Dispersion polymerization of N-vinyl caprolactam in supercritical carbon dioxide

Dispersion polymerization of N-vinyl caprolactam (NVCL) was carried out in supercritical carbon dioxide (scCO₂) using three surfactants. The polymerization was performed in the presence of fluorine-based poly(heptadecafluorodecyl acrylate) (PHDFDA), poly(heptadecafluorodecyl methacrylate) (PHDFDMA) or siloxane-based PDMS-g-pyrrolidonecarboxylic acid (Monasil PCA) as a surfactant. FE-SEM and image analyzer were used to characterize particle morphology, size, and size distribution. When fluorine-based surfactants were used, spherical PVCL particles were obtained. Using Monasil PCA resulted in agglomerated and irregular polymer particles. The effect of concentration of surfactants, initiators, and monomer, and reaction pressure on the particle morphology, average particle size and particle size distribution (PSD) was also investigated with fluorine-based surfactant, PHDFDA or PHDFDMA.