Formation of well-defined spherical particles during suspension polymerization of biodegradable poly(glycolide-co-p-dioxanone) in supercritical carbon dioxide

Abstract

Biodegradable particles of poly(glycolide-co-p-dioxanone) (PGDO) were directly synthesized by suspension copolymerization of glycolide (GA) and p-dioxanone (PDO) in supercritical carbon dioxide (scCO₂) using stannous octoate as the ring-opening catalyst and a fluorocarbon polymer surfactant as a stabilizer. Fine powdered products were achieved when more than 60% (w/w) GA was fed. Interestingly, some spherical particles formed when the feed content of GA was intermediate (70–90%), while other compositions resulted in irregular particles. The particle size and degree of aggregation was also affected significantly by copolymer composition. The mechanism for three cases of particle formation were discussed, and the crystallization behavior within the polymerizing droplets played a critical role in determining the final morphology of particles. Well-defined particles with spherical morphology could be achieved if a delicate balance between the two opposing effects of crystallization and plasticization was reached inside the droplets. The possibility that spherical particles for biodegradable polyesters could be fabricated directly by suspension polymerization in scCO₂ implies the potential use of this clean technique in biomedical fields.