A survey on surface morphology control of cross-linked poly(N-vinylpyrrolidone) polymer particle via inverse suspension polymerization

This study mainly centers on the preparation and characterization of the cross-linked poly(NVP) microspheres by means of inverse suspension polymerization technique. The effect of the cross-linker content, the volumetric ratio of dispersed phase to suspension phase (DP/CP), agitation rate, and the reaction temperature on the characteristics of the microparticles were investigated meticulously using SEM, and the optimum preparation conditions were determined. The findings revealed that the morphological and surface properties of the obtained particles could be controlled easily by changing these parameters. Accordingly, the microparticles having the perfect spherical with smooth surface and good roundness, dumbbell-shaped, snowman besides dented, sunked and macelike appearance were obtained. At low cross-linker content, bulky, distorted and accumulated particles were detected, while more stable, well-defined, and desired microspheres were observed at high content. Furthermore, as DP/CP decreased, the microspheres tended to have collapsed, distorted and little wrinkled (buckled) and indented morphologies due to the heterogeneous shrinkages in droplets. Additionally, it was apparent that the increment in stirring rates caused systematically decrement in the size of the microspheres. At relatively higher reaction temperature, the mace-like microparticles having needle-like occurrences extending outwardly perpendicular on the surface started to appear due to the stiff character of the cross-linker.