Spectrometric investigation on the thermooxidative degradation of ethylene oxide and tetra-hydrofuran co-polyether

The thermooxidative degradtion of ethylene oxide and tetra-hydroftiran (EO-THF) co-polyether has been studied by electron spin resonance (ESR), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The initial degradation site was found to be at the α-carbon of the ether bond. Two free radicals which derived from dehydrogenation and oxygen addition were successfully detected by spin-trapping technique which used α-phenyl-N-tert-butyl nitrone (PBN) as spin trap. Both FT-IR and NMR have been used to follow structural changes of the copolyether during degradation. Nearly 20 product fragments including formate, carbonate, methyl, alcohol, methylene-dioxy, hydroperoxide and semiformal have been characterized by ¹D and ²D NMR. The thermooxidtion of co-polyether preferred to occur on the THF units especially at the alternating linkage of EO and THF. Antioxidant (BHT) not only retarded the thermooxidation but also modified the degradation products with less ester and methylene-dioxy groups but more hydroxyl and methyl groups.