氢化丁苯共聚物结构的核磁共振波谱表征——Ⅱ.微观结构的定量计算

在氢化丁苯共聚物~(13)C-NMR谱脂肪碳部分谱带归属的基础上,根据各谱带的主要来源,推导出六个二单元浓度的计算公式。计算出二单元、一单元的相对含量,各结构单元的数均序列长度、嵌段含量和其它结构参数。加氢前后的~1H-和~(13)C-NMR谱的组成计算结果基本一致。初步探讨了作为粘度指数改进剂的氢化丁苯共聚物微观结构与性能的关系,为合成提供了依据。     

无规丁苯共聚物的核磁共振波谱——13C-NMR谱带的归属

基于对不同组成的丁苯共聚物的测定、经验计算和参考文献值,对¹³C NMR谱图高场部分的21组谱带以及低场部分的11组谱带进行了归属,它们来自不同二单元结构环境中的各个碳原子。借助于超导NMR波谱,对谱带指认提出了一些新的看法。     

氧化铁在ZnO上分散的结构状态及其表征

采用（ＮＨ_４）_３［Ｆｅ（Ｃ_２Ｏ_４）_３］·ｘＨ_２Ｏ的水溶液含浸，Ｆｅ（ＮＯ_３）_３．９Ｈ_２Ｏ水溶液饱和浸渍（含浸）以及Ｆｅ（ＡｃＡｃ）_３的甲苯溶液热吸附三种方法制备了在ＺｎＯ上分散的氧化铁体系。用多种物理化学手段对用不同方法制备的分散体系进行了细致的表征，氧化铁在ＺｎＯ上形成单层分散是困难的。Ｆｅ~（３＋）一般进入到ＺｎＯ载体的表层，结构环境类似于ＺｎＦｅ_２Ｏ_４微晶中的Ｆｅ~（３＋），分散的Ｆｅ~（３＋）通常处于高自旋态，配位对称性并不是正交畸变。在ＺｎＯ上形成尖晶石的趋势最强。在亚单层铁含量范围内，通常形成表面ＺｎｘＦｅ_ｙＯ_ｚ。当铁含量超过单层阈值时，既生成ＺｎＦｅ_２Ｏ_４簇也有ＦｅＯ_ｘ簇存在。无论是ＦｅＯ_ｘ或ＺｎＦｅ_２Ｏ４簇还是表面的Ｚｎ_ｘＦｅ_ｙＯｚ，其Ｆｅ_（３＋）在实验温度范围内，很难被还原为零价铁，ＦｅＯ_ｘ较之Ｚｎ_ｘＦｅ_ｙＯ_ｚ物种难以还原且比体相ａ－Ｆｅ_２Ｏ_３中Ｆｅ~（３＋）要难还原得多。由热吸附法制得的ＦｅＯ_ｘ和ＺｎＦｅ_２Ｏ_４簇具有很低的催化活性，而由含浸法制得的表面Ｚｎ_ｘＦｅ_ｙＯｚ的反应性能有明显的改善。ＺｎＯ载体上不同含铁物种的反应性由Ｆｅ~（３＋）的还原性及是否存在活泼     

Derivatized fullerenes bearing multiple electron donors: synthesis and charge transfer properties

A series of methano-C60 adducts bearing up to six electron donating N,N-dimethylaniline units (denoted as D compounds), along with their analogues without the dimethylamino groups as references (R compounds), were synthesized. The redox properties of the D compounds in solutions were evaluated spectroscopically in reference to the R compounds. According to UV/vis absorption results, there are obviously ground-state intramolecular charge-transfer complexes in the D series, and the charge-transfer effects apparently become saturated with only two donor units in the molecule. The photoinduced intramolecular electron-transfer properties of the D compounds were investigated via fluorescence measurements. The emission from intramolecular exciplexes can be found only in the D molecule with two electron donor units. Throughout the D series, the fluorescence properties are highly sensitive to the solvent polarity, with the emission completely quenched for all of the molecules in a polar solvent like methylene chloride. Mechanistic implications of the results are discussed.     

氧化铁在γ—Al2O3上的分散状态及对反应性能的影响

采用(NH_4)_3[Fe(C_2O_4)_3]·XH_2O的水溶液含浸,Fe(NO_3)_3·9H_2O水溶液饱和浸渍以及Fe(AcAc)_3的甲苯溶液热吸附三种方法制备了在γ-Al_2O_3上分散的氧化铁体系。用多种物理化学手段对用不同方法制备的分散体系进行了细致的表征和比较,结果表明用第一和第三种方法制备的样品中Fe~(3+)是充分分散或单层分散的,但用饱和浸渍法制备时即使在低的载量时(3wt％Fe_2O_3)仍有氧化铁微晶。对于Fe_2O_3/γ-Al_2O_3,分散的结构状态还强烈地依赖于制备条件(参数)的选择。单层分散的Fe~(3+)处于高自旋态,具有正交畸变的局部配位对称性。单层分散的Fe~(3+)在氢气氛中即使升温至973K也只能被还原为Fe~(2+)状态。与单层MoO_x,VO_x,WO_x物种不同,单层分散的FeO_x物种既不能用XRD也很难被FTIR-DRS以及LRS所检测,丁烯脉冲反应表明单层的Fe~(3+)已可满足反应要求,但与晶相α-Fe_2O_3具有不同的选择性。CO脉冲实验表明与充分分散Fe~(3+)相关的晶格氧数目是少的而且较不活泼,流动态的CO+H_2反应结果表明,对于甲烷及其它低碳烃的生成主要取决于铁的价态而与分散的结构变化关系较小。在合成气中的程序升温反应结果进一步证实了这一结论。     

Fe2O3在ZrO2上的分散状态及其对催化性能的影响

用多种物理化学手段, 对用不同方法制备的在ZrO_2上分散的氧化铁体系进行了细致的表征和比较. 对氧化铁在ZrO_2上分散的结构状态及其对催化性能的影响有了较为全面的了解.     

Syntheses and structures of the first heavy-alkali-metal tris(trimethylsilyl)germanides

The first heavy-alkali-metal tris(trimethylsilyl)germanides were obtained in high yield and purity by a simple one-pot reaction involving the treatment of tetrakis(trimethylsilyl)germane, Ge(SiMe3)4, with various alkali metal tert-butoxides. The addition of different sizes of crown ethers or the bidentate TMEDA (TMEDA=N,N,N',N'-tetramethylethylenediamine) provided either contact or separated species in the solid state, whereas in aromatic solvents the germanides dissociate into separated ions, as shown by 29Si NMR spectroscopic studies. Here we report on two series of germanides, one displaying M-Ge bonds in the solid state with the general formula [M(donor)n Ge(SiMe3)3] (M=K, donor=[18]crown-6, n=1, 1; Rb, donor=[18]crown-6, n=1, 4; and M=K, donor=TMEDA, n=2, 6). The silicon analogue of 6, [K(tmeda)2Si(SiMe3)3] (7) is also included to provide a point of reference. The second group of compounds consists of separated ions with the general formula [M(donor)2][Ge(SiMe3)3] (M=K, donor=[15]crown-5, 2; M=K, donor=[12]crown-4, 3; and M=Cs, donor=[18]crown-6, 5). While all target compounds are highly sensitive towards hydrolysis, use of the tridentate nitrogen donor PMDTA (PMDTA=N,N,N',N',N'-pentamethyldiethylenetriamine) afforded even more reactive species of the composition [K(pmdta)2Ge(SiMe3)3] (8). We also include the silanide analogue [K(pmdta)2Si(SiMe3)3] (9) for sake of comparison. The compounds were typically characterized by X-ray crystallography, and 1H, 13C, and 29Si NMR and IR spectroscopy, unless extremely high reactivity, as observed for the PMDTA adducts 8 and 9, prevented a more detailed characterization.     

不同分子量可德胶水悬浮液的粘弹性研究

采用动态粘弹性测量研究了不同分子量的生物大分子可德胶 (Curdlan)水悬浮液 (ASC)的流变学特性 .室温下观察到ASC具有弹性 (Solid like)行为 ,储能模量G′在测量范围内轻微依赖频率 ,而损耗模量G″和损耗角正切tanδ存在最小值 .ASC粘弹性随可德胶分子量和浓度的增加而增强 .ASC的流动特性符合Herschel Bulkley模型 ;其弹性行为可以通过渗流理论的标度弹性模型来描述 .网络结构是由于可德胶颗粒聚集或絮凝而形成的 ,当可德胶含量超过临界浓度cs=0 3 %时 ,弹性模量G′与可德胶浓度存在标度关系G′=Goεt,其中标度指数t=2 5 4.     

Structural features of crystallized poly(ethylene terephthalate) polymers

Polyethylene terephthalate (PET) is a widely used polymeric material. In this work, the microstructural features before and after the solid‐state polymerization (SSP) of several DuPont PET products were investigated by low‐voltage scanning electron microscopy (LV‐SEM) and atomic force microscopy (AFM). The microstructural features on the cross section of various PET samples included crystallites, voids, boundaries, defects, and amorphous phases. The SEM images revealed layered and stepped structural features at the micron and 10‐micron scales that are highly crystallized at the near‐edge region of the cross section for both linear and branched PET samples after the SSP process. The AFM images demonstrate that the degree of crystallization for the linear and branched PET samples increases gradually from the central area to the edge on the cross section. The linear crystallized PET has a higher degree of orientation than the branched crystallized PET in the 10‐micron to micron scales, but their crystalline structures have no significant differences in the submicron to nanometer scales. The PET crystallization process occurs when the molecular chains in the amorphous phase are aligned and folded to form straight molecular chains at the nanometer scale, and small crystallites are formed. The crystallites aggregate and align together into a polygon rod‐like‐shaped crystallites at the submicron scale. Finally, large crystallites at the micron size are formed that appear on the edge area of the cross section. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 245–254, 2002     

七氟丁酰氨基酸正丁酯的GC/MS分析

本文报道了19种蛋白质氨基酸的七氟丁酰正丁酯衍生物的GC/MS分析方法;优选了衍生反应条件;建立了GC分离、定量分析方法,最小检测量为0.1ng;研究了衍生物的EI质谱数据,确定了可作为定性依据的特征离子;测定了儿童用复方氨基酸注射液及儿童血清样品,得到了满意的结果。