A B S T R A C T Ring-opening polymerization of PLGA-PEG diblock copolymers was studied using supercritical CO2 -SCCO2-. The results of the SCCO2 method were compared with a melting procedure using a three-necked flask. A pressure of 317 bar, temperature of 132 °C, and time of 14 h resulted in the maximum molecular weight -10,138 g/mol- and yield -88.15 w/w %-; these results were significantly higher than those for the melting method -Mw =6664.5 g/mol, yield=57.95 w/w %-. Furthermore, the reaction time for achieving maximum Mw and yield via SCCO2 -14 h- was lower than with the melting method -24 h-. The lactide-to-glycolide molar ratio and percent by weight of methoxy PEG matched well with the initial value when SCCO2 was used. The critical micelle concentration -CMC-, and particle size in SCCO2 were higher than with the melting method, as the molecular weight of SCCO2 obtained using was higher.

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