Glycolide is used to synthesize polyglycolic acid

which is highly demanded due to the promising mechanical property

biocompatibility and especially biodegradability for sustainable developement. The synthesis of polyglycolic acid is therefore significantly affected by the glycolide. Glycolide is generally prepared from glycolic acid (ester). However

the polycondensation of glycolic acid (ester) requires high energy consumption including vacuum and high temperature. Herein

we report a azeotropic polycondensationdepolymerization method for the synthesis of glycolide

enabling the polycondensation of glycolic acid into polyglycolic acid oligomers under mild conditions with recoverable solvent and no catalyst

which are subsequently depolymerized into glycolide finally. Polyglycolic acid oligomers was comprehensively characterized as a kind of semi-crystalline polymers with the number average molecular weight of 1900 g/mol and the crystallinity of 33.1% by X-ray powder diffraction

Fourier transform infrared spectroscopy

differential scanning calorimetry and other methods. The glycolide product is obtained from the depolymerization polyglycolic acid oligomers with a yield of 81.26% and a purity of 89.29%. Furthermore

the depolymerization reaction residues of polyglycolide acid oligomers can be reused to produce more glycolide. Our method provides a green way for the production of glycolide and polyglycolic acid oligomers

and should contribute to the sustainable development and energy-saving of polyglycolic acid in the areas of material

industry and environment