Synthesis of polyester by means of polycondensation of diol ester and dicarboxylic acid ester through ester–ester exchange reaction

AbstractBased on our finding that the ester‐ester exchange reaction between butyl benzoate and ethyl 4‐phenylbenzoate in the presence of a metal alkoxide is faster than the ester‐alcohol exchange reaction of butyl benzoate and ethanol, we investigated the synthesis of polyester through ester‐ester exchange reaction under various conditions. The polycondensation of diol formate and methyl dicarboxylate in the presence of a catalytic amount of potassium tert‐butoxide (tBuOK) in diglyme at 120 °C under reduced pressure (90–100 Torr) afforded high‐molecular‐weight polyesters. Methyl dicarboxylate containing an amino group could be used for this polycondensation, although the corresponding diacid chloride containing an amino group was not isolable. The ester‐ester exchange reaction could proceed even at the polyester backbone, and the reaction of poly(1,12‐dodecamethylene isophthalate) (PEs1) with poly(ε‐caprolactone) (PCL) in the presence of tBuOK at 140 °C afforded a copolymer PEs1‐stat‐PCL, the structure of which was confirmed by 13C NMR spectroscopy and DSC thermal analysis. A similar copolymer was also obtained by the polycondensation of dodecane‐1,12‐diol formate and dimethyl isophthalate in the presence of PCL and tBuOK at 120 °C under reduced pressure.