Methylene Proton Magnetic Resonance of Some Partially Deuterated Polypropylenes

Zambelli, Adolfo; Zetta, Lucia; Sacchi, C.; Wolfsgruber, C.

doi:10.1021/ma60028a019

Cited by 28 publications

(8 citation statements)

References 3 publications

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“…The concentrations of regio-defects were determined from their specific resonances. 30,33 The metallocene-catalyzed polymers listed in Table I can be conveniently placed in three groups, as is indicated. The polymers in group A have no stereo-defects, essentially a constant concentration of regio-defects, and a fourfold variation in molecular weight.…”

Section: Methodsmentioning

confidence: 99%

The degree of crystallinity of monoclinic isotactic poly(propylene)

Isasi

Mandelkern

Galante

et al. 1999

J. Polym. Sci. B Polym. Phys.

103

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The degree of crystallinity of a set of monoclinic (alpha) isotactic poly(propylenes), prepared by a metallocene‐type catalyst, were determined at room temperature. Three different methods were used: density, enthalpy of fusion, and wide‐angle X‐ray scattering, and the results compared. The relation between the heat of fusion and the specific volume of these poly(propylenes) was found to be nonlinear, thus precluding any linear extrapolation to obtain the heat of fusion of the pure crystal (ΔHu). The value of ΔHu obtained from depression of the melting temperature by diluents is used. Based on the unit cell density of monoclinic crystals formed from a low defected fraction, the density obtained crystallinity levels were found to be between 0.l5–0.25 higher than those calculated from the heat of fusion. This relatively large difference holds for the isothermally crystallized and quenched isotactic poly(propylenes), and reflects the contribution of the interphase to the density determined crystallinity, which does not contribute to the heat of fusion. Paralleling results found in other systems, the crystallinity levels obtained from wide‐angle X‐ray scattering agree with those obtained from density, indicating a significant contribution of the partially ordered phase to the total diffraction. Emphasis is given on the need to account for the large differences in the crystallinities of poly(propylene) measured by different techniques when evaluating the dependence of properties on this quantity. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 323–334, 1999

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Section: Methodsmentioning

confidence: 99%

The degree of crystallinity of monoclinic isotactic poly(propylene)

Isasi

Mandelkern

Galante

et al. 1999

J. Polym. Sci. B Polym. Phys.

103

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“…Techniques . The chain structure was characterized by high-resolution 13 C NMR following assignments previously reported. − The concentration of stereo defects was calculated from the mmmr pentads as mmmr/2. The fractional content of 2,1 or 1,3 additions was computed from their respective assigned resonances. − The 13 C NMR spectra were obtained in polypropylenes free of atactic fraction to avoid complications in analyzing the spectra from overlapping peaks.…”

Section: Methodsmentioning

confidence: 99%

Structural and Kinetic Factors Governing the Formation of the γ Polymorph of Isotactic Polypropylene

Alamo¹,

Kim²,

Galante³

et al. 1999

Macromolecules

228

419

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The molecular, thermodynamic, and kinetic factors that govern the formation and concentration of the α and γ polymorphs in metallocene-catalyzed isotactic poly(propylenes) have been studied with a set of polymers that have a wide range in molecular weight and defect contents. With these polymers it was possible to investigate the influence of molecular weight on γ formation at a fixed defect concentration, as well as the role of the defect concentration at constant molecular weight. The major experimental techniques used were wide-angle X-ray scattering and differential scanning calorimetry complemented by microscopy. From these studies the role of chain microstructure, the crystallization temperature, and the thermodynamic and kinetic requirement for the formation of the γ form could be established in more quantitative detail than heretofore. A particular important finding was the fact that at fixed defect concentration the fractional content of the γ polymorph goes through a maximum with crystallization temperature. The results that were obtained establish a quantitative framework within which the underlying bases that lead to formation of the γ form, and its unique crystalline structure, are discussed.

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“…9,10 The concentrations of regio defects were calculated from the corresponding NMR peaks. [10][11][12] The stereo defects were determined from half of the fraction of mmmr pentads.…”

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confidence: 99%

“…The molecular weight distributions were obtained by standard GPC methods . The concentrations of stereo and regio defects were determined by high-resolution 13 C NMR. , The concentrations of regio defects were calculated from the corresponding NMR peaks. − The stereo defects were determined from half of the fraction of mmmr pentads.…”

mentioning

confidence: 99%