Measurement of the Physical Characteristics of Polymers by Vibrational Spectroscopy

Abstract The usefulness of vibrational spectroscopy in the structural study of polymer materials has been revealed by reviewing various examples of phase transitions, crystallization, mechanical deformation, and so on. (1) The characteristic infrared (and Raman) bands are pointed out, which are sensitive to the regular chain conformation, the crystallinity, the chain packing mode in the crystal lattice, and the change in morphology or higher‐order structure. (2) The crystallization phenomenon is reviewed, which has been studied by the temperature‐ and/or time‐dependent measurements of infrared (Raman) spectra during the heating/cooling process or in the atmosphere of organic solvent vapor. (3) The microscopically‐viewed mechanical property of crystalline polymers has been discussed using the infrared and Raman data taken under the application of tensile force. (4) The observed frequency shift, which is due to the stress‐induced change in molecular geometry and force constant, is affected more or less by the difference in the morphology of the sample, from which the heterogeneous stress distribution in the sample is estimated on the basis of a complex mechanical model. (5) The simultaneous measurement of X‐ray diffraction and Raman spectra is outlined. The simultaneous measurement technique of viscoelastic modulus and infrared spectra under the control of humidity is also described.