RAMAN ANALYSIS OF A CONFORMATIONAL DISTRIBUTION OF POLY(ETHYLENE OXIDE) AND ITS MODEL-COMPOUND IN THE LIQUID-STATE

Isotropic Raman spectra of poly(ethylene oxide) in aqueous solution an d in the melt show differences in the skeletal stretching vibration ba nds near 800 cm(-1) and in the disordered longitudinal acoustic mode f eature in the 200-400 cm(-1) region. These spectra may be simulated by superposing calculated spectra resulting from a series of normal coor dinate calculations performed for an Ensemble of conformers. The confo rmational distribution for poly(ethylene oxide) in the molten state ap pears to favor the tgg' conformer, which dominates the spectrum calcul ated to match closely the observed isotropic Raman spectrum. It appear s that the experimental data suggest that the tgg' conformation is pre sent by a greater amount than is predicted by previous simulation meth ods. On the same basis, it appears that the aqueous solution of poly(e thylene oxide) contains mostly tgt conformers. The results for poly(et hylene oxide) were supported by measurements and computations made usi ng 1,2-dimethoxyethane as a model.