Abstract: The series of ethylene terephthalate-ethylene oxide segmented copolymers withdifferent long soft segments and different hard segment contents have been synthesized.Thehard segment contents are measured by ¹H NMR.Four PET-PEOsegmented copolymerswere separated into soluble and insoluble parts in chloroform.The results have revealed avery evident compositional heterogeneity in these four samples,which depends on the molec-ular weight of soft segment and hard segment content.Simultaneously the melting and ther-mal spectra of the four PET-PEOsegmented copolymers were obtained by DSC.The solubleand insoluble parts have shown the quite different crystallizability both for soft and hard seg-ments, which has the good correspondence with the compositional heterogeneity.

Key words: Ethylene terephthalate-ethylene oxide segmented copolymer, Compositional heterogeneity, Crystallizability