Synthesis of poly(ethylene adipate) and poly(ethylene adipate-co-terephthalate) via ring-opening polymerization

Syntheses of poly(ethylene adipate) (ROP-PEA) and poly(ethylene adipate-co-terephthalate) (ROP-PEA-co-PET) were achieved via ring-opening polymerization of corresponding cyclic oligoesters. In case of ROP-PEA, cyclic oligo(ethylene adipate) (C-OEA) was equilibrated in the presence of di-n-butyltin oxide as a catalyst under high-concentration conditions at 180 and 200 °C for 1-24 h. The polymer products were obtained in yields up to 100% with the and in the ranges of 3000-23 000 g/mol and 5000-60 000 g/mol, respectively. The ROP-PEA-co-PET was prepared by equilibrating an equimolar amount of C-OEA and cyclic oligo(ethylene terephthalate) (C-OET) using di-n-butyltin oxide catalyst under high-concentration conditions at 250 °C for 24 h. The copolyester produced was obtained in yield of 97% with the and of 18 000 and 46 000 g/mol, respectively. ¹H NMR spectrum of ROP-PEA-co-PET showed two new proton signals of ethylene unit representing the existence of heterolinkage with different chemical environment in the copolymer. This indicated the random transesterification of C-OEA and C-OET resulting in random structure in copolyester. In addition, the result of ROP-PEA-co-PET from DSC showed the glass transition temperature in the values of −8 °C with no melting temperature indicating thermoplastic elastomeric behavior.