<b>Stereospecific Catalysts for the Head-To-Tail Polymerization of Propylene to a Crystalline Syndiotactic Polymer</b>

Natta, G.; Pasquon, I.; Zambelli, Adolfo

doi:10.1021/ja00867a029

Cited by 266 publications

(131 citation statements)

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“…Syndiotactic polypropylene (sPP) was first synthesized in the early 1960s with a Ziegler Natta catalyst [1]. Unfortunately, this new stereoregular polypropylene exhibited low syndiotacticity and had poor mechanical and thermal properties which prevented it for many applications.…”

Section: Introductionmentioning

confidence: 99%

“…A shoulder is also observed on the spectra at 50.1 ppm together with the broadening of bands of CH and CH 3 corresponding to the contributions of amorphous chains. In the blends iPP/sPP and virgin iPP, iPP crystallizes in % form while crystalline sPP chains are mainly in conformations of type helical 4 1 . The amorphous chains of sPP are in various conformations as indicated by broad bands detected by MAS 13 C NMR.…”

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confidence: 99%

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Characterization of the morphology of iPP/sPP blends with various compositions

Bourbigot¹,

Garnier²,

Revel³

et al. 2013

Express Polym. Lett.

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Abstract. The paper investigates the morphology and the structural properties of blends of isotactic polypropylene (iPP) and syndiotactic polypropylene (sPP) having different compositions using different techniques. Solid-state nuclear magnetic resonance (NMR) permits via appropriate sequence to measure the composition, conformation and dynamics, and intimacy of mixing of polymeric materials. Measurement of relaxation times gives information on local structure of phases with different mobility. The morphology is directly related to the structural organization of the blends. The crystallization rate decreases as a function of the sPP content. The minor component is dispersed as a nodule in the main component of the blend and it plays the role of nucleating agent on it. Besides, morphology changes occur for the composition 50/50 (wt/wt) of the blend iPP/sPP. Different phases are identified, namely free amorphous, constrained amorphous and crystalline regions which exhibit different molecular mobilities. It is also shown at the interphase matrix-nodules, the nodules create a constrained amorphous zone.

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Characterization of the morphology of iPP/sPP blends with various compositions

Bourbigot¹,

Garnier²,

Revel³

et al. 2013

Express Polym. Lett.

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“…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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“…6 This remarkable finding that a stereospecific polymer is formed starting from a non-chiral catalyst led to extensive studies of the polymerization mechanism.…”

Section: The Stereospecific Polymerization Of Propenementioning

confidence: 99%

Homogeneous Vanadium‐Based Catalysts for the Ziegler—Natta Polymerization of α‐Olefins

2003

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Although their activity is often inferior to that of other systems, the use of vanadium-based catalysts in homogeneous Ziegler-Natta polymerizations allows the preparation of high-molecular-weight polymers with narrow molecularweight distributions, ethene/a-olefin copolymers with high a-olefin incorporation, and syndiotactic polypropene. The main reason for the low activity of these catalysts is their deactivation during catalysis by reduction of active vanadium species to low-valent, less active or inactive species. We here present an up-to-date review of this area with particular emphasis on the attempts to improve catalyst performance and stability by the use of additives or ancillary ligands.

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Stereospecific Catalysts for the Head-To-Tail Polymerization of Propylene to a Crystalline Syndiotactic Polymer

Cited by 266 publications

References 2 publications

Characterization of the morphology of iPP/sPP blends with various compositions

Characterization of the morphology of iPP/sPP blends with various compositions

Diffusion and morphological properties of syndiotactic polypropylene (sPP) films

Homogeneous Vanadium‐Based Catalysts for the Ziegler—Natta Polymerization of α‐Olefins

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