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.