Structural studies on polyethers, [‐(CH₂)_m‐O‐]_n. II. Molecular structure of polyethylene oxide

TLDR

The molecular structure of polyethylene oxide (PEO) was investigated using X‑ray diffraction and infrared absorption spectroscopy. The authors performed X‑ray diffraction on highly oriented PEO samples analyzed with a Fourier‑transform helix method, synthesized fully deuterated PEO to record polarized infrared spectra, and carried out factor‑group and normal‑coordinate analyses. The crystalline PEO adopts a helical structure comprising seven chemical units and two turns per 19.3 Å repeat, with internal rotation angles τ(OCCO)=64°58′ and τ(CCOC)=188°15′, corresponding to a sequence of nearly trans‑trans‑gauche conformations.

Abstract

Abstract The molecular structure of polyethylene oxide (PEO), (—CH 2 CH 2 O‐) n , was studied by the X‐ray diffraction and infrared absorption spectroscopic methods. The X‐ray diffraction data were observed for the highly oriented PEO samples and were analyzed by use of the method of FOURIER transform of the helix proposed by COCHRAN et al. Fully deuterated PEO was synthesized, and the polarized infrared spectra of PEO and PEO‐d 4 were measured in the 4000–80 cm −1 region. The factor group analysis and the normal coordinate treatments were carried out. From the results of these studies, it was concluded as follows. The PEO molecule in the crystalline state has a helical structure which contains seven chemical units and two turns in the fiber identity period 19.3 Å. The internal rotation angles of this molecule are τ(OCCO) = 64°58′ and τ(CCOC) = 188°15′, and this corresponds to the succession of nearly trans, trans , and gauche conformations.