Preparation of single-hole hollow polymer nanospheres by raspberry-like template method

Single-hole hollow polymer nanospheres were fabricated by raspberry-like template method using "graft-from" strategy through atom transfer radical polymerization (ATRP). Nanometer-sized silica spheres were covalently attached onto the surfaces of micrometer-sized silica spheres. Crosslinked polymer shells on the nano-sized spheres outside the attached area were formed by "graft-from" strategy through ATRP. After removal of the silica cores, single-hole hollow crosslinked polymer nanospheres were obtained. In this strategy, most of ATRP monomers may be used and thus many functional groups can be easily incorporated into the single-hole hollow crosslinked polymer nanospheres.     

Preparation of hollow silica beads via soft template calcinating route

Heat treated hollow silica beads have been prepared via a two-step method: the fast synthesis of mesoporous hollow silica beads via soft template method and the closing of the porosity of as prepared hollow silica beads in a vertical furnace at more than 1,000 °C. The experiment results showed that the size of the as prepared hollow silica beads was greatly affected by the size of the octylamine vesicles, which increased as the mixing rate decreased, and the optimal synthesis time was 5 min. Fourier transform-infrared spectroscopy results indicated that the soft template was incorporated in as prepared hollow silica beads. The optical photographs and the X-ray diffraction results indicated that the shell of as prepared hollow silica beads was fully densified in the high temperature furnace. In addition, the morphology observation of polypropylene/polyolyaltha olfin/heat treated hollow silica beads ternary composites indicated that this type of silica beads possessed high intensity and strength to blend with the polypropylene/polyolyaltha olfin composites.     

Preparation of highly sulfonated polystyrene model colloids

Previous attempts to prepare monodisperse styrene/sodium styrene sulfonate copolymer latexes by batch, seeded, and semicontinuous emulsion polymerization were unsuccessful at high concentrations of the functional comonomer. Broad, and sometimes bimodal, size distributions, and large amounts of water soluble homopolymer were obtained. After removal of free monomer, solute and adsorbed homopolymer and copolymer, the overall incorporation of the functional comonomer was found to be low. To overcome these problems, a two stage “shot-growth” or in situ seeding technique was developed. A first stage copolymerization was carried out with a low concentration of sodium styrene sulfonate: the purpose of the functional comonomer was to enhance the stability and regulate the size of the seed particles. When this reaction had reached high conversion (> 90%), a second stage monomer mixture was added. The ratio of styrene to sodium styrene sulfonate in this mixture determined the final surface charge density. The mechanism by which the NaSS is incorporated in the polymer particles is considered to be by solution copolymerization with solute styrene monomer to form surface active oligoradicals. These radicals adsorb on the particle surface, initiate polymerization and become inextricably bound, preventing their transfer back to the aqueous phase. By this means, it was possible to vary independently the particle size and surface charge density. High concentrations of functional comonomer could be polymerized without undue wastage (incorporations were only slightly less than 100%) or loss of monodispersity. In extreme cases, the area per functional group fell below the theoretical minimum, indicating considerable hydration of the surface layers.     

Wetting behavior of lightly sulfonated polystyrene ionomers on silica surfaces

The wetting/dewetting behavior of thin films of lightly sulfonated low molecular weight polystyrene (SPS) ionomers spin-coated onto silica surfaces were studied using atomic force microscopy (AFM), contact angle measurements, and electron microscopy. The effects of the sulfonation level, the choice of the cation, the solvent used to spin-coat the films, and the molecular weight of the ionomer were investigated. Small angle X-ray scattering was used to determine the bulk microstructure of the films. The addition of the sulfonate groups suppressed the dewetting behavior of the PS above its glass transition temperature, e.g. no dewetting occurred even after 240 h of annealing at 120 degrees C. Increasing the sulfonation level led to more homogeneous and smoother surfaces. The choice of the cation used affected the wetting properties, but not in a predictable manner. When tetrahydrofuran (THF) or a THF/methanol mixed solvent was used for spin-casting, a submicron-textured surface morphology was produced, which may be a consequence of spinodal decomposition of the film surface during casting. Upon annealing for long times, the particles coalesced into a coherent, nonwetted film.     

Preparation of flame retardant and thermal insulation polystyrene foams via high internal phase emulsion template

Expanded polystyrene foam (EPSF), valued for its excellent insulation properties, faces a significant flammability challenge due to its cellular structure. Traditional flame retardant methods such as physical blending and layer-by-layer assembly have poor applicability to EPSF. Therefore, it is necessary to find other more effective methods for synthesizing flame-retardant EPSF. The high internal phase emulsion (HIPE) template is one of the simplest and most commonly used methods for synthesizing porous materials, which have features such as adjustable pore structures and high porosity. In this work, ammonium polyphosphate (APP)/starch was added to the dispersed phase of the HIPE to prepare the flame-retardant EPSF by one-pot method. The morphology, thermal stability and flame retardancy of the foams were investigated. When the addition of APP/starch (the weight ratio is 1:1) reached 30 wt.%, the peak heat release rate (PHRR), total heat release (THR), and total smoke release (TSR) of the composite foam decreased by 74.7%, 65.9%, and 24.7%, respectively, compared to the pure PS foam. Meanwhile, its limiting oxygen index (LOI) value reached 25.8%, and the UL-94 rating reached V-1 level, indicating significant improvement in flame retardancy. This study provides an effective strategy for synthesizing flame-retardant porous materials.     

Preparation of anisotropic silica nanoparticles via controlled assembly of presynthesized spherical seeds

A facile solution process for the preparation of anisotropic silica nanoparticles (ASNPs) is presented. ASNPs are prepared via controlled self-assembly of spherical silica seeds (22 nm) in alcohol-water mixed media, followed by their in situ fixation and overgrowth with tetraethoxysilane (TEOS). Ethanol and L-arginine (Arg) are used to modify the dielectric constant and ionic strength of the reaction media, by which seed assembly is controlled through the adjustment of electrostatic interaction. Ethanol and Arg also serve as a cosolvent and a catalyst for hydrolysis and condensation of TEOS, respectively, which enables us to produce ASNPs in a simple one-pot process. In addition to ASNPs with wormlike structures, different kinds of NPs (bimodal spherical NPs, monodisperse spherical NPs, and spherical aggregates) have also been obtained by changing the concentrations of ethanol and Arg. The length, thickness, or both of ASNPs are controlled systematically by varying the concentrations of Arg, seed NPs, and TEOS. Other alcoholic cosolvents, such as methanol, 1-propanol, 2-propanol, and t-butanol, are also effective to give ASNPs when the dielectric constant of the alcohol-water mixed media is properly adjusted, showing the versatility of the present method.     

Preparation of hemispherical hollow silica microcapsules with different affinity surface by using spherical vaterite calcium carbonate as template

We developed a method to prepare hemispherical hollow silica microcapsules (HHSM) with different affinity surfaces using spherical vaterite calcium carbonate (SVCC) as a template. The preparation process composed of the adhesion of calcium carbonate onto the surface of methyl methacrylate (MMA) droplets followed by suspension polymerization, the partial etching of calcium carbonate on the polymethyl methacrylate (PMMA) mother particle, the formation of silicon dioxide powder by sol–gel reaction and their deposition onto the etched flat surface of calcium carbonate, the surface modification of deposited silicon dioxide with silane coupling agent, the removal of the mother particle with acetone, the formation of silicon dioxide powder by sol–gel reaction and deposition onto the exposed hemispherical surface of calcium carbonate, and the surface modification of deposited silicon dioxide with silane coupling agent. The synthesized microcapsules had a complete hemispherical structure and both hydrophilic and hydrophobic surfaces. Copyright © 2007 John Wiley & Sons, Ltd.     

Layer-by-layer assembly of partially sulfonated isotactic polystyrene with poly(vinylamine)

The stereoregular synthetic polymer isotactic polystyrene bearing partially sulfonated groups (SiPS) was used as a layer-by-layer assembled thin film for the first time. When a low molecular weight compound was employed as the pair for the alternative layer-by-layer (LbL) assembly, the frequency shift was very small using quartz crystal microbalance (QCM) analysis, whereas poly(vinylamine) (PVAm) formed an effective pair for the construction of LbL films with SiPS. When it was neutralized, SiPS was not assembled, probably due to the loss of effective polymer-polymer interactions. The ionic strength conditions revealed a slight difference of the assembly behavior on the isotactic polymer as compared to the atactic one. The assembled LbL film showed the same peaks over the range from 1141 to 1227 cm(-1) and 700 cm(-1) in the FT-IR/ATR spectra as the bulk complex of SiPS/PVAm, and the thickness on one side was calculated at 76 nm by QCM analysis. The surface roughness of the film was also observed by AFM.     

高芯材含量聚苯乙烯石蜡微胶囊的制备及性能研究

为解决石蜡在使用过程中的一系列问题,以聚苯乙烯为壁材,58~#石蜡为芯材,采用悬浮聚合法制备了高芯材含量的微胶囊.考察了二己烯基苯(DVB)用量、芯壁比、复合改性时共聚单体种类和用量对微胶囊的影响.采用FT-IR、SEM、DSC、TG表征了微胶囊的结构、形貌、储热性能及热稳定性能.实验结果表明,DVB用量11%、芯壁比3∶1制备的微胶囊大小均匀,无团聚现象;交联改性的同时,加入20%MA单体共聚改性制备的微胶囊形貌好,热稳定性最佳,微胶囊中石蜡含量为91.7%时储热性能最优.     

Preparation of macroporous SAPO-34 microspheres by a spray drying method using polystyrene spheres as hard template

Macroporous microspheres of SAPO-34 (MAMISAPO-34) were fabricated using polystyrene spheres (PS, 2 μm) as hard template. Cubic SAPO-34 (1 μm) synthesized by the conventional hydrothermal method was mixed with kaolin, silica sol, aluminium phosphate sol, template, and deionized water. Spray drying was then performed to prepare 30–50 μm microspheres which were converted to macroporous SAPO-34 by post-hydrothermal and calcination treatments. For comparison, 30–50 μm non-macroporous microspheres (NOMISAPO-34) were also obtained without using PS. XRD, NH₃-TPD, and SEM analyses were used to characterize the macroporous and non-macroporous SAPO-34. The results showed that MAMISAPO-34 was more crystalline and had more strong acid sites than NOMISAPO-34. When used in MTO (methanol to olefins) reactions, MAMISAPO-34 had better catalytic performance than NOMISAPO-34, because of its greater crystallinity.     

多齿配体-硅胶色谱介质的制备与评价

以新型环保多齿螯合剂——亚氨基二琥珀酸(IDS)为配体,在优化条件下,合成了IDS-Silica固定相。用电位滴定法测定了固定相上IDS的键合量。考察了IDS-Silica柱的色谱特性以及金属螯合特性。使用制备柱成功地分离了标准蛋白质混合物,该制备柱展现出了典型的阳离子交换特性。用电感耦合等离子体原子发射光谱法考察了金属离子在IDS-Silica固定相上的键合特性。结果表明,金属离子在IDS-Silica固定相上键合量的变化规律与它们同该固定相螯合的强弱顺序一致。通过比较金属Cu~(2+)在4种不同氨羧类配体硅胶柱上的键合量,发现IDS对金属离子具有强的螯合能力。IDS对金属离子的强螯合特性为其今后作为固定金属亲和色谱填料奠定了基础,为缓解亲和柱在使用过程中固定金属离子的流失提供了一种有效的解决方法。     

Preparation of well-defined polystyrene/silica hybrid nanoparticles by ATRP

Immobilization of the atom transfer radical polymerization (ATRP) macroinitiators at the silica nanoparticle surfaces was achieved through surface modification with excess toluene-2,4-diisocynate (TDI), after which the residual isocyanate groups were converted into ATRP macroinitiators. Structurally well-defined polystyrene chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined, densely grafted outer polystyrene by ATRP, which was initiated by the as-synthesized silica-based macroinitiator. FTIR, NMR and gel permeation chro-matography (GPC) were used to characterize the polystyrene/silica hybrid particles.     

Preparation of polystyrene/silica nanocomposites by radical copolymerization of styrene with silica macromonomer

A two-stage process has been developed to generate the silica-based macromonomer through surface-modification of silica with polymerizable vinyl groups. The silica surfaces were treated with excess 2,4-toluene diisocynate (TDI), after which the residual isocyanate groups were converted into polymerizable vinyl groups by reaction with hydroxypropylacrylate (HPA). Thus, polystyrene/silica nanocomposites were prepared by conventional radical copolymerization of styrene with silica macromonomer. The main effecting factors, such as ratios of styrene to the macromonomer, together with polymerization time on the copolymerization were studied in detail. FTIR, DSC and TGA were utilized to characterize the nanocomposites. Experimental results revealed that the silica nanoparticles act as cross-linking points in the polystytene/silica nanocomposites, and the glass transition temperatures of the nanocomposites are higher than that of the corresponding pure polystyrene. The glass transition temperatures of nanocomposites increased with the increasing of silica contents, which were further ascertained by DSC.     

Preparation and structure of highly confined intercalated polystyrene/montmorillonite nanocomposite via a two-step method

A two-step approach with a combination of emulsion polymerization and melt intercalation with higher clay loading of 33 wt.% is disclosed to highly confine the polystyrene (PS) chains by montmorillonite. The product of the emulsion polymerization is an easily crushable fine powder. And the powder is readily processible by open mill to form a transparent sheet. In the melt intercalation process, further intercalation of polystyrene narrows the space among the tactoids and results a highly confined intercalated nanocomposite. The results of dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) showed that the cooperative motions of PS segments were substantially depressed, indicative of the highly intercalated structure formed in the nanocomposites. A structural model is proposed to explain the highly confined mesostruture of the PS/MMT nanocomposite.     

复凝聚法辣椒油树脂微胶囊的制备

以辣椒油树脂为芯材,明胶和阿拉伯胶为壁材,采用复凝聚法制得辣椒油树脂微胶囊.考察了45℃、体系浓度为5%时,pH值、乳化剂的用量、搅拌速度等几个因素对微胶囊形成的影响.     

Synthesis and properties of porous silica obtained by the template method

Micromesoporous samples of SiO₂ were synthesized by the sol-gel method using tetraethoxysilane as a starting reagent and 1–5 wt % cetylpyridinium chloride as a template under the conditions of preadsorption of colloid silica by polyethyleneglycol macromolecules. The adsorption and texture of the samples were studied by the low-temperature nitrogen adsorption-desorption technique. Preadsorption of silica sol was shown to affect the adsorption and capillary-condensation properties of silica. The surface area and the volume of mesopores increased at cetylpyridinium concentrations higher than 1 wt %. The micropore volume increased to a maximum. The capillary-condensation hysteresis loop of H4 type transformed into an H3 loop according to the IUPAC classification.     

Preparation and characterization of sulfonated polyimide ionomers via post‐sulfonation method for fuel cell applications

This paper describes our work on the synthesis of a series of sulfonated homo‐/co‐polyimides (SPI) which were obtained by post‐sulfonation method over three steps. In the first step, 4,4′‐oxydianiline (ODA) and 4,4′‐diaminodiphenylsulfone (DDS) dissolved in N‐methyl pyrrolidone (NMP) were reacted with benzophenonetetracarboxylic dianhydride (BTDA) in order to yield poly(amic acid) (PAA). Secondly, precipitated PAA was sulfonated via concentrated sulfuric acid (95–98%) at room temperature to give post‐sulfonated PAA (PSPAA). Finally, PSPAA was converted into post‐sulfonated PI (PSPI) by the thermal imidization method. PSPIs with ion exchange capacity (IEC) ranging from 0.20 to 0.67 meq/g were prepared. The thermal properties of the PSPIs were evaluated and high desulfonation temperature was found in the range of 190–350°C, suggesting the high stability of sulfonic acid groups. In water, PSPI‐5 membrane displayed similar proton conductivity to Nafion®117, whereas this membrane showed poor conductivity in dry state. All PSPIs displayed good solubility in common polar aprotic solvents such as NMP and dimethylacetamide (DMAc). Furthermore, the effects of post‐sulfonation reaction on chemical structure, thermal oxidative behavior, and physical properties of the PSPI membranes such as membrane quality/stability and water uptake were discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

以L-苯甘氨酸衍生物为模板制备介孔SiO_2纳米空心球

用L-苯甘氨酸合成了L-苯甘氨酸衍生物阳离子两亲化合物,以其自组装体为模板,采用四乙氧基硅烷为硅源,制备了介孔SiO_2空心球.结果表明,制备的介孔SiO_2纳米粒子直径50~200nm,孔径3.8nm左右,孔道成平行排列.     

二氧化锆微球表面键合磺化交联聚苯乙烯固相萃取填料的制备及应用

以聚合诱导胶体凝聚法(PICA)制备二氧化锆微球,用钛酸酯偶联剂对其进行表面改性,使其接枝上碳碳双键基团。在溶液体系中,该双键与单体苯乙烯和二乙烯苯在自由基引发下交联聚合,形成的聚合物包覆在二氧化锆微球表面。再通过磺化方法将磺酸基离子连接到苯环上,得到阳离子交换固相萃取填料。通过红外光谱、扫描电镜/X射线能谱等手段对其进行了表征。将装填得到的固相萃取柱与高效液相色谱联用,测定了水中的甲基磺草酮、阿特拉津和乙草胺。3种化合物的色谱峰面积与质量浓度呈良好的线性关系,相关系数(r²)均大于0.99;甲基磺草酮、阿特拉津和乙草胺的检出限分别为5.41、6.72和13.4 μg/L。结果表明,制得的聚合物包覆二氧化锆微球的粒径为6~8 μm,用该填料制成的固相萃取小柱对3种目标物的吸附率高。     

仿生微胶囊的组装及其应用

在生物物理和生物医药研究领域中,在分子水平上组装功能化的仿生微胶囊具有重要的理论和应用价值.在现有制备微胶囊的技术手段中,层层组装技术以其能够控制胶囊的尺寸、形状、囊壁的厚度和组成以及易于实现功能化等特点,引起了人们越来越多的研究兴趣.本文将着重介绍如何利用层层组装技术,以磷脂、蛋白质和其他生物大分子为组装基元构筑仿生微胶囊、以及如何将微胶囊进行生物界面化的修饰.此外,以仿生微胶囊为药物载体,探讨其在光动力治疗方面的应用也作简单介绍.