Polyglycolic acid copolymers from one‐step cationic polymerization of formaldehyde, carbon monoxide, and epoxides derived from PEG

Abstract

Biodegradable polyglycolic acid (PGA) is conventionally produced via the ring‐opening polymerization of glycolide, the cyclic dimer form of glycolic acid, in the presence of mostly tin‐based catalyst initiators which are rather known to be cytotoxic materials. Our previous studies revealed an alternative method for the synthesis of PGA from the perfectly alternating copolymerization of formaldehyde (from trioxane) and carbon monoxide (CO) under BrØnsted acidic conditions. The poor physical properties of PGA (insolubility in many organic solvents, brown color, etc.) limit its use in other marketing applications in the industry. To improve on the physical properties of PGA, such as solubility and appearance, copolymerization of trioxane, CO, and a minor amount of epoxides derived from polyethylene glycol (PEG) were performed under the same reaction conditions for PGA synthesis (in DCM, at 800 psi CO pressure, with triflic acid catalyst, reaction duration of 72 hours). The results have shown that the addition of minor quantities of epoxide comonomers vastly improves the appearance of the obtained PGA copolymers and allows for the control of the polymeric properties, such as solubility and melting temperature.

One‐Step Solvent‐Free Synthesis of Polyglycolic Acid from Sustainable C1 Feedstocks

“…[ 24 ] Incorporation of HDO in PGA backbone likely occurs through attack of an intermediate acylium ion by the HDO followed by a ring opening of the resultant cyclic oxonium ion ( Figure ). Previously, terpolymerization of formaldehyde, CO and epoxides to form PGA based poly(ester‐ether) was accomplished in DCM solvent at 110 °C in 72 h. [ 24–26 ] We now prove that terpolymerization using epoxides with trioxane and CO can be achieved even in solvent‐free conditions. Synthesized PGA from formaldehyde and CO (Table 1, entry 8) had brown color, whereas colors of the obtained poly(ester‐ether)s from Table 3 were light brown to off‐white.…”