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1.
Mariagrazia Napoli Rosa Ricciardi Antonia Memoli Pasquale Longo 《Journal of polymer science. Part A, Polymer chemistry》2008,46(4):1476-1487
C2‐symmetric group 4 metallocenes based catalysts (rac‐[CH2(3‐tert‐butyl‐1‐indenyl)2]ZrCl2 (1) , rac‐[CH2(1‐indenyl)2]ZrCl2 (2) and rac‐[CH2(3‐tert‐butyl‐1‐indenyl)2]TiCl2 (3) ) are able to copolymerize styrene and 1,3‐butadiene, to give products with high molecular weight. In agreement with symmetry properties of metallocene precatalysts, styrene homosequences are in isotactic arrangements. Full determination of microstructure of copolymers was obtained by 13C NMR and FTIR analysis and it reveals that insertion of butadiene on styrene chain‐end happens prevailingly with 1,4‐trans configuration. In the butadiene homosequences, using zirconocene‐based catalysts, the 1,4‐trans arrangement is favored over 1,4‐cis, but the latter is prevailing in the presence of titanocene (3) . Diad composition analysis of the copolymers makes possible to estimate the reactivity ratios of copolymerization: zirconocenes (1) and (2) produced copolymers having r1 × r2 = 0.5 and 3.0, respectively (where 1 refers to styrene and 2 to butadiene); while titanocene (3) gave tendencially blocky styrene–butadiene copolymers (r1 × r2 = 8.5). The copolymers do not exhibit crystallinity, even when they contain a high molar fraction of styrene. Probably, comonomer homosequences are too short to crystallize (ns = 16, in the copolymer at highest styrene molar fraction). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1476–1487, 2008 相似文献
2.
Mariagrazia Napoli Annaluisa Mariconda Ivano Immediata Pasquale Longo 《Journal of polymer science. Part A, Polymer chemistry》2008,46(14):4725-4733
Half titanocenes (CpCH2CH2O)TiCl2 (1), (CpCH2CH2OCH3)TiCl3 (2), and CpTiCl3 (3), activated by methylaluminoxane (MAO) were tested in copolymerization of ethylene with internal olefins such as cyclopentene. All the catalysts were able to give incorporation of cyclopentene in polyethylene matrix. 13C NMR analysis of obtained copolymers showed that the catalytic systems have low regiospecificity. In fact, in ethylene–cyclopentene copolymers, cyclic olefin inserts with both 1,2 and 1,3‐enchainment. X‐ray powder diffraction analysis of these copolymers confirmed that 1,2 inserted cyclopentene units are excluded from crystalline phase, whereas 1,3‐cyclopentene units are included, giving rise to expansion of unit cell of crystalline polyethylene. Titanium‐based catalysts were investigated also in the copolymerization of ethylene with E and Z‐2‐butene. Only complex (1) was able to give copolymers and 13C NMR analysis of products showed 2‐3, 1‐3, and 1‐2 insertion of 2‐butene. Differential scanning calorimetry analysis displayed that ethylene–cyclopentene, as well as ethylene‐2‐butene, copolymers are crystalline and their melting point decreases by increasing the comonomer content. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4725–4733, 2008 相似文献
3.
Naofumi Naga Yukio Imanishi 《Journal of polymer science. Part A, Polymer chemistry》2003,41(7):939-946
The copolymerization of styrene and 1,3‐butadiene (Bd) or isoprene (Ip) was carried out with half‐sandwich titanium(IV) Cp′TiCl3 catalysts (where Cp′ is cyclopentadienyl 1 , indenyl 2 , or pentamethylcyclopentadienyl 3 ) with methylaluminoxane as a cocatalyst. For the copolymerization with Bd, catalyst 3 gave the copolymers containing the highest amount of Bd among the catalysts used. The resulting copolymers were composed of a styrene–Bd multiblock sequence. High melting points were observed in the copolymers prepared with catalyst 1 . The structures of hydrogenated poly(styrene‐co‐Bd) were studied by 13C NMR spectroscopy, and the long styrene sequence length was detected in the copolymers prepared with catalyst 1 . For styrene/Ip copolymerization, random copolymers were obtained. Among the used catalysts, catalyst 1 gave the copolymers containing the highest amount of Ip. The copolymers prepared with catalyst 1 showed a steep melting point depression with increasing Ip content because of the high ratio of 1,4‐inserted Ip units and/or the low molecular weights of the copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 939–946, 2003 相似文献
4.
Carmine Capacchione Antonio Proto Henner Ebeling Rolf Mülhaupt Jun Okuda 《Journal of polymer science. Part A, Polymer chemistry》2006,44(6):1908-1913
Copolymerization of ethylene with styrene, catalyzed by 1,4‐dithiabutanediyl‐linked bis(phenolato) titanium complex and methylaluminoxane, produced exclusively ethylene–styrene copolymers with high activity. Copolymerization parameters were calculated to be rE = 1.2 for ethylene and rS = 0.031 for styrene, with rE rS = 0.037 indicating preference for alternating copolymerization. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with styrene content up to 68%. The copolymer microstructure was fully elucidated by 13C NMR spectroscopy revealing, in the copolymers with styrene content higher than 50%, the presence of long styrene–styrene homosequences, occasionally interrupted by isolated ethylene units. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1908–1913, 2006 相似文献
5.
Kyung‐Sun Son Robert M. Waymouth 《Journal of polymer science. Part A, Polymer chemistry》2010,48(7):1579-1585
A series of monocyclopentadienyl titanium complexes containing a pendant amine donor on a Cp group ( A = CpTiCl3, B = CpNTiCl3, C = CpNTiCl2TEMPO, for Cp = C5H5, CpN = C5H4CH2CH2N(CH3)2, and TEMPO = 2,2,6,6‐tetramethylpiperidine‐N‐oxyl) are investigated for styrene homopolymerization and ethylene–styrene (ES) copolymerization. When activated by methylaluminoxane at 70 °C, complexes with the amine group ( B and C ) are active for styrene homopolymerization and afford syndiotactic polystyrene (sPS). The copolymerizations of ethylene and styrene with B and C yield high‐molecular weight ES copolymer, whereas complex A yields mixtures of sPS and polyethylene, revealing the critical role that the pendant amine has on the polymerization behavior of the complexes. Fractionation, NMR, and DSC analyses of the ES copolymers generated from B and C suggest that they contain sPS. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1579–1585, 2010 相似文献
6.
This article discusses a chemical route to prepare new ethylene/propylene copolymers (EP) containing a terminal reactive group, such as ?‐CH3 and OH. The chemistry involves metallocene‐mediated ethylene/propylene copolymerization in the presence of a consecutive chain transfer agent—a mixture of hydrogen and styrene derivatives carrying a CH3 (p‐MS) or a silane‐protected OH (St‐OSi). The major challenge is to find suitable reaction conditions that can simultaneously carry out effective ethylene/propylene copolymerization and incorporation of the styrenic molecule (St‐f) at the polymer chain end, in other words, altering the St‐f incorporation mode from copolymerization to chain transfer. A systematic study was conducted to examine several metallocene catalyst systems and reaction conditions. Both [(C5Me4)SiMe2N(t‐Bu)]TiCl2 and rac‐Et(Ind)2ZrCl2, under certain H2 pressures, were found to be suitable catalyst systems to perform the combined task. A broad range of St‐f terminated EP copolymers (EP‐t‐p‐MS and EP‐t‐St‐OH), with various compositions and molecular weights, have been prepared with polymer molecular weight inversely proportional to the molar ratio of [St‐f]/[monomer]. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1858–1872, 2005 相似文献
7.
Li‐Ming Tang Yan‐Guo Li Wei‐Ping Ye Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2006,44(20):5846-5854
Ethylene–propylene copolymerization, using [(Ph)NC(R2)CHC(R1)O]2TiCl2 (R1 = CF3, Ph, or t‐Bu; R2 = CH3 or CF3) titanium complexes activated with modified methylaluminoxane as a cocatalyst, was investigated. High‐molecular‐weight ethylene–propylene copolymers with relatively narrow molecular weight distributions and a broad range of chemical compositions were obtained. Substituents R1 and R2 influenced the copolymerization behavior, including the copolymerization activity, methylene sequence distribution, molecular weight, and polydispersity. With small steric hindrance at R1 and R2, one complex (R1 = CF3; R2 = CH3) displayed high catalytic activity and produced copolymers with high propylene incorporation but low molecular weight. The microstructures of the copolymers were analyzed with 13C NMR to determine the methylene sequence distribution and number‐average sequence lengths of uninterrupted methylene carbons. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5846–5854, 2006 相似文献
8.
Random propene/4‐methyl‐1‐pentene copolymers synthesized with C2 symmetric highly isospecific metallocenes 下载免费PDF全文
Maria Carmela Sacchi Simona Losio Luigi Fantauzzi Paola Stagnaro Roberto Utzeri Maurizio Galimberti 《Journal of polymer science. Part A, Polymer chemistry》2015,53(22):2575-2585
Propene (P)/4‐methyl‐1‐pentene (Y) copolymers in a wide range of composition were prepared with isospecific single center catalysts, rac‐Et(IndH4)2ZrCl2 ( EBTHI ), rac‐Me2Si(2‐Me‐BenzInd)2ZrCl2 ( MBI ), and rac‐CH2(3‐tBuInd)2ZrCl2 ( TBI ). 13C NMR analysis of copolymers and statistical elaboration of microstructural data at triad level were performed. Unprecedented and surprising results are here reported. Random P/Y copolymers were prepared with the most isospecific catalyst, TBI , that is known to prepare ethene/propene and ethene/4‐methyl‐1‐pentene copolymers with long homosequences of both comonomers, whereas longer homosequences of both comonomers were observed in copolymers from the less enantioselective metallocenes EBTHI and MBI . These findings, which are against what is acknowledged in the field, can pave the way for the preparation on a large scale of random propene‐based copolymers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2575–2585 相似文献
9.
Synthesis and Characterization of Crystalline Styrene‐b‐(Ethylene‐co‐Butylene)‐b‐Styrene Triblock Copolymers 下载免费PDF全文
Fei Lin Chunji Wu Dongmei Cui 《Journal of polymer science. Part A, Polymer chemistry》2017,55(7):1243-1249
By merit of dual catalysis of the cationic rare‐earth complex [(η5‐Flu‐CH2‐Py)Ho(CH2SiMe3)2(THF) (Flu = fluorenyl, Py = pyridyl) for the living polymerizations of butadiene (BD) and styrene (St), the crystalline styrene‐butadiene‐styrene (SBS) triblock copolymers consisting of elastic polybutadiene (PBD) sequences with suitable 1,4 regularity (about 70%) and crystalline syndiotactic polystyrene (sPS, [rrrr] > 99%) sequences were successfully synthesized through sequential addition of St, BD, and St monomers. The catalytic system showed high polymerization activities for St and BD in a controlled manner. The crystalline styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene (SEBS) triblock copolymers were obtained by hydrogenation of the above SBS copolymers. The observation of a strong endothermic peak at 266 °C in their differential scanning calorimetry (DSC) curves confirmed the existence of the sPS blocks in the crystalline SEBS different from the industrial product Kraton SEBS‐1652. Thermal degradation temperature of the crystalline SEBS (418 ± 2 °C) indicated the well thermostability and process window of this polymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1243–1249 相似文献
10.
S. Martínez M. T. Exposito J. Ramos V. Cruz M. C. Martínez M. Lpez A. Muoz‐Escalona J. Martínez‐Salazar 《Journal of polymer science. Part A, Polymer chemistry》2005,43(4):711-725
Styrene was copolymerized with ethylene using the geometry constrained Me2Si(Me4Cp)(N‐tert‐butyl)TiCl2 Dow catalyst activated with methylaluminoxane. Increasing the styrene/ethylene ratio in the reactor feed had the effects of reducing both the activity of the catalyst and the molecular weight of the copolymers produced. However, the higher the styrene/ethylene ratio used, the greater the amount of styrene that became incorporated in the copolymer. We discuss these experimental findings within the framework of a computational analysis of ethylene/styrene copolymerization performed through hybrid density functional theory (B3LYP). In general, there was good agreement between the experimental and theoretical results. Our findings point to the suitability of combining experimental and theoretical data for clarifying the copolymerization mechanisms that take place in α‐olefin‐organometallic systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 711–725, 2005 相似文献
11.
The synthesis and characterization of copolymers from styrene and 1,3‐pentadiene (two isomers) are reported. Styrene/1,3‐pentadiene (1:1) copolymerization with carbanion initiator yield living, well‐defined, alternating (r1 = 0.037, r2 = 0.056), and highly stereoregular copolymers with 90%–100% trans‐1,4 units, designed Mns and low ÐMs (1.07–1.17). The first‐order kinetic resolution and NMR spectra demonstrate that the copolymers obtained possess strictly alternating structure containing both 1,4‐ and 4,1‐enchaiments. Also a series of copolymers with varying degrees of alternation are synthesized from para‐alkyl substituted styrene derivatives and 1,3‐pentadiene. The degree of alternation is strongly dependent on the polarity of solvent, reaction temperature, type of trans‐cis isomer of 1,3‐pentadiene and para‐substituted group in styrene. The macro zwitterion forms (SPC) through the distribution of electronic charges from the donor (1,3‐pentadiene) to the acceptor (styrenes) are proposed to interpret the carbanion alternating copolymerization mechanism. Owing to the versatility of the carbanion‐initiating reaction, the present alternating strategy based on 1,3‐pentadiene (especially cis isomer) can serve as a powerful tool for precise control of polymer chain microstructure, architecture, and functionalities in one‐pot polymerization.
12.
Kana Nishimori Mitsuo Sawamoto Makoto Ouchi 《Journal of polymer science. Part A, Polymer chemistry》2019,57(3):367-375
This work deals with design of maleimide monomer toward more precise control of alternating sequence for radical copolymerization with styrene. Crucial in this study is sequence analysis by MALDI‐TOF‐MS for resultant copolymers that was obtained via ruthenium‐catalyzed living radical copolymerization with a malonate‐based alkyl halide initiator showing selective initiation ability. The copolymers of a simple N‐alkyl maleimide [e.g., N‐ethyl maleimide (EMI)] with styrene gave complicated peak patterns for the MALDI‐TOF‐MS spectra indicating low degree of alternating sequence, in contrary to expectation from the reactivity ratios (almost zero). A simple substitution of methyl group (CH3) of EMI with trifluoromethyl (CF3: CF3‐MI) made the peak patterns much simpler giving the copolymer with higher alternating sequence. More interestingly, the peak interval of the copolymer at earlier polymerization stage was equal to sum of the molecular weights of CF3‐MI and styrene, suggesting possibility of the pair propagation of the monomers. Indeed, 1H NMR analyses of the mixture of maleimide with styrene suggested stronger interaction of CF3‐MI than EMI. Based on the results, maleimide derivatives carrying a substituent‐designable electron‐withdrawing group [ROC(?O)N–: R = substituent] were newly designed toward incorporation of functional side chains. They also gave higher alternating sequence for the copolymerization with styrene. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 367–375 相似文献
13.
L. F. Sun R. X. Zhuo Z. L. Liu 《Journal of polymer science. Part A, Polymer chemistry》2003,41(18):2898-2904
Copolymers of 2‐methylene‐1,3‐dioxepane (MDO) and methyl acrylate (MA) containing ester units both in the backbone and as pendant groups were synthesized by free‐radical copolymerization. The influence of reaction conditions such as the polymerization time, temperature, initiator concentration, and comonomer feed ratio on the yield, molecular weight, and copolymer composition was investigated. The structure of the copolymers was confirmed by 1H NMR, 13C NMR, and IR spectroscopy. Differential scanning calorimetry indicated that the copolymers had a random structure. An NMR study showed that hydrogen transfer occurred during the copolymerization. The reactivity ratios of the comonomers were rMDO = 0.0235 and rMA = 26.535. The enzymatic degradation of the copolymers obtained was carried out in the presence of proteinase K or a crude enzyme extracted from earthworms. The experimental results showed that the higher ester molar percentage in the backbone caused a faster degradation rate. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2898–2904, 2003 相似文献
14.
Chengang Cao Junfeng Zou Jin‐Yong Dong Youliang Hu T. C. Chung 《Journal of polymer science. Part A, Polymer chemistry》2005,43(2):429-437
This article discusses a facile and inexpensive reaction process for preparing polypropylene‐based graft copolymers containing an isotactic polypropylene (i‐PP) main chain and several functional polymer side chains. The chemistry involves an i‐PP polymer precursor containing several pendant vinylbenzene groups, which is prepared through the Ziegler–Natta copolymerization of propylene and 1,4‐divinylbenzene mediated by an isospecific MgCl2‐supported TiCl4 catalyst. The selective monoenchainment of 1,4‐divinylbenzene comonomers results in pendant vinylbenzene groups quantitatively transformed into benzyl halides by hydrochlorination. In the presence of CuCl/pentamethyldiethylenetriamine, the in situ formed, multifunctional, polymeric atom transfer radical polymerization initiators carry out graft‐from polymerization through controlled radical polymerization. Some i‐PP‐based graft copolymers, including poly(propylene‐g‐methyl methacrylate) and poly(propylene‐g‐styrene), have been prepared with controlled compositions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 429–437, 2005 相似文献
15.
A novel linked‐half‐sandwich lutetium–bis(allyl) complex [(C5Me4? C5H4N)Lu(η3‐C3H5)2] ( 1 ) attached by a pyridyl‐functionalized cyclopentadienyl ligand was synthesized and fully characterized. Complex 1 in combination with [Ph3C][B(C6F5)4] exhibited unprecedented dual catalysis with outstanding activities in highly syndiotactic (rrrr>99 %) styrene polymerization and distinguished cis‐1,4‐selective (99 %) butadiene polymerization, respectively. Strikingly, this catalyst system exhibited remarkable activity (396 kg copolymer (molLu h)?1) for the copolymerization of butadiene and styrene. Irrespective of whether the monomers were fed in concurrent mode or sequential addition of butadiene followed by styrene, diblock copolymers were obtained exclusively, which was confirmed by a kinetics investigation of monomer conversion of copolymerization with time. In the copolymers, the styrene incorporation rate varied from 4.7 to 85.4 mol %, whereas the polybutadiene (PBD) block was highly cis‐1,4‐regulated (95 %) and the polystyrene segment remained purely syndiotactic (rrrr>99 %). Correspondingly, the copolymers exhibited glass transition temperatures (Tg) around ?107 °C and melting points (Tm) around 268 °C; typical values for diblock microstructures. Such copolymers cannot be accessed by any other methods known to date. X‐ray powder diffraction analysis of these diblock copolymers showed that the crystallizable syndiotactic polystyrene (syn‐PS) block was in the toluene δ clathrate form. The AFM micrographs of diblock copolymer showed a remarkable phase‐separation morphology of the cis‐1,4‐PBD block and syn‐PS block. This represents the first example of a lutetium‐based catalyst showing both high activity and selectivity for the (co)polymerization of styrene and butadiene. 相似文献
16.
Andreia Valente Philippe Zinck Andre' Mortreux Marc Bria Marc Visseaux 《Journal of polymer science. Part A, Polymer chemistry》2011,49(17):3778-3782
The Cp*La(BH4)2(THF)2/n‐butylethylmagnesium (BEM) catalytic system has been assessed for the coordinative chain transfer copolymerization of styrene and 1‐hexene. Poly(styrene‐co‐hexene) statistical copolymers were obtained with number‐average molecular weight up to 7600 g/mol, PDI around 1.4 and 1.5 and up to 23% hexene content. The occurence of chain transfer reactions in the presence of excess BEM is established in the course of the statistical copolymerization. Thanks to this transfer process, the quantity of 1‐hexene in the copolymer is increased by a factor of about 3 for high ratio of hexene in the feed, extending the range of our concept of a chain transfer induced control of the composition of statistical copolymers to poly(styrene‐co‐hexene) copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
17.
Mariagrazia Napoli Chiara Costabile Gabriella Cavallo Pasquale Longo 《Journal of polymer science. Part A, Polymer chemistry》2006,44(19):5525-5532
The behaviors of rac‐[CH2(3‐tert‐butyl‐1‐indenyl)2]ZrCl2 ( 1 ) and Cp2ZrCl2 ( 2 ) activated by methylaluminoxane in ethene/1,4‐pentadiene copolymerization are compared. In the presence of 1 , inserted methylene‐1,3‐cyclobutane units, a large number of crosslinks, and a small number of methylene‐1,3‐cyclohexane units are obtained. Differently, a polyethene containing only 1,3‐cyclohexane rings is achieved with 2 as the catalytic precursor. Polymer microstructures are compared with those obtained with 1 and 2 in ethene/1,6‐heptadiene copolymerization, which leads only to polyethene containing cyclohexane rings. A tentative rationalization of the experimental data is reported. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5525–5532, 2006 相似文献
18.
Simon H. Stelzig Matthias Tamm Robert M. Waymouth 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6064-6070
Monocyclopentadienyl titanium imidazolin‐2‐iminato complexes [Cp′Ti(L)X2] 1a (Cp′ = cyclopentadienyl, L = 1,3‐di‐tert‐butylimidazolin‐2‐imide, X = Cl), 1b (X = CH3); 2 (Cp′ = cyclopentadienyl, L = 1,3‐diisopropylimidazolin‐2‐imide, X = Cl); 3 (Cp′ = tert‐butylcyclopentadienyl, L = 1,3‐di‐tert‐butylimidazolin‐2‐imide, X = Cl), upon activation with methylaluminoxane (MAO) were active for the polymerization of ethylene and propylene and the copolymerization of ethylene and 1‐hexene. Catalysts derived from imidazolin‐2‐iminato tropidinyl titanium complex 4 = [(Trop)Ti(L)Cl2] (Trop = tropidinyl, L = 1,3‐di‐tert‐butylimidazolin‐2‐imide) were much less active. Narrow polydispersities were observed for ethylene and propylene polymerization, but the copolymerization of ethylene/hexene led to bimodal molecular weight distributions. The productivity of catalysts derived from the dialkyl complex 1b activated with [Ph3C][B(C6F5)4] or B(C6F5)3 were less active for ethylene/hexene copolymerization but yielded ethylene/hexene copolymers of narrower molecular weight distributions than those derived from 1a/MAO. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6064–6070, 2008 相似文献
19.
Sudip K. De Manish Bhattacharjee 《Journal of polymer science. Part A, Polymer chemistry》2009,47(23):6496-6503
[Cp2TiCl2] has been found to be an effective precatalyst for room temperature aqueous homo‐ and copolymerization of methyl methacrylate and styrene in the presence of a cocatalyst, NaBPh4 and an emulsifier, sodium n‐dodecyl sulfate. The polymers obtained are of high molecular weight with low molecular weight distribution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6496–6503, 2009 相似文献
20.
Sonia Martínez Javier Ramos Víctor L. Cruz Javier Martínez‐Salazar 《Journal of polymer science. Part A, Polymer chemistry》2006,44(16):4752-4761
A density functional theory (B3LYP) computational study of the ethylene–styrene copolymerization process using meso‐Et(H4Ind)2Zr(CH3)2 as the catalyst is presented. The monomer insertion barriers in meso species are evaluated and compared with previously obtained barriers in rac diastereoisomers. Differences related to ethylene homopolymerization and ethylene–styrene copolymerization activities as well as styrene incorporation into the copolymer are found between the meso and rac diastereoisomers. Nevertheless, a migratory insertion mechanism seems to hold for both diastereoisomeric species. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4752–4761, 2006 相似文献