Synthesis of polyglactin by melt/solid polycondensation of glycolic/L-lactic acids

Polyglactin was successfully synthesized by the melt/solid polycondensation of a mixture of glycolic acid (GA) and L‐lactic acid (LA) mostly at a GA to LA monomer ratio of 90/10. In the polymerization procedure, a solid polycondensate was first prepared by melt‐polycondensation at 150–190 °C, mechanically crushed into particles of various sizes (150–180, 180–210, 210–250, 250–300 and 300–355 µm), and subjected to solid‐state post‐polycondensation at 170 °C for 10–20 h. The polyglactin finally obtained was a colourless solid. Catalyst screening revealed that the single use of methanesulfonic acid gave the highest molecular weight of the product. Starting from the crushed melt‐polycondensate with a diameter range of 180–250 µm, the highest number‐average molecular weight of attained was 80 000 Da. This process can afford a facile route to large‐scale synthesis of polyglactin with high molecular weight. Copyright © 2004 Society of Chemical Industry