多核钕-铝双金属配合物催化丁二烯聚合V.甲基铝氧烷的影响

以外添加的方式,考查了甲基铝氧烷(MAO)对多核钕-铝双金属配合物催化了二烯聚合的影响,并与烷基铝存在下的作用结果相比较.结果表明,MAO用量较低时(n(Al)/n(Nd)在5～20之间),即可较烷基铝更大程度提高稀土配合物的催化活性,获得顺式聚了二烯;MAO的链转移作用较烷基铝的低.     

Formation of Pyrrolidin-1-ylcyclopentadienes via Cyclization of Alkyl 2-Dimethoxyacetyl-and 2-Ethoxalyl-4-oxopentanoates

ＦｏｒｍａｔｉｏｎｏｆＰｙｒｒｏｌｉｄｉｎ┐１┐ｙｌｃｙｃｌｏｐｅｎｔａｄｉｅｎｅｓｖｉａＣｙｃｌｉｚａｔｉｏｎｏｆＡｌｋｙｌ２┐Ｄｉｍｅｔｈｏｘｙａｃｅｔｙｌ┐ａｎｄ２┐Ｅｔｈｏｘａｌｙｌ┐４┐ｏｘｏｐｅｎｔａｎｏａｔｅｓ＊ＺＨＵＹｉ－ｑｉａｎｇ,...     

聚乙烯-聚异戊二烯两嵌段共聚物的合成和表征

以正丁基锂为引发剂,阴离子聚合合成了聚丁二烯-聚异戊二烯两嵌段共聚物,然后以2-乙基己酸钴/三乙基铝配位络合催化体系,将其中丁二烯段进行选择性氢化,制备了聚乙烯-聚异戊二烯两嵌段共聚物.对这两种嵌段产物分别用红外光谱、GPC,粘度法、DSC、X-射线衍射和动态力学谱等方法进行了表征.     

杂原子分子筛(Ⅱ)——B-Si Pentasil型沸石分子筛晶体结构的研究

应用多晶X射线衍射法测定了B-SiPentasil型沸石分子筛的晶体结构并经Rietveld法修正.其晶胞参数为:α=19.983(1)Å;b=19.973(1)Å;c=13.303(1)Å.空间群为D_2h¹⁶-P_nma.晶体的骨架结构与所报导的Si-AlZSM-5相似.结构测定的结果表明:硼原子进入了沸石分子筛的骨架.     

乙醇法合成硼硅Pentasil型分子筛

七十年代,美国Mobil公司^[1]发表了ZSM-5型沸石分子筛的专利,该沸石具有独特的结构和良好的催化性能,在石油化工技术中业已展现出广阔的应用前景.1980年,M.Taramasso^[2]等人用四丙基胺、正硅酸乙酯等原料合成出了四种硼硅分子筛.1981年,作者^[3]在国内首次用有机胶合成出硼硅Pentasil型分子筛(ZSM-5型).本文以水玻璃、白炭黑为硅源,用乙醇取代有机胺,在微量导向剂存在下,合成了硼硅pentasil型分子筛;并用正交实验的方法探讨了合成中诸因素对分子筛结晶度的影响.     

丁二烯的NdCl3·2Phen-HAl(i-Bu)2催化定向聚合

本文报导了一种新的二元氯化稀土定向聚合催化剂,系由氯化钕邻菲罗啉络合物(NdCl₃·2Phen)与氢化二异丁基铝(HAl(i-Eu)₂)所组成。该体系可在较宽范围内改变聚丁二烯的分子量。本文研究了该体系作用下丁二烯聚合的一般规律,着重考察了影响产物分子量的主要因素,表明HAl(i-Bu)₂是聚合过程中的主要链转移剂,HAl(i-Bu)₂/单体比是控制产物分子量的关键变量,文内对邻菲罗啉络合分子在控制产物分子量过程中可能起的作用进行了讨论。     

Influence of the soliton in anharmonic molecular crystals with temperature on Mössbauer effect

The influence of a soliton on the properties of the M?ssbauer effect resulting from the gamma-active nuclei situated at lattice sites in quasi-one-dimensional anharmonically organic molecular chains, in which the active nuclei emit gamma-photons, has been theoretically studied by a quantum vibrational model. An expression for the gamma-radiated M?ssbauer transition probability as a function of the temperature and non-linear interaction has been obtained. Finally we give some new properties of this effect from numerical calculation in such a case, which present a way to experimentally confirm the soliton existence in molecular crystals. Received 9 April 1998 and Received in final form 11 December 1998     

Nd-Al双金属配合物催化双烯聚合反应动力学

以Ｎｄ－Ａｌ双金属配合物为催化剂,考察了丁二烯和异戊二烯聚合反应的动力学,得到稳态聚合速率方程为Ｒｐ＝ｋ〔Ｍ〕〔Ｎｄ〕＾ｎ（ｎ＝１）;丁二烯比异戊二烯有更大的表观增长速率常数ｋ,这些与聚合体系中是否存在过量的烷基铝无关。对多组分稀土催化剂作用下异戊二烯聚合反应动力学方程中出现较高ｎ值的现象进行了初步的探讨。     

DNA-modified electrodes. Part 6. A new method for the determination of binding constants and binding site sizes

A new method was developed to obtain the binding constant (K) and binding site size (n) for the interaction of DNA with other molecules using DNA-modified gold electrodes. This method is simple and microsample-consuming compared with conventional solution methods. A Q-basic program was designed to calculate K and n values. The results show that the K and n values obtained by the new method approach those obtained by conventional electrochemical methods, indicating the suitability of this method. Received: 22 July 1998 / Revised: 24 November 1998 / Accepted: 27 November 1998