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  • 1
    Electronic Resource
    Electronic Resource
    Molecular mechanics study of zirconocenium catalyzed isospecific polymerization of propylene (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 125-135 
    Details
    ISSN: 0887-624X
    Keywords: isospecific polymerization ; stereocontrol energy ; agostic interaction ; steric insertion probability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereocontrol energy (ΔE0) is investigated as a measure of enantioselectivity of ansa-zircoocenium catalyst in propylene polymerization; it was calculated with MM2 (molecular mechanics) force field using π complex (°C) and transition state (TS) geometries obtained by ab initio molecular orbital methods. Both rac-ethylenebis (1-η5-indenyl) - (1) and rac-ethylenebis (1-η5-4,5,7,8-tetrahydroindenyl) (2) zirconocenium species are isospecific in either the π-complexes or the transition states. The stereoselectivity is greater if there is α-agostic interaction; it is lowered in the cases of β and γ agostic interactions. The 13C-NMR steric pentad distribution indicates the poly(propylene) to be much less stereoregular than that predicted by ΔE0. Following the occurrence of a regiochemical insertion error, the addition of another monomer via any mode is prohibitively unfavorable. The catalyst suffers loss of stereospecificity as temperature of polymerization increases. Insertion via transition states involving different agostic interactions could be one explanation for the observed loss. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330115
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  • 2
    Electronic Resource
    Electronic Resource
    Olefin terpolymerizations. II. 4-vinylcyclohexene and cyclooctadiene (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2787-2793 
    Details
    ISSN: 0887-624X
    Keywords: Ziegler-Natta catalysis ; EPDM synthesis ; metallocene catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4-Vinylcyclohexene (VCH) and cyclooctadiene (COD) were investigated as termonomers in EPDM (ethylene/propylene/diene) synthesis by using rac-ethylenebis (1-η5-indenyl) zir-conium dichloride (1) as a catalyst precursor. Homopolymerizations of VCH, vinylcycloh-exane and cyclohexene were compared. The parameter Kπκp, which is the apparent rate constant for Ziegler-Natta polymerization, is about the same for VCH and vinylcyclohexanebut is 10 times smaller for cyclohexene. Therefore, the linear olefinic double bond is more active than the cyclic internal double bond. VCH reduces ethylene polymerization rate but not propylene polymerization rate in copolymerizations. In terpolymerizations, VCH tends to suppress ethylene incorporation especially at elevated polymerization temperature and Lowers the polymer MW by about two-fold. COD has very low activity as a termonomer. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331612
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  • 3
    Electronic Resource
    Electronic Resource
    ansa-Zirconocenium catalysis of syndiospecific polymerization of propylene: Theory and experiment (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1085-1094 
    Details
    ISSN: 0887-624X
    Keywords: Ziegler-Natta catalysis ; zirconocene catalysts ; molecular modeling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syndiospecific propylene polymerizations catalyzed by isopropylidene(cyclopentadienyl)(fluorenyl)- and (2,2-dimethylpropylidene)(cyclopentadienyl)(fluorenyl)-zirconocenium (1+ and 2+) have been investigated theoretically and compared with experimental observations. With the ab initio calculated structures for the transition state (TS) of 1+(M)P and 2+(M)P (M = propylene, P = 2-methylpentyl), their steric energies (E°) have been computed using MM2 force-field. The difference between steric energies E°(m) and E°(r) for the meso and racemic enchainment of propylene, respectively, is defined as the stereocontrol energy [δE°(m - r)] for syndiotactic propagation. The δE°(m - r) for the TS of 1+ (M)P is about 2.1 kcal/mol, the value is 1 kcal/mol greater for 2+(M)P. The observed steric pentad distributions of the syndiotactic poly(propylene) obtained by these catalysts are consistent with smaller effective stereocontrol energy, which is about two-third as large as δE°(m - r) values calculated for the MM2 optimized structure. Syndiotactic enchainment is favored over isotactic enchainment for all combinations of site configurations in the catalyst. α-Agostic interaction seems to enhance syndioselectivity, whereas γ-agostic interaction changes the stereoselectivity to meso enchainment. The mirror plane symmetry of the syndiotactic propagating species renders the stereoselectivity of the polymerization insensitive to reaction conditions. These catalysts are also highly regiospecific. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330711
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  • 4
    Electronic Resource
    Electronic Resource
    Polymerizations of olefins and diolefins catalyzed by monocyclopentadienyltitanium complexes containing a (dimethylamino)ethyl substituent and comparison with ansa-zirconocene systems (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 319-328 
    Details
    ISSN: 0887-624X
    Keywords: metallocenes ; Ziegler-Natta catalysis ; olefin polymerizations ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: {[2-(dimethylamino)ethyl]cyclopentadienyl}titanium trichloride (CpNTiCl3, 1) was activated with methylaluminoxane (MAO) to catalyze polymerizations of ethylene (E), propylene (P), ethylidene norbornene (ENB), vinylcyclohexene (VCH), and 1,4-hexadiene (HD). The dependence of homopolymerization activity (A) of 1/MAO on olefin concentration ([M]n) is n = 2.0 ± 0.5 for E and n = 1.8 ± 0.2 for P. The value of n is 2.4 ± 0.2 for CpTiCl3/MAO catalysis of ethylene polymerization; this system does not polymerize propylene. 1/MAO catalyzes HD polymerization at one-tenth of AH for 1-hexene, probably because of chelation effects in the HD case. The copolymerization of E and P has reactivity ratios of rE = 6.4 and rP = 0.29 at 20°C, and rErP = 1.9, which suggests 1/MAO may be a multisite catalyst. The copolymerization activity of CpTiCl3/MAO is 50 times smaller than that of CpNTiCl3/MAO. Terpolymerization of E/P/ENB has A of 105 g of polymer/(mol of Ti h), incorporates up to 14 mol % (∼ 40 wt %) of ENB, and high MW's of 1 to 3 × 105. All of these parameters are surprisingly insensitive to the ENB concentration. The E/P/VCH terpolymerization has comparable A value of (1.3 ± 0.3) × 105 g/(mol of Ti h). The incorporation of VCH in terpolymer increases with increasing [VCH]. Terpolymerization with HD occurs at about one-third of the A of either ENB or VCH; the product HD-EPDM is low in molecular weight and contains less than 4% of HD. These terpolymerization results are compared with those obtained previously for three zirconocene precursors: rac-ethylenebis(1-η5-indenyl)dichlorozirconium (6), rac-(dimethylsilylene)bis(1-η5-indenyl)dichlorozirconium (7), and ethylenebis(9-η5-fluorenyl)dichlorozirconium (8). The last compound is a particularly poor terpolymerization catalyst; it incorporates very little VCH or HD and no ENB at all. 7/MAO is a better catalyst for E/P/VCH terpolymerization, while 6/MAO is superior in E/P/HD terpolymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 319-328, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Olefin terpolymerizations. I. 1,4-hexadiene (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 979-987 
    Details
    ISSN: 0887-624X
    Keywords: Ziegler-Natta polymerization ; EPDM ; metallocene catalysts ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethylene (E), propylene (P), and 1,4-hexadiene (HD) were terpolymerized with rac-1,2-ethylenebis (1-η5-indenyl) zirconium(IV) dichloride and methylaluminoxane (Et[Ind]2ZrCl2/MAO), and compared with the copolymerizations of E/P, E/HD, P/HD, and terpolymerization using ethylidene norbornene (ENB) as the termonomer. HD lowers the polymerization activity, the effect is more pronounced for P/HD and E/P/HD using large amount of P, than for E/HD and E/P/HD using feed low in P. The polymer molecular weight is most strongly affected by the temperature of polymerization (Tp), whereas the E/P ratio in the feed has virtually no effect. The reactivity ratios rE and rP are 3.0 and 0.3, respectively, at 20°C but rP becomes larger than rE at TP = 70°C. 1H-NMR spectra showed occurrence of cycloaddition in the homopolymerization of HD; on the other hand, HD is incorporated in the terpolymer only by linear 1,2-addition. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330612
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  • 6
    Electronic Resource
    Electronic Resource
    Olefin terpolymerizations. III. Symmetry, sterics, and monomer structure in ansa-zirconocenium catalysis of EPDM synthesis (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2795-2801 
    Details
    ISSN: 0887-624X
    Keywords: Ziegler-Natta catalysis ; EPDM synthesis ; metallocene catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethylenebis (η5-fluorenyl) zirconium dichloride (1) and rac-dimethylsilylene bis (1-η5-in-denyl) zirconium dichloride (2) were activated with methylaluminoxane (MAO) to catalyze ethylene (E) propylene (P) copolymerizations. The former produces high MW copolymer at 20°C rich in ethylene with reactivity ratio values of rE = 1.7 and rP 〈0.01, whereas the latter produces lower MW random copolymers with rE = 1.32 and rp = 0.36. Ethylidene norbornene (ENB) complexes with 1/MAO but does not undergo insertion in the presence of E and P. In contrast, 2/MAO catalyzes terpolymerization incorporating 9-15 mol % of ENB with slightly lower MW and activity than the corresponding copolymerizations. In comparison, 1,4-hexadiene was incorporated by 2/MAO with much lower A and MW. Terpolymerizations were also conducted with vinylcyclohexene using both catalyst systems. The steric and electronic effects in these processes were discussed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331613
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  • 7
    Electronic Resource
    Electronic Resource
    Syndioselective propylene polymerizations by ansa-zirconocenium catalyst (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2945-2953 
    Details
    ISSN: 0887-624X
    Keywords: metallocene ; Ziegle-Natta catalysis ; syndioselective polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of reaction conditions, including catalyst concentration, temperature, and immobilization on support, have been investigated for syndioselective propylene polymerization by the “bare” zirconocenium ion generated from 1,1-diphenyl-methylidene(1-η5-cyclopentadienyl)(9-η5-fluorenyl)zirconium-dichloride precursor (2). Neither variation of the catalyst concentration nor immobilization of 2 on silica support affect the syndiospecificity of polymerization. The stereoregularity of the syndiotactic polypropylene, as judged from the melting transition temperature and homosteric r-pentad population by 13C-NMR, were found to be proportional to polymer molecular weight. These behaviors are compared with a typical isoselective catalyst ethylenebis(4,5,6,7-tetrahydroindenyl) Zr precursor (4). They are in close resemblance in the case of the S-enantiomeric complex of 4, but the racemic mixture of 4 is markedly inferior. The origins of stereo- and regio-errors are discussed. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Heptane-soluble homogeneous zirconocene catalyst: Synthesis of a single diastereomer, polymerization catalysis, and effect of silica supports (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2093-2108 
    Details
    ISSN: 0887-624X
    Keywords: zirconocene ; ethylene polymerization ; propylene polymerization ; silica-supported catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(1-indenyl)-di[1′S, 2′R, 5′S)-methoxy]silane (1) was converted into a mixture of corresponding ansa-diastereomeric zirconocenes. Further purification afforded a single dia-stereomer, di[(1′S, 2′R, 5′S)-methoxy] silylene-bis[η5-1(R, R)-(+)-indenyl] dichlorozirconium (2), which is optically active and hydrocarbon soluble. Extremely rapid ethylene, propylene, and ethylene-hexene polymerizations were observed both in toluene and n-heptane solutions; for instance, at 50°C, activity for ethylene polymerization reaches ∼ 1.5×1010 (g of PE/((mol of Zr) · [C2H4] · h). The “bare” zirconocenium ion generated from 2/TIBA/Ph3CB(C6F5)4 exhibits unusual polymerization behaviors; the polymerization activity increases monotonically with temperature of polymerization (Tp) up to a conventional polymerization condition (50-70°C), and the 13C NMR study shows that the isotactic poly-propylene obtained has fairly high [mmmm] methyl pentad distributions at high Tp (≤25°C with [mmmm] ∼ 0.93-0.75) and a perfect stereoregularity at low Tp (≤0°C with [mmmm] 〉 0.99). The catalyst precursors 2 and Et(Ind)2ZrCl2 (3) supported on silica by different approaches produced poly(olefins) of different molecular weights and stereoregularities, and a methylaluminokane and Ph3CB(C6F5)4 free silica-supported zirconocene system was found to be activated by triisobutylaluminum. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331301
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  • 9
    Electronic Resource
    Electronic Resource
    Electroluminescent properties of self-assembled polymer thin filmsThis work was supported by the New Jersey Commission of Science and Technology through the Advanced Technology Center for Photonic and Optoelectronic Materials (ATC/POEM), as well as the Princeton Materials Institute (PMI), the National Science Foundation MRL Program (DMR-91-20668, TMS and MJM). (1995)
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 395-398 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19950070411
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  • 10
    Electronic Resource
    Electronic Resource
    A unified treatment of cure and degradation through the composite methodology (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 37-45 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The composite methodology, developed by Seferis and coworkers, was used to describe the kinetics for both a commercial and a model controlled-flow epoxy-based resin system throughout cure and degradation. By utilizing this previously developed generalized methodology, capable of describing two or more kinetic mechanisms acting in series or parallel, a fundamental understanding of the kinetic behavior of a prepreg system from cure through degradation was established. Differential scanning calorimetry (DSC), and simultaneous differential thermal analysis-thermogravimetric analysis (SDT) were utilized to provide the experimental kinetic information. Two approaches were used to determine the activation energies for each of the resin systems, and a comparison is made between these approaches and the two thermoanalytical techniques. Using the determined kinetic parameters, the kinetic model was compared with experimental kinetics throughout cure and degradation at heating rates from 2-20°C/min. The results show that the kinetic model fits the experimental data well. In addition, the results demonstrate that the same weighting factors are applicable to both the model and commercial controlled-flow resins. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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