Broadband terahertz spectroscopy of polypropylenes with different tacticities

We apply Fourier transform terahertz spectroscopy to an investigation of polypropylenes (PPs) with different tacticities. Terahertz (THz) absorption spectra were measured for isotactic, syndiotactic, and atactic samples over a frequency range of 1–11 THz. A clear difference in the spectra of the isotactic and syndiotactic PPs was observed, while that of the atactic PP did not display any clear characteristic absorption peaks. The spectral differences are thought to originate from not only the primary structure but also intermolecular vibrations of the well-packed PP-chains in the crystal structure. Broadband THz spectroscopy offers a nondestructive, noninvasive inspection technique for general-purpose plastics.