Fabrication of silica nanoparticles and hollow spheres using ionic liquid microemulsion droplets as templates

Silica products with two different morphologies were synthesized using nonaqueous ionic liquid microemulsion droplets as templates. The morphologies of the obtained products were characterized by both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). By adjusting the reaction conditions, ellipsoidal nanoparticles were formed under acidic conditions, while hollow silica spheres were obtained under alkaline conditions. It is demonstrated that the size distribution of hollow silica spheres was narrower than that of the ellipsoidal nanoparticles. The various vibration modes of different functional groups in the silica materials were revealed by Fourier transform infrared (FTIR) spectroscopy. The two samples were both shown to be amorphous, not crystalline by X-ray diffraction (XRD). A simple diagram of the formation process including the hydrolysis and condensation reactions is given. Furthermore, a probable mechanism for the formation of silica materials under acidic or alkaline conditions is presented, which may be helpful for better understanding the different silica materials obtained under different conditions.     

Vertically well aligned P-doped ZnO nanowires synthesized on ZnO-Ga/glass templates

Vertically well aligned P-doped ZnO nanowires were prepared on ZnO-Ga/glass templates at 550 degrees C by reactive evaporation without metal catalysts and the nanowires were found to be single crystalline with the würtzite structure, oriented in the c-axis direction; the P-doping shortened the physical lengths of the ZnO nanowires without changing their diameter, and furthermore, the introduction of P atoms resulted in a much weaker and broader ZnO band edge emission.     

A systematic methodology to design silica templates: Silica microemulsion formulation and nanodroplet type and size estimation

A systematic study of the design and characterization of silica-microemulsion templates is presented. The ternary phase diagrams in micro-heterogeneous systems, by using a non-ionic surfactant (Brij 30) and different silica precursors (MTEOS, TEOS, PTEOS), have been drawn. Based on Khalweit diagrams, the phase inversion temperature was estimated as close to 315 K, for both alchil (TEOS) and aril (PTEOS) types of alcoxides. By correlating the information obtained from phase diagrams at room temperature with that of size effects revealed by VIS absorption molecular probes (bromthymol blue dye), the phase inversion point, i.e. the transition point from water-in-oil to oil-in-water microemulsion, was also clearly established as corresponding to R ∼ 1. Besides technically attractive features such as a wide variety of inorganic and hybrid nanomaterials, high specific surface and highly efficient applicative properties of the final materials, the approach of silica-microemulsion-based templates can be seen as a route towards the Green Chemistry concept.     

一种新型的糖基型紫外线吸收剂的合成和表征

<正>紫外线是太阳光谱中波长200～400nm部分的电磁波,约占太阳辐射的6%,按波长不同,又可分为UVC(短波紫外线,200～280nm)、UVB(中波红斑效应紫外线,280～320nm)、UVA(长波黑斑效应紫外线,320～400nm)3个区段,其中UVC几乎全部被大气层阻滞,对人体无法造成伤害。     

可改变DNA构象的非离子糖基表面活性剂

通过Zeta电位及粒径分析考察发现随着体系中辛基葡萄糖多苷表面活性剂质量 农度的增加，DNA分子在溶液中的构趋于缩拢。通过DNA-C_8APG复合物的UV吸收及 CD谱图进一步考察了DNA二级结构变化。随后的扫描电子显微镜（SEM）照片也证实 DNA分子在水溶液中的构象缩拢。通过表面张力UV图谱分析，推测非离子糖基表面 活性剂与DNA分子复合物结合的可能结构是表面活性剂与DNA之间的疏水作用及 多羟基的糖类的亲水头基结构与DNA带负电的核酸磷酸骨架以氢健的方式结合。     

DNA与非离子糖基表面活性剂相互作用的研究

用动态表面张力法、键合等温线、紫外光谱及荧光光谱等方法研究了不同链长烷基葡萄糖苷(APG)与DNA的相互作用．研究发现APG对DNA键合可分为两阶段,第一阶段：多苷依靠多羟基结构与DNA形成动力学稳定的复合物;第二阶段：随时间延长,单苷由于其较小的空间位阻而与DNA形成能量更低的热力学稳定复合物．由平衡渗析法得到的单苷与DNA相互作用键合等温线显示,APG与DNA键合为一非协同过程．证实了其非离子氢键吸附的本质,同时也支持了DNA对胶束及预胶束的缠绕模型．紫外光谱结果证明了在APG与DNA作用过程中疏水作用的重要性．以溴化乙锭为探针,荧光光谱法研究证明,随APG链长增加,DNA构象缩拢程度加大,但即使是C2APG也仅能使DNA构象部分缩拢,推测DNA仅是部分链段对APG胶束进行包裹,其它链段仍处于伸展状态．与阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)可使DNA构象强烈缩拢的事实相比,证明了静电作用在大分子与表面活性剂相互作用中的主导性．     

Semicontinuous microemulsion polymerization

Batch microemulsion polymerization is a process that allows the synthesis of oil-soluble and water-soluble nanoparticles, nanocomposites and nanogels smaller than ca. 50 nm with larger molecular weights (ca. 10⁷ g/mol); however, the large amounts of surfactant required by this process to produce small amounts of polymer have hindered its industrial scaling. Semicontinuous O/W and W/O microemulsion polymerizations allow increasing the polymer content without adding more surfactant to the original reacting formulation. The several schemes of semicontinuous microemulsion polymerization that have been proposed, semibatch, semicontinuous feeding or lot additions of monomer to the reacting microemulsion, are reviewed here. Semicontinuous inverse microemulsion polymerization, which is a process to synthesized water-soluble polymer nanoparticles that have important applications as superabsorbents and flocculants, are also reviewed. Moreover, alternative processes, denoted by our group as normal and inverse semicontinuous heterophase polymerizations, which allows the synthesis of even larger concentration of polymer employing smaller amounts of surfactant compared to microemulsion polymerization, are examined.     

Sugar-based phosphite and phosphoroamidite ligands for the Cu-catalyzed asymmetric 1,4-addition to enones

A modular sugar-based phosphoroamidite L1–L5a–g and phosphite L6–L9a–g ligand library was tested in the asymmetric Cu-catalyzed 1,4-conjugate addition reactions of β-substituted (cyclic and linear) and β,β′-disubstituted (cyclic) enones. The selectivity depended strongly on the configuration of carbon atom C-3, the size of the sugar backbone ring, the flexibility of the ligand backbone, the substituents and configurations in the biaryl phosphoroamidite moieties a–g, the type of functional group attached to the ligand backbone and the substrate structure. Therefore, by carefully selecting the ligand parameters, enantioselectivities of up to 60% for cyclic substrates and 72% for linear ones were achieved.     

Resorcinarenes as templates

Metal ions are superb at templating the synthesis of small macrocycles that are decorated with Lewis basic sites. However, for the synthesis of larger macrocycles, or the synthesis of macrocycles devoid of an array of Lewis basic sites, metal ions are less useful. Here we demonstrate that resorcinarenes can be used as templates to engender the efficient formation of large crown ethers. A three step process of 1). tethering moieties to the template, 2). linking those moieties, and 3). then cleaving off the template leads to the efficient formation of a family of aromatic crown ethers. If adaptable, this approach will prove useful for the construction of macrocycles that are hard to obtain from a step-wise synthesis.     

阿司匹林微乳的制备及性质研究

关于阿司匹林的研究至今已有百年的历史,它具有镇痛、消炎、解热的作用.上世纪60年代末期,人们又发现阿司匹林具有新的用途,阿司匹林能够影响血小板功能,并通过抑制血小板环氧化酶及血栓A2的形成完成其抗血栓形成和预防心血管血栓栓塞性疾病的作用.     

Modeling inverse microemulsion polymerization

A mathematical model for inverse microemulsion polymerization has been developed. The model has been used to fit experimental results of the effect of initiator concentration, light intensity, emulsifier concentration, and dispersed phase weight fraction on the monomer conversion evolution, particle size, and polymer molecular weight in the inverse microemulsion polymerization of 2-methacryloyl oxyethyl trimethyl ammonium chloride (MADQUAT) initiated by UV light in the presence of AIBN. A good fitting of the experimental data was achieved. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2167–2178, 1999     

Emulsifier for microemulsion polymerization

 By introducing an hydroxyl group and a lipophilic branch into the middle of lipophilic head of emulsifier 12-oxy-9-octadecenoic acid, a new emulsifier was synthesized and applied in microemulsion polymerization. When the emulsifier content in the microemulsion was kept to about 12%, the highest monomer content in microemulsion could achieve 35% for BA, 20% for St and MMA. The microemulsion with high monomer content remained clear after polymerization, and the average diameters of polymer particles were 38.9 nm for St microemulsion, 47.4 nm for BA, and 50.7 nm for MMA. Received: 18 November 1997 Accepted: 16 January 1998     

Progress in microemulsion characterization

Microemulsions are technologically important complex fluids. In many applications, they are required to accommodate functional additives such as drugs, polymers, and nanoparticles, which increase the complexity of the systems further. Multiple complementary techniques are required in order to understand and manipulate microemulsion behavior. Recent advances in analytical techniques as well as theoretical models have allowed observation of the nanoscale morphology of different microemulsion forms of increasing complexity at ever greater resolution. At the same time, there is increasing interest in the study of dynamic processes within microemulsions using scattering techniques as well as techniques such as fluorescence correlation spectroscopy and ultrafast IR spectroscopy. This paper reviews these and other recent developments in the characterization of microemulsion systems.     

Sugar-based gemini surfactants with peptide bonds-synthesis, adsorption, micellization, and biodegradability

The sugar-based gemini surfactant with peptide bonds, N,N'-bisalkyl-N,N'-bis[2-(lactobionylamide)ethyl]hexanediamide (2C(n)peLac, in which n represents hydrocarbon chain lengths of 12 and 16), was synthesized by reacting adipoyl chloride with the corresponding monomeric surfactant N-alkyl-N'-lactobionylethylenediamine (C(n)peLac), which was obtained by reacting ethylenediamine with alkyl bromide and lactobionic acid. The adsorption and micellization properties of C(n)peLac and 2C(n)peLac were characterized by the measurement of their equilibrium and dynamic surface tension, steady-state fluorescence using pyrene as a probe, dynamic light scattering (DLS), and time-resolved fluorescence quenching (TRFQ), and their biodegradability was also investigated. The critical micelle concentration (cmc) decreases with an increase in the hydrocarbon chains from monomeric to gemini surfactants, whereas it increases with an increase in the chain length from 12 to 16 for both systems. The increases in both the hydrocarbon chain and the chain length of sugar-based surfactants reduce surface activities such as the ability to lower the surface tension, the occupied area per molecule, and the adsorption rate at the air/water interface. The sugar-based surfactants C(n)peLac and 2C(n)peLac exhibit unique aggregation behavior in aqueous solution. The DLS results indicate that the apparent hydrodynamic diameter of C(n)peLac micelles decreases sharply with increasing concentration, whereas that of 2C(n)peLac micelles decreases gradually. From the TRFQ measurement, it was observed that, as concentration increases, the aggregation numbers are almost constant for C(n)peLac, whereas they increase for 2C(n)peLac. These results imply that loosely packed micelles formed by sugar-based surfactants become tightly packed micelles as the concentration increases. Furthermore, it was found that 2C(n)peLac shows lower biodegradability than does C(n)peLac because it contains tertiary amines in the molecule.     

Polymerization in inverse microemulsion

Homopolymerization of acrylamide as well as that of methyl methacrylate and the copolymerization of acrylamide with methyl methacrylate and/or styrene in inverse microemulsion toluene/water 10: 1 by weight have been studied. Water-soluble ammonium peroxodisulfate, partially water-soluble 2,2′-azobisisobutyronitrile, and oil-soluble dibenzoyl peroxide were used for initiation of these polymerizations at 60°C. Redox initiation system consisting of ammonium peroxodisulfate and tetramethylethylenediamine has been used for an effective initiation of the reactions studied at 30°C. Polymerizations in inverse microemulsions were found start in the interlayer oil macrophase/water microphase. The initial rates of copolymerizations reactions studied depended only on the comonomer mixture composition. The type of the initiator used affected only the exhibited inhibition period.     

Universal cyclic polymer templates

Two unique molecular templates for generating polymeric materials with a cyclic molecular architecture were developed by combining ring-expansion metathesis polymerization and click chemistry. These two universal cyclic polymers were used in three examples to demonstrate the wide range of potential materials enabled. They include functional cyclic polymers, cyclic polymer brushes, and cyclic gels.     

非离子型微乳液的热力学性质Ⅲ:盐类和PH值的影响

以非离子型表面活性剂(Triton X-100)、十六烷、正已醇和水所组成的微乳液,研究醇从油相向界面层转移时的体系Gibbs函数变化,并从热力学关系式得出焓和熵的变化关系.本文研究了相中不同盐类和PH值对这些热力学函数的影响,发现这些热力学函数与盐类中阳离子价数和PH值都呈线性关系.     

Sugar-based diphosphoroamidite as a promising new class of ligands in Pd-catalyzed asymmetric allylic alkylation reactions

We have designed a new family of readily available modular diphosphoroamidite ligands from d-xylose for Pd-catalyzed asymmetric allylic alkylation reactions. This constitutes the first example of diphosphoroamidite ligands applied to this process. Good-to-excellent activities (TOFs up to 850 mol substratex(mol Pdxh)-1) and enantioselectivities (ee's up to 95%) have been obtained for several substrates with different electronic and steric properties. The results indicate that catalytic performance is highly affected by the substituents and the axial chirality of the biaryl moieties of the ligand. We also discuss the synthesis and characterization of the Pd-pi-allyl intermediates to get more insight into the origin of enantioselectivity using these catalytic systems.