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41.
Akikazu Matsumoto Ryuji Kotaki Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1991,29(12):1707-1715
Bulk polymerization of alkyl N,N-dialkylfumaramates (FAE) and maleamates (MAE) was performed in the presence of a radical initiator. It has been found that FAE is more reactive than MAE when the reactivity of the two geometrical isomers was compared for their homo- and copolymerizations. From investigation on the effect of ester and N-substituents of these monomers, it has been found that the isopropyl ester shows a higher reactivity than the methyl ester and that N-ethyl and n-butyl substitution gives polymers with high molecular weight of more than several thousands. The resulting substituted polymethylenes from FAE and MAE were characterized and compared with each other. The isomerization of MAE to FAE with morpholine as an isomerization catalyst and monomer-isomerization radical polymerization were also investigated. 相似文献
42.
D. Duracher F. Sauzedde A. Elaissari A. Perrin C. Pichot 《Colloid and polymer science》1998,276(3):219-231
Cationic hydrophilic copolymer latexes were synthesized at 70 °C either by batch or two-step emulsifier-free emulsion poly-merization
of styrene (St), N-iso-propylacrylamide (NIPAM), and aminoethylmethacrylate hydro-chloride (AEM) using 2,2′-azobis (2-amidinopropane) dihydrochloride
as initiator. At first, batch polymerization kinetics were followed by gas chromatography (GC), revealing that NIPAM rapidly
homopolymerized, before the polymerization of styrene had started. Particle size analysis by quasi-elastic light scattering
(QELS) and transmission electron microscopy (TEM) showed that monodispersed particles were obtained with the formation of
a poly[NIPAM] rich shell. Adding a small amount of the cationic monomer caused a strong decrease of the particle size without
affecting the size monodispersity. When a shot process was used, a narrow particle size distribution was maintained, provided
that the monomer addition was performed at a relatively high conversion of the first batch step. The poly[NIPAM] rich shell
layer was larger with the shot process, but increasing the amino-containing monomer in the recipe resulted in a dramatic decrease
of the thickness. Combination of transmission, scanning and atomic force microscopy techniques showed that these hydrophilic
particles exhibited odd-shaped structures, the unevenness being dependent upon the performed process. Kinetic data and particle
morphology information were inferred for discussion of the polymerization mechanism of this system.
Received: 21 August 1997 Accepted: 22 October 1997 相似文献
43.
结晶聚合物的辐射效应:多官能团单体对LDPE的结晶成核作用 总被引:1,自引:2,他引:1
根据x射线、电镜、DSC和凝胶分数的测试结果,讨论了多官能团单体结构对低密度聚乙烯聚集态结构的影响以及结晶度与辐射交联(或剂量)的关系。发现由于单体的存在导致低密度聚乙烯结晶度增加而结晶尺寸变小(即结晶成核效应);成核效应越大,增强辐射交联的效果也越大。添加具有高结晶成核作用的单体有利于低密度聚乙烯的辐射交联,同时也加速其结晶结构的破坏。 相似文献
44.
Börries Kübel 《Monatshefte für Chemie / Chemical Monthly》1982,113(6-7):781-792
Aliphatic amidoximesR—C (NH2)=NOH react with diketene to yield 5-acetonyl-3-alkyl-1,2,4-oxadiazoles, which are susceptible to a wide variety of reactions at the keto-group as well as at the methylene-group. Their transformations into 1-methyl-2-oxadiazolyl-vinylN,N-dimethylcarbamates, 2-chloro-1-oxadiazolylpropenes, 1-oxadiazolyl-2-(1,2,4-triazol-1-yl)propenes, 1,1-dichloro-1-oxadiazolylacetones and 3-hydroxy-2-oxadiazolyl-crotonic amides are described as well as their reactions with diazonium salts, with sodium nitrite and with carbon disulfide. Further products obtained are carbamates of of 1-oxadiazolyl-2-oxo-propane-1-oximes, 2-chloro-2-oxadiazolylvinyl phosphates and an oxadiazolyl pyrimidine.
Herrn Prof. Dr.Klaus Weissermel zu seinem 60. Geburtstag. 相似文献
45.
从两二酸二乙酯、氯乙酸乙酯和氯苄出发,经LiAlH4还原,合成新的二元醇,进而合成新的螺环化合物:3,9-二羟乙基-3',9'-二苯甲基-1,5,7,11-四氧杂螺[5,5]十一烷.该化合物的结构由它的氢和碳-13核磁共振谱、红外光谱和元素分析得到证明.该单体在三氟化硼乙醚络合物的作用下进行开环聚合反应.由于环上四个取代基的稳定作用,聚合物的收率比较低(产率10%左右).通过对聚合物的结构分析,提出了这一单体的阳离子开环聚合反应机理.对随聚合温度升高,聚合物中酯基/苯基的克分子比降低,以及本体聚合时得到交联聚合物等一系列现象作了探讨. 相似文献
46.
47.
新型螺环单体的合成和自由基聚合反应的研究王宏鲁剑涛冯品珍(中国科学技术大学研究生院化学部北京100039)关键词自由基聚合,新单体合成,螺环单体,自由基共聚虽然离子型开环聚合早已为人熟知,但是自由基开环聚合反应的研究和应用开发还刚刚起步.... 相似文献
48.
F Schneider 《Angewandte Chemie (International ed. in English)》1978,17(8):583-592
The presence of histidine in the active center of an enzyme can be demonstrated by kinetic measurements, chemical modification, NMR spectroscopy or X-ray structure analysis. Histidine is the only naturally occurring amino acid to contain an imidazole residue as a side chain. The role of histidine in enzyme catalysis depends, inter alia, upon the special features of the imidazole residue: it thus tends to form hydrogen bonds, combines donor and acceptor properties and can take part in either nucleophilic or base catalysis. In some of these enzymes the position of each atom is known; however, the theories as to how the catalysis proceeds at a molecular level are controversial. 相似文献
49.
Shu Jiang ZHANG Yan Feng LI Xiao Long WANG Da Xue YIN Yu SHAO Xin ZHAO 《中国化学快报》2005,16(9):1165-1168
A new aromatic diamine monomer containing pyridine unit, 2,6-bis (4-aminophenoxy- 4'-benzoyl)pyridine(BABP), was synthesized in three steps, starting from 2,6-pyridinedicarboxyl chloride. A series of novel pyridine-containing polyimides were prepared v/a the polycondensation of BABP with various aromatic dianhydrides through poly(amic acid) precursors, and thermal or chemical imidization of the precursors. The polyimides exhibit desirable properties, e.g., good solubility in N-methyl-2-pyrrolidone and m-cresol, excellent thermal stability and film-forming capability, as well as high inherent viscosity, indicating high molecular weight. 相似文献
50.
水中痕量钼(Ⅵ)的4-(2-吡啶偶氮)-间苯二酚螯合活性炭吸附富集分光光度法测定 总被引:5,自引:0,他引:5
提出了一种简单快速预富集水中痕量钼(Ⅵ)的新方法,方法的机理在于4-(2-吡啶偶氮)-间苯二酚(PAR)与钼(Ⅵ)螯合后被活性炭中附,然后用NaOH解吸下来,再用水杨基荧光酮与钼(Ⅵ)显色,分光光度法测定钼(Ⅵ)的含量;详细研究了影响Mo-PAR螯合物定量吸附于活性炭上的各种参数,找出了最佳吸附-解吸条件,包括吸附酸度、PAR用量、吸附时间、解吸酸度等;该法的主要优点是操作简单、快速,干扰小,避免了常规方法中用浓硝酸消化活性炭费时和污染大的解吸方法,该法已用于测定水中痕量钼(Ⅵ),加标回收率达到94%-97%。 相似文献