Synthesis of gradient copolymers with simultaneously tailor‐made chain composition distribution and glass transition temperature by semibatch ATRP: From modeling to application

Recent studies have demonstrated that gradient copolymers exhibit unique thermal properties. Although these properties can be determined by copolymer composition, other factors such as chain and sequence lengths and their distributions can also influence them. Accordingly, the synthesis of gradient copolymers requires simultaneously tailor‐made chain structure and thermal properties. In this work, we carried out a systematic study on the preparation of poly(methyl methacrylate‐grad‐2‐hydroxyethyl methacrylate) [poly(MMA‐grad‐HEMA)] with synchronously tailor‐made chain composition distribution and glass transition temperature (T_g) through semibatch atom transfer radical polymerization. First, a comprehensive model for simultaneously predicting gradient copolymer microstructure and T_g was presented using the concept of pseudo‐kinetic rate coefficients and Johnston equation. The model was validated by comparing simulation results with the classical reference data. Furthermore, the model was used to guide the experimental synthesis of the poly(MMA‐grad‐HEMA) gradient copolymers potentially as excellent damping material. The thermal properties of these gradient copolymer samples were evaluated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation and performance of a novel polyimide foam

A new type of polyimide foam (PIF) was prepared and characterized based on a one‐pot process by the reaction of a first solution with different ratios of a second solution. The first solution was comprised of pyromellitic dianhydride (PMDA), N, N‐dimethyl formamide (DMF), methanol, water, surfactant, and catalysts, while the second solution contained polyaryl polymethylene isocyanate (PAPI). In the present study, the relationships among compositions, structures, and properties of PIFs were investigated. The results indicated that with the increase in the weight ratio of PAPI/(first solution), the foaming degrees of PIFs increased from 10.14 to 10.52 times and the apparent densities before postcure decreased from 15.96 to 14.51 kg/m³. The open cell contents, average sound absorption coefficients, and average cellular diameters of PIFs after postcure increased with increase in the weight ratio of PAPI/(first solution). The glass transition temperatures (T_g) of PIFs after postcure first increased from 287 to 299°C, then decreased to 292°C, and the 5% weight loss temperatures and 10% weight loss temperatures presented the same trend as well. The compressive and flatwise tensile properties scaled very well with the relative densities of the foams after postcure, with the highest compressive strength of 0.03 MPa and the highest flatwise tensile strength of 0.15 MPa. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of Er3+:Y3Al5O12 and its effects on the solar light photocatalytic activity of TiO2–ZrO2 composite

The Er³⁺:Y₃Al₅O₁₂ as an upconversion luminescence agent, which can transform visible light into ultraviolet light, was synthesized by nitrate?Ccitrate acid and calcined method. Then, a novel photocatalyst, Er³⁺:Y₃Al₅O₁₂/TiO₂?CZrO₂, was prepared using ultrasonic dispersion and liquid boiling method. The samples were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). In succession, the degradation process of organic dye was monitored by UV?CVis spectrum and ion chromatography for verifying the photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/TiO₂?CZrO₂. The influences on its photocatalytic activity such as Ti/Zr molar ratio, heat-treated temperature, and time were studied. In addition, the influences of initial concentration, Er³⁺:Y₃Al₅O₁₂/TiO₂?CZrO₂ amount, solar light irradiation time, and organic dye category on the photocatalytic degradation efficiency were also investigated. It was found the photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/TiO₂?CZrO₂ was superior to Er³⁺:Y₃Al₅O₁₂/TiO₂ and Er³⁺:Y₃Al₅O₁₂/ZrO₂. Therefore, the Er³⁺:Y₃Al₅O₁₂/TiO₂?CZrO₂ is a useful photocatalytic material for the wastewater treatment duo to efficient utilization of solar light.     

Palladium-catalyzed intermolecular coupling of aryl halides and amides

[formula: see text] The first general intermolecular C-N bond-forming reactions between aryl halides and amides were realized using a palladium catalyst with Xantphos as the ligand. Aryl triflates, carbamates, and sulfonamides are also viable substrates for the amidations, which proceed at 45-110 degrees C with 1-4 mol% of Pd catalyst in 66-99% yields and exhibit good functional group compatibility.     

Fabrication and evaluation of bacterial cellulose-polyaniline composites by interfacial polymerization

The fabrication and evaluation of nanocomposites based on microbial cellulose and polyaniline (PANi) are described. Microbial cellulose, so called, bacterial cellulose (BC) was introduced to interfacial polymerization of aniline. Two different phases based on water and chloroform made it easy for nanosized PANi particles to be synthesized on BC. Without any help of a surfactant or templates, BC played a critical role of supporting the growth of PANi. As a function of aniline concentration, the corresponding PANi content and volume resistivity were checked. From morphological images observed by FE-SEM, PANi nanoparticles were densely arrayed along every fiber of BC. The conjugated backbone of PANi was thought to contribute to the improvements of thermal stability of PANi/BC composites. The stiffness and brittleness of PANi were compensated by more ductile BC, suggesting BC can be a promising substrate for it. By the simple and facile interfacial polymerization, the electrical conductivity of PANi/BC composites reached up to 3.8?×?10^?1?S/cm when 0.32?M of aniline was used. This PANi/BC nanocomposite can be useful in applications requiring biocompatibility and electrical conductivity such as biological and chemical sensors.     

紫外光引发剂907及其反应中间体的气相色谱测定

建立了光引发剂907合成工艺控制中反应原料、中间体及产物的气相色谱分析方法。采用SE-54石英毛细管柱,程序升温进行分离,氢火焰离子化检测器(FID)进行检测。结果表明,原料苯甲硫醚,反应中间体807A、807B、907C和产物907线性范围分别为0.2～14.0μg/mL、0.4～20.0μg/mL、0.5～22.0μg/mL和0.6～19.0μg/mL,线性相关系数R均大于0.999,相对标准偏差小于2.5%,回收率为93.6%～106.8%。产物结构通过红外光谱进行表征。该方法线性关系、准确度和精密度良好,适用于光引发剂907合成工艺的快速监控及产品定量分析。     

煤焦在燃烧过程中孔隙结构变化的模拟

煤焦在燃烧过程中的物理特性，如比表面积和孔径分布会发生连续变化，直接测量煤焦在燃烧过程中的孔隙结构变化很困难，但可以通过合适的数学模型来观察，二维的圆柱孔模型已大量用来对煤焦气化与燃烧过程中表面积和孔隙结构的变化进行模拟，这个模型把孔隙分成两大部分－－大孔与小孔，因为小孔构成比表面的绝大部分，所以在反应过程中比表面积的变化可以由单一小孔模型来拟合，本文采用了用Ｔｓｅｎｇ和Ｅｄｇａｒ提出的孔模型对几     

A New Synthetic Route for 2,4-Dibromo-5-fluorobenzoic Acid

Fluoroquinolonesareeffectivemedicinesagainstbacteria,evenagainsttumor.Overtenexcellentfluoroquinol0nemedicineshavebeen0nthemarket.Duet0thehigherselectivity,yieldatbrondnationof3-flu0rotoluenethanchlorination,and0theradvantages'-',2,4-dibromo-5-flu0r0benzoicacidhasreplaced2,4-dichloro-5-fluor0-benzoicacidandbecomethekeystartingmaterialofpreparingfluoroquinoIonemedicines'.S0itisofgreatsignificancetofindaneffectivesyntheticpathfor2,4-dibromo-5-fluor0benz0icacid.Therehavebeenproposedtwomethodsf0r…     

Two New Sesquiterpenes from Atractylodes macrocehpala

AtractylodesmacrocephalaKoidz(Compositae)isaperennialherbmainlydistributedintheZhejiangandAnhuiProvincesofChina.ItsrhizomehasbeenusedasatraditionalChinesemedicinefromancienttimesl'2.Twonewsesquiterpenes,BeishulenolideA1andPeroxiatractylenolideill2havebeenisolatedfromapetfoleumetherextractofthisherb.TheirstrUctureswereelucidatedonthebasisofspectralevidence,especiallyZDNMRmethodsandchemicalconversion.Compound1wasisolatedascolorlessneedlesfromethylacetate.HREIMSshoweditspeakatinjz=232.14…     

The Aggregation Kinetics of Colloidal Particles of Basic Yttrium Carbonate

Studyofthegrowthprocessofcolloidalparticlesofnonequilibriumandirreversibilityisanactiveareaofresearch.Therecognitionofcolloidalaggregatesasfractalobjectshasinspiredalargenumberofexperimentalandtheoreticalstudiesonthestructuralandkineticaspectsofaggregationprocesses"'.Morerecently,kineticsofhematiteaggregationbypolyacrylicacidhavebeenstudiedbyzhangandBume3.Theprimaryhematiteparticleswerequiteuniformandfairlyspherical.Inthispaper,wewillreportthesizeevolutionoffractalaggregatesofinitiallypolydis…