Crystal Structure, Morphology, and Phase Transitions in Syndiotactic Polypropylene

Rodrlguez-Arnold, Jonahira; Bu, Zhengzheng; Cheng, Stephen Z. D.

doi:10.1080/15321799508014591

Cited by 34 publications

(4 citation statements)

References 63 publications

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“…The first metallocene -and the first catalyst in general- able to produce highly syndiotactic polypropene ( s -PP), was the C s -symmetric Me 2 C(Cp)(9-Flu)ZrCl 2 ( C s - 1 in Chart ) . The behavior of this catalyst 46,113 and the characterization of s -PP − have been extensively reviewed. A number of studies on the thermal behavior, crystal structures, and morphology of s -PP have appeared in the literature. − A T m ° of 214 °C and a Δ H u of 1.4 kJ/mol for fully syndiotactic polypropene have been extrapolated .…”

Section: B Syndiotactic Polypropene: C S -Symmetric Metallocenesmentioning

confidence: 99%

“…The behavior of this catalyst 46,113 and the characterization of s -PP − have been extensively reviewed. A number of studies on the thermal behavior, crystal structures, and morphology of s -PP have appeared in the literature. − A T m ° of 214 °C and a Δ H u of 1.4 kJ/mol for fully syndiotactic polypropene have been extrapolated . Hence, the T m ° of s -PP would be notably higher than that of i -PP (186 °C), although in practice s -PP has always lower melting points than i -PP of comparable stereoregularity and molecular weights.…”

Section: B Syndiotactic Polypropene: C S -Symmetric Metallocenesmentioning

confidence: 99%

See 1 more Smart Citation

Selectivity in Propene Polymerization with Metallocene Catalysts

Resconi¹,

Cavallo²,

Fait³

et al. 2000

Chem. Rev.

1,366

1,411

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Section: B Syndiotactic Polypropene: C S -Symmetric Metallocenesmentioning

confidence: 99%

Section: B Syndiotactic Polypropene: C S -Symmetric Metallocenesmentioning

confidence: 99%

Selectivity in Propene Polymerization with Metallocene Catalysts

Resconi¹,

Cavallo²,

Fait³

et al. 2000

Chem. Rev.

1,366

1,411

View full text Add to dashboard Cite

“…This may be viewed as a slightly disordered state of form III. Several slight modifications of the crystal structures have also been reported. − Other polymorphisms may also form at even lower T c , such as the all- trans -conformation orthorhombic phase and triclinic intermediate phase …”

Section: Introductionmentioning

confidence: 99%

Crystallization, Melting and Morphology of Syndiotactic Polypropylene Fractions. 4. In Situ Lamellar Single Crystal Growth and Melting in Different Sectors

Zhou¹,

Cheng²,

Putthanarat³

et al. 2000

Macromolecules

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Over a wide crystallization temperature (Tc) range, elongated rectangular lamellar single crystals of syndiotactic polypropylene (s-PP) grown from the melt of thin films exhibit sectorization along both diagonal directions to form the (010) [with the (010) free edge] and the (100) [with the (100) free edge] sectors. They can be observed by transmission electron and atomic force microscopy (TEM and AFM). Electron diffraction experiments show that the crystals in both sectors are form III orthorhombic structure, as recently proposed. 1-4 The observation of this sectorization is due to the thickness difference between these two sectors with different fold planes. In situ observations of the single-crystal growth are monitored using an AFM coupled with a hot stage. The Tc-dependent crystal growth rates along both the (100) and (010) normal can be measured, and they are anisotropic. This leads to a large aspect ratio of the rectangular single crystal. AFM results also show that the thickness difference between the two sectors is dependent upon crystallization time (tc). In the initial stage of single-crystal development, the ratio between the thickness difference and the (100) sector thickness is large [∼35% of the thickness of the (100) thick sectors]. With increasing tc, this ratio of the thickness difference gradually decreases to ∼15%. Multiple-step cooling and isothermal experiments in a successive Tc-decreasing sequence reveal that each Tc produces a unique lamellar thickness. With reducing Tc, the thickness decreases. Room-temperature TEM observations show that the (010) thin sectors are molten while the (100) thick sectors remain after the single crystals are annealed on a temperature-gradient bar for a prolonged time. In situ single crystal melting monitored by AFM reveals different melting pathways of these two sectors. When the isothermally grown single crystals are heated to 5°C above T c (120°C), the melting first appears in the (100) thick sectors in the form of molten domains. These domains can be repaired via recrystallization if the samples are annealed at this temperature for a long period of time. As further increasing the temperature, the melting of the (100) thick sectors again starts in molten domains along the (100) free edges of the single crystals. In the (010) thin sectors the melting takes place on the free edges of the single crystals, and progresses toward the inner area of the sectors.

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“…Syndiotactic polypropylene (sPP) exhibits a complex crystalline polymorphism based on different chain conformations and packing schemes . The more stable chain conformation is of the type trans−trans-gauche−gauche (ttgg or t 2 g 2 ).…”

Section: Introductionmentioning

confidence: 99%

Isochiral Form II of Syndiotactic Polypropylene Produced by Epitaxial Crystallization

Zhang¹,

Yang²,

Thierry³

et al. 2001

Macromolecules

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Epitaxial crystallization of syndiotactic polypropylene (sPP) on 2-quinoxalinol (2-Quin) yields, in the lower part of the crystallization range, the less common and metastable form II based on the packing of isochiral helices, rather than the stable antichiral form I. The contact plane is (110) II. Form II exits only as a thin layer (< ≈50 nm) near the substrate surface. During further growth away from the surface, a transition takes place to the disordered form I, observed in "conventional" thin film growth. The epitaxial relationship rests only partly on dimensional matching with the chain axis repeat distance (which would be valid for both forms I and II) and on interchain distances. Whereas a better dimensional match would be achieved with form I, selection of the isochiral form II results from better correspondence of the surface topographies of the deposit (110) II sPP and substrate 2-Quin (001) contact faces.

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Crystal Structure, Morphology, and Phase Transitions in Syndiotactic Polypropylene

Cited by 34 publications

References 63 publications

Selectivity in Propene Polymerization with Metallocene Catalysts

Selectivity in Propene Polymerization with Metallocene Catalysts

Crystallization, Melting and Morphology of Syndiotactic Polypropylene Fractions. 4. In Situ Lamellar Single Crystal Growth and Melting in Different Sectors

Isochiral Form II of Syndiotactic Polypropylene Produced by Epitaxial Crystallization

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