Preparation and polymerization of ethylene 2,6-naphthalenedicarboxylate cyclic oligomers

Ethylene 2,6-naphthalenedicarboxylate cyclic oligomers (ENCs) were prepared by the ring/ chain equilibration (cyclodepolymerization) of poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) in dilute solution of biphenyl and poly merized with antimony trioxide. ENCs thus prepared consisted of a distribut ion of oligomeric species displaying a broad melting range from 330 to 370 degrees C. ENC trimer (C-a) was recrystallized from ENCs solution in 1,4-di oxane, and its purity was assessed by the matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF) mass spectrometric analysis. C-3 is t he main component in ENCs, and its melting temperature is 370 degrees C. EN Cs containing the diethylene glycol (DEG) unit were detected in the high-pr essure liquid chromatography and MALDI-TOF analysis. ENCs and ENCs/ethylene terephthalate cyclic oligomers (ETCs) blends were polymerized with 0.5 mol %. antimony trioxide at temperatures ranging from 320 to 365 degrees C for 5 min under a nitrogen atmosphere. The highest molecular weight (MW) (IV = 0.41 dL/g) was obtained from the polymerization of ENCs at 355 degrees C f or 5 min. In the case of ENCs/ETCs blends, although the polymerization temp eratures were decreased by adding ETCs, high MW polyesters were not obtaine d due to polymerization temperatures that nevertheless were still too high. PEN polymerized from ENCs showed the same thermal behaviors as the commerc ial product. Consequently, it was found that antimony trioxide is an effect ive catalyst for ENCs polymerization. but the melting and polymerization te mperatures of ENCs need to be decreased to obtain PEN of higher MW.