Study On Monodisperse PAM Microspheres And SiO₂/PAM Core/shell Composite Microspheres By Dispersion Polymerization

Monodisperse PAM microspheres and SiO₂/PAM core/shell composite microspheres composed of SiO₂ core and PAM shell were prepared by dispersion polymerization method respectively.Using PVP as the stabilizer and AIBN as the initiator, monodisperse PAM microspheres sized in submicron were prepared in ethyl acetate/ethanol medium by dispersion polymerization method. The influences of polymerization parameters, such as concentration of stabilizer, initiator, monomer and solvent composition, etc. on particle size and size distribution, the conversion efficiency and molecular weight were investigated. Both adsorption and graft stabilization mechanism were concurring in this system and the latter is dominant. The size distribution is narrow when the volume ratio of ethyl acetate and ethanol ranges from 5:5 to 7:3. Paticle size decreases with the increase of the concentrations of stabilizer and the decrease of the concentration of initiator, moreover, monodisperse microspheres cannot be obtained when the concentration of monomer is too high or too low. At early period of dispersion polymerization, auto-accelerate phenomenon was observed, and molecular weight gradually increased with the increase of conversion because of gel effect. Conversion efficiency increased as the concentrations of stabilizer, initiator and monomer increased. Molecular weight increased with the increase of the concentration of ethyl acetate, stabilizer and monomer increase, and the decrease of the concentrations of the initiator, but when the concentration of stabilizer is too high, the molecular weight decreased.SiCVPAM core/shell composite microspheres composed of SiO₂ core and PAM shell were prepared by dispersion polymerization successfully. Firstly, monodisperse SiO₂ particles were synthesized by the Sto|¨ber method, particle sizes increased from when the concentrations of TEOS and ammonia increased. Secondly, g-SiO₂ particles were obtained using coupling agent KH-570 to modify SiO₂ particles. The TEM show that the g-SiO₂ particles were still in monodisperse and the size of particles increased. Finally, the SiO₂ particles and g-SiO₂ particles were encapsulated by dispersion polymerization of AM, and then were investigated by TEM and IR. The results show that the core/shell structure were obtained using g-SiO₂ particles as core, The particle size of core/shell composite microspheres was about 163 nm and the layer of PAM encapsulation was about 30nm.