Infrared Spectroscopy in the Analysis of Polymer Crystallinity

Abstract

Abstract This article provides a comprehensive review of the application of infrared (IR) spectroscopy in the analysis of polymer crystallinity. A brief description of the theory behind the analysis of orientation in polymers using IR spectroscopy is followed by a comparison of various sampling methods for Fourier transform infrared spectroscopy. These include transmission, attenuated total reflectance (ATR), external reflection, diffuse reflectance, photoacoustic, and emission spectroscopic techniques. Various modes of measurement such as polarized IR measurements, deuteration, and rheo‐optical measurements to obtain more information from IR spectra and make the interpretation of spectra easier, as well as new techniques to combine imaging and IR spectroscopy and real‐time measurements during processing are also discussed. The use of IR spectroscopy in analyzing both semicrystalline polymers as well as liquid crystalline polymers is presented. In the case of semicrystalline polymers, applications involve measuring phase transformations, chain conformation/packing, degree of crystallinity, crystallization kinetics, isomer ratios, and chain alignment during mechanical treatment. In the case of liquid crystalline polymers, IR spectroscopy has been used to analyze molecular orientation, segmental mobility, photo‐induced reorientation, and phase characterization/transformations. A comparison of IR measurements with other techniques used to analyze crystallinity in polymers such as X‐ray diffraction (XRD), differential scanning calorimetry (DSC), nuclear magnetic resonance spectroscopy (NMR), Raman spectroscopy, and neutron scattering has been presented.