Revealing formation process of microcapsules during in situ polymerization via confocal laser scanning fluorescence microscopy

Paraffin core/polystyrene shell microcapsules were prepared by in situ polymerization, the formation process of the microcapsules was monitored using confocal laser scanning fluorescence microscope (CLSM) and scanning electron microscopy (SEM). Three-dimensional images were reconstructed with CLSM, which presented the early stage morphology transformation process of the microcapsules along with polymerization as described below: firstly, the separated patch appeared on the equator of the emulsified droplets, next congregated to form a belt, and then changed into a bowl-like structure. SEM observation clearly revealed that the subsequent morphologies of the microcapsules turned into a shell with a hole, and finally, a complete filled shell was achieved. The conversion of styrene was studied by Fourier transform infrared spectroscopy. The formation process of microcapsules was proved to be formed by the two processes: chemical reaction-induced separation and physical migration. Furthermore the mechanics analysis was conducted on the intermediate states of core/shell particles. The results were consistent with the CLSM and SEM observation, which supply effective evidence for the mechanism of the microcapsule-forming process on the basis of particles rotation.