Infra-red spectra of polyethylene glycols and O-deuterated derivatives

Abstract

Infra-red spectra of ethylene through heptaethylene glycols in the liquid and crystalline states, and their O-deuterated derivatives in the liquid state have been measured in the region 4000–400 cm −1. Vibrations of the chain part and those of the terminal group are discerned and the nature of the observed bands is discussed with reference to the results of the normal co-ordinate treatments of ethylene glycol, its O-deuterated derivative, polyethylene glycol of infinite helical chain, and p-dioxane. Spectral changes depending upon the chain length provide informations about the chain conformation in both states. In the liquid state the molecular chain is randornly coiled, while in the crystalline state the chain takes the regularly ordered form. The low melting point of polyethylene glycol may be attributed partially to the random coil conformation in the liquid state.