PREPARATION AND MAGNETIC-PROPERTIES OF [P(ST-CO-AA)]NI MICROSPHERES

Seeded emulsifier-free emulsion polymerization was used to prepare pol y(- styrene-co-acrylic acid) [P(St-co-AA)] microspheres. There are car boxyl groups on the surface of the P(St-co-AA) microspheres. Under app ropriate conditions, the carboxyl react with NiCl2, etc., to form magn etic [P(St-co-AA)]Ni microspheres which exhibit ferromagnetic properti es. ESCA analysis shows that the valence of nickel on the surface of t he magnetic [P(St-co-AA)]Ni microspheres is 2. IR analysis confirmed t hat there are carboxylate groups present in the magnetic [P(St-co-AA)] Ni microspheres. Magnetic properties of this kind of polymer microsphe res were studied. Results showed that the magnetic susceptibility decr eased with decreases in temperature. The result of magnetic hysteresis loop studies showed that the obtained magnetic microspheres are categ orized as magnetically soft materials. The coercive force (Hc) is 32 O e, and the saturation magnetization is 1.79 emu/g. (C) 1997 John Wiley & Sons, Inc.