Normal Vibrations of the Polymer Molecules of Helical Conformation. IV. Polyethylene Oxide and Polyethylene-<i>d</i>4 Oxide

Abstract

Polarized infrared spectra of polyethylene oxide (PEO), —(CH2CH2O)n— and PEO-d4, —(CD2CD2O)n—, have been measured in the region from 4000 to 80 cm—1. The spectra of PEO at various temperatures (about —130°, 20°, 65°, and 80°C) were also observed, and splittings of some perpendicular bands were found at the low temperature. The selection rules for the PEO molecule are derived under the factor group D(4π/7). The normal vibrations of PEO and PEO-d4 are calculated for the Raman-active A1 symmetry species, the infrared-active A2 species, and the Raman- and infrared-active E1 species, by use of the GF matrix method with the Urey—Bradley force field taking into account the torsional displacement coordinates of the skeleton. The results show fairly good agreement between the observed and calculated frequencies, and give strong support to the 72 helix conformation proposed by the authors previously. The assignments of the bands are given and discussed.