Preparation of medium- and high-molecular-weight poly(glycolic acid) by melt/solid-state polycondensation

Poly(glycolic acid) (PGA) is usually prepared by ring-opening polymerization of glycolide and melt polycondensation of glycolic acid. However, the ring-opening polymerization process of glycolide is complicated, resulting in the high cost of PGA. In contrast, the preparation of PGA by melt polycondensation of glycolic acid has simple process and low cost, but it is difficult to obtain the medium- and high-molecular-weight PGA. In this work, the effects of polymerization process conditions such as catalyst type and content, esterification temperature and solid-state polycondensation temperature on the appearance, intrinsic viscosity and thermal stability of PGA were systematically studied in the melt/solid-state polycondensation route. It is found that bismuth trifluoromethanesulfonate had good catalytic effect on the melt polycondensation of glycolic acid. The optimal melt/ solid-state polycondensation conditions were as follows: the catalyst content of 0.20%(mass), the esterification temperature of 180℃, the melt polycondensation and solid-state polycondensation temperatures of 210℃, and the solid-state polycondensation time of 12 h. Under such optimal melt polycondensation conditions, the highest intrinsic viscosity of PGA was 0.36 dl/g. The intrinsic viscosity of PGA can be increased to 0.59 dl/g by further solid-state polycondensation. © 2023 Chemical Industry Press. All rights reserved.