增粘树脂对湿固化聚氨酯热熔胶性能的影响

针对湿固化聚氨酯热熔胶,考察增粘树脂中松香树脂、萜烯树脂和萜烯酚醛树脂的加入对湿固化聚氨酯热熔胶初粘强度、终粘强度、熔融粘度、开放时间等性能的影响。结果表明,萜烯酚醛树脂作为增粘树脂所得的湿固化聚氨酯热熔胶熔融粘度低,粘结强度大,热稳定性高,增粘效果显著。     

阳离子聚丙烯酰胺的制备及其絮凝性能

研究了氧化还原引发剂质量分数、偶氮类引发剂质量分数、阳离子度等因素对所制备的阳离子聚丙烯酰胺特性粘数的影响,探讨了pH值、阳离子聚丙烯酰胺特性粘数、阳离子度、用量等因素对污泥絮凝性能的影响. 较佳的制备条件为:复合引发体系中(NH4 )2 S2 O8 和CH3 NaO3 S·2H2 O总质量分数为0.015 0%、偶氮类引发剂质量分数为0.012 5%、单体质量分数为40%、阳离子度为40%,产物特性粘数为13.1 dL/g. 在污泥pH=6.0、阳离子聚丙烯酰胺特性粘数为11.9 dL/g、阳离子度为40%、用量为0.027%的较佳絮凝条件下,污水的透光率达98.0%,絮凝率达66.0%,脱水率达70.0%.     

环糊精功能化疏水缔合丙烯酰胺聚合物的制备与性能评价

以十六烷基二甲基烯丙基氯化铵(C₁₆DMAAC)为疏水单体、烯丙基环糊精(A-CD)为环糊精功能化单体,与丙烯酰胺(AM)通过自由基共聚作用制备了环糊精功能化疏水缔合丙烯酰胺聚合物P(AM/A-CD/C₁₆DMAAC)。采用红外光谱和电子扫描电镜对P(AM/A-CD/C₁₆DMAAC)的结构进行表征。并考察了聚合物的水溶性、粘浓性质、特性粘数和粘均分子量。发现聚合物具有良好的空间结构和溶解特性,临界缔合浓度为1600mg/L,粘均分子量达5.5×10⁶g/mol,聚合物具备作为三次采油的应用潜能。     

LW-1型增效剂对聚丙烯酰胺水溶液增粘的实验研究

研究了LW 1型增效剂对聚丙烯酰胺水溶液的增粘效果 ,考察了增效剂含量、溶液中金属离子浓度、剪切强度、聚合物浓度、pH值对增粘效果的影响 .结果表明 ,增效剂能起到显著的增粘效果 ,对提高原油采收率具有重大意义 .此外 ,初步分析了LW 1型增效剂对聚丙烯酰胺水溶液增粘的可能机理     

从GPC和特性粘数计算高聚物各种平均相对分子质量的新方法

聚合物相对分子质量表征问题可以从ＧＰＣ数据和特性粘数较可靠地迅速解决，同时求出其烽均、粘均、重均，动力学平均相对分子质量及相对分子质量－特性粘数关联参数。为些须对以往方法作较大的改进，其关键是用迭代法进行特性粘数与相对分子质量的关联。方法经用聚甲基丙烯酸甲酯验证后用于聚碳酸亚乙酯（ＰＥＣ）和聚碳酸亚丙酯（ＰＰＣ）分别得到关系式。     

丹皮酚与钙粘素相互作用的分析研究

丹皮酚对多种肿瘤细胞具有抑制作用,而钙粘素是与肿瘤产生和恶化密切相关的一类糖蛋白.本研究运用荧光光谱法和原子力显微技术探索了丹皮酚与钙粘素的相互作用.荧光光谱法研究结果表明,丹皮酚对钙粘素的荧光具有显著的猝灭作用,通过猝灭常数随温度变化趋势推断为静态猝灭过程.丹皮酚与钙粘素形成复合物的热力学参数分别为ΔH=-4.3×10.5 J/mol和ΔS=-1.3×10.3 J/(mol·K), 表明此结合过程以氢键和范德华力为主.原子力显微观察结果表明,钙粘素分子间可形成有序长链结构,丹皮酚加入后能显著破坏这种组装结构而形成短链结构,这是由于丹皮酚与钙粘素末端色氨酸残基的作用而影响相邻钙粘素分子结构域间的交错作用所致.本研究结果表明,钙粘素可能是丹皮酚体现其活性的一个重要作用靶点.     

聚乳酸扩链及热性能研究

采用L-乳酸熔融缩聚,制备了粘均相对分子质量较低的聚乳酸,并以亚磷酸三苯酯和1,4-丁二醇二缩水甘油醚为扩链剂对其扩链。亚磷酸三苯酯和1,4-丁二醇二缩水甘油醚可以有效提高聚乳酸的粘均相对分子质量,但是,扩链产物PLLA-TPPi和PLLA-BDDE的粘均相对分子质量未随亚磷酸三苯酯和1,4-丁二醇二缩水甘油醚的用量呈线性变化,而是表现为一峰值。PLLA-TPPi和PLLA-BDDE的玻璃化温度均随扩链产物的粘均相对分子质量的增大而提高;与PLLA-BDDE相比,PLLA-TPPi链中的TPPi结构更能有效促进PLLA链的结晶。     

高聚物各种平均相对分子质量的绝对测定——GPC和特性粘数法

从GPC数据和特性粘数能较准确迅速求出高聚物的数均、粘均、重均、Z均相对分子质量及相对分子质量与特性粘敷关联参数。该方法经聚甲基丙烯酸甲酯验证后,用其表征了聚碳酸亚乙酯(PEC)和聚碳酸亚丙酯(PPC)。     

树状高分子的特性粘数与代数的关系

从爱因斯坦的粘度理论出发 ,联系树状高分子的分子结构参数 ,计算了树状高分子的特性粘数 ,得到了树状高分子的特性粘数与代数的内在关系 ,分析了树状高分子特性粘数特异行为的内在原因 ,使得对树状高分子特性粘数的理论预测成为可能     

基团贡献法研究环型聚苯乙烯稀溶液流体力学参数

首次采用基团贡献法,根据内聚能、摩尔体积、摩尔吸引常数和临界特性粘数等分别计算并通过实验数据验证了环型和线型聚苯乙烯的溶度参数,特性粘数、摩尔极限粘数函数、临界分子量和Mark-Houwink参数,详细地讨论了计算大环高分子的K_(θ,r)值所取用的临界分子量应具有的理论意义。     

"Alpha"-, "beta"- and "delta"-anhydrodigitoxigenin

The syntheses of 3β-hydroxy-5β-carda-14, 20:22-dienolide (= «β»-anhydro-), 3β-hydroxy-5β-carda-8:14, 20:22-dienolide (= «α»-anhydro-) and «δ»-anhydro-digitoxigenin (= probably 3β-hydroxy-5β, 14β-carda-8, 20:22-dienolide) by the best ways known to date, have been described. «δ»-Anhydro-digitoxigenin represents the thermodynamically most stable isomer. In this isomer the double bond in position 8 is unaffected by hydrogenation with Pt in acetic acid; with perbenzoic acid an epoxide results from which, on hydrogenation, the double bond can be regenerated in its original position. Analogous reactions are known to occur in the 8:14-epoxides.     

化“材”为“筑”

Chemistry is a central, practical and creative discipline. The development of chemistry plays an important role in the progress of science and society, as well as the improvement of the quality of human life. This paper introduces the chemical knowledge of stone, concrete, glass and other inorganic nonmetallic building materials by the anthropomorphically story. Taking nanomaterials as an example, the prospect of building materials development in the future is put forward.     

Making "wheels" and "cubes" from triangles

[Mn(IV)Mn(II)3] triangular units directed by the presence of tripodal alcohols self-assemble in the presence of azide and acetate ligands to form either a [Mn24] "wheel" or a [Mn32] "cube".     

"Turn-on" fluorescent sensing with "reactive" probes

Chemical probes are valuable tools for the investigation of biochemical processes, diagnosis of disease markers, detection of hazardous compounds, and other purposes. Therefore, the development of chemical probes continues to grow through various approaches with different disciplines and design strategies. Fluorescent probes have received much attention because they are sensitive and easy-to-operate, in general. To realize desired selectivity toward a given analyte, the recognition site of a fluorescent probe is designed in such a way to maximize the binding interactions, usually through weak molecular forces such as hydrogen bonding, toward the analyte over other competing ones. In addition to such a supramolecular approach, the development of fluorescent probes that sense analytes through chemical reactions has witnessed its usefulness for achieving high selectivity, in many cases, superior to that obtainable by the supramolecular approach. Creative incorporations of the reactive groups to latent fluorophores have provided novel chemical probes for various analytes. In this feature article, we overview the recent progress in the development of turn-on fluorescent probes that are operating through chemical reactions triggered by target analytes. Various chemical reactions have been implemented in the development of many reactive probes with very high selectivity and sensitivity toward target analytes. A major emphasis has been focused on the type of chemical reactions utilized, with the hope that further explorations can be made with new chemical reactions to develop reactive probes useful for various applications.     

"Decoking" of a "coked" zeolite catalyst in a glow discharge

'Decoking' of a 'coked' zeolite catalyst in a glow discharge in oxygen is investigated. The 'decoking' process involves reactions of atomic oxygen (O atoms) with 'coke' and yields gases such as CO, CO₂ as well as other gaseous products that could be easily pumped out.Three different modes of discharge were investigated including a static mode, a flowing-gas mode, and a periodic-purge mode where the oxygen and other gaseous products of the discharge were replaced by fresh O₂ gas after short but regular intervals of time. In some cases, additional heating was also used to provide base temperatures of the order of 100 °C to facilitate penetration of oxygen atoms into the inner layers and cages of the zeolite catalyst.This paper presents some results of spectroscopic analytical techniques used to monitor the atomization of oxygen, oxidation of 'coke', and to confirm the process of 'decoking'. More specifically, radiation emission on the 3 s ⁵S– 3p ⁵P transitions of O around 777.2–777.5 nm were selected for monitoring the atomization of O₂. On the other hand, X-ray photo-electron spectroscopy (XPS) was used to determine the amount of residual carbon and extent of 'decoking'. Furthermore, evolution of CO and CO₂ gases as a function of time was systematically monitored in real time. For CO, the 451.1 nm band head belonging to the B¹ - A¹ bands of the Angstrom system of the CO spectrum was used, while for CO₂, the band head at 353.4 nm belonging to the CO₂⁺ spectrum was used. The rates of evolution of CO and CO₂ were related to the rate of 'decoking' of the catalyst. It is noted that in the periodic-purge mode, about 63% of the total yield of CO from a given sample of the catalyst appears in the first 3-min exposure to discharge whereas it takes up to 15 min to remove nearly 94% of the removable carbon under our experimental conditions.     

营养化学课程翻转课堂的探索与实践

With its tailored learning content, flexible learning environment and directed teacher guidance, the flipped classroom in "nutrition chemistry" has effectively solved the problems of students' specialty, large number and limited time in the course of elective course. The teaching mode based on the cultivation of students' ability and the core of improving scientific literacy was constructed.     

Size evolution study of "molecular" and "atom-in-cluster" polarizabilities of medium-size gold clusters

A study on static polarizabilities for a family of gold clusters (Au(n), n = 6, 12, 20, 34, 54) is presented. For each cluster, a density functional theory perturbation theory calculation was performed to compute the cluster polarizability and the polarizability of each atom in the cluster using Bader's "quantum theory of atoms in molecules" formalism. The cluster polarizability tensor, α(cluster), is expressed as a sum of the atom-in-molecule tensors, α(cluster)=∑(Ω)α(Ω). A strong quadratic correlation (R(2) = 0.98) in the isotropic polarizability of atoms in the cluster and their distance to the cluster center of mass was observed. The cluster polarizabilities are in agreement with previous calculations.