title: Sub-micrometer-sized biodegradable particles of poly(L-lactic acid) via the gas antisolvent spray precipitation process.
abstract: Sub-micrometer-sized particles of poly(L-lactic acid) may be formed by using near-critical or supercritical carbon dioxide as an antisolvent to precipitate poly(L-lactic acid) from droplets of methylene chloride solution sprayed into a carbon dioxide continuous phase. Particle sizes may be controlled by varying the density of the carbon dioxide; at constant temperature in the supercritical region, higher carbon dioxide densities yield larger particles. Two methods (one batch and one continuous) for introducing the poly(L-lactic acid) solutions into carbon dioxide are demonstrated. Although the two methods use very different mechanisms for forming the droplets, similar particle sizes are observed as a function of carbon dioxide density. We suggest that mass transport, rather than jet breakup and hydrodynamics, controls particle sizes in the near-critical and supercritical regions.
authors.affiliation: Department of Chemical Engineering, Yale University, New Haven, Connecticut 06520.
authors.forename: T W
authors.initials: TW
authors.lastname: Randolph
authors.forename: A D
authors.initials: AD
authors.lastname: Randolph
authors.forename: M
authors.initials: M
authors.lastname: Mebes
authors.forename: S
authors.initials: S
authors.lastname: Yeung
mesh_terms: D001673:Biodegradation, Environmental; D002245:Carbon Dioxide; D011232:Chemical Precipitation; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D003692:Delayed-Action Preparations; D007700:Kinetics; D007773:Lactates / Q000138:chemical synthesis*; D019344:Lactic Acid; D010316:Particle Size; D011091:Polyesters; D011108:Polymers / Q000138:chemical synthesis*; D011312:Pressure; D012997:Solvents; D013696:Temperature
chemical_list: D003692:Delayed-Action Preparations; D007773:Lactates; D011091:Polyesters; D011108:Polymers; D012997:Solvents; D002245:Carbon Dioxide; D019344:Lactic Acid; C033616:poly(lactide)