Self-assembly of polyaniline nanowires into polyaniline microspheres

High quality microspheres self-assembled from nanowires of polyaniline (PANI) are prepared by a self-assembly process using ammonium peroxydisulfate as oxidant in aqueous solution. The microspheres of about 2.6 μm average diameter are composed of uniform nanowires with 40-60 nm in diameter. The formation process of PANI microsphere indicates that its evolution of morphologies can be divided into three stages. First, a large quantity of PANI nanowires form, then porous microspheres develop, and finally most of nanowires transform into microspheres. The morphology and uniformity of the PANI microspheres mainly depend on the mole ratio of aniline to ammonium peroxydisulfate. The BET specific surface area and conductivity of the polyaniline porous microsphere at room temperature are 53 m² g^− 1 and 3.3 × 10⁻¹ S cm^− 1, respectively.     

Self-assembly of polystyrene microspheres within spatially confined rectangular microgrooves

A convective self-assembly of mono-sized polystyrene spheres with diameters ranging from 262 to 1000 nm was conducted on patterned silicon wafers with one-dimensional, periodic rectangular microgrooves of different widths (0.65–6 μm). The latex beads were driven into the spatially confined microgrooves by the capillary interactions and the confined wall during solvent evaporation, resulting in a range of packing structures. Processing variables including evaporation temperature, particle size (D), groove width (W), and groove height (H) were examined experimentally, and geometrical models were proposed to explain the various packing structures obtained. The degree of spatial freedom for the particles to rearrange themselves in the confined channels is found critical to the assembled particle-packing structure.     

Novel PEGylated pH-sensitive polymeric hollow microspheres

Novel PEGylated pH-sensitive poly[methacrylic acid-co-poly(ethylene glycol) methyl ether methacrylate] [P(MAA-co-PEGMA)] hollow microspheres were synthesized by a two-stage distillation precipitation polymerization. PMAA@P(MAA-co-PEGMA) core shell microspheres were synthesized by the second-stage polymerization of MAA and PEGMA, using the N,N′-methylenebisacrylamide (MBAAm) as crosslinker in the presence of non-crosslinked PMAA microspheres. The cavity was formed by selective removal of PMAA core in ethanol. The resulted PEGylated hollow microspheres were characterized with Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR). The shrink and swelling behavior under different pH was studied by Dynamic Light Scattering (DLS).     

Self-assembly in sugar-oil complex glasses

In aqueous systems, the hydrophobic effect drives the self-assembly of amphiphiles into a broad range of micellar, rod-like, bicontinuous and liquid-crystalline complex fluids. Many of these are relevant to biological matter or technological applications. However, amphiphilic self-assembly is not limited to aqueous systems. Replacement of water with supercritical carbon dioxide, for example, results in complex fluids that combine the properties of gases and liquids. Along this vein, we explore the self-assembly of surfactants in anhydrous sugars. Our study reveals that anhydrous powders of sugars and surfactants suspended in oil spontaneously form molten glasses with nanometre-size domains of sugar and liquid oil without mixing. The low cost, water solubility, low toxicity and stabilizing properties of glassy sugars make them ideal water replacements for many pharmaceutical, food and materials synthesis applications. The optical clarity and solid appearance of these glasses at room temperature belie their inclusion of more than 50% (vol.) oil, which confers liquid-like diffusivity. The unique combination of solid- and liquid-like properties may lead to applications in sensors and optical devices.     

Enhanced thermal properties of graphene oxide-incorporated polymeric microspheres

Polystyrene (PS) microspheres coated with graphene oxide (GO) were prepared and the variation of their thermal properties according to the GO loading was examined. The GO content in the PS-GO nanocomposites was controlled by the GO dispersions at various concentrations. The GO was coated onto the surface of the PS microspheres through the strong ionic interaction between polyvinylpyrrolidone and the GO sheet. The thermal properties of the GO incorporated PS microspheres were affected by the GO, which disturbed the chain activity and exhibited effective heat shielding. It also delayed the permeation of oxygen and hindered the escape of volatile degradation products from the PS-GO nanocomposites. In addition, the thermal degradation temperature of the nanocomposites was increased above 15 degrees C and their T(g) was also increased above 4.0 degrees C. PS-GO exhibited higher thermal conductivity (0.173 W/mK) than that of pure PS (0.117 W/mK).     

沉淀聚合法制备的高分子微球及其色谱性能

以二乙烯基苯(DVB)为交联剂、甲基丙烯酸甲酯(MMA)为功能单体,采用沉淀聚合法合成了聚(二乙烯基苯-co-甲基丙烯酸甲酯)[P(DVB-co-MMA)]微球。傅立叶变换红外吸收光谱(FT-IR)表征表明交联剂与功能单体实现了共聚,扫描电子显微分析(SEM)显示微球表面无大孔结构,粒径统计分析表明制备的微球为粒径单分散。采用反相液相色谱模式考察了微球的色谱性能,结果显示固定相具有较高的柱效和良好的色谱性能。研究表明沉淀聚合法制备的高分子微球在高效液相色谱法(HPLC)固定相方面具有较好的应用前景。     

含蒽醌生色团聚合物微球的制备及表征

在二氯甲烷中使丙烯酰氯与1-氨基蒽醌(1-AQ)反应合成了反应性1-丙烯酰胺基蒽醌(N-AQ)黄色染料,采用傅里叶变换红外光谱(FT-IR)和质子核磁共振(1H NMR)对其进行表征,表明制得的N-AQ结构明确。进而通过分散聚合法,使N-AQ与甲基丙烯酸甲酯(MMA)共聚,成功制备了黄色P(MMA-co-N-AQ)聚合物微球。由扫描电子显微镜(SEM)和zeta电位及粒度分析仪对微球的形态、大小及分布进行了表征,并利用可见光-紫外光谱仪(UV-Vis)对微球中引入的N-AQ含量进行了定量分析。结果表明,反应性染料的转化率达93.6%,在聚合反应中改变N-AQ的用量,可将所制备的微球粒径控制在1.3～3μm之间,球形完好、表面光滑、粒径均一,可望应用于彩色激光打印。     

Generation of polymeric structures on a computer

Our simulations of mechanical and tribological behavior of polymeric materials rely on the creation of realistic materials on a computer. They follow previous work with one- and two-phase two-dimensional materials [9, 10, 11]. We now report a procedure of creation of three-dimensional polymers. Related issues are those of characterization in terms of the average chain length and the average end-to-end distance and also of visualization of the structures before, during and after a tribological or mechanical simulated "experiment." Electronic Publication     

可生物降解聚合物微球的制备及载药应用

综述了近年来合成生物降解聚合物微球的种类、制备方法及作为药物载体的应用.结果表明,这类聚合物微球具有良好的安全性、生物相容性和生物降解性,在药物缓释、控释和疾病的治疗中具有非常重要的作用和应用前景.     

Preparation of inorganic/polymeric composite microspheres by direct suspension polymerization

Spherical polystyrene powders coated uniformly by-Fe₂O₃ or RuO₂ were obtained by means of a direct suspension polymerization. Starting reactant mixture was a complex disperse system comprising a fine powdered material, droplets of styrene monomer containing lauroyl peroxide as an initiator; and an aqueous medium. By varying the ratio between monomer and water, amount of powders as well as of the initiator, factors dominating particle size, volume fraction-of fine powders adhered and the degree of polymerization were elucidated     

氧化乐果分子印迹微球的制备及其性能研究

以氧化乐果为模板分子,甲基丙烯酸（MAA）为功能单体,利用悬浮聚合法制备了粒径分布范围较窄的氧化乐果分子印迹微球（MIPMs）和空白对照微球（NMIPMs）。通过紫外光谱及红外光谱说明了MAA与氧化乐果之间的结合作用,并利用扫描电子显微镜（SEM）观察了所制微球的外观形态和粒径分布。静态吸附实验证明MIPMs对氧化乐果的吸附量明显大于NMIPMs。Scatchard分析表明,MIPMs在识别氧化乐果过程中存在两类结合位点：高亲和位点的解离常数KD1=0.131mmol/L,最大表观结合量Qmax1=3.890μmol/g,低亲合位点解离常数为KD2=5.178mmol/L,最大表观结合量Qmax2=62.232μmol/g。选择性吸附实验结果表明MIPMs对氧化乐果的吸附量最大,具有很好的选择性能。     

Preparation of porous zirconia microspheres by internal gelation method

A modified internal gelation process for the preparation of porous zirconia microspheres has been developed. The conventional method has been modified by adding a surfactant in the feed broth. The effects of variation of surfactant concentration, washing techniques and temperature of calcination on the pore volume and the surface area of the microspheres have been studied. The conditions were optimized to obtain porous stable microspheres suitable for various applications. The microspheres were characterized by surface area analysis, pore volume analysis, thermogravimetric analysis and X-ray diffraction. The ion exchange behavior was studied using pH titration.     

Self-assembly of carbon nanotubes and boron nitride nanotubes into coaxial structures

Coaxial carbon nanotube/boron nitride nanotube (CNT/BNNT) multi-walled structures are ideal components in nanoelectronic systems. Our molecular dynamics simulations show that separate CNTs and BNNTs can self-assemble into stable coaxial structures in water under appropriate conditions. In case study three types of representative coaxial structures: (5, 5) CNT/(10, 10) BNNT, (5, 5) BNNT/(10, 10) CNT and (5, 5) BNNT/(10, 10) BNNT are obtained. Simulation results also reveal that the self-assembly time between two separate BNNTs is increased remarkably due to the polarization of BNNTs in water. The mechanism of self-assembly among these tubes is demonstrated in detail. Further, coaxial (10, 10) BNNT/(10, 10) CNT/(15, 15) BNNT nanoheterojunctions are achieved for potential application in nanoelectronic systems. The present work shows the feasibility to fabricate the coaxial nanodevices such as insulating high-strength cables, high frequency oscillators and nanojunctions using self-assembly approach.     

Self-assembly of polyamines as a facile approach to fabricate permeability tunable polymeric shells for biomolecular encapsulation

In this article, the self-assembly of polyamines as a facile approach to fabricate permeability tunable polymeric shells for encapsulation of relatively low molecular weight (LM(w)) hydrophilic biomacromolecules (M(w) ≈ 4000 Da) is presented. The entire process is performed in organic solvents within 2 to 4 h to allow for nearly 100% encapsulation yield. The polymeric shells are fabricated by a two-step process: 1) The self-assembly of polyamines (nonionized poly(allylamine) (niPA) or branched nonionized polyethyleneimine (niPEI)) within porous agarose microbeads via an inwards buildup self-assembly process. 2) Stabilization of assembled polyamines either via covalent (cross-linkers) or ionic bonding (complex with nonionized poly(styrene sulfonic acid) (niPSS)). Stable and distinct polymeric shells are formed in both cases. The shell thickness is demonstrated to be tunable within a range of 1 to 14 μm; and as the inwards buildup self-assembly technique is not a self-limiting process, shells with broader thicknesses can be achieved. Also, it is demonstrated that the polymer density of the shell can be tuned. Depending on the fabrication parameters, the resulting polymeric shells have been demonstrated to have different permeability characteristics for relatively LM(W) dextran (M(W) ≈ 4000 Da). For example, niPEI shells are observed to have a higher permeability than niPA shells. Therefore, polymeric capsules can be fabricated via this facile approach for either retention of relatively LM(w) hydrophilic biomacromolecules or designed to passively or responsively release the biomacromolecule payload. This two-step shell fabrication process represent an alternative and facile approach for the fabrication of self-assembled polymeric shells in the fields of capsule-based reactors/sensors and drugs/gene delivery where relatively LM(w) macromolecules are concerned.     

ZnO nanostructured microspheres and grown structures by thermal treatment

Synthesis of flower-shaped ZnO nanostructures composed of ZnO nanosticks was achieved by the solution process using zinc acetate dihydrate, sodium hydroxide and polyethylene glycol-20000 (PEG-20000) at 180°C for 4 h. The diameter of individual nanosticks was about 100 nm. Detailed structure characterizations demonstrate that the synthesized products are wurtzite hexagonal phase, grown along the [001] direction. The infrared (IR) spectrum shows the standard peak of zinc oxide at 571 cm⁻¹. Raman scattering exhibits a sharp and strong E ₂ mode at 441 cm⁻¹ which further confirms the good crystal and wurtzite hexagonal phase of the grown nanostructures.     

SA/PU共混水凝胶微球的制备及性能研究

得到性能良好的SA/PU共混微球以用于药物缓控释;方法:利用预聚-扩链-中和-分散法合成阴离子型PU水溶液;将SA水溶液与PU水溶液按质量比为1∶1,1∶2,1∶3,1∶4,1∶5混合,用滴制法制备共混微球;测定了微球的凝胶化、圆整性及溶胀性能.结果表明:用TDI与PEG-6000和PEG-4000反应才能制备出PU水溶液,而只有水溶液才能和海藻酸钠水溶液混合完全得到理想的共混溶液;SA/PU共混微球28h后凝胶化完全,SA微球48h后可凝胶化完全.PEG-6000合成的PU与海藻酸钠共混得到的微球圆整性要好于PEG-4000合成的PU与海藻酸钠共混得到的微球.且随着复合微球中PU的含量增大,微球的圆整性变好;SA/PU复合微球在蒸馏水(pH7)和盐酸(pH1)中均不溶胀,在磷酸缓冲溶液(pH6.86)中快速溶胀,在4～5h后开始崩解.结论:SA/PU复合微球在胃液中保持原状,在肠液中溶胀,可作为药物的缓释载体.     

Synthesis and photocatalytic activity of titania microspheres with hierarchical structures

A combined sol-gel and solvothermal process was introduced to fabricate the titania microspheres with hierarchical structures by using lauryl alcohol as the structure-directing agent. Scanning electron microscope, high-resolution transmission electron microscope, Fourier transform infrared spectrograph and powder X-ray powder diffraction indicated that the molar ratio of lauryl alcohol, water and tetra-n-butyl titanate was the key factor for the formation of the mono-dispersed titania with anatase phase and the optimal ratio was 1.2:4:1. The diameter of the end-product was 523 ± 74 nm and it was composed of smaller nanoparticles with about 6.8 nm size in diameter. Photocatalytic activity of the end-product was investigated by employing Rhodamine B and Methylene blue as the model compounds. The target microspheres exhibited the higher photocatalytic efficiency compared with commercial Degussa P25 titania and this result might be due to the hierarchical structures of microspheres according to the analysis of Brunauer-Emmett-Teller specific surface areas.     

Electronic structures of interfacial states formed at polymeric semiconductor heterojunctions

Heterojunctions between organic semiconductors are central to the operation of light-emitting and photovoltaic diodes, providing respectively for electron-hole capture and separation. However, relatively little is known about the character of electronic excitations stable at the heterojunction. We have developed molecular models to study such interfacial excited electronic excitations that form at the heterojunction between model polymer donor and polymer acceptor systems: poly(9,9-dioctylfluorene-co-bis-N,N-(4-butylphenyl)-bis-N,N-phenyl-1,4-phenylenediamine) (PFB) with poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), and poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) with F8BT. We find that for stable ground-state geometries the excited state has a strong charge-transfer character. Furthermore, when partly covalent, modelled radiative lifetimes (approximately 10(-7) s) and off-chain axis polarization (30 degrees) match observed 'exciplex' emission. Additionally for the PFB:F8BT blend, geometries with fully ionic character are also found, thus accounting for the low electroluminescence efficiency of this system.