Abstract

Raman spectroscopy is used to investigate the α- and β-crystalline polymorphs of isotactic polypropylene. Raman spectra of the polymorphs show some minor differences, in particular the wavenumber shifting of certain scattering bands, which reflect the environment of an isolated macromolecular chain within the packing unit cell of the different crystal forms. For example, the shifting of the 842 cm^–1 scattering band, which is the most susceptible band to cause intermolecular interactions, is used to generate a structural map of one β-spherulite among α-spherulites with a well-defined resolution. Anisotropy of the crystalline phase orientation within a β-spherulite is also investigated by performing polarized Raman spectroscopy measurements. Differences in the polarized spectra are then finely exploited to map the radial lamellae orientation distribution within one β-spherulite.

Laser-Excited Raman Scattering by Isotactic Polypropylene

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