in the polymerization of HEMA in the presence of butyrolactam. FT-IR, XPS, 1H NMR, GPC and TGA were used to determine chemical structure and the grafted polymer quantities of the resulting product. The covalent bonding of PHEMA to the MWNTs dramatically improved the water dispersibility of MWNTs. The average thicknesses of the polymer brushes in the functionalized MWNTs were detected with electron microscopy (SEM and TEM) and images indicated that the nanotubes were coated with polymer layer.     

含氟硅聚氨酯-丙烯酸酯复合乳液的合成

以异佛尔酮二异氰酸(IPDI)、聚丙二醇(PPG)、端羟丙基硅氧烷(PDMS)、二羟甲基丙酸(DMPA)及1,4-丁二醇(BDO)为主要原料,采用溶液聚合法合成有机硅改性水性聚氨酯(SiPU)。以SiPU为种子乳液,并作为复合乳液的壳层,加入核层单体丙烯酸丁酯(BA)、甲基丙烯酸甲酯(MMA)及甲基丙烯酸十二氟庚酯(DFMA),通过乳液聚合得到氟硅改性聚氨酯-聚丙烯酸酯(FSiPUA)复合乳液。考察了PDMS及DFMA用量对乳液聚合过程及乳胶膜表面疏水性能的影响。采用FT-IR、CA、TEM、DSC及TG等表征复合乳液涂膜结构与性能。结果表明,FSiPUA复合乳液呈现核壳结构,在PDMS和DFMA的协同作用下,当PDMS和DFMA用量分别为m(PDMS)/m(PU)=5.5/100和m(DFMA)/m(AA)=15/100时,涂膜的表面自由能低至21.67 mN/m,对去离子水接触角达102.3°,涂膜耐热性有一定提高。     

Fabrication and biofunctionalization of selenium-polypyrrole core-shell nanoparticles for targeting and imaging of cancer cells

Selenium-polypyrrole core-shell nanoparticles are fabricated by an in-situ polymerization process and functionalized with transferrin for targeting and imaging of human cervical cancer cells. The shell thickness and chemical composition of the as-synthesized particles can be manipulated by controlling the precursor concentration. The presence of the polymer layer can greatly increase the thermal stability of the selenium nanoparticles. The presence of transferrin molecules on the surface of the core-shell nanoparticles can significantly enhance their cellular uptake. The tranferrin-conjugated core-shell nanoparticles can be potentially used for the targeting and imaging of cancer cells.     

纳米TiO2表面接枝甲基丙烯酸甲酯的聚合反应

利用表面接枝的方法,在纳米TiO2上接枝偶联剂-γMPS(3-(三甲氧硅基)丙基异丁烯酸)形成"杂化"单体,通过加入引发剂引发甲基丙烯酸甲酯(MMA)在粒子表面发生自由基聚合,形成PMMA/γ-MPS/TiO2纳米复合粒子。通过IR、元素分析、TGA等方法表征了PMMA/-γMPS/TiO2纳米复合粒子的结构,定量研究了TiO2/-γMPS单体接枝率和转化率,PMMA/-γMPS/TiO2纳米复合粒子的接枝率及其相应的影响因素。结果表明:PMMA以化学键的形式连接在纳米TiO2粒子表面并具有较高的接枝率。     

纳米银镓合金/聚甲基丙烯酸甲酯复合粒子的结构表征

在不加任何引发剂和金属还原剂的条件下, 超声辐射双原位引发乳液聚合制备纳米银镓合金/聚甲基丙烯酸甲酯(Ag-Ga/PMMA)复合粒子。利用HREM、 EDS、 XRD等对复合粒子进行了分析, 表明所制得的乳胶粒子具有典型的核壳结构, 粒径为80~200nm, 分布均匀, 单分散性好, 基本没有出现团聚。乳胶粒子中成壳部分的聚合物产生了一层层有序组装的现象。XRD证明, 有纳米合金Ag_0.72Ga_0.28存在; 此外还出现了2个新的衍射峰, 推断可能是新的银镓合金物质。      

纳米SiO2增韧增强聚丙烯的界面效应与逾渗行为

报道了聚苯乙烯辐射接枝纳米二氧化硅微粒(SiO₂-g-PS)填充聚丙烯(PP)的增强增韧作用,并从界面效应和逾渗行为的角度对此类复合材料的力学行为进行了分析。结果表明,接枝纳米微粒填充入聚合物时所形成的微粒/聚合物复合颗粒可以整体发挥协同作用,带来较强的界面效应,并有可能导致双逾渗行为,从而有利于发挥纳米微粒的特殊性能。     

Synthesis and characterization of PEG-iron oxide core-shell composite nanoparticles for thermal therapy

In this study, core-shell nanoparticles were developed to achieve thermal therapy that can ablate cancer cells in a remotely controlled manner. The core-shell nanoparticles were prepared using atomic transfer radical polymerization (ATRP) to coat iron oxide (Fe₃O₄) nanoparticles with a poly(ethylene glycol) (PEG) based polymer shell. The iron oxide core allows for the remote heating of the particles in an alternating magnetic field (AMF). The coating of iron oxide with PEG was verified through Fourier transform infrared spectroscopy and thermal gravimetric analysis. A thermoablation (55 °C) study was performed on A549 lung carcinoma cells exposed to nanoparticles and over a 10 min AMF exposure. The successful thermoablation of A549 demonstrates the potential use of polymer coated particles for thermal therapy.     

Thermal properties of PMMA/montmorillonite clay nanocomposites

Polymer/Clay offer tremendous improvement in wide range of physical and engineering properties for polymers with low filler loading. In nanotechnology polymer/clay nanocomposites use smectitetype clays that have layered structures. In this work, Poly (methyl methacrylate) (PMMA) was synthesized by free radical addition polymerization in the presence of high power ultrasound. The Poly (methyl methacrylate) (PMMA)-Montmorillonite (MMT) clay nanocomposites were synthesized by two different techniques viz., ultrasonic mixing and magnetic stirring. An analysis of the XRD data confirms that the composites are in the nanometer scale. The FTIR spectra show that there is strong interaction between the clay and the polymer that enhances the thermal stability. The thermal stability of the experimental nanocomposite prepared by the two processes is compared. Further analysis of XRD data shows that intercalation as well as exfoliation has taken place in both the types of nanocomposites preparation. An analysis of the TG, DTG curves reveal that the thermal stability is found to increase by nearly 30% for ultrasonic mixing than that of magnetic stirring.     

Use of polymer nanoparticles as functional nano-absorbents for low-molecular weight hydrophobic pollutants

To use amphiphilic polymer nanoparticles as a new nano-absorbent for improving environmental process, urethane acrylate nonionomer (UAN) chain having hydrophobic polypropylene oxide-based segment and hydrophilic polyethylene oxide-based segment at the same backbone was synthesized and dispersed as nanoparticles at water phase without using a surfactant or dispersion agent. These UAN nanoparticles were converted to crosslinked amphiphilic polymer (CAP) nanoparticles through soap-free emulsion polymerization and suspension agent-free suspension polymerization process. Emulsion polymerization process exhibited higher conversion of polymerization compared to suspension polymerization process. CAP nanoparticles showed interfacial activity and solubilize hydrophobic pollutants (phenanthrene and toluene) like surfactant micelles. This result indicates possible application of CAP nanoparticles as nano-absorbent for improving efficiency of soil washing and micellar-enhanced ultrafiltration (MEUF) process.     

Bi-layered polymer–magnetite core/shell particles: synthesis and characterization

Polymer magnetic core particles receive growing attention due to these materials owing magnetic properties which are widely used in different applications. The prepared composite particles are characterized with different properties namely: a magnetic core, a hydrophobic first shell, and finally an external second hydrophilic shell. The present study describes a method for the preparation of bi-layered polymer magnetic core particles (diameter range is 50–150 nm). This method comprises several steps including the precipitation of the magnetic iron oxide, coating the magnetite with oleic acid, attaching the first polymer shell by miniemulsion polymerization and finally introducing hydrophilic surface properties by condensation polymerization. The first step is the formation of magnetite nanoparticles within a co-precipitation process using oleic acid as the stabilizing agent for magnetite. The second step is the encapsulation of magnetite into polyvinylbenzyl chloride particles by miniemulsion polymerization to form a magnetic core with a hydrophobic polymer shell. The hydrophobic shell is desired to protect magnetite nanoparticles against chemical attack. The third step is the coating of magnetic core hydrophobic polymer shell composites with a hydrophilic layer of polyethylene glycol by condensation polymerization. Regarding the miniemulsion polymerization the influence of the amount of water, the mixing intensity and the surfactant concentration were studied with respect to the formation of particles which can be further used in chemical engineering applications. The resulting magnetic polymer nanoparticles were characterized by particle size measurement, chemical stability, iron content, TEM, SEM, and IR.     

Synthesis of dendrimer-stabilized gold-polypyrrole core-shell nanoparticles

Core-shell composite nanoparticles consisting of a gold core and polypyrrole shell were prepared and stabilized with the poly(amidoamine) dendrimer. An in situ redox polymerization technique was used in which pyrrole reduced Au3+ to Au and then oxidized to polypyrrole. The presence of gold nanoparticles as a core was characterized by its surface plasmon absorption peak at 534 nm. Fourier transform infrared spectroscopy confirmed the presence of polypyrrole on the nanoparticle surfaces. The average diameter of the core-shell nanoparticle is 8.7 +/- 1.8 nm with a shell thickness of approximately 1.5-2.0 nm as estimated from the transmission electron microscopy image. Dissolution of the Au core using KCN enabled the formation of hollow polymer nanospheres.     

硅丙乳液包覆Mg(OH)2核壳结构纳米粒子的制备与表征

为有效提高Mg(OH)_2纳米粒子在硅丙乳液中的相容性与分散稳定性,在油酸修饰Mg(OH)_2纳米粒子的基础上,以甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸与乙烯基三乙氧基硅烷为共聚单体,通过乳液聚合法制备出具有核壳结构的硅丙乳液包覆Mg(OH)_2复合材料。利用傅里叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)、透射电子显微镜(TEM)等测试手段对样品结构、形貌进行了表征。通过燃烧实验,研究了硅丙乳液包覆Mg(OH)_2纳米粒子对水性防火涂料阻燃性能的影响。结果表明,油酸通过酯化作用修饰在Mg(OH)_2纳米粒子表面,借助油酸分子中双键结构,丙烯酸类混合单体在纳米Mg(OH)_2表面完成聚合过程,形成以Mg(OH)_2纳米粒子为核、硅丙乳液为壳的复合材料。XRD与热分析表明经硅丙乳液包覆的纳米Mg(OH)_2晶体结构与热稳定性能未受影响。此外,掺杂0.1%(质量分数)的硅丙乳液包覆Mg(OH)_2可使水性防火涂料阻燃时间延长至113 min,较未掺杂水性涂料阻燃时间(91min)提高约23%。