Morphology dependent anomalous frequency shifts of infrared absorption bands of polymer crystals: Interpretation in terms of transition dipole–dipole coupling theory

摘要: For such crystalline linear polymers as trigonal poly(oxymethylene) (t‐POM), orthorhombic (o‐POM), and poly(ethylene oxide) (PEO), it has been found that the infrared bands polarized parallel to chain axis exhibit anomalously large high‐frequency shifts crystal morphology of sample goes from extended‐chain (ECC) folded‐chain (FCC). The common features remarkable spectral change were investigated systematically summarized follows: (1) anomalous bandshifts observed only for infrared‐active bands, (2) magnitude shift was proportional oscillator strength band, (3) overtones corresponding fundamental did not show a shift, (4) appearance in FCC ascribed folded molecular structure, but lamellar‐type morphology. morphology‐dependent interpreted quantitatively terms transition dipole–dipole coupling theory. By integrating interacting energy over cylindrical having various radius/height ratios, demonstrated due dipole interaction vanished idealized ECC became maximum infinitely thin lamellar crystal. magnitudes between two extreme cases calculated on basis absolute values strengths measured highly samples t‐POM, o‐POM PEO their structures. results agreed well with band gaps samples. absorption profiles simulated. result reproduced change.