Key techniques to control porous microsphere morphology in S/O/W emulsion system

A solid-in-oil-in-water (S/O/W) emulsion system has been developed to prepare porous polymeric microspheres. The obtained microspheres showed unique core–shell structure with a dense core and a surface porous layer. The emulsion system has two processes. In the first process, S/O/W1 viscous emulsion is prepared by dropping of S/O phase in the first water phase (W1). In the second process, the S/O/W1 emulsion is poured to another water phase (W2) as S/O/W1/W2 emulsion. During the process, S/O/W1 droplet becomes microsphere after organic medium completely diffusion. Emulsion techniques have various effective combinations such as additive and process conditions to design microsphere morphology. With regards to the proposed S/O/W system, addition of the solid phase in the system is a key factor to form the porous structure. When the medium diffusion starts, the solid makes W1 phase kept inside the S/O/W1 droplet. The remained W1 phase changes surface porous layer after purification. Affinity between the solid and oil phase should be adjusted as well. In this study, an optimization of the emulsion system was attempted considering solubility parameter and polarity. Additionally, it is found that process conditions could help to design microsphere morphology such as pore size and porous layer thickness.

Figure optionsDownload as PowerPoint slideResearch highlights▶ Affinities among solid, polymer, and organic phases control microsphere morphology. ▶ Optimum stirring time promotes the formation of porous layer. ▶ Fast stirring rate takes much amount of W1 phase and gives large sized pores.