Relationship between sequence distribution and transesterification of PEN/PET random/block copolyesters

The random and block copolyesters of poly(ethylene 2,6 naphthalate) (PEN) a nd poly(ethylene terephthalate) (PET) are synthesized and studied by H-1-n. m.r., DSC, X-ray. The block length decreases and the degree of transesterif ication increases at a similar composition ratio. The melting point depress ions occur with increasing the content of the other component, and melting peaks disappear at a similar composition ratio. The results of X-ray diffra ctograms match well with those of dyads fraction, block length, and DSC. It can be seen that a critical block length is needed for components in order to crystallize. (C) 1998 Elsevier Science Ltd. All rights reserved.