Syndiospecific propylene polymerizations with Group IVB metallocenes

Ewen, John A.; Jones, Robert L.; Razavi, Abbas; Ferrara, Joseph D.

doi:10.1021/ja00226a056

Cited by 945 publications

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“…These papers report that the decrease in syndiospecificity with the C s -symmetry zirconocene catalysts in polar solvent is ascribed to the 'chain migration without monomer insertion (skipped insertion)' and not to the 'selection miss of enantioface' (Scheme 6). 36 The change in the syndiospecificity observed by the present Ti complex can be also interpreted by the separation of an active ion pair. The dMMAO-polar solvent system produces a solvent-separated ion pair and, hence, allows the growing chain to migrate between the two enantiotopic sites on the Ti cation without monomer insertion.…”

Section: Activation With R 3 Al-free Modified Mao (Mmao)mentioning

confidence: 68%

Living polymerization of olefins with ansa-dimethylsilylene(fluorenyl)(amido)dimethyltitanium-based catalysts

Shiono

2011

Polym J

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This article reviews the living homopolymerization and copolymerization of propene, 1-alkene and norbornene with ansadimethysilylene(fluorenyl)(amido)dimethyltitanium, Me 2 Si(g 3 -C 13 H 8 )(g 1 -N t Bu)TiMe 2 and its derivatives, correlating the effects of cocatalysts, solvents, polymerization conditions and the substituents of the fluorenyl ligand with catalytic features, such as livingness, initiation efficiency, propagation rate, syndiospecificity and copolymerization ability. The synthesis of novel olefin block copolymers and their catalytic synthesis are also introduced using this living system. Polymer Journal (2011) 43, 331-351; doi:10.1038/pj.2011 Keywords: cycloolefin copolymer; living polymerization; norbornene; propene; single-site catalyst; syndiospecific polymerization; 1-alkene A living polymerization system, in which neither chain transfer nor deactivation occurs, affords polymers with predictable molecular weights and narrow molecular weight distributions (MWDs). Living polymerization techniques are utilized for the synthesis of terminally functionalized polymers and block copolymers. Another feature of living polymerization is its simple kinetics. Because neither chain transfer nor deactivation occurs in living polymerization, the number of polymer chains (N) is equal to the number of active centers ([C*]), and the number-average molecular weight (M n ) directly reflects the propagation rate. In living polymerization, the propagation rate can be evaluated from the M n value and the polymerization time. As chain transfer via b-elimination and/or transmetalation with trialkylaluminum as a cocatalyst is inevitable in conventional Ziegler-Natta catalytic systems; homogeneous V(acac) 3 /Et 2 AlCl (where acac is acetylacetonate or its analog) had previously been the only catalytic system that produced syndiotactic-rich living polypropylene (PP) atThe development of metallocene catalysts has enabled us to produce a variety of uniform olefin copolymers and to control the stereoregularity of poly(1-alkene)s. 3,4 The success of metallocene catalysts has stimulated research on transition metal complexes for olefin polymerization, 5-7 so-called single-site catalysts, which has also resulted in various transition metal complexes for the living polymerization of olefins. 8,9 We have also developed a living polymerization system using ansa-dimethysilylene(fluorenyl)(amido)dimethyltitanium, Me 2 Si(Z 3 -C 13 H 8 )(Z 1 -N t Bu)TiMe 2 (1), combined with a suitable cocatalyst. The catalytic system allows not only a syndiospecific living polymerization of propene and a 1-alkene but also a living homopolymerization and copolymerization of norbornene with a 1-alkene. We investigated the effect of cocatalyst, solvent and the ligand of the titanium complex on propene polymerization in terms of the livingness of the system. We also synthesized novel olefin block copolymers with the living system. This article reviews the characteristics of 1-based catalysts for tailor-made polyolefins. SYNTHESIS AND STRUCTURES OF TIT...

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Section: Activation With R 3 Al-free Modified Mao (Mmao)mentioning

confidence: 68%

Living polymerization of olefins with ansa-dimethylsilylene(fluorenyl)(amido)dimethyltitanium-based catalysts

Shiono

2011

Polym J

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“…We also obtained the flux of toluene, N tol , the toluene permeability, P and the partition coefficient, K, from Eqs. [3][4][5]. …”

Section: Resultsmentioning

confidence: 99%

“…Syndiotactic polypropylene (sPP) was first synthesized by Natta et al in 1960s [1,2], and improved sPP was reported by Ewen et al [3] in the 1980s using a metallocene catalytic system. The improved sPP has high crystallinity and melting temperature and has outstanding physical properties.…”

Section: Introductionmentioning

confidence: 99%

Diffusion and morphological properties of syndiotactic polypropylene (sPP) films

Yamashita

Fujiwara

Fujikawa

et al. 2009

Polymer Engineering & Sci

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Four different fabrication procedures were used for casting thin films of syndiotactic polypropylene (sPP). A hot press system operated at 200°C and 30 MPa pressure was used to melt polypropylene powder and make the cast films. Different cooling procedures were used to anneal the films, including cooling in liquid nitrogen (LN), ice water, and air at room temperature (RT). The morphological and mass transfer properties of the films were studied with XRD, polarized optical microscopy, bulk flow, and diffusion experiments. All sPP films contained amorphous and crystalline phases. The crystalline phase was determined to be disordered Form I. The sPP films annealed with LN had the lowest crystallinity whereas the sPP films cooled in air at RT had the highest crystallinity. Diffusion of toluene in the films and comparison with Maxwell's equation indicated that the crystalline phase mass permeability is much lower than the amorphous phase, which causes films with low crystallinity to have a higher effective diffusion constant and permeability compared with high crystallinity films. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

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“…A much improved s-PP was successfully synthesized in 1988 by Ewen et al 3 based on a novel metallocene catalysis. The new catalyst systems made it possible to produce s-PP with much improved purity and yields, which led to renewed interest in scientific research 4 and industrial applications.…”

Section: Introductionmentioning

confidence: 99%

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Supaphol

2001

J of Applied Polymer Sci

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ABSTRACT:The melting behavior of syndiotactic polypropylene (s-PP) after isothermal crystallization from the melt state was studied using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) techniques. Three melting endotherms were observed for isothermal crystallization at high degrees of undercooling. The minor endotherm, located closed to the corresponding crystallization temperature, was postulated to be the melting of the secondary crystallites formed at the crystallization temperature. The low-temperature melting peak was found to be the melting of the primary crystallites formed, and the high-temperature melting peak was a result of the melting of the crystallites recrystallized during a heating scan. The triple-melting behavior observed in subsequent melting endotherms of s-PP was therefore described as contributions from melting of the secondary crystallites and their recrystallization, partial melting of the less stable fraction of the primary crystallites and their recrystallization, melting of the primary crystallites, and remelting of the recrystallized crystallites formed during the heating scan. In addition, determination of the equilibrium melting temperature for this s-PP resin according to the linear and nonlinear Hoffman-Weeks extrapolations provided values of 143.1 and 185.6°C, respectively.

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Syndiospecific propylene polymerizations with Group IVB metallocenes

Cited by 945 publications

References 0 publications

Living polymerization of olefins with ansa-dimethylsilylene(fluorenyl)(amido)dimethyltitanium-based catalysts

Living polymerization of olefins with ansa-dimethylsilylene(fluorenyl)(amido)dimethyltitanium-based catalysts

Diffusion and morphological properties of syndiotactic polypropylene (sPP) films

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

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