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

Based 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 ((BuOK)-Bu-t) in diglyme at 120 degrees 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(epsilon-caprolactone) (PCL) in the presence of (BuOK)-Bu-t at 140 degrees C afforded a copolymer PEs1-stat-PCL, the structure of which was confirmed by C-13 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 (BuOK)-Bu-t at 120 degrees C under reduced pressure.

Automated summary

The ester-ester exchange reaction proved to be faster than the ester-alcohol exchange reaction, leading to the successful synthesis of high-molecular-weight polyesters under various conditions. The copolymerization of different compounds through ester-ester exchange also resulted in the formation of new copolymers with confirmation from C-13 NMR spectroscopy and DSC thermal analysis.