α,α’-邻二甲苯基桥联二茂基钐(Ⅱ)配合物对聚ε-己内酯进行开环聚合机理的研究

茂金属化合物中两个茂环可以通过一个或两个桥基相连接,形成桥联茂金属催化剂。本文通过合成新型茂金属α,α'-邻二甲苯基桥联二茂基钐()配合物,考察对其ε-己内酯进行开环聚合的研究。实验结果显示,此新型催化剂具有很高的催化活性,在单体/催化剂用量(mol)为3000时仍有催化活性,聚合物的分子量高达35万,此催化剂的催化活性及所得聚合物分子量都比目前所报道的高。     

茂金属聚丙烯催化剂概述

聚丙烯是一种生活中应用非常广泛的材料,其中丙烯聚合催化剂的进步是聚烯烃工业蓬勃发展的关键。具有独特性能和优势的茂金属聚丙烯催化剂在过去的几十年中引起了人们极大的研究兴趣。综述了茂金属聚丙烯催化剂的结构、组成,助催化剂以及茂金属催化丙烯聚合机理。重点介绍了非桥联茂金属催化剂以及桥联茂金属催化剂,其中桥联茂金属化合物因桥基的刚性骨架结构,使得其与聚丙烯规整度紧密相连。还详细介绍了C_2、C_(2v)、C_s、C_1不同对称性对聚丙烯规整度的影响。     

茂金属化合物催化极性烯类单体活性聚合的研究进展

综述了CGC催化剂、单茂催化剂、多核茂金属催化剂、桥联茂金属催化剂,非茂金属催化剂催化极性烯类单体均聚合及极性烯类单体与非极性烯类单体共聚合的研究.茂金属催化剂催化极性烯类单体聚合的机理包括配位聚合机理与活性自由基聚合机理.采用茂金属催化体系可以制备极性烯类单体的均聚物及极性烯类单体与非极性烯类单体的共聚物.不仅拓宽了茂金属催化剂的应用范围,而且可开发出具有新性能的极性聚烯烃树脂.     

二茂型稀土金属对乙烯聚合反应的催化性能研究进展

概述了茂金属有机络合物的发展,重点介绍了无助催化剂的非桥二茂稀土金属络合物、桥联二茂稀土金属络合物和加助催化剂的非桥二茂稀土金属络合物三类二茂型稀土金属络合物对乙烯聚合的催化活性的研究进展,说明二茂型有机稀土络合物在催化乙烯聚合反应中有优良活性并极具开发价值。     

茂金属化合物及其制法和在烯烃聚合催化剂中的应用

本发明公开了一类含有2个由亚烷基桥连的环戊二烯基环的茂金属化合物。这类茂金属化合物适合用作烯烃聚合的催化剂组分，特别是，使丙烯在基于这些茂金属化合物的催化剂存在下聚合，可以得到高收率，并具有很高的全同规整度，高的分子量和窄的分子量分布的聚合物。     

日本出光公司研发出低等规茂金属聚丙烯

<正>为了生产相对柔软的聚丙烯材料,可以采用丙烯与乙烯或其他a-烯烃无规共聚或抗冲共聚的方法,此外还可以通过降低聚丙烯的立构规整性,从而得到低模量聚丙烯。在对茂金属化合物催化丙烯聚合的研究中,人们发现与单桥联茚基茂金属相比,双桥联茚基茂金属会降低聚合物的立构规则性。对于单桥联茚基茂金属催化剂,     

非茂双核烯烃聚合催化剂研究和应用进展

综述了非茂双核烯烃催化剂近十年的研究进展。重点阐述了配体上各种取代基电子效应和空间结构与催化乙烯聚合性能关系,分析了双核非茂金属烯烃催化剂催化聚合特点,指出了烯烃聚合用双核非茂催化剂发展方向。     

烯烃配位活性聚合催化剂的研究进展

综述了茂/单茂金属催化剂、二元胺前过渡金属催化剂、α-二亚胺后过渡金属催化剂和水杨醛亚胺前过渡金属催化剂在烯烃配位活性聚合中的研究进展,以及各种催化剂催化烯烃配位活性聚合的实例和影响配位活性聚合的关键因素。这四种烯烃配位活性聚合催化剂中,茂/单茂金属催化剂的研究结果最成熟,但其他三种非茂体系的催化剂具有制备容易、催化烯烃配位活性聚合的条件温和、在实际应用中易实现的优势。此外,采用多重活性聚合的方法能解决配位活性聚合时催化剂利用率低的问题。     

非茂双核烯烃聚合催化剂研究和应用进展(续)

综述了非茂双核烯烃催化剂近十年的研究进展。重点阐述了配体上各种取代基电子效应和空间结构与催化乙烯聚合性能关系,分析了双核非茂金属烯烃催化剂催化聚合特点,指出了烯烃聚合用双核非茂催化剂发展方向。     

离子型茂金属催化丙烯聚合的研究进展

综述了以硼化合物为助催化剂的离子茂金属催化剂催化丙烯聚合的研究进展,介绍了用不同催化体系制备的不同结构的聚丙烯的性能及用途,并对聚合机理进行了探讨 。     

Synthesis of melamine-formaldehyde microcapsules containing oil-based fragrances via intermediate polyacrylate bridging layers

A general and versatile strategy to prepare melamine-formaldehyde (MF) microcapsules encapsulating oil-based fragrances by combining solvent evaporation and in situ polymerization was proposed in this work. The oil-based fragrance was pre-encapsulated by an inner polyacrylate membrane via solvent evaporation, followed by in situ polymerization of MF precondensates as an outer shell. The polyacrylate membrane is used as an intermediate bridging layer to stabilize the oil-based fragrance, and to provide driving forces for in situ polymerization of MF precondensates through electrostatic attractions between carboxyl groups and ammonium ions. It was demonstrated that MF microcapsules containing clove oil were prepared successfully. The amount and the composition of the intermediate polyacrylate bridging layer were critical. Smooth and sphere-shaped MF-clove oil microcapsules were prepared when the weight ratio of polyacrylate to clove oil was over 60 wt% and the concentration of acrylic acid (AA) increased to 10 wt% in polyacrylate. In addition, MF microcapsules containing sunflower oil and hexyl salicylate were prepared by using this method. The work suggests that this new approach can be potentially used to encapsulate various core materials, tuning the shell properties of microcapsules such as thickness, mechanical strength and release properties.     

含缩水甘油基／氨基丙烯酸酯共聚物乳液的聚合稳定性

研究了乳胶粒组成对含有缩水甘油基,羧基和胺基的丙烯酸酯多层核壳型乳液聚合稳定性的影响规律,探讨了聚合过程的凝聚机理。研究表明：官能团间的交联凝聚作用和水溶性聚合物的架桥凝聚作用是本体系凝聚物形成的主要原因。     

二丁基氧化锡在糖衍生物选择性合成中的应用

二丁基氧化锡和糖上的羟基选择性地形成亚甲锡烷基缩醛,通过聚合作用使处于聚合体不同位置的羟基显示了不同的电负性和亲核性,进行选择性反应合成糖衍生物.因此,利用二丁基氧化锡这种反应特性,分别对其在活性糖的保护、形成糖聚合体和糖基化等方面的应用进行了阐述,为该试剂在糖衍生物合成中的广泛应用提供参考.     

The Role of Bridging Group of Cyclopentadienyl Ligands for the Ziegler–Natta Catalysis: Theoretical Study

The potential energy surfaces of the initial reactions of ethylene insertion for the Ziegler–Natta catalysis with bridging groups of Cp ligands were studied by ab initio MO and density functional methods. Three metals (Ti, Zr, and Hf) in the Zeigler-Natta catalysis and eight bridging groups (BH, CH₂, NH, O, AlH, SiH₂, PH, and S) were treated. For the complex formation between ethylene and metallocenes, two type structures (vertical and horizon) were found. The vertical type structures are more stable in energy than the horizon types. The formation energy of the complex between ethylene and the metallocenes by incorporation of bridging atom or group is related to the geometrical hindrance and the bond interaction as shown in the case of boron bridging system.     

C60高分子衍生物的制备与应用

从合成方法的角度，详细的介绍了C60的高分子衍生物的制备方法。包括Fridel—Crafts烷基化反应、形成桥键的加成反应、Diels-Alder环加成反应、胺加成反应、自由基加成反应(一般自由基加成反应和活性自由基聚合)、离子聚合及配位聚合等。同时也介绍了在光学、电学、色谱学、生物医学及摩擦学等方面的应用。     

Functional group selective polymerization of (4-maleimidophenyl)oxirane as a new type of bifunctional monomer

A novel bifunctional monomer, (4-maleimidophenyl)oxirane (MAPO), with very reactive maleimido and epoxy groups, was prepared through the selective oxidation of the two carbon–carbon double bonds of N-(4-vinylphenyl)maleimide. Either of the two different polymerizable groups (vinylene of the maleimide moiety and the mono-substituted epoxide) of MAPO was able to be selectively polymerized by choosing the polymerization method. For radical polymerization, MAPO gave poly{p-[1,2-(epoxyethyl)phenyl]maleimide} (PEPM) with dense pendent epoxy groups in 76% yield without cross-linking. MAPO also gave poly(maleimidostyrene oxide) (PMSO) with dense pendent maleimido groups through cationic polymerization in 60% yield. On the other hand, anionic polymerization with an of MAPO produced only insoluble gel-like materials due to unselective polymerization of the two polymerizable groups (Scheme 1). The vinylene group of the maleimide moiety in PMSO easily reacted with the mercapto group, and the ring-opening reaction of the epoxy groups in PEPM with amino groups took place.     

Dinuclear,tetrakis(acetato)-bridged lanthanide(III) complexes from the use of 2-acetylpyridine hydrazone

The first employment of 2-acetylpyridine hydrazone in lanthanide(III) chemistry has led to dinuclear complexes with four bridging acetate groups of two different types and chelating 2-acetylpyridine hydrazone ligands.     

Studies on the initiation of a free‐radical condensation hybrid polymerization system

Compositions of hexamethoxymethyl melamine (HMMM)–ether polyol and acrylate can be cured by a hybrid polymerization comprising condensation polymerization and free‐radical polymerization, in the presence of a latent acid catalyst at high temperature. It was found that the initiating free radical was derived from the decomposition of hydroperoxides, which was formed by the oxidation of active methylene groups catalyzed by HMMM. It was also found that strong acid could accelerate the free‐radical polymerization in the hybrid system. To make the formulations more flexible, the activities of different types of methylene groups were investigated and two compounds with more active methylene groups and hydroxyl were synthesized, characterized, and used as crosslinker–initiators in the hybrid polymerization system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1195–1200, 2001     

Acidity of sulfated zirconia as studied by FTIR spectroscopy of adsorbed CO and NH3 as probe molecules

The acid properties of pure and sulfated zirconias were studied by FTIR spectroscopy of adsorbed CO and NH₃ as probe molecules. Whereas pure monoclinic zirconia shows only Lewis acidity, sulfation of tetragonal and monoclinic zirconia creates new bridging OH groups. Two types of Brønsted-acidic centers and two types of Lewis-acidic centers with enhanced acid strength were identified. A communication between the different types of Lewis-acidic sites and the related adsorbed sulfate molecules could be shown. The coordination of basic molecules such as CO onto Lewis-acid sites induces a decrease of the intrinsic Brønsted-acidity of the bridging OH groups. These effects are discussed on the basis of a model of the acidic centers that was previously proposed.On leave from Department of Chemistry, Faculty of Science, Minia University, El-Minia, Egypt.     

Aromatic diazenes containing azulen-1-yl moieties Part 2: The synthesis,characterization, electronic spectra and basicity of novel,bis aromatic diazenes containing two azulen-1-yl moieties

Bis aromatic diazenes which possess either two identical or two different azulene-1-yl groups substituted at either 1,3 or 1,4-positions in the bridging phenylene moiety were synthesized in good yield via diazotization of the 3- or 4-azulen-1-ylazo-phenylamines followed by coupling with azulene in a buffered medium. The electronic spectra of the synthesized compounds were analyzed by comparison with those of previously published compounds. The isosbestic points obtained by protonation of the compounds enabled their pK_a values to be determined.