Infrared spectra of high polymers Part IX. Polyethylene terephthalate.

Infrared spectra of polyethylene terephthalate and three of its deuterated analogs have been obtained in the region of 70 to 3600 cm-1, polarized spectra having been obtained down to 330 cm-1. On the basis of analysis of the predicted spectrum, and with the aid of data from benzene and substituted benzenes, a complete assignment of the spectrum has been made. This assignment suggests a modification of the proposed chain structure of this polymer. It also leads to the conclusion that the changes in the spectrum which occur upon crystallization of the polymer are not associated with different isomeric forms of the ---OCH2CH2O--- portion of the chain, but rather with changes in the symmetry and resonance characteristics of the substituted benzenoid ring frame-work.