Preparation of microcapsules containing ionic liquids with a new solvent extraction system

Ionic liquids have recently attracted much attention as newly developed green solvents, but their high viscosity greatly limits their application. Immobilizing these ionic liquids using microencapsulation may solve this problem. In this study, a new extraction system for preparing microcapsules was developed in which a mixture of poly(dimethylsiloxane) and n-butyl acetate was used as the continuous phase, and polyacrylonitrile and ionic liquids were dissolved in N,N-dimethylformamide for the dispersed phase. The emulsion was prepared using a microfluidic device. The solidification of droplets was realized by extracting N,N-dimethylformamide from the dispersed phase to the continuous phase. Three different ionic liquids, [BMIM][PF6], [BMIM][BF4] and [HMIM][BF4], were successfully encapsulated with the average diameter of the microcapsules in the range of 200-350 mu m. The properties of microcapsules - the surface structure, the loading ratio and the mean diameter - could be controlled by changing the operating conditions such as phase composition and the flow rate of two phases. (C) 2008 Elsevier Ltd. All rights reserved.