Selective Functionalization of Hollow Nanospheres with Acid and Base Groups for Cascade Reactions

The inner‐surface functionalization of hollow silica spheres has rarely been reported and is still a challenging topic. Herein, we report a deacetalization–Henry cascade reaction catalyzed by dual‐functionalized mesoporous silica hollow nanospheres with basic amine groups (?NH₂) on the internal shell and carboxylic acid groups (?COOH) on the external shell. The selective functionalization has been realized by a combination of “step‐by‐step post‐grafting” and “cationic surfactant‐assisted selective etching” strategy. Compared to unisolated catalyst, the selectively isolated acidic and basic dual catalyst provides excellent catalytic performance for the deacetalization–Henry cascade reaction in terms of both activity (>99 %) and selectivity (95 %).     

Architecture of micron-scale hollow spheres composed of silica nanoparticles and approach to luminescent spheres

Micron-scale hollow spheres were successfully constructed with silica nanoparticles by templating of polymer spheres. Subsequently, the use of 3-aminopropyltriethoxysilane (APTES) introduces carbon and oxygen defects in the silica nanoparticles resulting from calcination of the aminopropyl group. In this approach, the template of micron-scale polymer spheres was prepared from dispersion polymerization. Subsequent St?ber process results in the formation of a silica layer attached to the polymer sphere surfaces. After calcination, the obtained micron-scale hollow silica spheres were then studied on the relationship between the particle diameter and the surface morphology. The luminescence of hollow spheres was prepared through using APTES in St?ber process, and which of related the appearance of luminescence to the APTES concentration and calcination temperature. The results of this study can provide useful information for the structure of micron-scale hollow spheres and their application to luminescent materials.     

制备核-壳结构聚合物纳米微球和空心球的原位聚合方法的普适性研究

采用原位聚合制备核-壳结构聚合物纳米微球和空心球的新方法, 利用甲基丙烯酸2-羟丙酯(HPMA)和乙酸乙烯酯(VAc)两种单体, 在类似的反应条件下, 成功地制备了以聚(ε-己内酯)(PCL)为核, 分别以交联PHPMA和PVAc为壳的纳米微球; 将微球的核酶解后, 分别得到了对应的交联PMAA空心球和交联PVA空心球. 结果表明, 原位聚合制备核-壳结构聚合物微球的新方法具有一定的普适性, 适用于单体可溶于水而生成的聚合物不溶于水的体系.     

Silica nanobottles templated from functional polymer spheres

Nanosized hollow silica spheres with holes in the wall (denoted as silica nanobottles) have been successfully prepared by assembly of functional polymer nanospheres with tetraethoxysilane (TEOS) through hydrothermal methods, coupled with removal of the core by programmed calcination. The functional polymer nanospheres were obtained by emulsifier-free emulsion copolymerization of styrene and (ar-vinylbenzyl) trimethylammoium chloride. The silica nanobottle sample was characterized by thermogravimetric analysis (TG), differential thermal analysis (DTA), transmission electron microscopy (TEM), and nitrogen adsorption techniques. The above characterizations confirm that the silica nanobottles have holes of about 8 nm in the wall and this unique structural feature might be useful for their encapsulation. Furthermore, characterization by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and UV-visible absorption (UV-vis) showed that the luminescent material Eu(TTA)(3)(TPPO)(2) could be effectively encapsulated in silica nanobottles. This reveals that silica nanobottles have potential applications for nanotechniques.     

Synthesis and utilization of monodisperse hollow polymeric particles in photonic crystals

We developed a process to fabricate 150-700 nm monodisperse polymer particles with 100-500 nm hollow cores. These hollow particles were fabricated via dispersion polymerization to synthesize a polymer shell around monodisperse SiO(2) particles. The SiO(2) cores were then removed by HF etching to produce monodisperse hollow polymeric particle shells. The hollow core size and the polymer shell thickness, can be easily varied over significant size ranges. These hollow polymeric particles are sufficiently monodisperse that upon centrifugation from ethanol they form well-ordered close-packed colloidal crystals that diffract light. After the surfaces are functionalized with sulfonates, these particles self-assemble into crystalline colloidal arrays in deionized water. This synthetic method can also be used to create monodisperse particles with complex and unusual morphologies. For example, we synthesized hollow particles containing two concentric-independent, spherical polymer shells, and hollow silica particles which contain a central spherical silica core. In addition, these hollow spheres can be used as template microreactors. For example, we were able to fabricate monodisperse polymer spheres containing high concentrations of magnetic nanospheres formed by direct precipitation within the hollow cores.     

Generalization of in-situ polymerization method for preparing core-shell polymeric nanospheres and hollow spheres

According to the new method of preparing core-shell nanospheres developed by our group, by using two monomers, 2-hydroxypropyl methacrylate(HPMA) and vinyl acetate(VAc), two kinds of core-shell nanospheres with poly(ɛ-caprolactone) (PCL) as the core and crosslinked poly(2-hydroxypropyl methacrylate) (PHPMA) or poly(vinyl acetate) (PVAc) as the shell were successfully prepared under similar conditions. After degrading the PCL cores of the two kinds of nanospheres by lipase, the corresponding crosslinked poly(methyl acrylic acid) hollow spheres and crosslinked poly(vinyl alcohol) hollow spheres were obtained. Results indicate that the new method we proposed for preparing core-shell polymeric nanospheres via in-situ polymerization can be generalized to a certain extent, and it is suitable for many systems provided the monomer used is soluble in water, while its corresponding polymer is insoluble in water. Translated from Chemical Journal of Chinese University, 2006, 27(9): 1762–1766 [译自: 高等学校化学学报]     

A NOVEL METHOD TO PREPARE CROSSLINKED POLYETHYLENEIMINE HOLLOW NANOSPHERES

A novel method to prepare crosslinked polyethyleneimine(CPEI)hollow nanospheres was reported.Uniform silica nanospheres were used as templates,3-aminopropyl trimethoxysilane(APS)was immobilized on the surface of silica nanospheres as couple agent.Aziridine was initiated ring-opening polymerization with the amino groups in APS to form polyethyleneimine(PEI)shell layer.1,4-Butanediol diacrylate was utilized to crosslink PEI polymeric shell.The silica nanospheres in core were etched by hydrofluoric acid to obtain hollow CPEI nanospheres.The hollow nanospheres were characterized by X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM),and thermogravimetric analysis(TGA).     

锆酸钡/聚合物复合中空纳米球的水热合成

采用聚合物辅助水热合成方法, 在强碱条件下加入PAA和PVA的混合液,实现了聚合物/锆酸钡复合中空纳米球的软化学一步合成, 而且球壳为有机-无机复合材料, 有望用于吸附分离、催化剂载体、轻质陶瓷和涂料等方面.     

Growth of lightly crosslinked PHEMA brushes and capsule formation using pickering emulsion interface‐initiated ATRP

In this work, growth of lightly crosslinked poly(2‐hydroxyethyl methacrylate) (PHEMA) brushes and subsequent capsule formation using Pickering emulsion interface‐initiated atom transfer radical polymerization (PEII‐ATRP) were investigated. Initiator‐immobilized silica nanoparticles (2.5 initiators/nm²) assembled at the interface of paraffin oil‐in‐water emulsions and ultimately stable Pickering emulsions were formed. PEII‐ATRP was conducted in the water phase of Pickering emulsions from the part of the surfaces of initiator‐immobilized silica nanoparticles exposed to water by using copper(I) chloride/bipyridine as catalyst at 35 °C. As PHEMA has a character of lightly crosslinking when the polymerization occurs in water, novel hybrid capsules (“colloidosomes”) can be obtained and were observed by confocal laser scanning microscope (CLSM) and optical microscopy (OM). The semipermeability of the resultant hollow capsules was demonstrated by the diffusion of 1‐phenylazo‐2‐naphthol. Meanwhile, the conformation of PHEMA chains can be varied in different solvents, which affects the semipermeability of these hybrid hollow capsules. We expect these hollow capsules can be further utilized to develop microdevices for drugs or cells delivery. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1354–1367, 2009     

模板法制备复合中空微球

本文报道以一种商品化的聚苯乙烯中空球为模板, 采用溶胀聚合技术合成了具有IPN(Inter-Penetrating Network)结构的复合中空球; 对其中的一种高分子网络进行化学改性引入所需官能团, 制得带有羧基的聚合物凝胶中空球; 利用凝胶诱导生长特性, 成功制得聚合物复合中空球. 此方法无需去除模板就可批量制备各种复合功能中空球.     

Biomolecule‐Assisted Construction of Cadmium Sulfide Hollow Spheres with Structure‐Dependent Photocatalytic Activity

In this study, we report the synthesis of monodispersive solid and hollow CdS spheres with structure‐dependent photocatalytic abilities for dye photodegradation. The monodispersive CdS nanospheres were constructed with the assistance of the soulcarboxymthyi chitosan biopolymer under hydrothermal conditions. The solid CdS spheres were corroded by ammonia to form hollow CdS nanospheres through a dissolution–reprecipitation mechanism. Their visible‐light photocatalytic activities were investigated, and the results show that both the solid and the hollow CdS spheres have visible‐light photocatalytic abilities for the photodegradation of dyes. The photocatalytic properties of the CdS spheres were demonstrated to be structure dependent. Although the nanoparticles comprising the hollow spheres have larger sizes than those comprising the solid spheres, the hollow CdS spheres have better photocatalytic performances than the solid CdS spheres, which can be attributed to the special hollow structure.     

以聚合物乳胶为模板经表面引发原子转移自由基聚合制备空心二氧化硅纳米微球

均匀的空心纳米及微米球因具有可裁剪结构及良好的光学性能和表面性能,而具有非常广泛的应用前景,空心胶囊是一类重要的材料,它是通过不同的化学和物理方法,直接除去壳-核粒子的内核而获得的,目前主要是通过控制表面沉积。或利用静电相互作用层层组装。制备空心胶囊,但前者易于产生独立的无机粒子沉淀,后者的步骤太过繁琐。     

含氟聚合物修饰碳纳米管及其聚氨酯复合疏水膜的研究

利用羟基碳纳米管上的羟基与2-溴异丁基酰溴之间的简单反应, 在碳纳米管上引入了含溴ATRP引发剂, 并进一步引发含氟丙烯酸酯的ATRP聚合, 从而在碳纳米管表面接枝上了低表面能的含氟聚合物. 红外光谱(FT-IR)、热重分析(TGA)和透射电镜(TEM)的研究结果表明碳纳米管与含氟聚合物之间为化学键连接. 以此低表面能聚合物包裹的碳纳米管作为填充粒子, 采用溶液浇铸方法制备了聚氨酯/碳纳米管复合膜, 并利用溶剂四氢呋喃(THF)刻蚀表面获得了不同碳纳米管裸露程度的复合膜材料. 静态接触角测试结果表明, 无论是羟基碳纳米管还是低表面能修饰的碳纳米管均可提高其复合膜的疏水性能, 且其疏水性能随碳纳米管含量的增加而增加; 相同含量时, 含氟聚合物接枝后的碳纳米管使复合膜具有更佳的疏水性能, 膜表面经溶剂刻蚀后可显著提高其疏水性能. 采用扫描电子显微镜(SEM)研究了加入碳纳米管和溶剂刻蚀对聚合物表面微观结构以及材料表面疏水性能的影响. 上述结果表明: 利用接枝聚合物可改变碳纳米管本身的疏水性能, 并可进一步制备新型的具有表面疏水性能的聚合物纳米复合材料.     

以阴离子多肽为模板合成二氧化硅纳米空心球

以聚阴离子多肽(聚谷氨酸钠)控制合成了微孔二氧化硅空心球. 在合成过程中, 以3-氨丙基三甲氧基硅烷(APMS)和正硅酸乙酯(TEOS)为硅源, 聚谷氨酸钠为模板. 硅源与阴离子多肽模板之间的组装依照以阴离子表面活性剂为模板剂组装合成介孔二氧化硅的机理, 即S-N+-I-机理, 其中S表示阴离子多肽, I表示TEOS, N表示共结构导向剂APMS. 组装过程中质子化的APMS与阴离子多肽之间形成静电相互作用, 同时, AMPS和TEOS共同水解聚合形成围绕阴离子多肽模板的二氧化硅骨架, 多肽的二级结构为微孔孔道的模板. 以阴离子多肽为模板可以在不同的实验条件下控制微孔纳米空心球, 微孔亚微米空心球和实心球形貌的合成. 在生物矿化过程中, 阴离子多肽往往控制碳酸钙或磷酸钙的沉积, 而我们的实验结果表明, 在适当的硅源存在下, 阴离子多肽也可以诱导二氧化硅的沉积.     

Facile access to ultrasmall Eu2O3 nanoparticle-functionalized hollow silica nanospheres based on the spontaneous formation and decomposition of a cross-linked organic/inorganic hybrid core

We report a promising strategy for the facile synthesis of ultrasmall nanoparticle-functionalized hollow silica nanospheres by using a functional cross-linked organic/inorganic hybrid core, which can be obtained simply through successive spontaneous reactions in water.     

Facile route to synthesize polyurethane hollow microspheres with size-tunable single holes

Synthesis of polymer hollow spheres with single holes has been a challenging task in materials science. In this work, polyurethane (PU) hollow microspheres with size tunable single holes were fabricated through a facile self-assembly-diffusion process. Firstly, the as-synthesized PU polymers were dissolved in chloroform. By adding 10 times volume of water, the PU polymers were self-assembled into micelles in which the chloroform was encapsulated. The PU micelles were then transferred to methanol solution to allow the diffusion of chloroform. The formation of the single holes in shells of the resultant PU hollow spheres was induced by the out-diffusion of the encapsulated chloroform in methanol. By adjusting the diffusion time from 5 to 20 hours, the hole size could be tuned from 75 to 210 nm. The resultant PU hollow spheres with single holes demonstrated high loading efficiency of various guest materials such as nanospheres, nanoparticles, and chemical species, suggesting their promising applications in controlled release, chemical protection, catalysis, and so forth.     

Sonochemical synthesis of hollow PbS nanospheres

PbS hollow nanospheres with diameters of 80-250 nm have been synthesized by a surfactant-assisted sonochemical route. The nanostructures were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), (high-resolution) transmission electron microscopy [(HR)TEM], and scanning electron microscopy (SEM) images. Structural characterization indicates that shells of the hollow spheres are composed of PbS nanoparticles with diameters of about 12 nm. The formation of the hollow nanostructure was explained by a vesicle-template mechanism, in which sonication and surfactant play important roles. Furthermore, uniform silica layers were successfully coated onto the hollow spheres via a modified St?ber method to enhance their performance for promising applications.     

Microporous Silica Hollow Nanospheres Templated by Anionic Polypeptide

Anionic polypeptide, the poly(sodium L-glutamate), was applied to fabricate microporous silica hollow nanospheres templated by the secondary structures of the polypeptide as porogens. In the synthesis, 3-aminopropyltrimethoxysilane (APMS) and tetraethyl orthosilicate (TEOS) were used as the silica sources, and the coassembly followed the mechanism of the anionic surfactant-templated mesoporous silica (AMS) through a S_-N₊-I_- pathway, where S indicates the anionic polypeptide, I indicates inorganic precursors (TEOS), and N indicates costructure-directing agent (APMS), which interacted with the negatively charged anionic polypeptide secondary structures electrostatically and cocondensed with silica source to form the silica framework. The product was subjected to characterizations of X-ray diffraction (XRD), infrared (IR) spectroscopy, thermogravimetric (TG) analysis, scanning electron microscopy (SEM), transmitted electron microscopy (TEM), and nitrogen adsorption-desorption measurement. It was found that the pH value of the synthesis solution was an important factor to the morphological control of the silica products. Besides the microporous hollow nanospheres, microporous submicron silica solid and hollow spheres were also obtained facilely by changing the synthesis parameters. Our study further implied that anionic polypeptides, which were able to control mineralization of calcium carbonate and calcium phosphate, could also induce silica condensation in the presence of proper silica precursors. It was also expected that functional calcium carbonate (phosphate)/silica-nanocomposite materials would be fabricated under the control of the anionic polypeptide.     

结构规整的高密度两亲性接枝聚合物刷的合成及其自组装研究

大分子单体通过两种可控聚合方法, 即开环易位聚合(ROMP)和原子转移自由基聚合(ATRP)的联用, 合成一种新型两亲性接枝聚合物刷. 具有高环张力的降冰片烯单侧链大分子单体norbornene-graft-poly(ε-caprolactone)/Br (PCL- NBE-Br)首先进行ROMP反应, 生成聚合物主链, 每个单体单元上含有一条PCL链和一个溴官能团; 然后用含溴的ROMP聚合物poly(norbornene)-graft-poly(ε-caprolactone)/Br (PCL-PNBE-Br)作为大分子引发剂引发单体2-(dimethyl- amino)ethyl methacrylate)的ATRP反应, 生成结构明确的高密度两亲性接枝聚合物刷poly(norbornene)-graft-poly(ε- caprolactone)/poly(2-(dimethylamino)ethyl methacrylate) (PCL-PNBE-PDMAEMA), 其主链每个单体单元上均含有一条疏水性PCL接枝链和一条亲水性PDMAEMA接枝链. 最后, 研究此类高密度两亲性接枝聚合物刷的自组装行为, 用动态激光光散射(DLS)研究其在混合溶剂(THF/H2O)中的胶束行为, 考察胶束溶液的浓度以及不同长度的亲水性接枝链对胶束尺寸的影响; 利用透射电镜(TEM)观察胶束为球形, 具有类似线团或草莓状的形态.     

以手性两亲小分子为模板剂制备介孔二氧化硅纳米空心球

以L-亮氨酸为手性源合成了手性阳离子两亲性小分子化合物L-18Leu6NEtBr,用其自组装体作为模板,氢氧化钠为催化剂,经溶胶-凝胶过程制备出介孔二氧化硅纳米空心球;分析了介孔二氧化硅纳米空心球的尺寸和孔径.结果表明,所制备的二氧化硅空心球直径约100nm;其介孔孔道平行于壳表面,孔径为3.1nm.