J. polym. sci., C Polym. symp.

1973

DOI: 10.1002/polc.5070400128

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Antioxidants and stabilizers. XXXIX. GPC analyses of the additives for polyolefins and pvc used as food wrappings

¹

,

J. Pospı́šil

²

,

³

Abstract: Gel permeation chromatography (GPC) method, either alone or in combination with thin‐layer chromatography (TLC) or PC, has been used for determining the number of mononuclear and binuclear phenolic antioxidants used for the stabilization of polyethylene, and of some organophosphites and organotin compounds suitable for the stabilization of poly(vinyl chloride) (PVC). A differential flow refractometer and a UV detector were used for the detection of the compounds by GPC. Qualitative determination of the compone… Show more

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Cited by 16 publications

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“…The hot solutions were filtered using a 0.5 μm stainless steel filter. A polystyrene relative calibration was carried out using narrow molecular weight distribution polystyrene standards from Polymer Laboratories with Ionol (4-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3-buten-2-ol) added as the flow marker . Alternatively, GPC measurements were performed on a Polymer Laboratories PL-GPC 220 instrument using 1,2,4-trichlorobenzene solvent (stabilized with 125 ppm BHT) at 150 °C.…”

Section: Methodsmentioning

confidence: 99%

Bimetallic Effects in Homopolymerization of Styrene and Copolymerization of Ethylene and Styrenic Comonomers: Scope, Kinetics, and Mechanism

Guo¹,

³

2008

J. Am. Chem. Soc.

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This contribution describes the homopolymerization of styrene and the copolymerization of ethylene and styrenic comonomers mediated by the single-site bimetallic "constrained geometry catalysts" (CGCs), (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](TiMe2)}2 [EBICGC(TiMe2)2; Ti2], (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 [EBICGC(ZrMe2)2; Zr2], (mu-CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](TiMe2)}2 [MBICGC(TiMe2)2; C1-Ti2], and (mu-CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 [MBICGC(ZrMe2)2; C1-Zr2], in combination with the borate activator/cocatalyst Ph3C+ B(C6F5)4- (B1). Under identical styrene homopolymerization conditions, C1-Ti2 + B1 and Ti2 + B1 exhibit approximately 65 and approximately 35 times greater polymerization activities, respectively, than does monometallic [1-Me2Si(3-ethylindenyl)(tBuN)]TiMe2 (Ti1) + B1. C1-Zr2 + B1 and Zr2 + B1 exhibit approximately 8 and approximately 4 times greater polymerization activities, respectively, than does the monometallic control [1-Me2Si(3-ethylindenyl)(tBuN)]ZrMe2 (Zr1) + B1. NMR analyses show that the bimetallic catalysts suppress the regiochemical insertion selectivity exhibited by the monometallic analogues. In ethylene copolymerization, Ti2 + B1 enchains 15.4% more styrene (B), 28.9% more 4-methylstyrene (C), 45.4% more 4-fluorostyrene (D), 41.2% more 4-chlorostyrene (E), and 31.0% more 4-bromostyrene (F) than does Ti1 + B1. This observed bimetallic chemoselectivity effect follows the same general trend as the pi-electron density on the styrenic ipso carbon (D > E > F > C > B). Kinetic studies reveal that both Ti2 + B1 and Ti1 + B1-mediated ethylene-styrene copolymerizations follow second-order Markovian statistics and tend to be alternating. Moreover, calculated reactivity ratios indicate that Ti2 + B1 favors styrene insertion more than does Ti1 + B1. All the organozirconium complexes (C1-Zr2, Zr2, and Zr1) are found to be incompetent for ethylene-styrene copolymerization, yielding only mixtures of polyethylene and polystyrene. Model compound (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)][Ti(CH2Ph)2]}2 {EBICGC[Ti(CH2Ph)2]2; Ti2(CH2Ph)4} was designed, synthesized, and structurally characterized. In situ activation studies with cocatalyst B(C6F5)3 suggest an eta(1)-coordination mode for the benzyl groups, thus supporting the proposed polymerization mechanism. For ethylene-styrene copolymerization, polar solvents are found to increase copolymerization activities and coproduce atactic polystyrene impurities in addition to ethylene-co-styrene, without diminishing the comonomer incorporation selectivity. Both homopolymerization and copolymerization results argue that substantial cooperative effects between catalytic sites are operative.

“…The hot solutions were filtered using a 0.5 μm stainless steel filter. A polystyrene relative calibration was carried out using narrow molecular weight distribution polystyrene standards from Polymer Laboratories with Ionol (4-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3-buten-2-ol) added as the flow marker . Alternatively, GPC measurements were performed on a Polymer Laboratories PL-GPC 220 instrument using 1,2,4-trichlorobenzene solvent (stabilized with 125 ppm BHT) at 150 °C.…”

Section: Methodsmentioning

confidence: 99%

Bimetallic Effects in Homopolymerization of Styrene and Copolymerization of Ethylene and Styrenic Comonomers: Scope, Kinetics, and Mechanism

Guo¹,

³

2008

J. Am. Chem. Soc.

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This contribution describes the homopolymerization of styrene and the copolymerization of ethylene and styrenic comonomers mediated by the single-site bimetallic "constrained geometry catalysts" (CGCs), (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](TiMe2)}2 [EBICGC(TiMe2)2; Ti2], (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 [EBICGC(ZrMe2)2; Zr2], (mu-CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](TiMe2)}2 [MBICGC(TiMe2)2; C1-Ti2], and (mu-CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 [MBICGC(ZrMe2)2; C1-Zr2], in combination with the borate activator/cocatalyst Ph3C+ B(C6F5)4- (B1). Under identical styrene homopolymerization conditions, C1-Ti2 + B1 and Ti2 + B1 exhibit approximately 65 and approximately 35 times greater polymerization activities, respectively, than does monometallic [1-Me2Si(3-ethylindenyl)(tBuN)]TiMe2 (Ti1) + B1. C1-Zr2 + B1 and Zr2 + B1 exhibit approximately 8 and approximately 4 times greater polymerization activities, respectively, than does the monometallic control [1-Me2Si(3-ethylindenyl)(tBuN)]ZrMe2 (Zr1) + B1. NMR analyses show that the bimetallic catalysts suppress the regiochemical insertion selectivity exhibited by the monometallic analogues. In ethylene copolymerization, Ti2 + B1 enchains 15.4% more styrene (B), 28.9% more 4-methylstyrene (C), 45.4% more 4-fluorostyrene (D), 41.2% more 4-chlorostyrene (E), and 31.0% more 4-bromostyrene (F) than does Ti1 + B1. This observed bimetallic chemoselectivity effect follows the same general trend as the pi-electron density on the styrenic ipso carbon (D > E > F > C > B). Kinetic studies reveal that both Ti2 + B1 and Ti1 + B1-mediated ethylene-styrene copolymerizations follow second-order Markovian statistics and tend to be alternating. Moreover, calculated reactivity ratios indicate that Ti2 + B1 favors styrene insertion more than does Ti1 + B1. All the organozirconium complexes (C1-Zr2, Zr2, and Zr1) are found to be incompetent for ethylene-styrene copolymerization, yielding only mixtures of polyethylene and polystyrene. Model compound (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)][Ti(CH2Ph)2]}2 {EBICGC[Ti(CH2Ph)2]2; Ti2(CH2Ph)4} was designed, synthesized, and structurally characterized. In situ activation studies with cocatalyst B(C6F5)3 suggest an eta(1)-coordination mode for the benzyl groups, thus supporting the proposed polymerization mechanism. For ethylene-styrene copolymerization, polar solvents are found to increase copolymerization activities and coproduce atactic polystyrene impurities in addition to ethylene-co-styrene, without diminishing the comonomer incorporation selectivity. Both homopolymerization and copolymerization results argue that substantial cooperative effects between catalytic sites are operative.

“…The hot solutions were filtered using a 0.5 µm stainless steel filter. A polystyrene universal calibration was carried out using narrow molecular weight distribution polystyrene standards from Polymer Laboratories with Ionol (4- (2,6,6-trimethyl-2cyclohexen-1-yl)-3-buten-2-ol) 6 added as the flow marker.…”

Section: Methodsmentioning

confidence: 99%

Significant Proximity and Cocatalyst Effects in Binuclear Catalysis for Olefin Polymerization

¹

,

²

,

³

2005

Macromolecules

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We describe here the implementation of methylene-bridged binuclear “constrained geometry catalyst” (μ-CH2-3,3‘){(η5-indenyl)[1-Me2Si( t BuN)](ZrMe2)}2 (C1-Zr2) to produce high-M w branched polyethylene. In ethylene homopolymerization, ∼70× increases in molecular weight are achieved with(C1-Zr2) vs (μ-CH2CH2-3,3‘){(η5-indenyl)[1-Me2Si( t BuN)](ZrMe2)}2 (C2-Zr2) under identical polymerization conditions using(Ph3C+)2[1,4-(C6F5)3BC6F4B(C6F5)3]2- (B2) as the cocatalyst for both. With MAO as the cocatalyst, ∼600× increases in polyethylene molecular weight are achieved with (μ-CH2CH2-3,3‘){(η5-indenyl)[1-Me2Si( t BuN)](ZrCl2)}2 (C2-Zr2Cl4) and (μ-CH2-3,3‘){(η5-indenyl)[1-Me2Si( t BuN)](ZrCl2)}2 (C1-Zr2Cl4) vs mononuclear [1-Me2Si(3-ethylindenyl)( t BuN)]ZrCl2 (Zr1Cl2). In the ethylene + 1-hexene copolymerization, C1-Zr2 enchains 3× more 1-hexene than does C2-Zr2 under identical polymerization conditions (B2 as cocatalyst). With MAO as the cocatalyst, C2-Zr2Cl4 enchains 3.5× more, and C1-Zr2Cl4 4.2× more, 1-hexene than does Zr1Cl2. When the polar solvent C6H5Cl is used as the polymerization medium, dramatic compression in the dispersion of polymerization activities and molecular weights is found. Both homopolymerization and copolymerization results argue that achievable Zr−Zr spatial proximity significantly influences chain transfer rates and selectivity for comonomer enchainment and that such proximity effects are highly cocatalyst and solvent sensitive.

Selective separation of phenolic compounds on μbondagel columns

¹

1983

J. High Resol. Chromatogr.

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Short CommunicationsPoor recovery is observed for nitrite ion, possibly because of oxidation of nitrite to nitrate during the sample cleanup. This technique has also been successfully used for analysis of acetate by utilizing a slightly different mobile phase at pH 4.0.The sample cleanup procedure described here provides a convenient and economical way to analyze highly caustic samples, even those containing large amounts of organic material, by nonsuppressed ion chromatography. Recovery of chloride, bromide, nitrate, and sulfate is excellent, and detection limits are better than could be obtained otherwise.

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