Synthesis of telechelic polyesters by means of transesterification of an A + B polycondensation-derived cyclic polyester with a functionalized diester

End-functionalized linear polyesters (LPEs) were synthesized by means of base-catalyzed transesterification of a cyclic polyester (CPEs), obtained by A 2 + B 2 polycondensation, with a symmetric functional diester as an exchange reagent (ExR). Among the metal alkoxides examined, t BuOK was the most effective for transesterification of cyclic poly(dodecamethylene isophthalate) ( CPEs-1 ) with dodecamethylene bis(4-bromobenzoate) (ExR- 1 ) at room temperature, affording LPEs with bromophenyl ends ( LPEs-1 -BrPh). However, CPEs-1 in the lower-molecular-weight region remained even after 95 h. Examination of the time course of the transesterification of CPEs-1 with ExR- 1 and the reaction of LPEs with t BuOK revealed that the transesterification reached equilibrium between LPEs and CPEs within 1 min, and that the remaining CPEs-1 in the lower-molecular-weight region represented not the starting materials but the equilibrium products. Accordingly, the transesterification was carried out at a higher concentration to obtain LPEs-1 -BrPh selectively, while the formation of CPEs was suppressed. End-functionalized linear polyesters were synthesized by means of base-catalyzed transesterification of a cyclic polyester, obtained by A 2 + B 2 polycondensation, with a symmetric functional diester as an exchange reagent.