Size Control of Hollow Polylactic Acid Microcapsules and Hollow Polyelectrolyte Microcapsules in Bubble Template Method

Biodegradable hollow poly-lactic acid (PLA) microcapsules and hollow polyelectrolyte microcapsules made of poly-allylamine hydrochloride (PAH) were synthesized by directly adsorbing these polymers to N₂ (air) and CO₂ microbubbles respectively, using the bubble template method. To manufacture PLA microcapsules, droplets of a solution of PLA in methylene chloride (CH₂Cl₂) were emulsified in water. Then by solvent diffusion, N₂ microbubbles nucleated inside the droplets and PLA adsorbed to the bubble surface to form microcapsules. Likewise, for PAH microcapsules, when an aqueous solution of Na₂CO₃ including PAH is titrated with HCl, within a specific range 7.5 < pH < 9.0, colloidal PAH particles are formed and then adsorbs to the nucleated CO₂ microbubbles. This yields to hollow PAH microcapsules. If the solution pH is outside this range, colloidal particles can no longer exist, thus no microcapsules can be synthesized. This document mainly focuses on size control of these two types of microcapsules.