受限空间内聚苯乙烯微粒的制备

以(N,N-二甲氨基-4-吡啶)五氰合铁(II)封端的聚氧丙烯聚氧乙烯共聚物(EPE-Fe)与苯乙烯在水中自组装形成纳米体系(EPE-Fe-St), 在纳米尺度受限空间内进行了苯乙烯自由基聚合, 制备了聚苯乙烯微球(EPE-Fe-PS). 用Fe³⁺对自组装体系的纳米球壳进行固化后形成Fe-EPE-Fe-St 体系, 聚合后也制备了聚苯乙烯微球(Fe-EPE-Fe-PS). 研究结果表明,制备了粒径为60～200 nm 的不同粒径单分散聚苯乙烯微球, 聚合温度对纳米Fe-EPE-Fe-St 体系粒径影响较小, 而对EPE-Fe-St 体系较大. 在受限空间内苯乙烯的自由基聚合可得到数均分子量超过70 万的聚苯乙烯; 自组装体系中引发剂量增多使聚苯乙烯分子量下降, 聚合温度上升也使分子量下降, 而增加自组装的EPE-Fe 用量可增加聚苯乙烯的分子量. 两种受限条件下的聚苯乙烯微球的玻璃化转变温度(T_g)在90～135 ℃之间, 纳米反应器壳层的硬化提高了聚苯乙烯微球的T_g.     

Dry etching of colloidal crystal films

Two types of non-close-packed colloidal crystal films were prepared by etching the films made of polystyrene nanospheres using a hyperthermal neutral beam of oxygen gas. Etching without sintering above glass transition temperature of the polymer particles resulted in the non-close-packed structure of the nanospheres, in which polystyrene nanospheres in different lattice planes touched each other due to the reduction in the size of the nanospheres that occurred during the etching process. In contrast, a different non-close-packed structure with inter-connecting networks between etched nanospheres was generated by annealing of the colloidal crystal and a subsequent etching process. The photonic bandgap could be tuned during this dry etching of colloidal photonic crystals. This connected open structure could be used as a template for a silica inverse opal by chemical vapor deposition. An alternative dry etching process, reactive ion etching, mainly affected the morphology of particles near the top surface, and only a slight change in the stop band position of the colloidal crystal film was observed.     

单分散空心SiO2纳米微球的合成与表征

聚乙烯吡咯烷酮(PVP)功能化的聚苯乙烯(PS)粒子在SiO2包覆的同时被乙醇/氨水介质溶解, 得到了单分散空心SiO2纳米微球. 该空心SiO2纳米微球的尺寸和形态可以通过PVP, NH4OH和正硅酸乙酯(TEOS)的用量来调节. PVP用量增加导致PS粒子变小, 从而得到较小的空心SiO2纳米微球; NH4OH用量增加, 空心SiO2纳米微球表面变得粗糙; TEOS用量增加, 空心SiO2纳米微球的壳层厚度增加. 包覆(溶解)温度是控制空心SiO2纳米微球形成的最有效手段. 在70 ℃的包覆(溶解)温度下可以获得全部空心的SiO2纳米微球.     

Two‐dimensional non‐close‐packed arrays of nanoparticles via core‐shell nanospheres and reactive ion etching

Nanosized PTFE/polystyrene core‐shell particles were prepared by seed emulsion polymerization technique starting from PTFE seeds of 20 nm. At the end of the reaction, no residual PTFE nor secondary nucleation was observed and by appropriately choosing the ratio between the monomer and the PTFE seed it was possible to obtain particles, with predetermined size in the range 60–100 nm, featuring an extremely narrow size distribution. These particles were successfully employed as building blocks for the preparation of large scale nanosized monolayers through the floating technique. Reactive ion etching was further applied to modulate the size characteristics of the resulting 2D ordered nanostructure. Although for relatively short RIE times a peculiar continuous morphology was observed in which the particles are interconnected through thin arms, on further increasing the RIE time a well‐organized 2D arrangement of particles with size of about 30 nm was obtained. Considering the shell as an expendable ordering and spacing tool, the use of core‐shell nanospheres allows a wide variety of controlled morphologies to be designed and prepared thus opening new perspectives for nanostructure fabrication processes through nanosphere lithography (NSL). Copyright © 2011 John Wiley & Sons, Ltd.     

Superparamagnetic Ag@Fe3O4 core-shell nanospheres: fabrication, characterization and application as reusable nanocatalysts

Superparamagnetic Ag@Fe(3)O(4) nanospheres with core-shell nanostructures have been prepared by a facile one-pot method. The diameter of the as-synthesized nanospheres was about 200 nm and the core sizes were between 50 and 100 nm. By varying the concentrations, particles with tunable core size and total size are successfully achieved. Time dependent experiments were constructed to investigate the synthesis mechanism, which indicated that the present method corresponded to an Ostwald ripening progress. The BET area of the core-shell nanospheres is about 22.6 m(2)/g and this result indicates that the product shows a porous character. The saturated magnetization of the superparamagnetic Ag@Fe(3)O(4) nanospheres is 27.4 emu g(-1) at room temperature, which enables them to be recycled from the solution by simply applying a small magnet. Due to the unique nanostructure, these particles show high performance in catalytic reduction of 4-nitrophenol and can be used as reusable nanocatalysts.     

Micelles of poly(styrene-b-2-vinylpyridine-b-ethylene oxide) with blended polystyrene core and their application to the synthesis of hollow silica nanospheres

Core-shell-corona (CSC) micelles of asymmetric triblock copolymer, poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-PVP-PEO), containing polystyrene homopolymer (homo-PS) in the core were successfully prepared in aqueous media. The influence of homo-PS contents over the formation of the micelles was investigated thoroughly by various techniques such as dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence spectroscopy. It was found that the size of the PS core of the micelle was increased by the addition of homo-PS as observed by DLS and TEM techniques. The SEM and TEM measurements confirm the spherical morphology of the micelles and enlargement of PS core over the addition of homo-PS. The increase in the PS core volume of the PS-PVP-PEO micelles is attributed to the insertion of homo-PS in the PS core. The micelles have also been demonstrated as facile soft templates for synthesis of hollow silica nanospheres. The average diameter of the spherical hollow particles could be tuned between 30.6 and 38.8 nm with cavity sizes ranging from 20.7 to 28.5 nm using tetramethoxysilane as silica precursors under mild acidic conditions. The facile synthesis of hollow silica using the CSC micelles with different homo-PS contents indicates that the hollow void size can be controlled within a range of several nanometers.     

聚苯乙烯球模板法制备二氧化钛纳米环

TiO2 nanorings were synthesized using the polystyrene nanospheres of 85 nm prepared by micro-emulsion polymerization as template. The result TiO2 nanorings were characterized by FE-SEM and XRD. Results showed that the inner diameter of the TiO2 nanorings matched size of the polystyrene nanospheres used, and the thickness with nanometer size depended on that of the TiO2 gel coated on the PS surface.     

In situ polymerization and morphology of polypyrrole obtained in water‐soluble polymer templates

Several water‐soluble polymers were used as templates for the in situ polymerization of pyrrole to determine their effect on the generation of nanosized polypyrrole (PPy) particles. The polymers used include: polyvinyl alcohol (PVA), polyethylene oxide (PEO), poly(vinyl butyral), polystyrene sulfonic acid, poly(ethylene‐alt‐maleic anhydride) (PEMA), poly(octadecene‐alt‐maleic anhydride), poly(N‐vinyl pyrrolidone), poly(vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate), poly(N‐isopropyl acrylamide), poly(ethylene oxide‐block‐propylene oxide), hydroxypropyl methyl cellulose, and guar gum. The oxidative polymerization of pyrrole was carried out with FeCl₃ as an oxidant. The morphology of PPy particles obtained after drying the resulting aqueous dispersions was examined by optical microscopy, and selected samples were further analyzed via atomic force microscopy. Among the template polymers, PVA was the most efficient in generating stable dispersions of PPy nanospheres in water, followed by PEO and PEMA. The average size of PPy nanospheres was in the range of 160 nm and found to depend on the molecular weight and concentration of PVA. Model reactions and kinetics of the polymerization reaction of pyrrole in PVA were carried out by hydrogen ¹H NMR spectroscopy using ammonium persulfate as an oxidant. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Polymerizable Molecular Silsesquioxane Cage Armored Hybrid Microcapsules with In Situ Shell Functionalization

We prepared core–shell polymer–silsesquioxane hybrid microcapsules from cage‐like methacryloxypropyl silsesquioxanes (CMSQs) and styrene (St). The presence of CMSQ can moderately reduce the interfacial tension between St and water and help to emulsify the monomer prior to polymerization. Dynamic light scattering (DLS) and TEM analysis demonstrated that uniform core–shell latex particles were achieved. The polymer latex particles were subsequently transformed into well‐defined hollow nanospheres by removing the polystyrene (PS) core with 1:1 ethanol/cyclohexane. High‐resolution TEM and nitrogen adsorption–desorption analysis showed that the final nanospheres possessed hollow cavities and had porous shells; the pore size was approximately 2–3 nm. The nanospheres exhibited large surface areas (up to 486 m² g^?1) and preferential adsorption, and they demonstrated the highest reported methylene blue adsorption capacity (95.1 mg g^?1). Moreover, the uniform distribution of the methacryloyl moiety on the hollow nanospheres endowed them with more potential properties. These results could provide a new benchmark for preparing hollow microspheres by a facile one‐step template‐free method for various applications.     

Impact of initiators in preparing magnetic polymer particles by miniemulsion polymerization

Sub-micron sized polystyrene particles containing magnetite more than 30 wt.% were prepared by miniemulsion polymerization with commercially available ferricolloid. The effects of some water-soluble initiators and/or oil-soluble initiators on the particles characteristics, such as the size, morphology, magnetic properties and colloidal stability, were studied. The size of monomer droplets/polymer particles increased from 60 to 300 nm during polymerization, keeping magnetic in core when potassium persulfate (KPS) or ammonium persulfate (APS) was used as the sole initiator. These particles were easily separated from the medium within short time scale in external magnetic field, while such characteristics were controlled by the amount of persulfate used for the polymerization. In contrast, when 2,2′-azobis isobutyronitrile (AIBN) was used as the initiator, the size of droplets/particles was retained to be 90 nm at the most and magnetite nanoparticles located at the surface of polystyrene particles, which were so colloidally stable that they were not separated in external magnetic field. The above-mentioned effect of initiators on particle size in persulfate system was likely originated from the decrease of pH value and the increase of ionic strength, which induced the fusion of droplets/particles containing magnetite. Mixed-initiators system resulted in intermediate characteristics, compared with each initiator system. The location of magnetite in the particle seems to depend on where initiation/polymerization occurred in each initiator system.     

Facile Synthesis of Uniform Zinc-blende ZnS Nanospheres with Excellent Photocatalytic Activity toward Methylene Blue Degradation

Uniform and well-dispersed Zn S nanospheres have been successfully synthesized via a facile chemical route. The crystal structure, morphology, surface area and photocatalytic properties of the sample were characterized by powder X-ray diffraction(XRD), scanning electron microscopy(SEM), Brunauer-Emmett-Teller(BET) and ultraviolet-visible(UV-vis) spectrum. The results of characterizations indicate that the products are identified as mesoporous zinc-blende ZnS nanospheres with an average diameter of 200 nm, which are comprised of nanoparticles with the crystallite size of about 3.2 nm calculated by XRD. Very importantly, photocatalytic degradation of methylene blue(MB) shows that the as-prepared Zn S nanospheres exhibit excellent photocatalytic activity with nearly 100% of MB decomposed after UV-light irradiation for 25 min. The excellent photocatalytic activity of ZnS nanospheres can be ascribed to the large specific surface area and hierarchical mesoporous structure.     

Synthesis of ZnS Nanospheres in Microemulsion Containing Cationic Gemini Surfactant

The reverse microemulsion containing cationic gemini surfactant trimethylene‐1,3‐bis(dodecyldimethyl ammonium bromide) (12‐3‐12, 2Br^?) is applied to synthesize ZnS nanospheres. Narrow size distributed ZnS nanospheres with controllable size and uniform morphology are successfully fabricated by direct reaction of ZnCl₂ and Na₂S in the reverse microemulsion systems. Except for the appearance of large aggregates owing to quantum size effects when the incubation time is 2 h, with increasing the incubation time from 12 to 48 h, the diameter of the ZnS nanosphere can be controlled as 20–25 nm and 140 nm, respectively. X‐ray diffraction (XRD), transmission electron microscopy (TEM), and UV‐visible absorption spectroscopy are applied to characterize the resulting ZnS nanoparticles. In the system used in the present study uniform nanosphere morphology can be synthesized, with the incubation time as an important factor in controlling the size of as‐prepared products.     

Highly Stable Amorphous Calcium Phosphate Porous Nanospheres: Microwave‐Assisted Rapid Synthesis Using ATP as Phosphorus Source and Stabilizer,and Their Application in Anticancer Drug Delivery

Highly stable amorphous calcium phosphate (ACP) porous nanospheres with a relatively uniform size and an average pore diameter of about 10 nm have been synthesized by using a microwave‐assisted hydrothermal method with adenosine 5′‐triphosphate disodium salt (ATP) as the phosphorus source and stabilizer. The as‐prepared ACP porous nanospheres have a high stability in the phosphate buffer saline (PBS) solution for more than 150 h without phase transformation to hydroxyapatite, and the morphology and size were essentially not changed. The important role of ATP and effects of experimental conditions on the formation of ACP porous nanospheres were also investigated. The ACP porous nanospheres were characterized by X‐ray powder diffraction (XRD), Fourier‐transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This method is facile, rapid, surfactant‐free and environmentally friendly. The as‐prepared ACP porous nanospheres are efficient for anticancer drug (docetaxel) loading and release. The ACP porous nanosphere drug‐delivery system with docetaxel shows a high ability to damage tumor cells, thus, is promising for the application in anticancer treatment.     

Fabrication of size-tunable gold nanoparticles array with nanosphere lithography, reactive ion etching, and thermal annealing

Two-dimensional ordered arrays of gold (Au) nanoparticles were fabricated using two different variants of the nanosphere lithography technique. First, ordered arrays of polystyrene nanospheres on Si substrate were used as deposition masks through which gold films were deposited by electron beam evaporation. After the removal of the nanospheres, an array of triangular Au nanodisks was left on the Si substrate. After thermal annealing at increasing temperature, systematic shape transition of the nanostructures from original triangular Au nanodisks to rounded nanoparticles was observed. This approach allows us to systematically vary the size and morphology of the particles. In the second and novel technique, we made use of reactive ion etching to simultaneously reduce the dimension of the masking nanospheres and create arrays of nanopores on the substrate prior to the deposition of the Au films. These samples were subsequently annealed, which resulted in size-tunable and ordered Au nanoparticle arrays with the nanoparticles nested in the nanopores of the templated substrate. With the nanoparticles anchored in the nanopores, the substrate could be useful as a template for growth of other nanomaterials.     

Preparation of multilayered gold-silica-polystyrene core-shell particles by seeded polymerization

A preparation method for multilayered gold-silica-polystyrene core-shell composite particles is proposed. The gold-silica core-shell particles of 192-nm-sized, synthesized by coating the 18-nm-sized gold particles with silica by a seeded growth technique, were used as cores for succeeding polystyrene coating. After surface modification of gold-silica composite particles by methacryloxypropyltrimethoxysilane (MPTMS), polymerizations of styrene (0.16-0.4 M) were conducted with 8 x 10(-3) M of potassium persulfate initiator in the presence of 1 x 10(-3) M of sodium p-styrenesulfonate anionic monomer. Multilayered core-shell gold-silica-polystyrene particles that contained a single core could be obtained. The coefficient of variation of size distribution (CV) of the composite particles was less than 7%, and polystyrene shell thickness was in a range of 193 to 281 nm.     

pH-responsive hollow core zeolitic-imidazolate framework-8 as an effective drug carrier of 5-fluorouracil

To enhance the porosity and accessibility, a novel drug carrier, the hollow core zeolitic-imidazolate framework-8 (HZIF-8), is designed using polystyrene as a hard template to sequentially load and release 5-fluorouracil (FU). HZIF-8 is signified by a large surface area and pore volume, reaching 1727.1 m²/g and 0.99 cm³/g, respectively. The obtained HZIF-8 exhibits rhombic dodecahedron morphology with a uniform particle size of 450 nm. The integrated hollow core is observed at ca. 180 nm. Evaluation of the FU encapsulation behavior in HZIF-8 nanospheres is demonstrated via the adsorption kinetics, isotherm, and thermodynamic studies. The maximum FU uptake is monitored at 40 °C with the loading capacity of 161.9 mg/g. This study suggests that the FU uptake follows the pseudo-second-order law and multilayer mechanism. The governing mechanism is chemical binding in its first layer and physical interaction in the upper layers. The release study of FU from FU-loaded HZIF-8 shows that the cumulative release at pH 5.5 (92.03%) is four times higher than that at pH 7.4 (23.31%), indicating a stimulus-responsive release mechanism where pH is required as an internal stimulus factor.     

Nontoxic block copolymer nanospheres: design and characterization

Biodegradable polymers capable of self-assembly into hollow nanospheres of less than 100 nm have significant potential for biotechnology applications such as drug delivery and gene therapy. Here we describe the synthesis of a novel ABA-type triblock copolymer made from a hydrophobic tyrosine-derived core and two hydrophilic poly(ethylene glycol) end groups (poly(ethylene glycol)-block-oligo(desaminotyrosyltyrosine octyl ester suberate)-block-poly(ethylene glycol)). We describe the self-assembly of this triblock copolymer and characterize its particles as 100 nm size vesicular nanospheres. The vesicular nature of these particles was determined by light scattering and electron microscopy. The nanospheres did not exhibit any short-term cytotoxicity toward UMR-106 cells at a concentration up to 2 mg/mL.     

Size‐controlled/Surface‐Functionalized Polystyrene Nanospheres with Good Biocompatibility and High Encapsulation Efficiency of Cyclosporin A via Miniemulsion Polymerization in One Step

In this paper, size‐controlled and surface‐functionalized RhB‐labeled and Cyclosporin A (CsA)‐loaded polystyrene (PS) nanospheres were successfully synthesized via miniemulsion polymerization. The biophysical properties of PEG functionalized PS nanospheres from protein adsorption, blood compatibility, cell compatibility and cell penetrability showed the nanoparticles with high biocompatibility. These results indicated that PEG modified PS nanospheres showed outstanding properties as low size distribution (0.164), high encapsulation efficiency (98.3%), long re‐calcification time (50% than positive control), low hemolysis ratio (3.19%) and high cell viability (95.3%). This work could be used as a good drug delivery system for CsA.     

单分散SiO2/PS复合粒子的制备

聚合物包覆无机物的核一壳结构复合粒子研究长期以来受到关注,源于其应用广泛．根据表面性质要求对无机相或者有机相表面进行功能化,可使得到的复合粒子与不同的应用体系相匹配．这类聚合物包覆无机物的有机／无机复合粒子,已在光学器件、分离、药品、农业、涂料等很多领域有广泛和潜在应用．本文制备这类复合粒子用于石油工业模型催化剂和助剂．     

Polystyrene-silica nanocomposite particles via alcoholic dispersion polymerization using a cationic azo initiator

Submicrometer-sized polystyrene-silica nanocomposite particles have been prepared by alcoholic dispersion polymerization of styrene using commercial alcoholic silica sols of 13 or 22 nm diameter as the sole stabilizing agent. The key to the formation of colloidally stable nanocomposite particles is the selection of a cationic azo initiator (use of nonionic or anionic initiators leads either to the formation of silica-stabilized polystyrene latex particles with very low silica contents or to the precipitation of polystyrene, respectively). Neither surface modification of the silica sol nor the addition of surfactant or polymeric stabilizers is required for successful nanocomposite syntheses. The purified polystyrene-silica nanocomposite particles have relatively narrow particle size distributions, with mean diameters ranging from 331 to 464 nm as judged by disk centrifuge photosedimentometry. Thermogravimetric analyses indicated mean silica contents of 13-26 wt. %, depending on the synthesis conditions. Calcination of the polystyrene-silica nanocomposite particles leads to the formation of hollow silica shells, which indicates a well-defined core-shell morphology for the original nanocomposite particles.