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Methoxy poly(ethylene glycol)-b-poly(L-lactide) (MPEG-PLLA) diblock copolymer was synthesized via ring-opening polymerization, and MPEG-PLLA microparticles were then prepared using an aerosol solvent extraction system (ASES) technique with compressed carbon dioxide as antisolvent. The MPEG-PLLA microparticles were prepared at temperatures ranging from 25 o C to 55 o C and at pressures from 85 bar to 150 bar. The concentration of MPEG-PLLA copolymer, solution flow rate, and CO 2 flow rate were adjusted to be 0.5-3.0% (w/v), 0.3-1.0 mL/min, and 19 g/min, respectively. Relatively small spherical microparticles were prepared in the subcritical region at 25 o C, while agglomerated particles were obtained at temperatures above the critical point. The mean particle sizes of the MPEG-PLLA microparticles prepared by the ASES varied from 9.53 µm to 46.9 µm depending upon the operating conditions.

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