Synthesis of polystyrene/SiO2 composite microparticles by dispersion polymerization in supercritical fluid

A novel synthetic route to prepare polystyrene/SiO₂ composite microparticles in supercritical carbon dioxide (scCO₂) is presented. Silica particles with the size of 130 nm which were surface-modified with 3-(trimethoxysilyl) propyl methacrylate were used as seeds in the dispersion polymerization of styrene in the presence of a polymeric stabilizer, poly(1,1-dihydroheptafluorobutyl methacrylate-co-diisopropylaminoethyl methacrylate) to produce dry composite particles. The transmission electron microscopy analysis revealed that the composite microspheres contained several silica particles.     

MORPHOLOGY EVOLUTION OF POLY（St-co-BuA）/SILICA NANOCOMPOSITE PARTICLES SYNTHESIZED BY EMULSION POLYMERIZATION

Poly（St-co-BuA）/silica nanocomposite latexes were synthesized via conventional emulsion polymerization in the presence of 3-（trimethoxysilyl）propyl methacrylate modified colloidal nano-silica. The effects of surface property, particle size and content of colloidal nano-silica as well as the concentrations of monomer and surfactant on the morphology of nanocomposite latex particles were investigated by transmission electron microscope （TEM） and scanning electron microscope （SEM） in detail. Various interesting morphologies such as grape-like, Chinese gooseberry-like, pomegranate-like and normal core-shell structures were observed. Droplet nucleation mechanism competing with micelle nucleation mechanism was proposed to explain the morphological evolution of the nanocomposite particles.     

Nano-Templates from Thermoresponsive Poly(ethoxytriethyleneglycol acrylate) for Polymeric Nano-Capsules

Temperature responsive poly(ethoxytriethyleneglycol acrylate) (PETEGA) of Mn = 8000 and M_w/M_n = 2.30 was synthesized by ATRP. Dilute aqueous solutions of PETEGA exhibit lower critical solution temperature (LCST) at around 34 °C. We found that PETEGA can form nano-sized uniform colloidal aggregates (50-200 nm) above LCST either with or without an additional surfactant. Therefore PETEGA nano-aggregates were used as templates for the seeded free radical copolymerization of acrylamides or methacrylates together with a cross-linker to form acrylamide or methacrylate based core-shell particles. The formation of the PETEGA templates was investigated by dynamic light scattering (DLS) in order to find optimal conditions for obtaining narrow dispersed aggregates of desired sub-micron dimensions. Core-shell particles were characterized by DLS and scanning electron microscopy.     

Synthesis of tri-layer hybrid microspheres with magnetic core and functional polymer shell

Tri-layer magnetite/silica/poly(divinylbenzene) (Fe₃O₄/SiO₂/PDVB) core-shell hybrid microspheres were prepared by distillation precipitation polymerization of divinylbenzene (DVB) in the presence of magnetite/3-(methacryloxyl)propyl trimethoxysilane (MPS) modified silica core-shell particles as seeds. The polymerization of DVB was performed in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator to coat magnetite/MPS-modified silica particles through the capture of DVB oligomers with the aid of vinyl groups on the surface of inorganic seeds in absence of any stabilizer or surfactant. Other magnetite/silica/polymer tri-layer hybrid particles, such as magnetite/silica/poly(ethyleneglycol dimethacrylate) (Fe₃O₄/SiO₂/PEGDMA) and magnetite/silica/poly(ethyleneglycol dimethacrylate-co-methacrylic acid) (Fe₃O₄/SiO₂/P(EGDMA-co-MAA)) with various polarity and functionality, were also prepared by this procedure. Magnetite/silica/poly(N,N′-methylenebisacrylamide-co-methacrylic acid) (Fe₃O₄/SiO₂/P(MBAAm-co-MAA)) were synthesized with unmodified magnetite/silica particles as seeds. The resultant tri-layer hybrid particles were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), dynamic light scattering, and vibrating sample magnetometer (VSM).     

Biphasic synthesis of Au@SiO2 core-shell particles with stepwise ligand exchange

We report the synthesis of well-dispersed core-shell Au@SiO(2) nanoparticles with minimal extraneous silica particle growth. Agglomeration was suppressed through consecutive exchange of the stabilizing ligands on the gold cores from citrate to L-arginine and finally (3-mercaptopropyl)triethoxysilane. The result was a vitreophilic, stable gold suspension that could be coated with silica in a biphasic mixture through controlled hydrolysis of tetraethoxysilane under L-arginine catalysis. Unwanted condensation of silica particles without gold cores was limited by slowing the transfer across the liquid-liquid interface and reducing the concentration of the L-arginine catalyst. In-situ dynamic light scattering and optical transmission spectroscopy revealed the growth and dispersion states during synthesis. The resulting core-shell particles were characterized via dynamic light scattering, optical spectroscopy, and electron microscopy. Their cores were typically 19 nm in diameter, with a narrow size distribution, and could be coated with a silica shell in multiple steps to yield core-shell particles with diameters up to 40 nm. The approach was sufficiently controllable to allow us to target a shell thickness by choosing appropriate precursor concentrations.     

Design and synthesis of novel magnetic core-shell polymeric particles

A novel synthetic strategy was developed for the preparation of magnetic core-shell (MCS) particles consisting of hydrophobic poly(methyl methacrylate) cores with hydrophilic chitosan shells and gamma-Fe2O3 nanoparticles inside the cores via copolymerization of methyl methacrylate from chitosan in the presence of vinyl-coated gamma-Fe2O3 nanoparticles. The magnetic core-shell particles were characterized with transmission electron microscopy, field-emission scanning electron microscopy, particle size and zeta-potential measurements, vibrating sample magnetometry, and atomic force microscopy, respectively. The MCS particles were less than 200 nm in diameter with a narrow size distribution (polydispersity = 1.09) and had a good colloidal stability (critical coagulation concentration = 1.2 M NaCl at pH 6.0). Magnetization study of the particles indicated that they exhibited superparamagnetism at room temperature and had a saturation magnetization of 2.7 A m2/kg. The MCS particles were able to form a continuous film on a glass substrate, where magnetic nanoparticles could evenly disperse throughout the film. Thus, these new materials should be extremely useful in various applications.     

Synthesis of bifunctional core–shell particles with a porous zeolite core and a responsive polymeric shell

The aim of our work is the synthesis and characterization of colloidal core–shell particles with a zeolite core and an environmentally responsive shell. We have synthesized colloidal ZSM-5 zeolite and modified the surface with 3-(trimethoxysilyl)propyl methacrylate in order to introduce double bonds at the surface. The cross-linked polymeric shell was prepared by precipitation polymerization using the functionalized zeolite particles as seeds. We employed thermoresponsive poly(N-isopropylacrylamide) and pH-responsive poly(vinylpyridine) as the polymeric shell, respectively. The temperature- and pH-depending swelling and deswelling of the core–shell particles were characterized with dynamic light scattering techniques. Transmission electron microscopy pictures show the morphology of the synthesized particles. It is proposed that these types of bifunctional core–shell particles could be of use for controlled uptake and release applications and separation of molecules.     

ZnO/PS core-shell hybrid microspheres prepared with miniemulsion polymerization

The hybrid microspheres of ZnO/PS with different core-shell structures were prepared in miniemulsion polymerization. 3-(trimethoxysilyl)propyl methacrylate (MPS) was used as a functional co-monomer to enhance the surface polarity of ZnO nanoparticles and to prevent water from quenching the luminescent properties of ZnO. The morphology of hybrid particles was examined with a transmission electron microscope. The luminescence spectra were measured using a Shimadzu RF-5301 PC spectrofluorimeter (Xe source) at room temperature. The crystallization structure of samples was characterized with a Rigaku wide-angle X-ray diffractometer. The chemical composition and structure of the ZnO colloids, MPS-modified ZnO colloids, and ZnO/PS hybrid microspheres were analyzed with IR.     

Synthesis and characterization of magnetic and non-magnetic core-shell polyepoxide micrometer-sized particles of narrow size distribution

Core polystyrene microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxy ethanol. Uniform polyglycidyl methacrylate/polystyrene core-shell micrometer-sized particles were prepared by emulsion polymerization at 73 degrees C of glycidyl methacrylate in the presence of the core polystyrene microspheres. Core-shell particles with different properties (size, surface morphology and composition) have been prepared by changing various parameters belonging to the above seeded emulsion polymerization process, e.g., volumes of the monomer glycidyl methacrylate and the crosslinker monomer ethylene glycol dimethacrylate. Magnetic Fe(3)O(4)/polyglycidyl methacrylate/polystyrene micrometer-sized particles were prepared by coating the former core-shell particles with magnetite nanoparticles via a nucleation and growth mechanism. Characterization of the various particles has been accomplished by routine methods such as light microscopy, SEM, FTIR, BET and magnetic measurements.     

Synthesis of polystyrene/poly[2-(dimethylamino)ethyl methacrylate-stat-ethylene glycol dimethacrylate] core-shell latex particles by seeded emulsion polymerization and their application as stimulus-responsive particulate emulsifiers for oil-in-water emulsions

Surfactant-stabilized polystyrene (PS) latex particles with a mean hydrodynamic diameter of 155 nm were prepared by aqueous emulsion polymerization using 2,2'-azobis(2-amidinopropane) hydrochloride as a cationic radical initiator. Seeded aqueous emulsion copolymerizations of 2-(dimethylamino)ethyl methacrylate (DMA) and ethylene glycol dimethacrylate (EGDMA) were conducted in the presence of these PS particles to produce two batches of colloidally stable core-shell latex particles, in which the shell comprised a cross-linked P(DMA-stat-EGDMA) overlayer. Both the PS and PS/P(DMA-stat-EGDMA) latexes were characterized in terms of their particle size, morphology, and composition using dynamic light scattering, electron microscopy, and FT-IR spectroscopy, respectively. Using the PS/P(DMA-stat-EGDMA) latex particles as a pH-responsive particulate ('Pickering'-type) emulsifier, polydisperse n-dodecane-in-water emulsions were prepared at pH 8 that could be partially broken (demulsified) on lowering the solution pH to 3. These emulsions were characterized in terms of their emulsion type, mean droplet diameter, and morphology using electrical conductivity and Mastersizer measurements, optical microscopy, and scanning electron microscopy (using critical point drying for sample preparation).     

Preparation of starch-<Emphasis Type="Italic">g</Emphasis>-PMMA,starch-<Emphasis Type="Italic">g</Emphasis>-P(MMA/BMA) and starch-<Emphasis Type="Italic">g</Emphasis>-P(MMA/MA) nanoparticles and their reinforcing effect on natural rubber by latex blending: a comparative study

Nanoparticles including starch-graft-methylmethacrylate, starch-graft-(methylmethacrylate/methyl acrylate), starch-graft-(methyl methacrylate/butyl methacrylate) were synthesized via emulsifier-free emulsion polymerization and were blended with natural rubber latex at various mass ratios. Chemical structure of graft copolymers was confirmed by Fourier transform infrared. Transmission electron microscopy demonstrated the core-shell structures of the nanoparticles distributed uniformly around the natural rubble particles. The tensile strength of blend films was significantly enhanced by addition of graft copolymers. Besides, scanning electron microscopy and atomic force microscopy showed the blend film had smooth surface.     

Synthesis of Core-Shell (Pd-Au) Bimetallic Nanoparticles in Microemulsions

Palladium-gold core-shell nanoparticles were synthesized in the aqueous domains of water in oil microemulsions by the sequential reduction of H₂PdCl₄ and HAuCl₄. The nanoparticles were characterized by ultraviolet-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). The UV-vis spectra confirm the presence of palladium nanoparticles after reducing H₂PdCl₄. These particles have been used as seeds for the core-shell particles. UV-vis spectra show that, after reducing HAuCl₄, the surface plasmon absorption of the nanoparticles is dominated by gold, revealing the encapsulation of the palladium seeds. These results agree with crystallographic analysis performed with high-resolution TEM pictures, as well as with selected area electron diffraction. The TEM pictures show the core-shell nanoparticles with an average diameter of 9.1 nm, as compared with 5 nm for the palladium seeds, in good agreement with the used Pd:Au molar ratio.     

pH-responsive vesicles based on a hydrolytically self-cross-linkable copolymer

A new type of shape-persistent, pH-responsive vesicle was prepared by the self-assembly of a novel poly(ethylene oxide)-block-poly[2-(diethylamino)ethyl methacrylate-stat-3-(trimethoxysilyl)propyl methacrylate], PEO-b-P(DEA-stat-TMSPMA), copolymer. Vesicles were formed spontaneously in aqueous THF solution, with the hydrophilic PEO chains forming the corona and the pH-sensitive P(DEA-stat-TMSPMA) blocks being located in the membrane walls. Hydrolytic cross-linking within the hydrophobic membrane walls fixed the vesicle morphology. The resulting colloidally stable vesicles were characterized by 1H NMR, transmission electron microscopy (TEM), dynamic laser light scattering (DLS), and stopped-flow fluorescence experiments. The latter technique indicated that the permeability of the vesicle walls was sensitive to the pH of the aqueous solution, as expected. Gold-decorated vesicles were obtained by in situ reduction of AuCl4- anions to produce gold nanoparticles within the vesicle walls. (Yellow, hydrophilic PEO; green, pH-responsive DEA residues; blue, hydrolytically self-cross-linkable TMSPMA residues.)     

Synthesis of hafnium oxide-gold core-shell nanoparticles

Developing cheap composite nanoparticle systems that combines a high dielectric constant with good conductivity is important for the future of the electronic industry. In this study, two different sizes, 7.3 ± 2.2 and 5.6 ± 1.9 nm, of HfO(2)@Au core-shell nanoparticles are prepared by using a high-temperature reduction method. The core-shell nanoparticles are characterized by powder X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), and UV-visible absorption spectroscopy. HfO(2) exhibits no absorption in the visible region, but the HfO(2)@Au core-shell nanoparticles show a plasmon absorption band at 555 nm that is 25 nm red-shifted as compared to pure gold nanoparticles. According to transmission electron microscopy and energy dispersive X-ray analysis, the HfO(2) particles are coated with approximately three atomic layers of gold.     

Thermosensitive hollow Janus dumbbells

Thermosensitive hollow Janus dumbbells, consisting of two partially fused hollow poly (N-isopropylacrylamide) (PNIPAM) spheres, were prepared using dumbbell-shaped microgels as templates. One sphere has a shell completely made of PNIPAM while the other one has a hybrid shell, which is a poly(styrene-co-3-(trimethoxysilyl)propyl methacrylate) layer covered by PNIPAM. The morphology of hollow Janus dumbbells is fully characterized by cryo- and transmission electron microscopy, scanning force microscopy, and dynamic light scattering. Transmission electron microscopy demonstrates that the particles have a very narrow size distribution. The analysis by depolarized dynamic light scattering showed that the hollow Janus dumbbells exhibit a thermosensitive behavior comparable to the dumbbell-shaped microgels before the removal of the core.     

Organic/inorganic hybrid vesicles based on a reactive block copolymer

Presented in this communication is a novel hybrid vesicle with a cross-linked polyorganosiloxane wall based on a new reactive block copolymer, poly(ethylene oxide)-block-poly(3-(trimethoxysilyl)propyl methacrylate) (PEO-b-PTMSPMA), which was synthesized by atom transfer radical polymerization. The vesicles were prepared first by self-assembly of the block copolymer in a selective solvent, and then the PTMSPMA block was subjected to hydrolysis and polycondensation reaction to fix vesicle wall in the presence of triethylamine as a catalyst. Transmission electron microscopy, scanning electron microscopy, NMR, and light scattering have been used to characterize the vesicles.     

Surface plasmon spectroscopy of gold-poly-N-isopropylacrylamide core-shell particles

Highly uniform, core-shell microgels consisting of single gold nanoparticle cores and cross-linked poly-N-isopropylacrylamide (PNIPAM) shells were prepared by a novel, versatile protocol. The synthetic pathway allows control over the polymer shell thickness and its swelling behavior. The core-shell structure was investigated by electron microscopy and atomic force microscopy, whereas the swelling behavior of the shell was studied by means of dynamic light scattering and UV-vis spectroscopy. Furthermore, the latter method was used to investigate the optical properties of the hybrid particles. By modeling the scattering contribution from the PNIPAM shells, the absorption spectra of the gold nanoparticle cores could be recovered. This allows the particle concentration to be determined, and this in turn permits the calculation of the molar mass of the hybrid particles as well as the refractive index of the shells.     

Modification of gold nanoparticle composite nanostructures using thermosensitive core-shell particles as a template

We report the formation of novel thermosensitive hybrid core-shell particles via in situ synthesis of gold nanoparticles using thermosensitive core-shell particles as a template. The template core-shell particles, with cores composed mainly of poly(glycidyl methacrylate) (GMA) and shells composed mainly of poly(N-isopropylacrylamide) (PNIPAM), were synthesized in aqueous medium, and functional groups such as thiol groups were incorporated into each particle. We found that these particles containing thiol groups were effective for the in situ synthesis of gold nanoparticles in long-term storage. The obtained hybrid particles exhibited a reversible color change from red to purple, which originated from the surface plasmon resonance of gold nanoparticles and which was temperature-dependent in the range of 25-40 degrees C. In addition to their thermosensitive property, the hybrid particles exhibited the unique characteristic of uniform distribution on a solid substrate. The particles obtained by this approach have potential thermosensitive applications such as in sensors and photonic or electronic devices.     

Gold nanoparticle localization at the core surface by using thermosensitive core-shell particles as a template

We report novel thermosensitive hybrid core-shell particles via in situ gold nanoparticle formation using thermosensitive core-shell particles as a template. This method for the in situ synthesis of gold nanoparticles with microgel interiors offers the advantage of eliminating or significantly reducing particle aggregation. In addition, by using thermosensitive microgel structures in which the shell has thermosensitive and gel properties in water--whereas the core itself is a water-insoluble polymer--we were able to synthesize the gold nanoparticles only at the surface of the core, which had reactive sites to bind metal ions. After the gold nanoparticles were synthesized, electroless gold plating was carried out to control the thickness of the gold nanoshells. The dispersions of the obtained hybrid particles were characterized by dynamic light scattering and UV-vis absorption spectroscopy, and the dried particles were also observed by electron microscopy. Adaptation of the technique shown here will create a number of applications as optical, electronic, and biomedical functional materials.     

聚甲基丙烯酸甲酯-牛血清白蛋白核壳纳米粒子在金表面的吸附过程及在传感器中的应用

利用铜离子引发体系, 制备出核层为聚甲基丙烯酸甲酯(PMMA)壳层为牛血清白蛋白(BSA)的PMMA-BSA核壳纳米粒子. 通过透射电子显微镜(TEM)表征, 直接观察到PMMA-BSA纳米粒子的核壳结构.结合X射线光电子能谱(XPS)测试, 分析PMMA-BSA纳米粒子的表面成分, 证明PMMA-BSA纳米粒子的壳层是BSA. 利用带耗散的石英晶体微天平(QCM-D)研究了PMMA-BSA纳米粒子在金片表面的吸附行为. 频率的迅速下降, 耗散因子的快速上升, 说明PMMA-BSA粒子快速地吸附到金片表面. 利用磷酸盐缓冲液反复冲洗时, 频率和耗散没有变化, 表明PMMA-BSA 纳米粒子在金片上吸附较牢固. 以金电极为基底电极, 吸附PMMA-BSA纳米粒子后, 利用戊二醛修饰粒子壳层, 再通过氨基与醛基的反应来固定葡萄糖氧化酶, 制备出电流型葡萄糖传感器. 电化学测试表明该传感器对葡萄糖具有良好的电流响应, 在0.3 V的工作电位下, 响应电流与葡萄糖浓度在0.20-5.85 mmol·L^-1范围内呈现出较好的线性关系, 相关系数为0.989. 传感器的灵敏度高达28.6 μA·L·mmol^-1·cm^-2, 响应时间仅为11 s. 传感器还具有良好的稳定性, 在25℃下储存30 d, 响应电流仅下降了16%.