Porous microcapsule formation with microsieve emulsification

A simple route is presented to prepare core–shell Eudragit microcapsules through a solvent extraction method with the use of microsieve emulsification. Droplets from a solution of Eudragit FS 30D (a commercial copolymer of poly(methyl acrylate-co-methyl methacrylate-co-methacrylic acid) 7:3:1) and hexadecane in dichloromethane are dispersed into water, using a micro-engineered membrane with well-defined pores, in a cross-flow setting. The dichloromethane is extracted from the droplets, which induces demixing in the droplets, leading to a hexadecane-rich core, and an Eudragit-rich shell. The obtained microcapsules have a narrow size distribution due to the microsieve emulsification process. The capsules have a porous shell as shown by SEM and AFM measurements. Their porosity and pore size is dependent on the ratios of Eudragit and hexadecane in the dispersed phase. At pH 7.1 and above Eudragit (FS 30D) dissolves in water; this pH change is used to release the contents of the microcapsule.

Porous Eudragit microcapsule prepared from 3% polymer and 15% hexadecane in DCM by cross-flow microsieve emulsification.Figure optionsDownload high-quality image (70 K)Download as PowerPoint slideResearch highlights
► Microcapsules with a hydrophilic polymeric shell and a hexadecane core were made.
► Microsieve emulsification controls size and size distribution of microcapsules.
► The polymeric shell is stable below pH 7, but dissolves rapidly at alkaline pH.
► The microcapsules were characterized with several optical, SEM and AFM techniques.