Vibrational spectroscopic studies of conformation of poly(oxyethylene). II. Conformation–spectrum correlations

Detailed normal-coordinate analysis has been carried out on a large number of conformers of model molecules of poly(oxyethylene); the model molecules treated are CH₃(OCH₂CH₂)_nOCH₃ with n = 2,3, and 6. The systematic treatment provides well-defined correlations between conformation and vibrational spectra of poly(oxyethylene). The vibrations in the region 1050–800 cm^?1, which are associated with the C? O and C? C stretching and CH₂ rocking modes, are highly dependent on the conformation of the polymer chain. On the basis of these correlations, the infrared and Raman spectra of the molten state and of the aqueous solution are interpreted in terms of the conformational states. The analysis indicates that the following conformational fragments are present in these phases: GT-TG (T: trans; G: gauche), TT-TG, GT-GG, TT-TT, and TT-GG for the CH₂? CH₂? O? CH₂? CH₂ group, and TGT and TGG for the O? CH₂? CH₂? O group. Conformational fragments GT-TG′ and GT-G′G′ are also possible in the analogy to GT-TG and GT-GG.