Br?nsted酸性离子液体催化缩醛化反应合成聚甲氧基二烷基醚

聚甲氧基二烷基醚(RO(CH2O)nR)具有高的十六烷值(CN)和含氧量,能显著改善柴油的燃烧特性,有效提高热效率,大幅减少碳烟和NOx排放,被认为是一种优良的环保型燃油组分.随着–R基碳链的增长,CN值、热值和闪点逐渐增大,密度和冷凝点逐渐降低.同时,该类化合物具有优异的溶解及渗透性能,能与许多有机溶剂互溶,低毒,可以用作溶剂或颜料分散剂.近年来,聚甲氧基二甲基醚(CH3O(CH2O)nCH3,PODEn,DMMn)的制备及应用研究受到广泛关注,而对封端基团(–R)碳数大于1的多醚类化合物的研究鲜有文献报道.本文以Br?nsted酸性离子液体为催化剂,对甲醛和二乙氧基甲烷或脂肪醇(碳数 ≥2)缩醛化反应制备聚甲氧基二烷基醚的反应性能进行了研究,考察了离子液体结构和酸性对其催化性能的影响.结果表明,–SO3H功能化的离子液体[MIMBs]HSO4在催化三聚甲醛与二乙氧基甲烷的缩醛化反应中表现出最好的催化活性.考察了催化剂用量、原料配比、反应温度、反应压力和反应时间等因素对反应性能的影响,并得到了最佳反应条件,在n([MIMBs]HSO4):n(DEM1):n(HCHO)=1:80:80,140°C下反应4 h,甲醛转化率达到了92.6%,DEM2–8选择性为95.1%.考察了不同甲醛源(三聚甲醛和多聚甲醛)与提供封端基团化合物(二乙氧基甲烷、乙醇、丙醇和丁醇)的缩醛化反应.结果发现,在反应过程中不生成水或不引入水的条件下,具有更高的反应转化率和产物选择性.分别采用静置分层和萃取实现了催化剂的分离与重复使用.推测反应机理认为,三聚甲醛首先在氢键作用下分解生成甲醛单体,甲醛和二乙氧基甲烷通过碳正离子反应机理实现了DEMn的链增长.     

热溶液中Nafion膜电极电化学分析法测定偶氮二甲酰胺

基于偶氮二甲酰胺在热溶液中的高溶解度及其与Nafion膜电极的静电作用,建立了偶氮二甲酰胺的电化学分析法.考察了偶氮二甲酰胺溶解度的温度效应,研究了偶氮二甲酰胺在Nafion膜电极上还原反应的机理.利用热溶液中偶氮二甲酰胺在Nafion膜电极上的伏安响应,用差分脉冲伏安法测定了面粉中的偶氮二甲酰胺含量.在水浴恒温80℃、pH 6.0的实验条件和优化的测试参数下,Nafion膜电极的电流响应与偶氮二甲酰胺的浓度在0.93～ 10.5 μg/L范围内呈线性关系,检出限为0.58 μg/L(S/N=3),对实际样品测定的相对标准偏差小于5.9％,回收率为95.8％ ～ 104.0％,氨基脲和呋喃西林不干扰偶氮二甲酰胺的测定.     

Synthesis of star polymeric ionic liquids and use as the stabilizers for high internal phase emulsions

A series of well-defined core cross-linked star (CCS) polymeric ionic liquids (PILs) were synthesized via a three-step approach. First, the styrenic imidazole-based CCS polymer (S-PVBnIm) was prepared by the RAFT-mediated heterogeneous polymerization in a water/ethanol solution, followed by the quaternization of S-PVBnIm with bromoalkanes and anion exchange. The CCS polymers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The obtained CCS polymers were used as the effective emulsifiers for oil-in-water high internal phase emulsions (HIPEs). Multiple oils with different polarity including n-dodecane, undecanol, toluene and octanol were emulsified using 0.5 wt% S-PVBnIm aqueous solution under the acidic condition to form HIPEs with long-term stabilities. The excellent emulsification properties of CCS PILs were demonstrated by HIPE formation for a variety of oils. The properties of HIPEs in terms of emulsion type and oil droplet size were characterized by the confocal laser scanning microscopy (CLSM). The intriguing capability of CCS PILs to stabilize HIPEs of various oils holds great potentials for the practical applications.     

Efficient P3HT:PC61BM solar cells employing 1,2,4-trichlorobenzene as the processing additives

The efficiency of the poly(3-hexylthiophene)(P3HT) and [6,6]-phenyl C_(61)-butyric acid methyl ester(PC_(61)BM) based organic solar cells was enhanced by using 1,2,4-trichlorobenzene(TCB) as a processing additive to control the blend morphology. The addition of TCB improved the arrangement of P3HT which resulted in good phase separated blend films. Correspondingly, the optimized solar cells showed a power conversion efficiency(PCE) of 4.17% with a fill factor(FF) of 0.69, which were higher than those of common thermal annealing devices(PCE 3.84%, FF 0.67). The efficiency was further improved to 4.74% by thermal annealing at 150 °C for 10 min with a higher FF of 0.74.     

Synthesis and properties of allyloxy-based tolane liquid crystals with high negative dielectric anisotropy

A series of tolane liquid crystals (LCs) containing 2,3-difluorophenyl and allyloxy terminal groups have been synthesised via multi-step reactions. Their thermotropic mesophases, birefringences and dielectric anisotropy properties are discussed by comparison with the non-fluorinated analog. The results show that the allyloxy-based tolane LC 3TOV reveals a high value of the birefringence (0.29), negative dielectric anisotropy (?4.44) and a broad nematic mesophase with a low melting point and high clearing point. The effects of the terminal alkyl chains, the lateral fluoro substituents, the allyloxy terminal group and alkyne bridge on the mesomorphic and physical properties were also discussed. Meanwhile, Density Functional Theory (DFT) calculations of molecular conformation and polarisability were used to correlate the experimental findings.     

A Portable Plasma Sterilizer

An atmospheric microplasma jet system powered by an commercial transformer is developed for investigating the sterilizing efficiency of Escherichia coli in different conditions. The device can be hand-held and operated in the open air. The effect of carrier gas, gas flow rate, distance and treatment time of inactivation is studied. According to the experiment, plasma jet is able to inactivate all the bacteria on the surface in 20 s when the air flow rate is 5 L/min and the distance is 2.0 cm. Besides, the sterilization efficacy with different carrier gas follows an order as bellow: N₂ > air > O₂ > Ar. The measurements of malondialdehyde content, protein leakage quantity and Mg content are performed as well. In addition, the SEM after plasma treatment reveals that the integrity of E. coli cells is damaged and intracellular particles are excreted into the extracellular space. With discussions upon the mechanisms of surface sterilization, it is found that during the treatment of microplasma, it is mainly the etching actions of electrons and ions on the bacilli that kill the E. coli. Chemical effects rather than physical ones that are responsible for inactivation. Furthermore, the experiment results suggest that there may be better sterilization effect with gas mixture as carrier gas.     

Fabrication of Electrospun PVDF Nanofibers with Higher Content of Polar β Phase and Smaller Diameter by Adding a Small Amount of Dioctadecyl Dimethyl Ammonium Chloride

In this work,the effect of dioctadecyl dimethyl ammonium chloride(DDAC,a kind of alkyl ammonium salt) on polar β phase content and the diameter of electrospun PVDF nanofibers was investigated for the first time.Our experimental results show that the diameter of the electrospun PVDF nanofiber could be largely reduced and the content of polar β phase also become dominant immediately by just adding a little amount of DDAC.When the mass fraction of DDAC reached 4%,the content of polar β phase increased by about 39.1% compared with PVDF nanofibers without DDAC.Besides,the crystallinity of PVDF nanofibers also increased with the addition of DDAC.Based on the results,the possible mechanism of cooperative effect between electrospinning and DDAC on fiber diameter and formation of β phase in PVDF was discussed.     

<Emphasis Type="Italic">In situ</Emphasis> synthesis of block copolymer nano-assemblies by polymerization-induced self-assembly under heterogeneous condition

Controlled synthesis of amphiphilic block copolymer nanoparticles in a convenient way is an important and interest topic in polymer science. In this review, three formulations of polymerization-induced self-assembly to in situ synthesize block copolymer nanoparticles are briefly introduced, which perform by reversible addition-fragmentation chain transfer (RAFT) polymerization under heterogeneous conditions, e.g., aqueous emulsion RAFT polymerization, dispersion RAFT polymerization and especially the recently proposed seeded RAFT polymerization. The latest developments in several selected areas on the synthesis of block copolymer nano-assemblies are highlighted.     

Enhanced electron transfer ability <Emphasis Type="Italic">via</Emphasis> coordination in block copolymer/porphyrin/fullerene micelle

Inspired by structures of antenna-reaction centers in photosynthesis, the complex micelle was prepared from zinc tetra-phenyl porphyrin (ZnTPP), fullerene derivative (PyC₆₀) and poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL). The core-shell structure made the hydrophobic donor-acceptor system work in aqueous. In micellar core, coordination interaction occurred between ZnTPP and PyC₆₀ molecules which ensured the enhanced energy migration from the donor to the acceptor. The enhanced interaction between porphyrin and fullerene was confirmed by absorption, steady-state fluorescence and transient fluorescence. The generation of singlet oxygen and superoxide radical was detected by iodide method and reduction of nitro blue tetrazolium, respectively, which confirmed that electron transfer reaction in the complex micellar core occurred. Moreover, the complex micelle exhibited effective electron transfer performance in photodebromination of 2,3-dibromo-3-phenylpropionic acid. The complex micellar structure endowed the donor-acceptor system with improved stability under irradiation. This strategy could be helpful for designing new electron transfer platform and artificial photosynthetic system.     

Poly(<Emphasis Type="Italic">β</Emphasis>-cyclodextrin)-mediated polylactide-cholesterol stereocomplex micelles for controlled drug delivery

A series of host-guest interaction-adjusted polylactide stereocomplex micelles was prepared via the self-assembly of 4-armed poly(ethylene glycol)-block-poly(L-lactide/D-lactide)-cholesterol (4-armed PEG-b-PLLA/PDLA-CHOL) and poly(β-cyclodextrin) (PCD) with the molar ratios of CHOL/β-CD at 1:0.5, 1:1, and 1:2 in an aqueous environment. The hydrodynamic diameters of the micelles ranged from 84.1 nm to 107 nm depending on the molar ratio of CHOL/β-CD. It was shown that the micelle with the largest proportion of PCD possessed excellent abilities in drug release, cell internalization as well as proliferation inhibitory effect toward human A549 lung cancer cells. The results demonstrated that the stereocomplex and host-guest interactions-mediated PLA micelles exhibited great potential in sustained drug delivery.