Synthesis and Ring-Opening Polymerization of Poly(alkylene 2,6-naphthalenedicarboxylate) Cyclic Oligomers

Cyclic oligomers of poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) and poly(butylene 2,6-naphthalenedicarboxylate) (PBN) were prepared by reaction of 2,6-naphthalenedicarbonyl dichloride with the corresponding diol. The structures of the cyclic oligomers were confirmed by a combination of GPC, mass spectrometry, and NMR analysis. The PEN cyclics were obtained in 57% yield with a preponderance of the cyclic trimer. The PBN cyclics were obtained in 75% yield with a preponderance of the cyclic dimer. Ring-opening polymerization of either cyclic material was performed in the melt using either a tin or titanium catalyst. The inherent viscosity of PBN or PEN prepared via ring-opening polymerization was lower than that of commercial samples.