Spherical assembled microstructures: fabrication and their stabilization with assistance of supercritical carbon dioxide

Abstract

Spherical microstructures with core–shell features were assembled and stabilized by welding them in supercritical carbon dioxide (SC CO2). Hollow poly(styrene-co-divinylbenzene) (PS-co-DVB) capsules and polystyrene (PS) particles were used as building blocks and supporting cores, respectively. By adjusting the diameters of the PS “core”, the microstructure sizes can be adjusted simply from 2 to 19 μm. In addition, PS cores were selectively plastified to make the “satellite” capsule weld and even embed on their surface with the assistance of SC CO2. By varying a series of pressure (12 to 16 MPa), exposure time (2 to 6 h), and temperature (40, 50 °C) conditions, the welding or coalescence degrees of these PS-co-DVB capsules and PS cores were finely tuned. This is the first time that SC CO2 has been successfully applied to stabilize the spherical assembled microstructure.