Polyglycolic acid (PGA) is an aliphatic biodegradable polyester commonly synthesized through the ring opening polymerization of glycolide using mostly tin (II) octoate catalyst. Previously, a very convenient method for the synthesis of PGA from the cationic alternating copolymerization of formaldehyde (from trioxane) and carbon monoxide (CO) with triflic acid (TfOH) catalyst in dichloromethane (DCM) at 170 °C is described with 92% of yield. The need of using harmful DCM solvent for this polymerization directs to discover solvent-free polymerization of formaldehyde and CO. Here, one-step solventfree synthesis of PGA from the cationic alternating copolymerization of formaldehyde and CO is presented. Unlike the polymerization carried out in DCM solvent, optimum polymerization in solvent-free conditions with TfOH catalyst is achieved in 80% of yield at 130 °C. It is considered that utilization of solvent-free conditions and lower reaction temperatures compared to the previous report provides a more green and economic way of the synthesis of PGA. The method is also extended to copolymerization strategy by adding a minor amount of an epoxide compound to the reaction mixture, and PGAbased copolymer with improved physical properties (such as solubility and appearance) is obtained in solvent-free conditions.
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