Neodymium oxide-assisted melt free-radical grafting of maleic anhydride on isotactic-polypropylene by reactive extrusion

Rare earth oxide, neodymium oxide (Nd2O3), -assisted melt free-radical grafting of maleic anhydride (MAH) on isotactic-polypropylene (i-PP) was carried out by reactive extrusion. The experimental results reveal that the addition of Nd2O3 into reactive system leads to an enhancement of the grafting degree of MAH, along with an elevated degradation of i-PP matrix. When Nd2O3 content is 4.5 mmol %, the increment of the grafting degree of MAH (maximally) is up to about 30% compared with that of the related system without adding Nd2O3, while the severest degradation of i-PP matrix simultaneously occurs. On the basis of the reaction mechanism of PP-g-MAH proposed before, the sequence of beta-scission and grafting reaction is discussed in detail. It is found that, for the reactive system studied, most tertiary macroradicals first undergo beta-scission, and then, grafting reaction with MAH takes place at the new radical chain ends. The imported Nd2O3 has no effect on the aforementioned reaction mechanism, whereas it enhances the initiating efficiency of the initiator, dicumyl peroxide (DCP).

雪上一支蒿中乌头碱类生物碱的电喷雾串联质谱分析

利用电喷雾串联质谱 (ESI MS MS)对雪上一支蒿的乙醇提取液进行了直接分析 ,方法简便 ,直观 ,用样量少。ESI MS可以给出分子量信息 ,MS MS方法则可以从复杂体系中获得结构信息。在雪上一支蒿中发现乌头碱、去氧乌头碱及它们的水解产物和脂类生物碱等共 1 9种二萜生物碱 ,其中脂类生物碱为首次在该植物中发现

稀土Sm对于Cu/Zr基合成醇催化剂的改性作用

中国科学院山西煤炭化学研究所

Study on the transesterification of poly(beta-hydroxybutyrate) and poly(epsilon-caprolactone)

The transesterification of poly(beta-hydroxybutyrate) (PHB) and poly(epsilon-caprolactone) (PCL) was carried out by using stannous octoate as catalyzer in liquid phase. The effects of reaction conditions on the transesterification, including reaction temperature, reaction time and catalyzer content, were investigated. The sequence distribution, crystallization behavior and thermal stability of PHB-co-PCL copolyesters were studied by C-13-NMR, FTIR, DSC, WAXD and TGA. The results showed that the transesterification of PHB with PCL was confirmed to produce a block copolymer, and enhancing reaction temperature and increasing reaction time were advantageous to the transesterification. With the increase in PCL content in the block copolymer, the crystallization behavior of PHB-co-PCL copolyesters changed evidently. On the other hand, the introduction of PCL segment into PHB chains did not change its crystalline structure; moreover, thermal stability of PHB-co-PCL copolyesters was a little improved in air, comparing with that of pure PHB.

聚β-羟基丁酸酯和聚ε-己内酯的酯交换反应

以辛酸亚锡为催化剂 ,研究了聚 β 羟基丁酸酯 (PHB)与聚ε 己内酯 (PCL)在液相条件下的酯交换反应 .讨论了反应时间 ,反应温度和催化剂浓度对酯交换反应的影响 .采用1 3C NMR ,FTIR ,DSC ,WAXD和TGA等方法对PHB和PCL共聚酯 (PHB co PCL)的结构进行了表征 ,并对其结晶行为、晶体结构和热稳定性进行了研究 .结果表明 ,通过酯交换反应 ,所得到的共聚酯为嵌段共聚物 .提高反应温度和延长反应时间有利于酯交换反应的发生 .随着酯交换量的增加 ,PHB co PCL的结晶行为发生很大的变化 .但是 ,PHB co PCL晶体结构并没有因为PCL链段的引入而发生变化 ,而且它的热稳定性在空气气氛中略有提高

Layer-by-layer assembly of multilayer films consisting of silicotungstate and a cationic redox polymer on 4-aminobenzoic acid modified glassy carbon electrode and their electrocatalytic effects

A novel 4-aminobenzoic acid (4-ABA) monolayer film is formed on glassy carbon electrode (GCE) by amino cation radical method. Silicotungstic heteropolyanion (SiW12O404-, denoted as SiW12)-containing multilayer films have been fabricated on the 4-ABA modified GCE surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)(2)Cl](2+/+) (denoted as QPVP-Os). Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and X-ray reflectivity (XR) have been used to characterise the as-prepared multilayer films. It is proved that the multilayer films are uniform and stable. The average thickness for a bilayer of QPVP-Os/SiW12 in the multilayer film is 30.2 Angstrom. The electrocatalytic activities of the multilayer films have been investigated on the reduction of three substrates of important analytical interests, HNO2, BrO3- and H2O2. Especially, the influence of layer number of the multilayer films on the electrocatalytic reduction of HNO2 has been investigated in detail. (C) 2000 Elsevier Science B.V. All rights reserved.

Molecular heterogeneity and crystal morphology in metallocene short chain branch polyethylene (SCBPE)

Metallocene, a newer generation of commercial polymerization catalysts for polyolefins, is best known for its "single sitednss", and the intermolecular structural homogeneity of metallocene polyethylene copolymer is a very interesting research issue. The molecular segregation effects on the crystallization, melting and crystal morphologies of metallocene SCBPE have been investigated with DSC and TEM. The multiple endothermic peaks were observed in the DSC thermograms during heating experiments. The heterogeneity increases as branching content increases, the lamellae becomes thinner, and lamellae distribution becomes broader. Both macroscopic segregation (between two crystal aggregates) and microscopic segreation (between two lamellae) have been observed when SCBPE crystallized from phase separated melt.

茂金属聚乙烯的支化非均匀性与结晶形态

以美国Exxon公司生产的茂金属短支链聚乙烯 (SCBPE)为研究对象 ,用DSC热分级方法研究了不同支链含量聚乙烯的支化非均匀性 ,并用TEM表征茂金属聚乙烯在不同条件下熔体结晶的形态 .SCBPE经逐步结晶分级后 ,其DSC熔融曲线出现多峰 ,表明茂金属SCBPE仍具有很大的非均匀性 .支链含量愈高 ,熔点愈低 ,非均匀性增加 .SCBPE的晶体形态随平均支链含量的增加片晶厚度减小 ,片晶尺寸分布增加 ;含量较低时 ,SCBPE在不同温度下均生成球晶结构 .随结晶温度的降低支链含量较多的分子也能参与结晶 ,故生成的片晶厚度减小 .从相分离的熔体中结晶 ,大尺度的片晶集聚体间的分离和小尺度的片晶之间相分离同时存在.

稀土-铁石榴石的共价极化行为对光谱和穆斯堡尔谱的影响

利用平均能带模型研究了稀土 铁石榴石晶体化学键的性质 ,结果表明 ,这些晶体虽然包含的稀土离子不同 ,但计算得到的化学键参数值几乎相同。在每个化合物当中 ,金属离子与氧配体之间共价性随着Ln3+ (2 4c)、Fe3+ (16a)、Fc3+ (16d)的次序而增大。利用由共价性和极化率定义的化学环境因子h计算YIG中Fe3+ 的拉卡参数与实验值一致。建立了穆斯堡尔同质异能位移与h值的线性关系 ,讨论了居里温度与h值的相关性。

Synthesis and characterization of metallocenes containing tert-butyl substituted cyclopentadienyl ligands and their activities in ethylene polymerization

The metallocene complexes ((BuC5H4)-Bu-t)(2)MCl2 (M=Ti (1a), Zr (1b), Hf (1c)) and (tBu2C5H3)(2)MCl2 (M=Ti (2a), Zr (2b), Hf (2c)) were synthesized by the react ions of Li (BuC5H4)-Bu-t and (LiBu2C5H3)-Bu-t with metal tetrachloride in THF solution. The complexes were characterized by their IR, H-1-NMR and EI-MS. The molecular structure of Ic was determined by X-ray single-crystal structure analysis. The complexes (1a similar to 2c) exhibited high activities for ethylene polymerizatin (up to 3.2x10(6) gPE/mol.h) in the presence of methylaluminoxane (MAO) at room temperature.

Simultaneous spectrophotometric determination of trace iron (III) and aluminum (III) with hybrid linear analysis

Hybrid linear analysis (HLA) was applied to resolution of overlapping spectra of Fe3+-salicylfluorone and Al3+-salicylfluorone complexes and simultaneous spectrophotometric determination of Fe3+ and Al3+. The absorbance matrix of 7 standard mixtures at 41 measuring points ranged from the wavelength of 550 nm to 630 nm was used for calibration. To avoid the effect of interaction between the two components on the determination, the column vector of K matrix obtained from the standard mixtures with least squares was used as the pure spectrum of component. The recoveries of the two elements for the analysis of the synthetic samples were 93.3% similar to 107.5% in the range of the concentration ratio of Fe3+:Al3+ = 10:1 to 1:8. Comparing with the partial least squares (PIS) model, the HLA method was simple, accuracy and precise.

混合线性分析-分光光度法同时测定微量铁和铝

研究将混合线性分析（ｈｙｂｒｉｄ ｌｉｎｅａｒ ａｎａｌｙｓｉｓ，ＨＬＡ）用于光谱分辨同时光度测定Ｆｅ３＋和Ａｌ３＋。在碱性条件下，Ｆｅ３＋和Ａｌ３＋与水杨基荧光团生成光谱相互重叠的有色络合物，其浓度在０～３２０　ｇ／Ｌ Ｆｅ３＋和０～１６０ｇ／Ｌ Ａｌ３＋范围内与吸光度呈良好线性关系。在５５０ｎｍ～６３０ ｎｍ内取４１个波长测量７组标准混合溶液的吸光度作为校正集，用最小二乘法求得的系数矢量作为各组分的纯光谱。以ＨＬＡ法进行数据处理，在Ｆｅ３＋：Ａｌ３＋浓度为１０：１～１：８范围内测定回收率为９３．３％～１０７．５％。将本法与偏最小二乘法（ＰＬＳ）法进行了比较，本法获得了较好的准确度和精密度。

叔丁基取代的环戊二烯基钛、锆、铪二氯化物的合成及催化乙烯聚合

(tBuC5H4 ) 2 MCl2 (M =Ti(1a) ,Zr(1b) ,Hf(1c) )和 (tBu2 C5H3 ) 2 MCl2 (M =Ti(2a) ,Zr(2b) ,Hf(2c) )可以通过单叔丁基环戊二烯基锂或双叔丁基环戊二烯基锂与MCl4 (M =Ti,Zr,Hf)在四氢呋喃中反应制备得到 ,用IR、1H NMR和EI MS对这些化合物进行了表征 .采用X光单晶结构分析测定了 (tBuC5H4 ) 2 HfCl2 的晶体结构 .六个化合物均具有一定的催化乙烯聚合活性

X-ray photoelectron spectroscopy and mass spectrum of organic tin compounds

The relationship between the chemical displacement of the binding energy and the different chemical environment for 12 organic tin compounds was studied by means of X-ray photoelectron spectronscopy. The different substituents in the compounds have influence on the tin outer electron and Sn-O bond, which was discussed by Xray photoelectron spectroscopy and mass spectrum.