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  • 1
    Electronic Resource
    Electronic Resource
    New catalytic systems for the fixation of carbon dioxide. 1. Copolymerization of carbon dioxide and propylene oxide with new rare-earth catalysts-RE(P204)3-Al(i-Bu)3-R(OH)n (1991)
    s.l. : American Chemical Society
    Macromolecules 24 (1991), S. 5305-5308 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00019a014
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  • 2
    Electronic Resource
    Electronic Resource
    Highly active rare earth catalysts for the solution polymerization of ε-caprolactone (1996)
    Springer
    Polymer bulletin 37 (1996), S. 21-28 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary By using γ-butyrolactone (γ-BL) as the reaction media, highly active catalysts--light rare earth chloride-epoxidy-γ--BL-for the solution polymerization of ε-caprolactone, have been obtained for the first time. With these catalyst, PCL with molecular weight as his as 40x104(Mv) can be prepared at 60°C for 1.5 hr. The amount of epoxide in catalyst solution, catalyst aging temperature and time affect the catalyst activity significantly. The mechanism study shows that in γ-BL, the weakening of Ln-Cl bonds by the donation of coordinated γ-BL with Ln3+ and the homogenous effect promote the reaction between light rare earth chloride and epoxide. The produced rare earth alkoxide initiates CL polymerization via a ‘coordination-insertion’ mechanism with Acyl-oxygen bond cleavage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313814
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  • 3
    Electronic Resource
    Electronic Resource
    The Study of Chaotic Neural Network and its Applications in Associative Memory (1999)
    Springer
    Neural processing letters 9 (1999), S. 163-175 
    Details
    ISSN: 1573-773X
    Keywords: associative memory ; chaos ; chaotic neural networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Based on an analysis of current principal chaotic neural network models and their applications in information processing, we propose a one-dimensional, two-way coupled map network and a modified definition of an auto-associative matrix. The two-way coupled map network overcomes the weakness of the globally coupled map network and has the same abilities in pattern classification. Numerical simulation experiments have shown that the associative success rate and recall speed of our modified definition of the auto-associative matrix are an improvement them over existing methods. Moreover, the associative recall process of the network is analyzed in detail and explanations of improvement are given, basd on our theoretical analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018633610274
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of functional unsaturated polyesters using rare earth coordination catalysts, 3Part 2: cf. X. H. Chen, Y. F. Zhang, Z. Q. Shen, Chin. Chem. Lett., in press.. Mechanistic aspects of maleic anhydride-epichlorohydrin copolymerization with Nd[(RO)2 PO2]3/Al[CH2CH(CH3)2]3 as a catalyst (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 2989-2995 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ring-opening alternating copolymerization of maleic anhydride and epichlorohydrin was carried out at 70°C with rare earth coordination catalysts composed of Nd[(RO)2 PO2]3 (R = CH3(CH2)3CH(C2H5)CH2—)and trialkylaluminium. Anlaysis of end-groups showed that the copolymer chain contains one —OH and one —CH=CH—CO—CH2CH(CH3)2 end-group. IR, UV-Vis, 1H NMR and GPC results imply that a catalyst-maleic anhyride complex is formed in the initiation step that the ring-opening copolymerization proceeds via coordinate insertion mechanism accompanied with chain-transfer.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021931205
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  • 5
    Electronic Resource
    Electronic Resource
    Styrene polymerization with rare earth catalysts using a magnesium alkyl cocatalyst (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 3519-3525 
    Details
    ISSN: 0887-624X
    Keywords: rare earth coordination catalyst ; di-n-butylmagnesium ; polymerization of styrene ; polymerization kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new highly active rare earth coordination catalyst composed of rare earth phosphonate, di-n-butylmagnesium (MgBu), and hexamethyl phosphoramide (HMPA) for the polymerization of styrene has been developed for the first time. High molecular weight polystyrene (M̄ν = 50-70 × 104) in 100% conversion could be prepared at following conditions: [Nd] = 6-8 × 10-4 mol/L, [St] = 3.0 mol/L, Mg/Nd = 11, and HMPA/Mg = 1-1.5 (molar ratio). The catalytic activity of this new catalyst is 3530 g PSt/g Nd. Kinetics study shows that the polymerization rate is of first order with respect to both monomer concentration and catalyst concentration, and activation energy of the polymerization is 40.1 kJ/mol. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1996.879
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  • 6
    Electronic Resource
    Electronic Resource
    Ring-Opening polymerization of ε-caprolactone by rare earth coordination catalysts. I. Characteristics, kinetics, and mechanism of ε-caprolactone polymerization with nd(acac)3.3H2O-ALET3 system (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 597-603 
    Details
    ISSN: 0887-624X
    Keywords: ε-caprolactone ; ring-opening polymerization ; rare earth coordination catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ring-opening polymerization of ε-caprolactone has been carried out by using rare earth coordination catalysts for the first time. The rare earth compounds, RE(acac)3.3H2O, Nd(P204)3, Nd(P507)3, Nd(naph)3, Nd(BA)3.2H2O, etc. (where RE = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Lu, Y; acac = acetylacetone; BA = benzoylacetone), combined with trialkyl aluminum, greatly increased the degree of conversion and the molecular weight of poly(ε-caprolactone) (PCL). The influence of reaction conditions on the polymerization of ε-caprolactone catalyzed by the Nd (acac)3.3H2O-AlEt3 system has been examined in detail. The kinetics indicates that the polymerization rate has the first-order in monomer and a half-order in catalyst. The overall activation energy of the ring-opening polymerization amounts to 59.4 kJ/mol. By IR and UV-Vis spectra, 1H- and 13C-NMR data, it is assumed that the ring-opening polymerization of ε-caprolactone catalyzed by the Nd(acac)3.3H2O-AlEt3 system proceeds via complexation of monomer to catalyst, acyl-oxygen cleavage insertion propagation mechanism. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080320401
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  • 7
    Electronic Resource
    Electronic Resource
    Ring opening polymerization of propylene oxide by chitosan-supported rare earth catalytic system and its kinetics (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2177-2182 
    Details
    ISSN: 0887-624X
    Keywords: ring opening polymerization ; propylene oxide ; chitosan-supported rare earth complex ; kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ring opening polymerization of propylene oxide in the presence of a new type of catalytic system composed of chitosan-supported rare earth complex, triisobutyl aluminium, and acetylacetone and its kinetics have been studied for the first time. It has been found that the characteristics of this catalytic system are of high catalytic activity, of higher stereoselectivity, and of a high molecular weight polymer of 2 × 106. Kinetic studies show that the polymerization rate is first order with respect to monomer concentration and catalyst concentration, respectively. The apparent activation energy of the polymerization reaction is 37.1 kJ/mol. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2177-2182, 1997
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    A comparison of polymerization characteristics and mechanisms of ε-caprolactone and trimethylene-carbonate with rare earth halides (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 1339-1352 
    Details
    ISSN: 0887-624X
    Keywords: polymerization characteristics and mechanisms ; ε-caprolactone and trimethylene carbonate ; rare earth halides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Characteristics and mechanisms of the ring opening-polymerizations of ε-caprolactone (CL) and trimethylene carbonate (TMC) with rare earth halides have been compared for the first time. It has been found that rare earth halides show high catalytic activities for the polymerization of TMC, but very low activities for that of CL polymerization. The copolymerization of CL and TMC can proceed only in the presence of high contents of TMC in the comonomer feed. The copolymerization rate decreases rapidly with increasing molar fraction of CL in the feed. The mechanism study by IR, 1H-, 13C-, and 31P-NMR spectra shows that the first step reaction of the polymerization of TMC or CL with rare earth halide is the complexation of monomer to the rare earth ion. The strong coordination of TMC to rare earth ion induces the ring-cleavage of TMC and generation of the cationic species, which initiate the polymerization of TMC via a cationic process. However, the polymerization of CL with rare earth halide is an “activated-hydrolysis” process, in which rare earth catalyst does not initiate the polymerization but serves as an activator of CL. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1339-1352, 1997
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Ring-opening polymerization of chloromethylthiirane with SO42-/TiO2/Nd3+ as initiator (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 18 (1997), S. 769-773 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new type of solid superacid (SO42-/TiO2/Nd3+) was used for the ring-opening polymerization of chloromethylthiirane (CMT). TiO2 · H2O immersed in a sulfuric acid solution containing Nd3+ ions and calcined at 600°C gave the solid superacid for initiating the polymerization of CMT. The effects of polymerization temperature and amount of the initiator on the CMT polymerization were studied. Poly(CMT) obtained has higher molecular weight (M̄w = 52 000) than ever reported.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1997.030180903
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  • 10
    Electronic Resource
    Electronic Resource
    New catalytic systems for the fixation of carbon dioxide, 2.Part 1: cf. ref.8. Synthesis of high molecular weight epichlorohydrin/carbon dioxide copolymer with rare earth phosphonates/triisobutyl-aluminium systems (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 2003-2011 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymerization of carbon dioxide with epichlorohydrin to synthesize high molecular weight chlorine-containing poly(carbonate-ether) with RE(P204)3—Al[CH2CH(CH3)2]3 (with RE = La, Eu, Gd, Dy, Ho, Nd, Er, Yb, Lu, Y; P204 = (RO)2POO—, R = CH3(CH2)3CH(C2H5)CH2—) as a catalyst was carried out for the first time. The most favorable conditions for the copolymerization were: CO2 aged Y(P204)3—Al[CH2CH(CH3)2]3 as catalyst; mole ratio Al/Y = 8; reaction time 24 h; temperature 60-70°C; concentration [Y] = 3,31 · 10-2 mol/L; 1,4-dioxane as solvent. The highest yield, intrinsic viscosity [η] and CO2 content of the copolymer obtained reached 3 945 g per mole of rare earth element, [η] = 1,49 dL/g and f(CO2) = 30 mol-%, respectively. Results from differential thermal analysis/thermogravimetry showed that the copolymer has high thermal stability and decomposes at 320°C.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021950610
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