共查询到20条相似文献,搜索用时 15 毫秒
1.
Liming Jiang Yifeng Zhang Zhiquan Shen Lianfang Shen Hanzhen Yuan 《Macromolecular rapid communications》1996,17(6):427-431
A highly active rare earth coordination catalyst composed of neodymium acetylacetonate, dibutylmagnesium, and hexamethylphosphoramide (mole ratio 1:7:14) for the polymerization of N-phenylmaleimide (N-PMI) was developed. The resulting poly(N-PMI) has high molecular weight (M̄n = 9.0 × 104) and shows excellent thermal stability. 相似文献
2.
Zhiquan Shen 《Macromolecular Symposia》1994,84(1):5-13
The polymerization of acetylene and its derivatives by rare earth coordination catalysts and the characterization of the polymers so obtained in our laboratory are reviewed. Because of the metallic conductivity possessed by doped polyacetylene and the unique properties such as conductivity (semiconductivity), paramagnetism, migration and transfer of energy and chemical reactivity and complex formation ability often shown by acetylenic polymers, which seem promising as specialty polymers, there has been considerable interest in the polymers of acetylene and its derivatives. A wide variety of catalyst systems have been developed for the polymerization of acetylenes. But there has been no information concerning the use of rare earth compounds as catalysts in the polymerization of acetylene and its derivatives. We for the first time in 1981 have succeeded in the polymerization of acetylene with rare earth coordination catalysts, which in turn is a development based upon earlier work on the diene polymerization using rare earth coordination catalysts(Ref. 1). Using rare earth catalysts, acetylene can be polymerized conveniently into high cis polyacetylene films with metallic sheen at room temperature and phenylacetylene can also be polymerized into high molecular weight, high cis polyphenylacetylene films at ambient temperature. Thus new varieties of polyacetylenes have been developed and a novel family of coordination catalysts consisting of a rare earth compound plus trialkyl aluminum for the polymerization of acetylenes has been exploited. This article reviews our studies on the polymerization of acetylene and its derivatives with rare earth coordination catalysts and on the characterization of the polyacetylenes prepared. 相似文献
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M. G. Pérez‐García E. V. Torres I. Ceja L. A. Pérez‐Carrillo Raúl G. López F. López‐Serrano E. Mendizábal J. E. Puig 《Journal of polymer science. Part A, Polymer chemistry》2012,50(16):3332-3339
The synthesis of styrene‐acrylonitrile copolymers by semicontinuous heterophase polymerization is reported here. The effect of feed composition at a fixed addition rate of monomer mixture on kinetics, particle size, polymer content, and molar masses, was studied. This process permits the synthesis of nanolatexes containing narrow size‐distribution particles with number‐average diameter (Dn) of about 18 nm, polymer content as high as 23 wt %, and copolymer‐to‐surfactant weight ratios between 23 and 25, depending on monomer feeding rate, which are larger than those reported for microemulsion copolymerization of several comonomers. Copolymers with homogeneous composition similar to the feeding monomers composition were obtained thorough the reaction, which is difficult to achieve by batch polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
5.
Cationic rare earth metal alkyl species, generated by the treatment of mono(cyclopentadienyl) bis(alkyl) rare earth metal complexes with 1 equiv. of a borate compound such as [Ph3C][B(C6F5)4], act as an excellent catalyst for the polymerization and copolymerization of various olefins such as ethylene, 1-hexene, styrene, norbornene, dicyclopentadiene, and isoprene. These catalysts show unprecedented activity and regio- and stereo-selectivity and afford a series of new polymers which are difficult to be prepared previously. 相似文献
6.
Mujie Yang Xiaojun Zhang Jianfu Li Zhiquan Shen 《Journal of polymer science. Part A, Polymer chemistry》1992,30(1):63-69
The study of rare earth coordination catalysts for polymerization of 1-octene has been successfully carried out for the first time. Some features and kinetic behavior of polymerization of 1-octene by Nd(naph)3–AIEt3 catalyst system in tetrachloro-methane are described. The overall polymerization activation energy Ea measured was 74.5 kJ/mol and the rate equation could be expressed as Rp = kp [Nd] [M] (kp = 3.21 × 10?3 L/mol s, at 50°C). The catalytic activity of various rare earth elements in Ln (naph)3 and ligands in NdL3 for the polymerization was compared. A 1-octene oligomer with double bonds was obtained. It is either a white or pale yellow waxy semi-solid. Its number-average molecular weight is about 103 and the molecular weight distribution is less than 2. 相似文献
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Eiichi Kobayashi Nahoto Hayashi Sadahito Aoshima Junji Furukawa 《Journal of polymer science. Part A, Polymer chemistry》1998,36(2):241-247
Homo- and copolymerizations of butadiene (BD) and styrene (St) with rare-earth metal catalysts, including the most active neodymium (Nd)-based catalysts, have been examined, and the cis-1,4 polymerization mechanism was investigated by the diad analysis of copolymers. Polymerization activity of BD was markedly affected not only by the ligands of the catalysts but also by the central rare-earth metals, whereas that of St was mainly affected by the ligands. In the series of Nd-based catalysts [Nd(OCOR)3:R = CF3, CCl3, CHCl2, CH2Cl, CH3], Nd(OCOCCl3)3 gave a maximum polymerization activity of BD, which decreased with increasing or decreasing the pKa value of the ligands. This tendency was different from that for Gd(OCOR)3 catalysts, where the CF3 derivative led to the highest polymerization activity of BD. For the polymerization of St and its copolymerization with BD, the maximum activities were attained at R = CCl3 for both Nd- and Gd-based catalysts. The copolymerization of BD and St with Nd(OCOCCl3)3 catalyst was also carried out at various monomer feed ratios, to evaluate the monomer reactivity ratios as rBD = 5.66 and rSt = 0.86. The cis-1,4 content in BD unit decreased with increasing St content in copolymers. From the diad analysis of copolymers, it was indicated that Nd(OCOCCl3)3 catalyst controls the cis-1,4 structure of the BD unit by a back-biting coordination of the penultimate BD unit. Furthermore, the long range coordination of polymer chain by the neodymium catalyst was suggested to assist the cis-1,4 polymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 241–247, 1998 相似文献
9.
Victoria Dimonie Mohamed S. El-Aasser Andrew Klein John W. Vanderhoff 《Journal of polymer science. Part A, Polymer chemistry》1984,22(9):2197-2215
Seeded emulsion copolymerization of an azeotropic composition of styrene (St) and an acrylinitrile (AN) comonomer mixture in polystyrene (PS) seed at different polymerization temperature of 55–75°C were investigated. The kinetic data showed a transition temperature at 65°C, above which the activation energy of polymerization is low, 6.1 Kcal/mol, compared with 9.8 Kcal/mol below it. The particle-size results and thin layer chromatographic (TLC) data showed two types of particle of different composition and morphology in the final latex system: a smaller size of (St–AN) copolymer and a larger size of core-PS and (St–AN) copolymer shell, with a zone of PS grafted (St–AN) copolymer in between. Various polymerization parameters, that is emulsifier concentration, type of seed particle and its size, and monomer/polymer ratio, were studied and their effects on particle size and particle morphology were examined. The percent of grafted core-PS was 10% below a polymerization temperature of 65°C and 40% above that temperature. By adjusting the size and number of the seed particles, monomer-polymer ratio, and emulsifier concentration conditions were established in which a final copolymer latex with “perfect” core-shell morphology was achieved. 相似文献
10.
Robert A. Hayes 《Journal of polymer science. Part A, Polymer chemistry》1981,19(4):993-997
The copolymerization of styrene and styrene–acrylonitrile with polybutadienes of various microstructures was studied and the reactivity ratios determined. It was shown that for the styrene/acrylonitrile/polybutadiene systems the 1,2 structure is twice as reactive as the trans and four times as reactive as the cis. Studies in the temperature range of 50–80°C reveal that the reactivity of the polybutadiene increases as the temperature rises. When styrene is the monomer the reactivity of polybutadiene and the temperature effect is less intense than when styrene–acrylonitrile is used. 相似文献
11.
Yuanchang Shi Youshi Wu Jingcheng Hao Ganzuo Li 《Journal of polymer science. Part A, Polymer chemistry》2005,43(1):203-216
The microemulsion copolymerization of styrene and acrylonitrile in an n‐butanol/cetyltrimethylammonium bromide/oil/water microemulsion system was studied. The solubilization sites of the two monomers were determined with an NMR technique. The results showed that the solubilization behaviors of the two monomers were quite different. Most of the styrene was solubilized in the palisade layer of the microemulsion, whereas the acrylonitrile had an equilibrium distribution in the aqueous phase and palisade layer of the microemulsion. The reactivity ratios of styrene and acrylonitrile in the microemulsion system were different from those in other media. The effect of the monomer feed composition on the copolymerization kinetics was investigated, and the mechanism of nucleation of the latex particles was examined. The experimental results showed that the copolymerization loci were changed from the microemulsion droplets to the aqueous phase when the concentration of acrylonitrile in the monomer feed reached approximately 80%; this could be further proved by the effect of the monomer feed composition on the copolymerization kinetics. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 203–216, 2005 相似文献
12.
Mamoru Nomura Xiang Liu Fumihiko Mizutani Syuzaemon Sato Kazumi Fujita 《Macromolecular Symposia》1995,92(1):233-242
Effects of various operating variables on the kinetic behavior of the seeded emulsion copolymerization of styrene and acrylonitrile and on the monomer concentration in the copolymer particles were examined. Applicability of high-performance liquid adsorption chromatography to determination of the average composition and composition distribution of the resulting copolymer was also examined. 相似文献
13.
Investigations on free radical copolymerization of 1-vinyl naphthalene (1-VNph, monomerM
2) with styrene (St), methyl methacrylate (MMA) and acrylonitrile (AN) (monomersm
1) in bulk at 60°C with AIBN as initiator are presented. Relative reactivity ratios were calculated by the Kelen-Tüdös method yielding:r
st=0.70 ±0.23 andr
1–VNph=2.02 ±0.40 for system St/1-VNph;r
MMA=0.32 ±0.10 andr
1–VNph=0.57 ±0.07 for system MMA/1-VNph andr
AN=0.11 ±0.03 andr
1–VNph=0.45 ±0.09 for system AN/1-VNph.Q, e values for 1-VNph according to Alfrey, Price scheme were calculated toQ
1–VNph=1.02,e
1–VNph=–0.62. 相似文献
14.
Yuushou Nakayama 《Journal of organometallic chemistry》2004,689(24):4489-4498
This review article describes recent developments in rare earth metal complexes as polymerization catalysts, focusing on the polymerization of ethylene and α-olefins. Most of this kind of catalysts had been based on metallocene type complexes, and their catalytic behaviors are surveyed. Advanced series of half-metallocene and non-Cp type catalyst systems are also summarized. 相似文献
15.
Anionic or neutral allylic samarium or neodymium species catalyse the polymerization of styrene (catalyst/styrene ratio = 1:1000) without addition of a cocatalyst. Random syndiotactic‐rich material is obtained from tetra‐allyl‐lanthanides, whereas neutral trisallyl‐lanthanides or anionic ansa‐bis(cyclopentadienyl)bisallyl‐lanthanides afford isotactic‐rich polystyrene. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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18.
Joel L. Martin 《Journal of polymer science. Part A, Polymer chemistry》1984,22(12):3843-3850
Anhydrous chlorides of Mg, Mn, Y, and selected lanthanides were reacted with tri-n-butylphosphate and finally TiCI4 to prepare ethylene polymerization catalysts. With triethylaluminum as cocatalyst the highest activities were observed with Mg, Nd, and Pr, which correlate with the peak activity for Nd and Pr in diene polymerization catalysts prepared from the lanthanides. At a given hydrogen concentration molecular weights and molecular weight distributions and catalyst activities were similar for these three metals. The high activity for Nd and Pr is surprising because NdCI3 and PrCI3 adopt the UCI3 structure rather than a layer lattice structure common to MgCI2 and TiCI3. 相似文献
19.
Andreia Valente Philippe Zinck André Mortreux Marc Visseaux 《Journal of polymer science. Part A, Polymer chemistry》2011,49(7):1615-1620
A series of lanthanum and neodymium borohydrido complexes comprising the trisborohydrides Nd(BH4)3(THF)3 ( 1a ) and La(BH4)3(THF)3 ( 1b ) and the half‐lanthanidocenes Cp*Nd(BH4)2(THF)2 ( 2a ) (Cp* = C5Me5) and Cp*La(BH4)2(THF)2 ( 2b ) has been assessed for the chain transfer copolymerization of isoprene and styrene. A transmetalation process is occurring efficiently with the borohydride complexes in the presence of magnesium dialkyl. The transmetalation is accompanied by (i) a gradual decrease of the 1,4‐trans stereoselectivity of the reaction at the benefit of 3,4‐selectivity and (ii) an increase in the quantity of styrene inserted in the copolymer. This can be at least partially attributed to a magnesium induced co‐oligomerization of isoprene and styrene. By combining dialkylmagnesium and trialkylaluminum, a 1,4‐trans stereospecific reversible coordinative chain transfer copolymerization of isoprene and styrene is observed when the half‐lanthanocene 2b is used as precatalyst. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
20.
M. Yu. Zaremski E. S. Garina A. V. Plutalova V. B. Golubev 《Polymer Science Series A》2008,50(4):365-373
By the examples of chemically similar styrene-acrylonitrile and styrene-methacrylonitrile systems, substantially different mechanisms of TEMPO-mediated copolymerization have been theoretically predicted and experimentally verified. Living copolymer-TEMPO adducts capable of thermal decomposition and polymerization reinitiation via the pseudoliving mechanism predominantly form in the first system. The reaction proceeds under the steady-state regime and is characterized by the living growth of M n of the copolymer with conversion. In the second system, the probabilities of formation of living and dead macromolecules are equal. Therefore, the living growth of M n of the copolymer ceases and the reaction passes to the conventional copolymerization regime. 相似文献