Preparation of snowman-like poly(ionic liquid) microspheres by microwave-assisted seed emulsion polymerization

Non-spherical particles (e.g. snowman-like) have different properties from spherical particles due to morphology effect and show great potential for applications in optics, magnetism, rheology, etc. In this paper, snowman-like poly(ionic liquid) microspheres are prepared by microwave-assisted seed emulsion polymerization. First, the cross-linked poly(ionic liquid) seed microspheres are prepared by post-drop addition method. Then, the seed microspheres are swollen by ionic liquid monomer to form a snowman shape. Finally, the snowman-like poly(ionic liquid) microspheres are obtained by microwave polymerization. The preparation process are traced by optical microscope and the morphology of snowman-like poly(ionic liquid) microspheres are observed by scanning electron microscope. It shows that, different from the preparation of snowman-like neutral polymer microspheres, the snowman-like morphology has been formed during swelling of cross-linked poly(ionic liquid) seed microspheres. The microwave-assisted polymerization can produce snowman-like poly(ionic liquid) microspheres with more uniform morphology compared to conventional heating polymerization. The morphology of snowman-like poly(ionic liquid) microspheres can be adjusted by controlling the monomer/seed microsphere ratio, the size and cross-linking degree of cross-linked seed microspheres, and the concentration of monomer and seed microspheres.