SYNTHETIC PROCESS TO CONTROL THE TOTAL SIZE AND COMPONENT DISTRIBUTION OF MULTILAYER MAGNETIC COMPOSITE-PARTICLES

A new synthetic process to prepare composite particles with multilayers, comprised of usual polymer latices, ultra-fine magnetic particles, and a polystyrene layer was examined under various solution conditions. First, the synthetic conditions of heterocoagulates, consisted of polystyrene latices (2a = 180 approximately 900 nm) and NiO . ZnO . Fe2O3 particles (2a = 20 nm), were investigated as a function of medium pH, particle concentration, and particle size ratio, based on the concept of the heterocoagulation theory as applied by Harding et al. Regular heterocoagulates were generated under suitable medium and mixing conditions, and that their total size,can be controlled by selecting the size of the original polymer latices used as the core. Second, the best encapsulation condition of the heterocoagulates via emulsion polymerization with polystyrene monomer was surveyed. The encapsulation of the heterocoagulates was greatly promoted by pretreatment with oleate molecules, although there is no tendency for the encapsulation when the surfactant-free bare heterocoagulates are used as the core.