Imaging of Semicrystalline Polymers and Polymer Blends by FT-IR Microspectroscopy

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Abstract
It has been demonstrated that Fourier transform infrared (FT-IR) microspectroscopy can be used to study different types of spherulites of poly(vinylidene fluoride) formed by different crystal modifications. Because of selective IR bands of the α and the γ modification, respectively, it is possible to map the crystalline morphology by FT-IR microspectroscopy. Thus the different types of spherulites can be assigned unambiguously to different crystal modifications. It is also possible to map the morphology of phase-separated blends of isotactic polypropylene and syndiotactic polypropylene. There are selective IR bands in the crystalline state as well as in the melt. This characteristic allows for observation of the phase morphology of blends containing isotactic and syndiotactic polypropylene directly in the melt even though the blends appear completely transparent in the light microscope. This capability demonstrates the advantage of FT-IR microspectroscopy compared to light microscopy, which is restricted to samples with differences in the refractive index, which is not given for blends of isotactic and syndiotactic polypropylene above the melting point.