One-pot,one-step,and selective terpolymerization of ethylene oxide,propylene oxide,and COS to copoly(thioether)s with tunable thermal properties

Facile construction of sulfur-rich polymers using readily available raw chemicals is an area aggressively pursued but challenging. Herein we use common feedstocks of ethylene oxide (EO), propylene oxide (PO), and carbonyl sulfide (COS) to synthesize copoly(thioether)s which are traditionally produced from unpleasant and difficult to store episulfides. In this protocol, the EO/COS coupling selectively generates a pure poly(ethylene sulfide) (PES) with melting temperature (T_m) values up to 172°C and high yields up to 98%. The EO/PO/COS terpolymerization leads to the incorporation of soft poly(propylene sulfide) (PPS) and hard PES segments together, affording a random PES-co-PPS copoly(thioether) with the complete consumption of EO and PO. Additionally, by simply varying the EO/PO feeding ratio, the obtained copoly(thioether)s possess tunable thermal properties, T_m values in the range of 76–144°C, and excellent solubility. These copolymerizations are conducted in one-pot/one-step at industrially favored reaction temperatures of 100–120°C using catalysts of common organic bases, suggesting a facile and practical manner. Especially, the copoly(thioether) exhibits high refractive indices up to 1.68 owing to its high sulfur content, suggesting a broad application prospect in optical materials.     

MCNOs/CdS双效光催化剂的制备及其性能研究

水热合成法制备了不同磁性纳米洋葱碳(MCNOs)负载量(0%、1%、3%、5%)的MCNOs/CdS光催化剂。并通过X射线衍射分析(XRD)、扫描电子显微镜(SEM)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(XPS)、紫外可见光光谱(UV-Vis)、磁滞回线测定仪(VSM)对其进行表征,探究了MCNOs负载比例对催化剂在可见光下降解RhB性能及机理的影响。结果表明,MCNOs能有效提高CdS的光催化效果,复合3%MCNOs后降解率为96%,与纯CdS相比降解率提高了30%,磁性分析表明,其具有良好的顺磁性并能实现催化剂的有效回收。MCNOs/CdS在可见光下催化降解RhB的一级反应动力学直线有较好的拟合度,表明制备的催化剂有较好的催化活性。     

Influence of radiation on thin ZnS-Tb films

Changes in thin zinc-sulfide films under the action of the γ-radiation of Co⁶⁰ are studied by investigating electroluminescence spectra of terbium embedded in these films as a luminescent probe. It is shown that changes in the relation of the intensities of bands, a decrease in their halfwidth and the background component, and simplification of the spectrum are observed in a short-wave region of the Tb radiation spectrum that corresponds to⁵D₃→⁷F_j transitions. The same modification of the radiation spectrum is characteristic of ZnS films whose crystalline structure is ordered in the course of thermal annealing at a temperature of 350°C. Based on the analysis of the data obtained it is inferred that irradiating the ZnS films with small radiation doses of 10⁴–10⁵ rad leads to the ordering of their crystalline structure due to the elimination of one of the types of structural defects. Institute of Physics of Semiconductors, National Academy of Sciences of Ukraine, 45, Nauka Ave., Kiev-28, 252650. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 338–341, May–June, 1997.     

Synthesis of Dimethyl Carbonate from CO2 , Methanol, and Epoxides Using Re（CO） 5 Cl/K2 CO3 as Catalyst System

IntroductionOver the past few years, dimethyl carbonate(DMC) has been proven to be an efficientmethylating,methoxylating, and methoxycarbonylating agent inorganic syntheses, in which DMC is used to replace thetoxic methyl halides, dimethyl sulfate or carb     

裂解气相色谱质谱法研究增塑剂邻苯二甲酸二甲酯的热降解机理

用裂解气相色谱-质谱联用方法研究了橡胶产品中使用的增塑剂邻苯二甲酸二甲酯(DMP)在不同温度条件下的热裂解行为.对不同温度条件下裂解产物的分析表明,在初始阶段DMP的裂解产物主要为二氧化碳、苯、甲苯和苯甲酸甲酯.随着温度的升高苯甲酸甲酯进一步裂解成为分子质量更小的自由基,并发生稠环化反应形成更稳定的菲、蒽、间-联三苯、三亚苯等芳香族多环化合物.根据分析实验提供的裂解产物信息和有机物热裂解化学反应的原理对DMP的热裂解反应机理作了探讨,表明在废旧合成橡胶热裂解回收过程中,增塑剂DMP的高温裂解会产生多环芳烃污染物.应选择合适裂解工艺和裂解温度,以减少对环境的污染.     

Optical properties of cadmium sulfide nanocrystal film prepared by electrochemical synthesis at liquid-liquid interface

Dendritic nanocrystalline CdS film was deposited at liquid-liquid interface of surfactants and an electrolyte containing 4 mmol L⁻¹ cadmium chloride (CdCl₂) and 16 mmol L⁻¹ thioacetamide (CH₃CSNH₂) with an initial pH value of 5 at 15 °C by electrochemical synthesis. The nanofilm was characterized by transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), ultraviolet visible (UV-vis) absorption spectroscopy and fluorescence spectroscopy. The surface morphology and particle size of the nanofilm were investigated by AFM, SEM and TEM, and the crystalline size was 30-50 nm. The thickness of the nanofilm calculated by optical absorption spectrum was 80 nm. The microstructure and composition of the nanofilm was investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), showing its polycrystalline structure consisting of CdS and Cd. Optical properties of the nanofilm were investigated systematically by UV-vis absorption and fluorescence spectroscopy. A λ_onset blue shift compared with bulk CdS was observed in the absorption spectra. Fluorescence spectra of the nanofilm indicated that the CdS nanofilm emitted blue and green light. The nanocomposites film electrode will bring about anodic photocurrent during illumination, showing that the transfer of cavities produces photocurrent.     

Scanning probe microscopy studies of PbS surfaces oxidized in air and etched in aqueous acid solutions

Natural n-type PbS single crystals have been studied using AFM, STM and STS after long-term oxidation in air at ambient temperatures and extensive etching in aqueous acid solutions, in contrast to previous work devoted to initial corrosion of fresh surfaces. The exposure of PbS to atmosphere at high relative humidity for several days yields widespread loose oxidation products; the process is much slower at low humidity. Surface morphologies diverge after the treatment in 1 M perchloric and hydrochloric acid solutions at room temperature and become widely different at elevated temperatures, displaying commonly etch pits up to several micrometers in size and depth along with rather uniformly distributed 20-100 nm protrusions of PbS phase. The changes both in topography and semiconducting properties of PbS found by tunneling spectroscopy have been explained in terms of the non-uniform distribution of donor- and acceptor-type defects D⁺/D⁻ in the metal depleted surface layer, which are generated by chemical reactions and, in turn, determine the rates of the PbS corrosion. In particular, the D⁻ centers exhibit a self-catalyzing effect on the non-oxidative local dissolution of PbS in HCl media, resulting in the deep etch pits.     

Formation of 2,6-dioxabicyclo[3.3.0]-octa-3,7-dienes or multiply substituted o-benzoquinones from reactions of 1,4-dilithio-1,3-dienes with dimethyl oxalate

Reactions of 1,4-dilithio-1,3-dienes with dimethyl oxalates afforded multiply substituted o-benzoquinones or stereodefined 2,6-dioxabicyclo[3.3.0]-octa-3,7-dienes in good yields.     

肾上腺素与二甲亚砜氢键作用的理论研究

采用PM 3半经验方法对肾上腺素和二甲亚砜与肾上腺素形成的 1∶1复合物的结构进行了几何优化 .在此基础上用密度泛函理论 (DFT)的B3LYP方法 ,分别在 6 31G、6 31G 、6 31+G 基组水平上进行了精确计算 ,并通过单点能计算考察了它们之间在形成各种复合物前后的能量和分子结构参数变化特点 .在各基组水平上所有物种的能量均进行零点振动能 (ZPVE)校正 .计算结果表明 ,二甲亚砜与肾上腺素能形成 6种稳定的复合物 ,在这些复合物中都具有较强的氢键作用 .计算结果能够解释有关实验现象     

Microwave structural studies of organoselenium compounds 1. Microwave spectra, molecular structure, and methyl barrier to internal rotation of dimethyl diselenide

The rotational spectra of nine isotopomers of dimethyl diselenide, CH₃SeSeCH₃, have been measured with a molecular-beam Fourier transform microwave spectrometer. The spectra were complex due to the presence of many isotopomers in natural abundance and the splitting caused by the interactions with two methyl internal rotors. The spectra were assigned and fit to experimental precision to an effective rotational Hamiltonian for molecules with two periodic internal motions. The spectra of the symmetric isotopomers are consistent with a C₂ equilibrium structure. The rotational constants were used to determine the r_s structure of the C-Se-Se-C frame with the results r(SeSe)=2.306(3) Å, r(SeC)=1.954(6) Å, ?(CSeSe)=99.8(2)°, ?(CSeSeC)=85.2(1)°. A barrier to internal rotation of the methyl groups of 395 ± 2 cm⁻¹ was derived from the internal rotation splittings.