FTIR Imaging of Poly(3‐hydroxybutyrate) and Isotactic Poly(propylene oxide) Spherulites

Abstract

FTIR spectroscopic imaging is combined with linear dichroism measurements to investigate the structures of spherulites of poly(3‐hydroxybutyrate) and isotactic poly(propylene oxide). It is shown that this technique can be used to easily gain qualitative information about relative orientations of chemical bonds within a solid polymeric sample. Furthermore the imaging technique is shown to have the considerable advantage that the obtained images are easy to understand and easy to interpret even without deep knowledge of FTIR linear dichroism measurements.magnified image

Wavenumber Dependence of FT-IR Image of Molecular Orientation in Banded Spherulites of Poly(3-hydroxybutyrate) and Poly(l-lactic acid)

“…The periodic ring-band pattern of optical anisotropy in a polymeric spherulite is generally attributed to a concerted twisting of crystallographic orientation about the lamella growth direction. − The banded spherulite originating from the rhythmic crystal growth was also reported . Ring-banded spherulites are observed in some semicrystalline polymers, such as poly(ethylene) (PE), − poly(ε-caprolactone) (PCL), poly(trimethylene terephthalate) (PTT), − poly(butylene adipate) (PBA), , poly(ethylene adipate) (PEA), poly( l -lactic acid) (PLLA), − poly(3-hydroxybutyrate) (PHB), − and poly(3-hydroxyvalerate) (PHV). , Some polymer blends and copolymers also formulate the banded spherulites. ,,,− The crystallization temperature affects the appearance and pattern of band structures of some polymeric spherulites. ,,− ,,− Band spacing in polymeric spherulites has been reported as various values, from less than 1 to almost 100 μm, and tends to become larger under higher crystallization temperature. ,, Toda et al were experimentally examined the effect of gradient field of temperature on the structural evolution of polymer crystallization and revealed that the temperature gradient enlarge the band spacing due to wider lamellar width . The morphology and structure of banded spherulite were investigated with various measurements, for example, atomic force microscope (AFM), ,,,,,,,,, near-field scanning optical microscope (NSOM), electronic microscope (EM), ,,,,…”

“…72,73 Recently, the application of the FT-IR imaging method to polymer spherulite has increased. 26,[69][70][71]74 However, the quantitative analysis of band structure in polymeric spherulite using FT-IR imaging is seldom reported. We proposed the "four polarizations method" to visualize the magnitude of molecular chain orientation and the azimuth angle of the orientation axis independent of the polarizer angle using the FT-IR imaging method.…”

“…Assignment and Classification by Band Structure of Spherulite of Absorption Peaks of Infrared Spectrum of PHB26,[43][44][45]48 …”

Distribution of Polymorphic Crystals in the Ring-Banded Spherulites of Poly(butylene adipate) Studied Using High-Resolution Raman Imaging

“…Chemical imaging techniques, which combine macro morphology with micro molecular information, should be a powerful tool for this purpose. In recent years, chemical imaging techniques have been utilized more in research about polymer science and engineering, − and Fourier transform infrared spectroscopic (FTIR) imaging is used in the majority of these studies since it can be easily proceed. However, FTIR imaging is not always suitable for studies on ring-banded spherulites.…”

Imaging of Two-Dimensional Distribution of Molecular Orientation in Poly(ethylene oxide) Spherulite Using IR Spectrum and Birefringence

“…The imaging method is suited to analyze the morphology in polymer spherulite, having various kinds of lamellae orientations with different chemical structures and crystallization conditions. The Fourier transform infrared spectroscopic (FT-IR) imaging method has achieved the two-dimensional chemical imaging that has been applied to various systems. − Recently, the Hermans orientation function , has been visualized using FT-IR imaging that gives the degree of molecular chain orientation and chemical information at once. − Hikima et al proposed the method to visualize the magnitude of molecular chain orientation and the azimuth angle of the orientation axis independent of the polarizer angle. The FT-IR imaging method has been applied to the analysis of polymer spherulite with chemical imaging; − ,− however, the quantitative analysis of molecular chain orientation is still to be discussed.…”