中空微球及其制备方法

中空微球具有低密度、高比表面积且可以容纳客体分子等特点,在众多领域受到广泛关注.本文对聚合物中空微球、无机中空微球、聚合物/无机复合中空微球的制备方法进行了综述,并介绍了一种在使用过程中形成中空结构的可膨胀微球.     

海藻酸改性的中空SiO2微球的简易制备及应用

以CaCO3为模板,正硅酸四乙酯（TEOS）为硅源,用比较简单的方法制备了中空SiO2;然后将海藻酸钠嫁接在氨基化的中空SiO2表面;再利用海藻酸盐与钙离子的作用,在中空SiO2表面形成一个凝胶化层,制得海藻酸盐凝胶化的中空SiO2微球,粒径为1~2 μm。 采用FTIR、XRD、SEM、TEM和TGA等测试技术对微球进行表征。 此微球成功地用于柔红霉素的载负和缓释,最大载负率和载药量分别为55.6%和27.8%;缓释结果表明,海藻酸盐凝胶化层的存在,能更有效控制柔红霉素缓慢的释放,这种凝胶化载体对药效强、毒性较大的药物有潜在的临床应用前景。     

三维有序介孔/大孔TiO2微球的制备、表征及光催化性能

以聚甲基丙烯酸甲酯微球为模板,分别以钛酸四丁酯和四异丙醇钛为钛源,通过溶胶-凝胶法辅助模板法制得TiO2纳米微球前驱体,并用程序升温控制其焙烧温度,最终成功制得了具有三维有序介孔/大孔复合结构的TiO2微球.以罗丹明B(RhB)为模型污染物,探索了以不同钛源制备得到的介孔/大孔复合TiO2微球的光催化性能;并采用XRD、SEM、TEM、UV-vis DRS、比表面积测试、光催化性能测试等对样品的晶粒尺寸、物相、形貌、光吸收、比表面积及性能等进行了分析.结果表明,运用溶胶凝胶法辅助模板法能够合成结晶度高、形貌规整、比表面积大、光催化活性良好的锐钛矿相TiO2微球.     

聚合物模板微球表面电性对中空二氧化硅微球形貌的影响

分别以过硫酸钾和偶氮二异丁基脒盐酸盐为引发剂,以聚乙烯吡咯烷酮(PVP)为分散剂,在水中引发苯乙烯聚合制备了2种表面分别带负电性和正电性基团的聚苯乙烯(PS)模板微球.在氨水催化下,利用正硅酸乙酯的水解缩合,形成PS/SiO_2复合微球,去除模板后得到中空SiO_2微球,并对其进行FTIR、电子显微镜、TGA以及氮气吸附等分析表征.结果表明,PS模板微球表面的电性决定了OH-的分布,从而导致PS模板微球表面SiO_2壳层不同的形成机制.当以表面带负电的PS微球为模板时,可得到树莓状的中空SiO_2微球;而以表面带正电的PS微球为模板时,得到是表面光滑的,具有介孔结构的中空SiO_2微球.     

不良溶剂氛围中用breath figures法制备聚合物微球

通过使用操作简单、不需去除模板也不需使用乳化剂的breath figures(BFs)法,在多种非水氛围中制得聚合物微球,如丙烯腈-丙烯酸甲酯-苯乙烯三元共聚物(ASA)和聚丁二酸丁二醇酯(PBS)等;并研究了聚合物溶液浓度、不同氛围等对微球形貌的影响.结果表明,以甲醇、乙醇和正己烷为氛围时均可制得聚合物微球,而在乙酸中得到的是聚合物多孔膜.在乙醇氛围中随着聚合物浓度的增加,微球逐渐黏结,均一性变差;随着乙醇氛围中水含量的增加,形貌由微球过渡到微孔膜.     

制备方法对模板法制备SiO_2中空微球形貌的影响

模板法是制备无机中空微球的重要方法之一.首先通过苯乙烯和甲基丙烯酸的无皂乳液聚合法制得表面含羧基、粒径为360nm的单分散聚苯乙烯(PSt)乳胶粒,并以此为模板,分别采用表面改性-前驱体水解法(PHC)和SiO2纳米颗粒层层自组装法(LBL),制备出了不同壳层厚度的PSt/SiO2核壳结构复合微球,然后经500℃煅烧4h,得到SiO2中空微球.利用透射电镜和扫描电镜对微球结构形态进行了表征.研究表明,首先利用γ-氨丙基三乙氧基硅烷(KH-550)对PSt模板微球进行表面改性、然后再在乙醇-水混合介质中进行原硅酸乙酯(TEOS)水解与缩合反应的PHC法,是制备PSt/SiO2核壳结构复合微球的简便方法,复合微球经煅烧可制得表面均匀、结构致密、壳层厚度和形貌可控的SiO2中空微球;而LBL法制备PSt/SiO2核壳结构复合微球的工艺复杂,煅烧后所得SiO2中空微球结构疏松,易于破碎.     

聚合物中空微球的合成策略（英文）

在过去的20年中,聚合物中空微球由于其独特的结构和优异的性质受到了广泛的关注.它们表现出低密度、高比表面积和高负载力的特性,在催化、药物递送及能量存储等领域中展现出巨大的应用前景.本文综合评述了聚合物中空微球的合成策略,主要包括模板法、乳液聚合法、自组装与及微流控等,并详细阐述和讨论了这些合成策略的原理、典型过程以及优缺点.同时,还指出了现有合成策略面临的挑战以及聚合物中空微球存在的不足,并对聚合物中空微球的制备和应用前景进行了展望.     

中空TiO_2微球的制备及对聚丙烯酸酯薄膜性能的影响

采用阳离子聚苯乙烯微球作为模板,钛酸四丁酯为钛源,氨水为催化剂,制备了中空TiO_2微球.采用X射线衍射、扫描电镜及比表面测定仪对其形貌和结构进行了表征,并考察了模板粒径、钛源用量以及催化剂用量对中空TiO_2微球形貌的影响.通过物理共混法将其引入至聚丙烯酸酯乳液中并成膜,研究了复合薄膜的保温性能、抗紫外性能及力学性能.结果表明,锐钛矿相中空TiO_2微球模板粒径、钛源用量以及催化剂用量影响中空TiO_2微球的空心尺寸、壁厚及壳层致密性.中空TiO_2微球可显著提升聚丙烯酸酯薄膜的保温性能、抗紫外性能和力学性能.采用不同粒径的模板制备的中空TiO_2微球对复合薄膜的各项性能均有影响,其中模板粒径为140 nm时复合薄膜性能最优,光反射率提升63%,导热系数降低27%,且在波长小于360 nm范围内,紫外透过率几乎为0,抗张强度增加100%,断裂伸长率提升62%.     

新型室温酯化法接枝聚合物改性SiO_2纳米微粒

提出了一种在室温、大气环境等温和条件下通过酯化反应将端羧基聚合物链接枝到纳米SiO2微球表面从而制备有机/无机复合纳米微粒的新方法.该方法通过以下两个步骤得以实现,即第一,用3-环氧丙基三甲氧基硅烷对纳米SiO2微球表面进行改性处理,接着将引入到纳米SiO2表面的环氧基团转化为烷羟基基团;第二,通过引入到纳米SiO2微球表面的烷羟基与聚合物中的端羧基在室温下发生酯化反应,从而将聚合物接枝到纳米SiO2表面制得复合微球.利用XPS、FTIR、TEM和TGA等测试手段对纳米SiO2的改性过程以及聚合物接枝后得到的复合微球进行了表征.研究结果表明,该室温酯化接枝方法具有较高的接枝率,接枝到无机纳米微粒表面的聚合物占复合微球质量的55wt%～70wt%;接枝聚合物后,纳米SiO2微球的粒径从40nm增加到64～75nm,从而得到了以SiO2为核、以聚合物为壳的有机-无机复合微球.     

硫化物-高分子复合微球表面形貌与模板组成关系的研究

以N-异丙基丙烯酰胺(NIPAM)和甲基丙烯酸(MAA)为单体, 通过反相悬浮聚合法制备了多种MAA含量不同的阴离子型P(NIPAM-co-MAA)共聚微凝胶. 以这些共聚微凝胶为模板, 在不同表面活性剂存在下, 合成了一系列CuS(CdS、ZnS)-P(NIPAM-co-MAA)无机-有机复合微球材料, 研究了表面活性剂种类, 模板组成等因素对上述硫化物-高分子复合微球表面形貌的影响. 结果表明, 实验条件下所得复合微球表面均具有图案化结构, 该结构明显依赖于表面活性剂的种类和模板微凝胶的组成. 就模型体系而言, 随表面活性剂Span-20、Span-80和Span-85的HLB(亲水亲油平衡)值降低, 微球表面形貌趋于粗糙, 但仍然十分规整; 就模板组成而言, 模板中MAA含量增加使得复合微球的表面形貌变得更加精细. 据此, 认为通过选用合适的表面活性剂和微凝胶模板可以在一定范围内调控这些无机-有机复合微球的表面形貌, 从而为后续应用研究奠定基础.     

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.     

Fabrication of sub-micrometer-sized jingle bell-shaped hollow spheres from multilayered core-shell particles

Jingle bell-shaped hollow spheres were fabricated starting from multilayered particles composed of a silica core, a polystyrene inner shell, and a titania outer shell. Composite particles of silica core-polystyrene shell, synthesized by coating a 339-nm-sized silica core with a polystyrene shell of thickness 238 nm in emulsion polymerization, were used as core particles for a succeeding titania-coating. A sol-gel method was employed to form the titania outer shell with a thickness of 37 nm. The inner polystyrene shell in the multilayered particles was removed by immersing them in tetrahydrofuran. These successive procedures could produce jingle bell-shaped hollow spheres that contained a silica core in the titania shell.     

Preparation and characterization of silver/TiO2 composite hollow spheres

Silver-coated poly(methyl acrylic acid) (PSA) core-shell colloid particles were prepared by an in situ chemical reduction method. Crystalline silver/titania composite hollow spheres were obtained by coating the as-prepared PSA/silver particles with an amorphous titania layer and subsequently calcining in Ar atmosphere. SEM and TEM investigation indicated that the size of the as-prepared PSA/silver and PSA/silver/TiO(2) core-shell particles and silver/titania composite hollow particles was fairly uniform and the wall thickness of the hollow spheres was in the range of 40-80 nm. UV-vis absorption spectra were recorded to investigate their optical properties.     

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.     

Application of liquid phase deposited titania nanoparticles on silica spheres to phosphopeptide enrichment and high performance liquid chromatography packings

A novel core-shell composite (SiO(2)-nLPD), consisting of micrometer-sized silica spheres as a core and nanometer titania particles as a surface coating, was prepared by liquid phase deposition (LPD). Here, we show the resulting core-shell composite to have better efficient and selective enrichment for mono- and multi-phosphopeptides than commercially available TiO(2) spheres without any enhancer. The material exhibited favorable characteristics for HPLC, which include narrow pore size distribution, high surface area and pore volume. We also show that the core-shell composite can efficiently separate adenosine phosphate compounds due to the Lewis acid-base interaction between titania and phosphate group when used as HPLC packings. After coating the silica sphere with titania by LPD, the silanol of silica spheres will be shielded and that the stationary phase, C(18) bonded SiO(2)-3LPD, could be used under extreme pH condition.     

Aerosol assisted synthesis of silica/phenolic resin composite mesoporous hollow spheres

Hollow spheres of phenolic resin/silica composite are synthesized by macroscopic phase separation of a sorbitan monooleate surfactant Span 80 during aerosol-assisted spraying. The cavity can be evolved from multiple compartments to single hollow cavity with the increase of Span 80 content. The composite shell becomes mesoporous due to the release of small molecules after thermal treatment above 350 °C. After further thermal treatment at a higher temperature for example 900 °C in nitrogen or 1,450 °C in argon, the carbon/silica composite hollow spheres or crystalline silicon carbide hollow spheres are derived, respectively. Compared to the pure phenolic resin-based carbon spheres, thermal stability of the carbon-based composite spheres in air is essentially improved by the introduction of inorganic component silica. The carbon-based composite hollow spheres combine both performances of easy mass transportation through macropores and high specific surface area of mesopores, which will be promising to support catalysts for fuel cells. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Low‐Temperature Facile Template Synthesis of Crystalline Inorganic Composite Hollow Spheres

This report presents a facile approach for the low‐temperature synthesis of crystalline inorganic‐oxide composite hollow spheres by employing the bulk controlled synthesis of inorganic‐oxide nanocrystals with polymer spheres as templates. The sulfonated polystyrene gel layer can adsorb the target precursor and induce inorganic nanocrystals to grow on the template in situ. The crystalline phase and morphology of the composite shell is tunable. By simply adjusting the acidity of the titania sol, crystalline titania composite hollow spheres with tunable crystalline phases of anatase, rutile, or a mixture of both were achieved. The approach is general and has been extended to synthesize the representative perovskite oxide (barium and strontium titanate) composite hollow spheres. The traditional thermal treatment for crystallite transformation is not required, thus intact shells can be guaranteed. The combination of oxide properties such as high refractive index, high dielectric constant, and catalytic ability with the cavity of the hollow spheres is promising for applications such as opacifiers, photonic crystals, high‐κ‐gate dielectrics, and photocatalysis.     

A novel and facile preparation method of hollow silica spheres containing small SiO2 cores

This article presents a novel and facile preparation method of hollow silica spheres with loading small silica inside. In this approach, positively charged SiO₂/polystyrene core‐shell composite particles were synthesized first, when the silica shells from the sol‐gel process of tetraethoxysilane were then coated on the surfaces of composite particles via electrostatic interaction, the polystyrene was dissolved subsequently even synchronously in the same medium to form hollow silica spheres with small silica cores. TEM, SEM, and FTIR measurements were used to characterize these composite spheres. Based on this study, some inorganic or organic compounds could be loaded into these hollow silica spheres. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3431–3439, 2007     

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.     

Facile fabrication of hollow silica and titania microspheres using plasma-treated polystyrene spheres as sacrificial templates

By means of a plasma technique, the surfaces of monodisperse polystyrene (PS) colloids have been modified with hydroxyl groups. Using these surface-modified PS colloids as sacrificial templates, we have fabricated silica-coated PS colloids (PS@silica) and titania-coated PS colloids (PS@titania) composite microspheres as well as hollow and mesoporous silica and titania microspheres. This process not only demonstrated a facile, low-cost, environmentally benign way to fabricate hollow oxides structures but also offered a feasible alternative to the preparation of polymer/inorganic oxide composites by templating against the polymer substrate with hydrophobic surfaces.