Cationic polymerization of isobutylene coinitiated by AlCl3 in the presence of ethyl benzoate

<正>The cationic polymerizations of isobutylene(IB) coinitiated by AlCl_3 were carried out in solvent mixture of n-hexane /methylene dichloride(n-hex/CH_2Cl_2) of 60/40 V/V in the presence of ethyl benzoate(EB) at various temperatures range from-80℃to-30℃.The effects of EB concentration([EB]) and polymerization temperature on monomer conversion,weight-average molecular weight(M_w) and molecular weight distribution(MWD,M_w/M_n) of polyisobutylene (PIB) products were investigated.The rate of polymerization decreased while M_w of PIB products increased with increasing [EB].The polymers with high molecular weight could be prepared in the presence of a suitable amount of EB.Significantly, the polymers with high M_w of 80.2×10~4 and 65.4×10~4 could be produced at-80℃and-70℃at[EB]=0.24×10~(-3) mol/L respectively,which were much higher than that(M_w=57.9×10~4) of PIB prepared at-100℃in the absence of EB.A simple but effective method for preparing the high molecular weight polyisobutylenes was developed in this work.It has been also found that the activation energy for propagation(E_p) depended on the polymerization temperature range in the presence of EB.An obvious inflection of the linear plots of lnX_n versus 1/T_p occurred at the temperature range from-60℃to-50℃at four different concentrations of EB from 0.19×10~(-3) mol/L to 0.33×10~(-3) mol/L,and thus the inflection temperature(T_(inf)) was in the range of-60℃to-50℃.When[EB]was in the range of 0.24×10~(-3) mol/L to 0.33×10~(-3) mol/L,E_p was determined to be around-12 kJ/mol when the polymerization was carried out at temperatures from-80℃to T_(inf) and to be around-28 kJ/mol at temperatures from T_(inf) to-15℃respectively.     

Electrical conductivity of the ammonia-water system

The electrical conductivity (EC) of the ammonia-water system was studied in the concentration range 0.1–10 mol/L ammonia and the temperature range 15–60°C. The maximal EC of aqueous ammonia at a given temperature is proposed as the parameter for generalizing experimental results. The normalized EC was calculated as the ratio of the EC of aqueous ammonia of a given concentration to the maximal EC at a given temperature. Over the ranges of the concentrations and temperatures studied, all normalized ECs fall on one curve. The EC activation energy was analyzed as a function of ammonia concentration and temperature.     

离子液体电解质种类对活性炭电极超级电容器电化学性能的影响

本文将经水蒸气二次活化的椰壳活性炭（W-AC）作为电极材料,选择1-乙基-3甲基咪唑四氟硼酸盐（[EMIM]BF₄）作为电解质,结果表明W-AC电极的比电容量远高于未活化的椰壳活性炭（R-AC）.使用循环伏安、恒电流充放电、交流阻抗等方法研究了不同种类离子液体电解质对超级电容器电化学性能的影响.不同阴阳离子组成的离子液体作为电解质,直接影响超级电容器的电化学性能. 研究表明,由EMIM⁺和BMIM⁺阳离子与BF₄^-、TFSI^-阴离子构成的离子液体电解质较适用于W-AC电极. 其中在[EMIM]BF₄电解质中,单片电极的比电容量可高达153 F·g^-1;在1-丁基-3-甲基-咪唑四氟硼酸盐（[BMIM]BF₄）电解质中电位窗可达3.5V,能量密度可高达57 Wh·kg^-1.本研究对于构筑高性能超级电容器离子液体的选择提供参考,以满足不同应用领域需求.     

Distinct difference in ionic transport behavior in polymer electrolytes depending on the matrix polymers and incorporated salts

Two different electrolyte salts, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and a room temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI), were incorporated into network polymers to obtain ion-conductive polymer electrolytes. Network polymers of poly(ethylene oxide-co-propylene oxide) (P(EO/PO)) and poly(methyl methacrylate) (PMMA) were chosen as matrixes for LiTFSI and EMITFSI, respectively. Both of the polymer electrolytes were single-phase materials and were completely amorphous. Ionic conductivity of the polymer electrolytes was measured over a wide temperature range, with the lowest temperatures close to or below the glass transition temperatures (Tg). The Arrhenius plots of the conductivity for both of the systems exhibited positively curved profiles and could be well fit to the Vogel-Tamman-Fulcher (VTF) equation. The conductivity of the PMMA/EMITFSI electrolytes was higher at most by 3 orders of magnitude than that of the LiTFSI/P(EO/ PO) electrolytes at ambient temperature. When the ideal glass transition temperature, T0 (one of the VTF fitting parameters), was compared with the Tg, a difference in the ionic conduction was apparent in these systems. In the P(EO/PO)/LiTFSI electrolytes, the T0 and Tg increased in parallel with salt concentration and the T0 was lower than the Tg by ca. 50 degrees C. On the contrary, the difference between the T0 and the Tg increased with increasing content of PMMA in the PMMA/EMITFSI electrolytes, with the observed difference in the concentration range studied reaching up to ca. 100 degrees C. The conductivity at the Tg, sigma(Tg), for the LiTFSI/P(EO/PO) electrolytes was on the order of 10(-14-)10(-13) S cm(-1) and increased with increasing salt concentration, whereas that for the PMMA/EMITFSI polymer electrolytes reached 10(-7) S cm(-1) when the concentration of PMMA was high. The ion transport mechanism was discussed in terms of the concepts of coupling/decoupling and strong/fragile for the two different polymer electrolytes.     

Effects of sugars and polyols on the stability of azurin in ice

This study represents the first attempt to gain a quantitative estimate of the protective influence of sugars (sucrose and trehalose) and polyols (sorbitol and glycerol) on the thermodynamic stability (DeltaG degrees ) of a protein in low-temperature part-frozen aqueous solutions. The method, based on guanidinium chloride denaturation of the azurin mutant C112S from Pseudomonas aeruginosa, distinguishes between the effects of cooling to subfreezing temperatures from those induced specifically by the formation of a solid ice phase. The results point out that in the liquid state the generally stabilizing effect (at molar concentrations) of these polyhydric compounds is markedly attenuated on cooling to subfreezing temperatures such that at -15 degrees C, only sucrose still exerts a significant increase in DeltaG degrees . At this temperature, and in the absence of additives, the formation of ice caused a progressive destabilization of the native fold, DeltaG degrees decreasing up to 3-4 kcal/mol as the fraction of liquid water in equilibrium with ice (V(L) was reduced to less than 1%. Unexpectedly, denaturation profiles in ice at selected V(L) demonstrate that none of the above sugars and polyols counters effectively the decrease in protein stability at small V(L). Only trehalose was able to partly attenuate the ice perturbation, raising DeltaG degrees by a modest 0.6-0.8 kcal/mol relative to the salt reference. In all cases the reduction in DeltaG degrees caused by the solidification of water correlates with the decrease in m-value. The implication is that DeltaASA of unfolding is smaller in ice because protein-ice interactions either increase the solvent-accessible surface area (ASA) of the native fold (partial unfolding) or reduce the ASA of the denatured state (compaction), or both. Information on the protein tertiary structure in ice, in the absence and in the presence of sucrose or glycerol, suggests that these osmolytes play an important role in maintaining a compact native state that in their absence is expanded and partly unfolded. Thus, it appears that the prevailing mechanism by which these osmolytes act as cryoprotectants is through preservation of the native conformation in the liquidus rather than by increasing the thermodynamic stability of the native fold.     

Electrochemical reduction of O2 in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid containing Zn2+ cations: deposition of non-polar oriented ZnO nanocrystalline films

The influence of the Zn(2+) concentration and temperature on the electrochemical reduction of O(2) in a solution of zinc bis(trifluoromethanesulfonyl)imide (Zn(TFSI)(2)) salt in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR(14)TFSI) ionic liquid is presented. ZnO nanocrystalline films were then electrodeposited, under enhanced O(2) reduction, at temperatures in the 75-150 °C range. Their morphology, chemical composition, structural and optical properties were analyzed. In contrast to the polar-oriented ZnO usually obtained from aqueous and conventional solvent based electrolytes, nanocrystalline films oriented along non-polar directions, (11 ?10) and (11 ?20), were obtained from this ionic liquid electrolyte. A significant content of carbon was detected in the films, pointing to the active participation and crucial effect of pyrrolidinium cation (and/or byproducts) during the electrodeposition. The films showed semiconducting behavior with an optical gap between 3.43 and 3.53 eV as measured by optical transmittance. Their room temperature photoluminescence spectra exhibited two different bands centered at ～3.4 and ～2.2 eV. The intensity ratio between both bands was found to depend on the deposition temperature. This work demonstrates the great potential of ionic liquids based electrolytes for the electrodeposition of ZnO nanocrystalline thin films with innovative microstructural and optoelectronic properties.     

高效液相色谱法研究白藜芦醇光致异构化动力学与平衡常数

反式白藜芦醇有多种生理活性,自然资源丰富,但存在光不稳定现象。以光致异构平衡对照品溶液,采用高效液相色谱建立了同时测定顺、反异构体浓度的方法。方法学考察显示符合含量测定要求,反式异构体在1.5~60 μ mol/L、顺式异构体在1.5~55 μ mol/L范围内线性关系良好,R²均达0.999。将该方法应用于研究光致异构化动力学及平衡常数,结果显示反式白藜芦醇在室温避光条件下中性、偏酸性及乙醇介质中稳定;25 ℃时在50%（v/v）乙醇介质中的光异构平衡常数为11.7±0.3。以光致异构平衡液制作标准曲线的策略简单方便,具有可操作性;反式白藜芦醇的稳定性与介质有关,在pH < 7的溶液中光致异构化为一级反应。     

Electrodeposition of nano- and microcrystalline aluminium in three different air and water stable ionic liquids.

The present work shows, for the first time, a comparative experimental study on the electrodeposition of aluminium in three different water and air stable ionic liquids, namely 1-butyl-1-methylpyrrolidinium-bis(trifluoromethylsulfonyl)imide ([BMP]Tf2N), 1-ethyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide ([EMIm] Tf2N), and trihexyl-tetradecyl-phosphoniumbis(trifluoromethylsulfonyl)imide (P(14,6,6,6) Tf2N). The ionic liquids [BMP]Tf2N and [EMIm]Tf2N show biphasic behaviour in the AlCl3 concentration range from 1.6 to 2.5 mol L(-1) and 2.5 to 5 mol L(-1), respectively. The biphasic mixtures become monophasic at temperatures >/=80 degrees C. It was found that nanocrystalline aluminium can be electrodeposited in the ionic liquid [BMP]Tf2N saturated with AlCl3. The deposits obtained are generally uniform, dense, shining, and adherent with very fine crystallites in the nanometer size regime. However, coarse cubic-shaped aluminium particles in the micrometer range are obtained in the ionic liquid [EMIm]Tf2N. In this liquid the particle size significantly increases as the temperature rises. A very thin, mirrorlike aluminium film containing very fine crystallites of about 20 nm is obtained in the ionic liquid [trihexyl-tetradecyl-phosphonium]Tf(2)N at room temperature. At 150 degrees C, the average grain size is found to be 35 nm.     

Densities and apparent molar volumes of atmospherically important electrolyte solutions. 1. The solutes H2SO4, HNO3, HCl, Na2SO4, NaNO3, NaCl, (NH4)2SO4, NH4NO3, and NH4Cl from 0 to 50 °C, including extrapolations to very low temperature and to the pure liquid state, and NaHSO4, NaOH, and NH3 at 25 °C

Calculations of the size and density of atmospheric aerosols are complicated by the fact that they can exist at concentrations highly supersaturated with respect to dissolved salts and supercooled with respect to ice. Densities and apparent molar volumes of solutes in aqueous solutions containing the solutes H(2)SO(4), HNO(3), HCl, Na(2)SO(4), NaNO(3), NaCl, (NH(4))(2)SO(4), NH(4)NO(3), and NH(4)Cl have been critically evaluated and represented using fitted equations from 0 to 50 °C or greater and from infinite dilution to concentrations saturated or supersaturated with respect to the dissolved salts. Using extrapolated densities of high-temperature solutions and melts, the relationship between density and concentration is extended to the hypothetical pure liquid solutes. Above a given reference concentration of a few mol kg(-1), it is observed that density increases almost linearly with decreasing temperature, and comparisons with available data below 0 °C suggest that the fitted equations for density can be extrapolated to very low temperatures. As concentration is decreased below the reference concentration, the variation of density with temperature tends to that of water (which decreases as temperature is reduced below 3.98 °C). In this region below the reference concentration, and below 0 °C, densities are calculated using extrapolated apparent molar volumes which are constrained to agree at the reference concentrations with an equation for the directly fitted density. Calculated volume properties agree well with available data at low temperatures, for both concentrated and dilute solutions. Comparisons are made with literature data for temperatures of maximum density. Apparent molar volumes at infinite dilution are consistent, on a single ion basis, to better than ±0.1 cm(3) mol(-1) from 0 to 50 °C. Volume properties of aqueous NaHSO(4), NaOH, and NH(3) have also been evaluated, at 25 °C only. In part 2 of this work (ref 1 ) an ion interaction (Pitzer) model has been used to calculate apparent molar volumes of H(2)SO(4) in 0-3 mol kg(-1) aqueous solutions of the pure acid and to represent directly the effect of the HSO(4)(-) ? H(+) + SO(4)(2-) reaction. The results are incorporated into the treatment of aqueous H(2)SO(4) density described here. Densities and apparent molar volumes from -20 to 50 °C, and from 0 to 100 wt % of solute, are tabulated for the electrolytes listed in the title and have also been incorporated into the extended aerosol inorganics model (E-AIM, http://www.aim.env.uea.ac.uk/aim/aim.php) together with densities of the solid salts and hydrates.     

新型导电盐(三氟甲基磺酰)(三氟乙氧基磺酰)亚胺锂及其非水电解液的制备与性能

制备了一种新型含氟磺酰亚胺锂盐(三氟甲基磺酰)(三氟乙氧基磺酰)亚胺锂{Li[(CF₃SO₂)·(CF₃CH₂OSO₂)N], Li[TFO-TFSI]}及其与碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)混合溶剂(3∶7, 体积比)组成的非水电解液. 采用核磁共振波谱(NMR)、 红外光谱(IR)、 质谱(MS)、 元素分析(EA)和离子色谱(IC)等手段对合成锂盐Li[TFO-TFSI]进行了结构表征及纯度分析. 通过差示量热扫描(DSC)和热重分析(TG)对Li[TFO-TFSI]及其电解液1.0 mol/L Li[TFO-TFSI]-EC/EMC(3∶ 7)的热学性质进行了表征. 采用交流阻抗(EIS)、 循环伏安(CV)、 计时安培法及扫描电子显微镜(SEM)等对Li[TFO-TFSI]/碳酸酯电解液的基础物化和电化学性质进行了表征. 结果表明, Li[TFO-TFSI]/碳酸酯电解液具有较好的电化学稳定性; 在4.2 V(vs. Li/Li⁺)以下Al箔不发生腐蚀; 室温下基于Li[TFO-TFSI]/碳酸酯电解液的Li/人造石墨和人造石墨/LiCoO₂电池均保持较好的循环性能, 特别是人造石墨/LiCoO₂锂离子电池循环100周后, 其比容量保持率明显高于相应的基于LiPF₆/碳酸酯电解液体系的电池.     

Stabilized Zirconia-Based Nanostructured Powders for Solid-Oxide Fuel Cells

High-purity uniform powders of zirconia-based solid electrolytes stabilized with yttria (4 and 8 mol %) are synthesized by co-precipitation with subsequent annealing at different temperatures. The obtained powders were studied using X-ray analysis and transmission electron microscopy; the specific surface area was measured by nitrogen adsorption. The stabilized zirconia powder sintering was studied over temperature range from 1000 to 1600°C. The ionic conductivity of samples containing 8 mol % of yttria was 0.06–0.07 S/сm, that is comparable with that obtained with commercial solid electrolytes.     

计时电流法测定Fe3+在离子液体BPBF4中的扩散系数

室温离子液体(简称离子液体)作为新型的反应介质和功能材料受到学术界和产业界的高度关注,正在迅速成为多学科交叉的前沿研究领域和具有良好应用前景的“绿色”高新技术,过渡金属化合物是许多重要反应的催化剂,过渡金属离子在室温离子液体中的性质是工业界关心的课题,有关过渡金属的离子液体的研究,     

核黄素荧光猝灭法测定2,4,6-三硝基苯酚

基于核黄素与2,4,6-三硝基苯酚混合后产生荧光猝灭现象,建立了核黄素作为荧光探针测定2,4,6-三硝基苯酚的新方法。 在0.2 mol/L磷酸盐(NaH₂PO₄-Na₂HPO₄)缓冲溶液(pH=6.2)中,响应时间为1 min时,检测2,4,6-三硝基苯酚的线性范围为2.5~1000 μmol/L,相关系数为0.9938,检测限为0.55 μmol/L。 当加入5.00和20.00 μmol/L 2,4,6-三硝基苯酚到水样后,回收率在98.2%~103.5%之间。 方法简便,选择性好,线性范围宽,可用于实际水样中2,4,6-三硝基苯酚的定性定量分析。     

Dispersion properties of TiO2 nano-powder synthesized by homogeneous precipitation process at low temperatures

The dispersion stability of rutile TiO₂ powder with a unique nano-structure synthesized by homogeneous precipitation process at low temperatures (HPPLT) has been investigated with adding the various electrolytes in both pure aqueous and organic media. Zeta potential measurements have shown that the addition of electrolytes such as CsCl, CaCl₂, FeCl₃, and ZrCl₄ to aqueous and pure organic dispersion media leads to generally a charge reversal from negative to positive on the surface of TiO₂ particle. The electrostatic repulsive force acting on between TiO₂ particles dispersed in pure organic media was found to be significantly greater than that in aqueous media, which is closely related to the physical properties of the organic solvents, such as viscosities and dielectric constant. The surface potentials of TiO₂ particles have been greatly modified by the particulate properties, pH, dispersion medium, and valence of the ionic species, which governs the colloidal behavior of TiO₂ particles virtually.     

溴化1-十二烷基-3-甲基咪唑与甲基橙的相互作用

利用电导法和表面张力法,研究了离子液体表面活性剂溴化1-十二烷基-3-甲基咪唑(C12mimBr)与阴离子染料甲基橙(MO)之间的相互作用。 通过分别测定C12mimBr、MO以及C12mimBr与MO混合溶液的电导率,计算了C12mimBr与MO的结合特性。 C12mimBr与MO以等摩尔比结合,在288.1、298.1和308.1 K下的结合常数分别为4.89×105、4.88×104和5.76×103 L/mol,该结合反应属于焓驱动的自发放热反应。 分别测定了C12mimBr与MO等摩尔混合体系及其在NaBr溶液中的临界胶束浓度(cmc),加入MO使C12mimBr的cmc从9.1×10-3 mol/L降低到7.3×10-5 mol/L,显著提高了C12mimBr的表面活性。     

Study on the liquid membrane oscillation of water/oil/water system containing TTAB and picric acid

The liquid membrane oscillation of a novel water （aqueous tetradecyl trimethyl ammoniumbromide, TTAB and alcohol solution）/oil （picric acid in chloroform solution）/water （aqueous glucose solution） system was investigated. By using homemade device, the curves of various liquid membranes oscillation with different concentration of TTAB and picric acid, types of alcohol and other organic solvents at different temperature were measured. The results show that the water （aqueous 7 mmol/L of TTAB and 0.5 mol/L of n-propanol solution）/oil （0.5 mmol/L of picric acid in chloroform solution）/water （aqueous glucose solution） system performed sustained and stable oscillation at 30 ℃. And the novel system can recognise added amino acid.     

Regularity of conductivity of concentrated aqueous solutions of strong electrolytes

Conductivity of concentrated aqueous solutions of strong electrolytes is analyzed in a wide range of temperatures and concentrations. The highest conductivity of solutions at a given temperature and the concentration corresponding to the highest conductivity are used as the generalizing parameters. It is shown that in the temperature range from 0 to 100°C and the concentration range from 0.1 to 12 M, the values of reduced conductivity (the ratio between the conductivity and its maximum value at a given temperature) for KOH aqueous solution fall on a common curve, if the reduced concentration (the ratio between the concentration of solution and the concentration corresponding to the highest conductivity) is used as the argument. The reduced conductivities of strong acids, bases, and salts of some I-I, I-II, II-I, III-I, and II-II electrolytes fall on the same curve.     

基于ZIF-67的Co3O4/C修饰电极制备及对多巴胺传感性能研究

以金属有机骨架材料ZIF-67为前驱体,经氩气气氛高温处理制备得到了Co_2O4与碳复合材料(Co_3O4/C)。通过X射线衍射仪(XRD)和扫描电子显微镜(SEM)对Co_3O4/C的结构和形貌进行了表征。Co_3O4/C保持了前驱体ZIF-67正十二面体形貌,并发生明显皱缩现象。采用循环伏安、恒电位等方法研究了Co_3O4/C修饰玻碳电极(GCE)对多巴胺(DA)的传感性能。结果表明:在多巴胺浓度在5~500μmol/L范围内,Co_3O4/C/GCE的氧化峰电流与浓度存在良好的线性关系,检测灵敏度高达283.09μA·L/(mmol·cm2)。此外,Co_3O4/C/GCE还展示出良好的抗干扰能力、重现性和稳定性。     

Design and characterization of novel supramolecular liquid crystals involving multiple hydrogen bonds

A novel type of liquid crystalline system, namely 5-[4-(4-methoxyphenylazo)phenyloxyalkyloxy]isophthalic acidhydrazides (Dn, n = 3, 6, 10) was designed and synthesized. The FTIR spectra of the Dn compounds were examined in the range 4000-1000 cm^-1 at different temperatures. The results showed that the stretching vibration frequencies of the NH and C=O groups, and the NH₂ deformation shifted to lower frequencies with decrease of temperature, while out-of-plane NH bending shifted slightly to higher frequency. Intermolecular hydrogen bonding between NH, NH₂ and C=O groups is proposed and the schematic supramolecular Dn structure is given. This may explain the higher Dn transitional temperatures and their smectic phase behaviour compared with that of 5-[4-(4-methoxyphenylazo)phenyloxyalkyloxy]isophthalic acid diethyl esters.     

Au(111)-离子液体界面层状结构与温度关联的原位AFM力曲线研究

本文针对BMIPF6 和OMIPF6两种离子液体,在电极表面远离零电荷电位且以负电荷表面电位下,运用AFM力曲线详细地研究了其与Au(111)单晶电极界面所形成的层状结构与温度的关联. 在15 ~ 40 ^oC的温度范围内,温度越低其离子液体层状结构越稳定. 温度对OMIPF₆离子液体层状结构的稳定性和数目的影响较BMIPF₆缓和：温度变化5 ^oC,OMIPF₆靠近表面第一层层状结构的力值变化仅为1 ~ 2 nN,而BMIPF6第一层层状结构的力值变化为3 ~ 5 nN;较低温下,BMIPF₆中层状结构的数目有所增加,而OMIPF₆的层状数目始终保持两层,且随温度的变化并不敏感. 这可归因于两种离子液体的阳离子尺寸以及与电极表面的作用方式和强度不同;同时,OMIPF₆较粘稠,其热运动受温度的影响不甚敏感.