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1.
We present the preparation of advanced antistatic and anticorrosion coatings of polystyrene (PS) incorporating a suitable amount of dodecylbenzenesulfonic acid (DBSA)‐doped SiO2@polyaniline (SP) core–shell microspheres. First, aniline‐anchored SiO2 (AS) microspheres that were about 850 nm in diameter were synthesized using the conventional base‐catalyzed sol–gel process with tetraethyl orthosilicate in the presence of N‐[3‐(trimethoxysilyl)propyl]aniline. SP core–shell microspheres were then synthesized by chemical oxidative polymerization of aniline monomers with ammonium persulfate as an oxidizing agent in the presence of the AS microspheres. The polyaniline shell thickness of the as‐prepared core–shell microspheres was estimated to be about 120 nm. The AS and SP microspheres were further characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy. The as‐synthesized DBSA‐doped SP core–shell microspheres were then blended into PS using N‐methyl‐2‐pyrrolidone as solvent and then cast onto a cold–rolled steel (CRS) electrode to obtain antistatic and anticorrosion coatings with a thickness of about 10 µm. The corrosion protection efficiency of the as‐prepared coating materials on the CRS electrode was investigated using a series of systematic electrochemical measurements under saline conditions. The enhanced corrosion protection ability of the PS/SP composite coatings may be attributed to the formation of a dense passive metal oxide layer induced by the redox catalytic effect of the polyaniline shell of the as‐synthesized core–shell microspheres, as evidenced by electron spectroscopy for chemical analysis and SEM observations. Moreover, the PS composite coating containing 10 wt% of the SP core–shell microspheres showed an electrical resistance of about 3.65 × 109Ω cm?2, which meets the requirements for antistatic applications. Copyright © 2012 Society of Chemical Industry  相似文献   

2.
Spherical and well‐dispersed silica/poly[styrene‐co‐(acrylic acid)] (SiO2/PSA) core–shell particles have been synthesized using an improved phase‐inversion process. The resulting particles were successfully used as supports for polyolefin catalysts in the production of polyethylene with broad molecular weight distribution. Through the vapor phase, instead of the liquid phase in the traditional process, a non‐solvent was introduced into a mixture of micrometer‐sized SiO2 and PSA solution. The core–shell structure of the resulting SiO2/PSA microspheres was confirmed using optical microscopy, scanning electron microscopy, Fourier transfer infrared spectrometry, thermogravimetric analysis and measurement of nitrogen adsorption/desorption isotherms. In order to avoid agglomeration of particles and to obtain a good dispersion of the SiO2/PSA core–shell microspheres, the non‐solvent was added slowly. As the concentration of PSA solution increased, the surface morphology of the core–shell particles became looser and more irregular. However, the surface area and the pore volume remained the same under varying PSA concentrations. The SiO2/PSA core‐shell microspheres obtained were used as a catalyst carrier system in which the core supported (n‐BuCp)2ZrCl2 and the shell supported TiCl4. Ethylene/1‐hexene copolymerization results indicated that the zirconocene and titanium‐based Ziegler–Natta catalysts were compatible in the hybrid catalyst, showing high activities. The resulting polyethylene had high molecular weight and broad molecular weight distribution. Copyright © 2010 Society of Chemical Industry  相似文献   

3.
Guangyu Liu  Han Zhang  Yongmei Wang 《Polymer》2007,48(20):5896-5904
Monodisperse silica/polydivinylbenzene (SiO2/PDVB) and silica/poly(ethyleneglycol dimethacrylate) (SiO2/PEGDMA) core-shell hybrid microspheres were prepared by a two-stage reaction with silica particles' grafting of 3-(methacryloxy)propyltrimethoxysilane (MPS) as core and PDVB or PEGDMA as shell, in which the MPS-modified silica core with diameter of 238 nm was synthesized by Stöber method and subsequently grafted with MPS as the first-stage reaction. The PDVB or PEGDMA shell was then encapsulated over the MPS-modified silica core by distillation precipitation polymerization of divinylbenzene (DVB) or ethyleneglycol dimethacrylate (EGDMA) in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) initiator as the second-stage reaction. The encapsulation of PDVB and PEGDMA on modified silica core particles was driven by the capture of DVB or EGDMA oligomer radicals via the vinyl groups on the surface of the modified silica cores during the second-stage polymerization in the absence of any stabilizer or surfactant. The shell thickness of the core-shell hybrid particles was controlled by the feed of DVB or EGDMA monomer during the polymerization. Hollow PDVB or PEGDMA microspheres with various shell thickness were further developed after selective removal of the modified silica cores with hydrofluoric acid. The resultant core-shell hybrid materials and hollow microspheres were characterized by transmission electron microscopy (TEM), and Fourier transform infrared spectra (FT-IR).  相似文献   

4.
Copolymers with different weight ratios of AA/PAS (acrylic acid/poly(DL-aspartic acid)) were synthesized and blended with sol-gel precursors to prepare water-soluble PAA–PAS/SiO2 inorganic/organic hybrid materials. The PAS polymer or its copolymer in PAA–PAS/SiO2 formed hydrogen bonds with SiO2 and the amorphous structure of the hybrid material varied with the weight ratio of PAA. The hybrid materials exhibited enhanced thermal resistance over the copolymer alone. All hybrid materials were water-soluble and relatively insoluble in organic solvents.  相似文献   

5.
Polysilsesquioxanes (PSQ)-based core–shell fluorinated polyacrylate/silica hybrid latex coatings were synthesized with PSQ latex particles as the seeds, and methyl methacrylate, butyl acrylate, 3-(trimethoxysilyl) propyl methacrylate (MPS)-modified SiO2 nanoparticles (NPs), 1H,1H,2H,2H-perfluorooctyl methacrylate (PFOMA) as the shell monomers by emulsifier-free miniemulsion polymerization. The results of Fourier transform IR spectroscopy, transmission electron microscopy, and dynamic light scattering suggested the obtained hybrid particles emerged with trilayer core–shell pattern. Contact angle analysis, x-ray photoelectron spectroscopy, and atom force microscopy results indicated that the hybrid film containing SiO2 NPs showed higher hydrophobicity, lower surface free energy and water absorption, in comparison with the control system (without SiO2 NPs). Compared with the control system, the hybrid latex film containing SiO2 NPs in the fluorinated polyacrylate shell layer showed the higher content of fluorine atoms and a rougher morphology on the film surface. Additionally, thermogravimetric analysis demonstrated the enhanced thermostability of PSQ-based nanosilica composite fluorinated polyacrylate latex film.  相似文献   

6.
A core–shell nanosilica (nano‐SiO2)/fluorinated acrylic copolymer latex, where nano‐SiO2 served as the core and a copolymer of butyl acrylate, methyl methacrylate, and 2,2,2‐trifluoroethyl methacrylate (TFEMA) served as the shell, was synthesized in this study by seed emulsion polymerization. The compatibility between the core and shell was enhanced by the introduction of vinyl trimethoxysilane on the surface of nano‐SiO2. The morphology and particle size of the nano‐SiO2/poly(methyl methacrylate–butyl acrylate–2,2,2‐trifluoroethyl methacrylate) [P(MMA–BA–TFEMA)] core–shell latex were characterized by transmission electron microscopy. The properties and surface energy of films formed by the nano‐SiO2/P(MMA–BA–TFEMA) latex were analyzed by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, and static contact angle measurement. The analyzed results indicate that the nano‐SiO2/P(MMA–BA–TFEMA) latex presented uniform spherical core–shell particles about 45 nm in diameter. Favorable characteristics in the latex film and the lowest surface energy were obtained with 30 wt % TFEMA; this was due to the optimal migration of fluorine to the surface during film formation. The mechanical properties of the films were significantly improved by 1.0–1.5 wt % modified nano‐SiO2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

7.
Poly(dimethylsiloxane) (PDMS)-based hybrid materials were prepared by the sol-gel method on Si wafers, Al and polystyrene (PS) substrates. The reaction was monitored by attenuated total reflectance-infrared (ATR-IR) spectroscopy. The hybrid materials have always one surface made in contact with air and one with a substrate. These surfaces were investigated by using tapping mode atomic force microscopy (AFM), X-ray photo-electron spectroscopy (XPS), low-energy ion scattering (LEIS) and dynamic contact angle (DCA) analysis. The hybrid sample surfaces made in contact with air and substrates appeared to have different structures. The former have a silica-free PDMS top layer of ∼2 nm thick; while in the latter cases, SiO2 are located at or just beneath the outermost atomic layer. In air and at room temperature, SiO2 are likely beneath the outermost atomic layer. In contact with water, polar -OH groups at the surface of SiO2 can easily stretch out to the outermost atomic layer. No correlation was found between the roughness of the surfaces and the amount of in situ formed SiO2 present in the materials.  相似文献   

8.
Hongfen Ji 《Polymer》2009,50(1):133-178
Tri-layer poly(methacrylic acid-co-ethyleneglycol dimethacrylate)/silica/poly(ethyleneglycol dimethacrylate) (P(MAA-co-EGDMA)/SiO2/PEGDMA) and P(MAA-co-EGDMA)/SiO2/polydivinylbenzene hybrid microspheres were prepared by distillation precipitation polymerization of ethyleneglycol dimethacrylate (EGDMA) and divinylbenzene (DVB) in the presence of 3-(methacryloxy)propyl trimethoxysilane (MPS)-modified P(MAA-co-EGDMA)/SiO2 microspheres as the seeds. The polymerization of EGDMA and DVB was performed in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator to coat the MPS-modified P(MAA-co-EGDMA)/SiO2 seeds through the capture of EGDMA and DVB oligomer radicals with the aid of vinyl groups on the surface of modified seeds in the absence of any stabilizer or surfactant. Monodisperse P(MAA-co-EGDMA)/SiO2 core-shell microspheres were synthesized by coating of a layer of silica onto P(MAA-co-EGDMA) microspheres via a sol-gel process, which were further grafted by MPS incorporating the reactive vinyl groups onto the surface to be used as the seeds for the construction of hybrid microspheres with tri-layer structure. Hollow poly(ethyleneglycol dimethacrylate) (PEGDMA) and poly(divinylbenzene) (PDVB) microspheres with movable P(MAA-co-EGDMA) core were subsequently developed after the selective etching of the silica mid-layer from the tri-layer hybrid microspheres in hydrofluoric acid. The morphology and structure of the tri-layer polymer hybrids and the corresponding hollow polymer microspheres with movable P(MAA-co-EGDMA) core were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra and X-ray photoelectron spectroscopy (XPS).  相似文献   

9.
Hybrid titanium catalysts supported on silica/poly(styrene‐co‐acrylic acid) (SiO2/PSA) core‐shell carrier were prepared and studied. The resulting catalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, laser scattering particle analyzer and scanning electronic microscope (SEM). The hybrid catalyst (TiCl3/MgCl2/THF/SiO2·TiCl4/MgCl2/PSA) showed core‐shell structure and the thickness of the PSA layer in the two different hybrid catalysts was 2.0 μm and 5.0 μm, respectively. The activities of the hybrid catalysts were comparable to the conventional titanium‐based Ziegler‐Natta catalyst (TiCl3/MgCl2/THF/SiO2). The hybrid catalysts showed lower initial polymerization rate and longer polymerization life time compared with TiCl3/MgCl2/THF/SiO2. The activities of the hybrid catalysts were enhanced firstly and then decreased with increasing P/P. Higher molecular weight and broader molecular weight distribution (MWD) of polyethylene produced by the core‐shell hybrid catalysts were obtained. Particularly, the hybrid catalyst with a PSA layer of 5.0 μm obtained the longest polymerization life time with the highest activity (2071 kg PE mol?1 Ti h?1) and the resulting polyethylene had the broadest MWD (polydispersity index = 11.5) under our experimental conditions. The morphology of the polyethylene particles produced by the hybrid catalysts was spherical, but with irregular subparticles due to the influence of PSA layer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

10.
《Ceramics International》2021,47(22):31681-31690
A functional Fe3O4/SiO2 core–shell abrasive was synthesized via hydrolysis of tetraethyl orthosilicate. A silica shell was successfully coated on a Fe3O4 core, resulting in a core-shell particle with an average diameter of 140 nm. The prepared core–shell abrasives was utilized for ultrasound-assisted magneto-rheological polishing (UAMP) of sapphire substrate. The experimental results showed that the Fe3O4/SiO2 core–shell abrasives exhibited a remarkable polishing performance for the sapphire material, resulting in smooth and detect-free surfaces with a high material removal rate (MRR) compared to mixed abrasives (Fe3O4 and SiO2) and pure Fe3O4 particles. The application of ultrasonic vibration to the sapphire wafer further improved the MRR, which was approximately 3.4 times higher than that of traditional magneto-rheological polishing. The largest MRR (1.974 μm/h) and comparatively low surface roughness (0.442 nm) of the polished sapphire wafer were achieved by UAMP with the Fe3O4/SiO2 core–shell abrasives. The polishing mechanism of the sapphire wafer is discussed in terms of chemical reactions and mechanical polishing.  相似文献   

11.
SiC powder was coated with SiO2 layer by chemical vapor deposition, and the SiC(core)/SiO2(shell) composite powder was consolidated to a SiC/SiO2 composite with a mosaic microstructure by spark plasma sintering (SPS) at 1923 K for 1.8 ks. The SiC(core)/SiO2(shell) powder with a 80–100 nm thick SiO2 layer resulted in a SiC/SiO2 composite with a relative density of 97% and hardness and fracture toughness of 17.1 GPa and 8.4 MPa m1/2, respectively.  相似文献   

12.
Novel pH‐responsive PEGylated hollow nanocapsules (HNCaps) were fabricated through a combination of distillation–precipitation copolymerization and surface thiol–ene ‘click’ grafting reaction. For this purpose, SiO2 nanoparticles were synthesized using the Stöber approach, and then modified using 3‐(trimethoxysilyl)propyl methacrylate (MPS). Afterward, a mixture of triethyleneglycol dimethacrylate (as crosslinker), acrylic acid (AA; as pH‐responsive monomer) and MPS‐modified SiO2 nanoparticles (as sacrificial template) was copolymerized using the distillation–precipitation approach to afford SiO2@PAA core–shell nanoparticles. The SiO2 core was etched from SiO2@PAA using HF solution, and the obtained PAA HNCaps were grafted with a thiol‐end‐capped poly(ethylene glycol) (PEG) through a thiol–ene ‘click’ reaction to produce PAA‐g‐PEG HNCaps. The fabricated HNCaps were loaded with doxorubicin hydrochloride (DOX) as a model anticancer drug, and their drug loading and encapsulation efficiencies as well as pH‐dependent drug release behavior were investigated. The anticancer activity of the drug‐loaded HNCaps was extensively evaluated using MTT assay against human breast cancer cells (MCF7). The cytotoxicity assay results as well as superior physicochemical and biological features of the fabricated HNCaps mean that the developed DOX‐loaded HNCaps have excellent potential for cancer chemotherapy. © 2020 Society of Chemical Industry  相似文献   

13.
Min Ji  Junyou Wang 《Polymer》2009,50(25):5970-2549
Hollow polymer microspheres with movable quaternary pyridinium polyelectrolyte (PE) cores and various functional groups on the shell-layers, such as hydroxyl, amide, and carboxyl, were prepared by the selectively etching of mid-silica layer with hydrofluoric acid from the corresponding poly(ethyleneglycol dimethacrylate-co-methacrylic acid)@poly(ethyleneglycol dimethacrylate- co-4-vinylpyridinium benzylchloride)/silica/polymer (P(EGDMA-co-MAA) @P(EGDMA-co-VPyBzCl)/SiO2/polymer) tetra-layer microspheres. The tetra-layer hybrid microspheres were synthesized by a multi-stage reaction process, which included the combination of distillation precipitation polymerization for the formation of polymer-layers and the hydrolysis of tetraethyl orthosilicate (TEOS) via a modified Stöber sol-gel procedure to afford silica layer. The efficient electrostatic interaction between the cationic pyridinium species on the surface of P(EGDMA-co-MAA)@P(EGDMA-co-VPyBzCl) cores and the negative charges on the silica species was essential to get monodisperse tri-layer P(EGDMA-co-MAA)@P(EGDMA-co-VPyBzCl)/SiO2 microspheres during the hydrolysis of TEOS. The functional polymer shell was encapsulated over 3-(methacryloxy)propyl trimethacrylate (MPS) modified tri-layer polymer/silica seeds by distillation precipitation copolymerizations of N,N′-methylenebisacrylamide (MBAAm) crosslinker and comonomers with different functional groups, including N-isopropylacrylamide (NIPAAm), 2-hydroxyethylmethacrylate (HEMA) and methacrylic acid (MAA), with 2,2′-azobisisobutyronitrile (AIBN) as an initiator in neat acetonitrile. The morphology and structure of the tetra-layer hybrid microspheres and the corresponding hollow microspheres with movable PE core and functional polymer shell-layer were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), ξ-potential, and dynamic light scattering (DLS).  相似文献   

14.
Fe2O3 particles with diameter of 3–5 nm were encapsulated in polymer spheres (styrene/butyl acrylate/acrylic acid terpolymer latex) by emulsion polymerization. Control of the pH value of the medium and modification of the latex prior to the second polymerization were of importance in determining the microstructure and morphology of the composite particles. The interaction between Fe2O3 and seed latex was confirmed by IR spectral changes of the surface groups of the latex particles. Mossbauer spectra gave evidence for the changes of electric density and electric field symmetry around Fe2O3, and surface photovoltage spectra indicated that the Fe2O3 particles were encapsulated in polymer. It was shown by all the results that the composite microspheres of size 80 nm had a core–shell structure with trilayers of seed latex core, Fe2O3 nanoparticles middle layer and polymer shell. © 1997 SCI.  相似文献   

15.
Both silica/polystyrene (SiO2/PS) and silica/polystyrene‐b‐polymethacryloxypropyltrimethoxysilane (SiO2/PS‐b‐PMPTS) hybrid nanoparticles were synthesized via surface‐initiated atom transfer radical polymerization (SI‐ATRP) from SiO2 nanoparticles. The growths of all polymers via ATRP from the SiO2 surfaces were well controlled as demonstrated by the macromolecular characteristics of the grafted chains. Their wettabilities were measured and compared by water contact angle (WCA) and surface roughness. The results show that the nanoparticles possess hydrophobic surface properties. The static WCA of SiO2/PS‐b‐PMPTS hybrid nanoparticles is smaller than that of SiO2/PS hybrid nanoparticles, meanwhile, the surface roughness of SiO2/PS‐b‐PMPTS hybrid nanoparticles is yet slightly rougher than that of SiO2/PS hybrid nanoparticles, which shows that the combination and competition of surface chemistry and roughness of a solid material can finally determine its wettability. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers  相似文献   

16.
设计制备了以疏水性聚苯乙烯(PS)为核、以亲水性聚丙烯酸(PAA)为壳的PS/PAA核壳结构复合微球。首先利用无皂乳液聚合法制备了亚微米级的PS微球,再以其为种子,利用种子无皂乳液聚合法制备PS/PAA核壳微球。在种子聚合阶段,选用AIBN当引发剂,经过红外光谱(IR)表征,表明当使用油溶性引发剂偶氮二异丁腈(AIBN),使其最终形成PS/PAA核壳结构微球。这种方法解决了亲水性较强的单体在以水为介质时在PS微球溶于少量的苯乙烯(St),并在引发聚合之前经过充分的吸附溶胀,可使亲水性单体AAc在PS种子微球表面聚合生成壳层,解决表面不容易直接聚合生成壳层的问题。  相似文献   

17.
This report describes the novel preparation of silica/polystyrene (SiO2/PS) core–shell composite nanospheres by in situ radical dispersion polymerization in an ionic liquid (IL). Silica nanoparticles were first surface modified by the silane coupling agent methacryloxypropyltrimethoxysilane (MPTMS), which is capable of copolymerizing with styrene and provided a reactive CC bond. Transmission electron microscopy (TEM) revealed core–shell morphology with smooth surfaces. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that almost all of the SiO2 nanoparticles were encapsulated by the polymer. The composite particles were also analyzed by FT-IR spectroscopy and thermogravimetric analysis (TGA). In principle, this simple and environmentally-friendly synthetic procedure can be employed to prepare other inorganic oxide-containing polymer composites.  相似文献   

18.
The core–shell catalysts with Cu and Cu/ZnO nanoparticles coated by mesoporous silica shells are prepared for CO2 hydrogenation to methanol. With the confined effect of silica shell, the size of Cu nanoparticles is only about 5.0 nm, which results in high activity for CO2 conversion. The CH3OH selectivity is enhanced significantly with the introduction of ZnO. The core–shell structured catalysts endow the Cu nanoparticles trapped inside with excellent anti-aggregation and no deactivation is observed with time-on-stream. Therefore, the core–shell Cu/ZnO@m-SiO2 catalyst exhibits the maximum CH3OH yield with high stability.  相似文献   

19.
Polyimide/silica (PI/SiO2) nanocomposite films with 10 wt % of silica content were prepared by sol–gel process under the conditions with and without additional water. The presence of additional water has great effect on the silica particle size and thus on the properties of the prepared PI/SiO2 films. The results indicated that with additional water, the silica particles formed before the imidization of poly(amic acid) (PAA) and aggregated with the increasing of temperature and degree of the proceeding imidization process. For the nonaqueous process, the hydrolysis condensation reaction of tetraethoxysilane (TEOS) did not occur until the imidization of PAA took place, and no silica particles were found in the unimidized PAA films. The hydrolysis–condensation reaction of TEOS was initiated simultaneously by the trace water released from the imidization reaction, the self‐catalysis mechanism of the approach provide a means of achieving uniformly dispersed silica particles formed in the PI matrix with particle size in the range of 30–70 nm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1579–1586, 2007  相似文献   

20.
A facile and novel strategy was reported on the fabrication of raspberry‐like SiO2/polystyrene (SiO2/PS) composite particles by emulsion polymerization in the presence of vinyl‐functionalized silica (vinyl‐SiO2) particles, which were prepared via a one‐step sol–gel process using vinyltriethoxysilane as the precursor. The submicron vinyl‐SiO2 particles were used as the core, and nanosized PS particles were then adsorbed onto the vinyl‐SiO2 particles to form raspberry‐like composite particles during the polymerization process. The composition, morphology, and structure of the vinyl‐SiO2 particles and the SiO2/PS hybrid particles were characterized by thermogravimetric analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy. Superhydrophobic surface can be constructed by directly depositing the raspberry‐like SiO2/PS composite particles on glass substrate, and the water contact angle can be adjusted by the styrene/SiO2 weight ratio. In addition, the superhydrophobic film possessed a strong adhesive force to pin water droplet on the surface even when the film was turned upside down. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers  相似文献   

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