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1.
An on‐line electron spin resonance (ESR) technique was applied to investigate the oxidation states of the metallocene catalysts CpTiCl3, CpZrCl3, Cp2TiCl2, and Cp2ZrCl2. These metallocene catalysts were activated by modified methylaluminoxane (MMAO). It was found that the titanocene catalysts (CpTiCl3 and Cp2TiCl2) were readily reduced to the trivalent state while the zirconocene catalysts (CpZrCl3 and Cp2ZrCl2) were quite stable with respect to reduction. The concentrations of the trivalent species Ti(III) and Zr(III) showed linear relationships with the concentrations of metallocene catalyst precursors. However, their slopes were always smaller than unity indicating the existence of bimetallic interactions of the active sites. The ESR detectable Ti(III) and Zr(III) concentrations initially increased with the MAO/catalyst ratio and then leveled off after an 800–1000 Al/catalyst molar ratio. The deactivation processes were followed as a function of aging time over a range of temperature (25–100°C). The decay curves strongly depended on aging temperature with higher temperature giving faster decay rates. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1465–1472, 1999  相似文献   

2.
Copolymerization of styrene (St) and St‐terminated poly(ethylene oxide) macromonomer (SEOM) with CpTiCl3/methylaluminoxane (MAO) catalyst in toluene was investigated. The copolymerization of St and SEOM proceeded easily to give a graft copolymer consisting of syndiotactic polystyrene as the main chain and hydrophilic poly(ethylene oxide) as the side chain. A number of side chains in the graft copolymer could be controlled by the amount of SEOM in the feed. The reactivity of SEOM was determined from copolymerization of St and SEOM with the CpTiCl3/MAO catalyst, and the reactivity of SEOM depended on the molecular weight of SEOM. The thermal properties of the graft copolymer such as the melting temperature were influenced by the introduction of SEOM. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2904–2910, 2004  相似文献   

3.
Five new CpTiCl2(OR) alkoxyl-substituted half-sandwich complexes, where R was methoxyethyl ( 1 ), methoxypropyl ( 2 ), methoxyisopropyl ( 3 ), o-methoxyphenyl ( 4 ), or tetrahydrofurfuryl ( 5 ), were synthesized, characterized, and tested as catalyst precursors for the syndiospecific polymerization of styrene. These precursors were more active than (η5-cyclopentadienyl)trichlorotitanium (CpTiCl3). The different structures of the alkoxyl ligands affected the activity slightly. When the polymerization was carried out in bulk, all the complexes ( 1–5 ) exhibited high activities, even at the low molar ratio of Al/Ti = 300. The syndiotactic polystyrene (s-PS) percentage of the polymer produced by alkoxyl-substituted complexes was much higher than that of CpTiCl3. The really active center might be described as [CpTiMe]+ · [MAOX] · nMAO (where MAO is methylaluminoxane). The normal active species [CpTiMe]+ made up the core and the anion mass [MAOX] · nMAO surrounded the core and constituted the outer shell circumstance. They activated the syndiospecific polymerization of styrene as a whole. For a high concentration of MAO, the function of the alkoxyl group was weak because of the limited proportion in the outer shell. For a low concentration of MAO, the proportion of alkoxyl ligands in the outer shell increased greatly, and their influence also became significant, as reflected in a higher s-PS percentage of the obtained polymer. The existence of the additional oxygen atom in the alkoxyl ligand stabilized the active species more effectively; this was reflected in the higher temperature of the maximum activities. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1817–1824, 2001  相似文献   

4.
Based on coordination polymerization mechanism only, novel stereoregular graft copolymers with syndiotactic polystyrene main chain and isotactic polypropylene side chain (sPS‐g‐iPP) were synthesized via two steps of catalytic reactions. First, a chain transfer reaction was initiated by a chain transfer complex composed of a styrene derivative, 1,2‐bis(4‐vinylphenyl)ethane, and hydrogen in propylene polymerization mediated by rac‐Me2Si[2‐Me‐4‐Ph(Ind)]2ZrCl2 and MAO, which gave iPP macromonomer bearing a terminal styryl group (iPP‐t‐St). Then the iPP‐t‐St macromonomers of varied molecular mass were engaged in syndiospecific styrene polymerization over a typical mono‐titanocene catalyst (CpTiCl3/MAO) under different conditions to produce sPS‐g‐iPP graft copolymers of varied structure. With an effective purification process, well‐defined sPS‐g‐iPP copolymers were obtained, which were then subjected to differential scanning calorimetry (DSC) and polarized optical micrograph (POM) studies. The graft copolymers were generally found with dual melting and crystallization temperatures, which were ascribable respectively to the sPS backbone and iPP graft. However, it was revealed that the two segments displayed largely different melting and crystallization behaviors than sPS homopolymer and the precursory iPP‐t‐St macromonomer. Consequently, the graft copolymer exhibited much distinctive crystalline morphologies when compared with their individual components. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.  相似文献   

5.
Polymerizations of styrene were carried out with half-sandwich complexes supported on silica, CpTiX3/MAO/SiO2 (X = Cl, F). The optimum values for the polymerization time, the amount of cocatalyst and the Alsupport/Ti ratio were found for the trichlorinated system. The highest activity obtained was 3,100 g sPS/(mol Ti × h × mol/L styrene). The trihalogenated complexes were compared to one another with respect to their polymerization rate. CpTiCl3/MAO/SiO2 and CpTiF3/MAO/SiO2 behave in a similar manner, suggesting that the active species of both half-sandwich complexes on the support are the same. Furthermore, aging experiments were carried out with CpTiCl3/MAO/SiO2 and, surprisingly, deactivation was observed, as opposed to supported zirconocenes which gain stability against deactivation reactions when anchored to a carrier. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2959–2968, 1999  相似文献   

6.
A series of Me4Cp–amido complexes {[η51‐(Me4C5)SiMe2NR]TiCl2; R = t‐Bu, 1 ; C6H5, 2 ; C6F5, 3 ; SO2Ph, 4 ; or SO2Me, 5 } were prepared and investigated for olefin polymerization in the presence of methylaluminoxane (MAO). X‐ray crystallography of complexes 3 and 4 revealed very long Ti N bonds relative to the bonds of 1 . These complexes were employed for ethylene–styrene copolymerizations, styrene homopolymerizations, and propylene homopolymerizations in the presence of MAO. The productivities of the catalysts derived from 3 – 5 were much lower than the productivity of the catalyst derived from 1 for the propylene polymerizations and ethylene–styrene copolymerizations, whereas the styrene polymerization activities were much higher for the catalysts derived from 3 – 5 than for the catalyst derived from 1 . The polymerization behavior of the catalysts derived from the metallocenes 3 – 5 were more reminiscent of monocyclopentadienyl titanocene Cp′TiX3/MAO catalysts than of CpATiX2/MAO catalysts such as 1 containing alkylamido ligands. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4649–4660, 2000  相似文献   

7.
Nine new fluorinated half-sandwich titanocene complexes (1b–9b) based on substituted alkylindenes were synthesized, by reacting Me3SnF with the corresponding chloride species, and employed as catalyst precursors for the syndiospecific polymerization of styrene. When activated with methylaluminoxane (MAO), the new precursors 1b–9b exhibited increased activities by factors of 15-40 compared with the corresponding chlorinated compounds and provided improved syndiotacticity, enhanced melting temperature, and higher polymer molecular weights. The activities of indenyl and methyl- or phenyl-substituted indenyl complexes were found to be higher by factors of 4-12.5 than those of CpTiF3 and Cp*TiF3. More importantly, the amount of MAOcan be reduced to an Al : Ti molar ratio of 300 in the temperature range of 10-90°C. It is likely that Ti F, more polarized than the Ti Cl bond in the half-sandwich titanocenes, allows the formation of more active and stable active sites of Ti(III) complexes needed for the syndiospecific polymerization of styrene. Evidence in this direction is brought via the electron paramagnetic resonance (EPR) spectrum and redox titration. The higher activity and syndiospecificity of the fluorinated catalysts are attributable to a greater number, more stable Ti(III) active sites, and/or higher propagation rate constant. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2481–2488, 1999  相似文献   

8.
This article reports a practical method for preparing cis‐polybutadiene‐blocksyn‐polystyrene (cis‐PB‐bsyn‐PS) copolymers with long crystallizable syndiotactic polystyrene (syn‐PS) segments chemically bonded with high cis‐1,4‐polybutadiene segments through the addition of styrene (ST) to a cis‐specific 1,3‐butadiene (BD) living catalyst composed of cyclopentadienyl titanium trichloride (CpTiCl3) and modified methylaluminoxane (MMAO). The incorporation of ST into the living polybutadiene (PB) precursor remarkably depended on the polymerization temperature. A low temperature (?20 °C) suppressed the rate of ST incorporation, but a high temperature (50 °C) tended to decompose the livingness of the active species and enhance the rate of the aspecific ST polymerization initiated by MMAO. Consequently, temperatures of 0–25 °C seemed to be best for this copolymerization system. Because of the absence of ST livingness, the final products contained not only the block copolymer but also the homopolymers. Attempts to isolate the block copolymer were carried out with common solvent fractionation techniques, but the results were not sufficient. Cross‐fractionation chromatography was, therefore, used for the isolation of the cis‐PB‐bsyn‐PS copolymer. The presence of long syn‐PS segments was confirmed by the observation of a strong endothermic peak at 260 °C in the differential scanning calorimetry curve. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2698–2704, 2004  相似文献   

9.
Combination of coordination polymerization and atom transfer radical polymerization (ATRP) was applied to a novel synthesis of rod‐coil block copolymers. The procedure included the following steps: (1) monoesterification reaction of ethylene glycol with 2‐bromoisobutyryl bromide yielded a α‐bromo, ω‐hydroxy bifunctional initiator, (2) CpTiCl3 (bifunctional initiator) catalyst was prepared from a mixture of trichlorocyclopentadienyl titanium (CpTiCl3) and bifunctional initiator. Coordination polymerization of n‐butyl isocyanate initiated by such catalyst provided a well‐defined macroinitiator, poly(n‐butyl isocyanate)‐Br (PBIC‐Br), and (3) ATRP method of vinyl monomers using PBIC‐Br provided rod (PBIC)‐coil block copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4037–4042, 2007  相似文献   

10.
The copolymerization of ethylene (E) and norbornene (NB) was investigated using the commercially available and inexpensive catalyst system, cyclopentadienylzirconium trichloride (CpZrCl3)/isobutyl‐modified methylaluminoxane (MMAO), at a moderate polymerization temperature in toluene. For the CpZrCl3 catalyst system activated by aluminoxane with a 40 mol % methyl group and a 60 mol % isobutyl group (MMAO), the quantities of the charged NB and the polymerization temperature significantly affected the molecular weights, polydispersities, and NB contents of the obtained copolymers and the copolymerization activities in all the experiments. As the charged NB increased and thereby the NB/E molar ratio increased, the NB content in the copolymer increased and reached a maximum value of 71 mol %. The CpZrCl3/MMAO ([Al]/[Zr] = 1000) catalyst system with the [NB] of 2.77 mol L?1 and ethylene of 0.70 MPa at 50 °C showed the highest activity of 1690 kg molZr?1 h?1 and molecular weight of 21,100 g mol?1. The 13C NMR analysis showed that the CpZrCl3/MMAO catalyst system produced the E‐NB random copolymer with a number of NB homosequences such as the NN dyad and NNN triad. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7411–7418, 2008  相似文献   

11.
Tandem catalysis offers a promising synthetic route to the production of linear low‐density polyethylene. This article reports the use of homogeneous tandem catalytic systems for the synthesis of ethylene/1‐hexene copolymers from ethylene stock as the sole monomer. The reported catalytic systems employ the tandem action between an ethylene trimerization catalyst, (η5‐C5H4CMe2C6H5)TiCl3 ( 1 )/modified methylaluminoxane (MMAO), and a copolymerization metallocene catalyst, [(η5‐C5Me4)SiMe2(tBuN)]TiCl2 ( 2 )/MMAO or rac‐Me2Si(2‐MeBenz[e]Ind)2ZrCl2 ( 3 )/MMAO. During the reaction, 1 /MMAO in situ generates 1‐hexene with high activity and high selectivity, and simultaneously 2 /MMAO or 3 /MMAO copolymerizes ethylene with the produced 1‐hexene to generate butyl‐branched polyethylene. We have demonstrated that, by the simple manipulation of the catalyst molar ratio and polymerization conditions, a series of branched polyethylenes with melting temperatures of 60–128 °C, crystallinities of 5.4–53%, and hexene percentages of 0.3–14.2 can be efficiently produced. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4327–4336, 2004  相似文献   

12.
Copolymerizations of styrene and the polyhedral oligomeric silsesquioxane (POSS)–styryl macromonomer 1‐(4‐vinylphenyl)‐3,5,7,9,11,13,15‐heptacyclopentylpentacyclo [9.5.1.13,9.15,15.17,13] octasiloxane have been performed with CpTiCl3 in conjunction with methylaluminoxane. Random copolymers of syndiotactic polystyrene (sPS) and POSS have been formed and fully characterized with 1H and 13C NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. NMR data reveal a moderately high syndiotacticity of the polystyrene backbone consistent with this use of CpTiCl3 as a catalyst and POSS loadings as high as 24 wt % and 3.2 mol %. Thermogravimetric analysis of the sPS–POSS copolymers under both nitrogen and air shows improved thermal stability with higher degradation temperatures and char yields, demonstrating that the inclusion of the inorganic POSS nanoparticles makes the organic polymer matrix more thermally robust. The polymerization activity and thermal stability are also compared with those of reported atactic polystyrene–POSS copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 885–891, 2002; DOI 10.1002/pola.10175  相似文献   

13.
CpTiCl2(OC6H4X‐p) complexes (where X =­CH3, Cl, NO2,; Cp = cyclopentadienyl) activated with methylaluminoxane (MAO) were used in syndiotactic polymerization of styrene. High activity and selectivity for all catalysts were found. The styrene conversion and reaction selectivity depend on the catalyst ageing time and temperature, polymerization temperature and the nature of the substituent in the phenoxy ring. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

14.
Homopolymerization of a styrene‐terminated polyisoprene macromonomer (SIPM) by half‐titanocene catalysts in combination with methylaluminoxane (MAO) was investigated. Polymerization of the SIPM with CpTiCl3‐MAO as the catalyst was found to proceed readily to give a high molecular weight polymer. 1H and 13C NMR spectra of the poly(SIPM) after ozonolysis of the isoprene side chain revealed that poly(SIPM) is a highly syndiotactic polymer. Syndiotactic poly(SIPM) is soluble in usual solvents in spite of having highly syndiotactic sequences on its main chain and a considerable degree of polymerization.  相似文献   

15.
Copolymerization of styrene (St) and butadiene (Bd) with nickel(II) acetylacetonate [Ni(acac)2]-methylaluminoxane (MAO) catalyst was investigated. Among the metal acetylacetonates [Mt(acac)x] examined, Ni(acac)2 showed a high activity for the copolymerization of St and Bd giving copolymers having high cis-1,4-microstructure in Bd units in the copolymer. The effect of alkylaluminum as a cocatalyst on the copolymerization of St and Bd with the Ni(acac)2-MAO catalyst was observed, and MAO was found to be the most effective cocatalyst for the copolymerization. The monomer reactivity ratios for the copolymerization of St and Bd with the Ni(acac)2-MAO catalyst were determined to be rSt = 0.07 and rBd = 3.6. Based on the obtained results, it was presumed that the random copolymers with high cis-1,4-microstructure in Bd units could be synthesized with the Ni(acac)2-MAO catalyst without formation of each homopolymer. The polymerization mechanism with the Ni(acac)2-MAO catalyst was also discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3838–3844, 1999  相似文献   

16.
Sparteine was found to be an efficient ligand because when complexed with copper(I) halide it generated a homogeneous catalyst for the atom transfer radical polymerization of styrene or methyl methacrylate, which was initiated by (1-bromoethyl)benzene in the former case and by p-toluenesulfonyl chloride in the latter. The plots of ln([M]0/[M]) versus time and molecular weight versus monomer conversion exhibited linear dependencies, which indicated that the concentration of the living centers throughout polymerization was constant. The polydispersities of polystyrene and poly(methyl methacrylate) in both the bulk and solution polymerizations were quite low. An induction time was observed during the bulk polymerization of styrene; however, it was absent during the solution polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4191–4197, 1999  相似文献   

17.
Half titanocenes (CpCH2CH2O)TiCl2 1 and (CpCH2CH2 OCH3)TiCl3 2 , activated by methylaluminoxane are tested in styrene–1,3‐butadiene copolymerization. The titanocene 1 is able to copolymerize styrene and 1,3‐butadiene, with a facile procedure, to give products with high molecular weight. The analysis of microstructure by 13C‐NMR reveals that the styrene homosequences in copolymers are in syndiotactic arrangement, while the butadiene homosequences are, prevailingly, in 1,4‐cis configuration, according with behavior of 1 in the homopolymerizations of styrene and 1,3‐butadiene, respectively. The reactivity ratios of copolymerization are estimated by diad composition analysis. All obtained copolymers have r1 × r2 values much larger than 1, indicating blocky nature of homosequences. The structural characterization by wide‐angle X‐ray powder diffraction and differential scanning calorimetry indicates that all copolymers are crystalline, with Tm varying from 171 to 239 °C, depending on the styrene content. The titanocene 2 did not succeed in styrene–1,3‐butadiene copolymerization, giving rise to a blend of homopolymers. Compounds 1 and 2 were also tested in the polymerization of several conjugated dienes, and the obtained results were very useful to rationalize the behavior of both catalysts in the copolymerization of styrene and butadiene. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 815–822, 2010  相似文献   

18.
The copolymerizations of ethylene and cyclopentene with bis(β‐enaminoketonato) titanium complexes {[(Ph)NC(R2)CHC(R1)O]2TiCl2; R1 = CF3 and R2 = CH3 for 1a , R1 = Ph and R2 = CF3 for 1b ; and R1 = t‐Bu and R2 = CF3 for 1c } activated with modified methylaluminoxane (MMAO) as a cocatalyst were investigated. High‐molecular‐weight copolymers with cis‐1,2‐cyclopentene units were obtained. The catalyst activity, cyclopentene incorporation, polymer molecular weight, and polydispersity could be controlled over a wide range through the variation of the catalyst structure and reaction parameters, such as the Al/Ti molar ratio, cyclopentene feed concentration, and polymerization reaction temperature. The complex 1b /MMAO catalyst system exhibited the characteristics of a quasi‐living ethylene polymerization and an ethylene–cyclopentene copolymerization and allowed the synthesis of polyethylene‐block‐poly(ethylene‐co‐cyclopentene) diblock copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1681–1689, 2005  相似文献   

19.
CH2?CHCH2CpTiCl3 (1), CH2?CHCH2CH2CpTiCl3 (2) and CH3CH2CH3CpTiCl3 (3) have been synthesized and characterized. The influence of the alkenyl substituent groups on the catalyst activities in the syndiotactic polymerization of styrene was investigated. The catalyst activities decreased in the order CH2?CHCH2CH2CpTiCl3 > CH3CH2CH2CH2CpTiCl3 > CH3CH2CH2CpTiCl3 > CH2?CHCH2CpTiCl3 (Cp?C5H4). By using complex 1, the dependence of the activity on the concentration of methylaluminoxane, triisobutylaluminum and diisobutylaluminum hydride was investigated. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

20.
Several titanium(IV) complexes of the type Cp′Ti(NMe2)3 [Cp′ = cyclopentadienyl ( 1 ), (dimethylaminoethyl)cyclopentadienyl ( 2 ), indenyl ( 3 ), and pentamethylcyclopentadienyl ( 4 )] were prepared, and their catalytic properties in the polymerization of α‐olefins were examined. Complexes 1 and 2 catalyzed the polymerization of ethylene in the presence of methylaluminoxane with a much higher activity than 3 or 4 . Complexes 3 and 4 polymerized ethylene with an activity similar to that of CpTiCl3 ( 6 ). The preactivation of 2 , 3 , or 4 with trimethylaluminum (TMA) resulted in an increase in ethylene polymerization activities. Also, 1 and 2 were successfully used as ethylene/1‐hexene copolymerization catalysts, producing polymers with various amounts of 1‐hexene incorporation, depending on the amount of 1‐hexene in the feed mixture. Complex 1 likewise effectively polymerized styrene with a higher activity and higher syndiospecificity than the other three catalysts. Complexes 3 and 4 polymerized styrene with low syndiospecificity, whereas 2 produced only atactic polystyrene. The preactivation of 3 or 4 with TMA resulted in an increase in styrene polymerization activities and increased the syndiotacticity percentage of the polymers produced. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 313–319, 2001  相似文献   

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