Polyester polyols: Synthesis and characterization of diethylene glycol terephthalate oligomers

The composition of polyester polyols derived from terephthalic acid (TPA) and diethylene glycol (DEG) was examined. The synthesis of individual oligomers 1,n is described. The compounds were characterized with 1H and 13C NMR, mass spectrometry, and elemental analyses. The resonance signals arising from aromatic protons in 1,n = 1–3 were identified in 1H NMR spectra of TPA‐DEG condensates. From 1H NMR studies and chromatographic separation, it was concluded that the condensation of TPA and DEG in a 1:2 molar ratio results in a mixture of linear oligomers 1 with the average ñ varying from 1.1 to 2.2, and containing about 2% of cyclic oligomer 2.