Preparation of Crosslinked Poly(styrene-methyl methacrylate) Microspheres and Magnetization Processing on Their Surfaces by Electroless Nickel Plating

Crosslinked poly(styrenemethyl methacrylate) microspheres（P(StMMA)）were prepared by dispersion polymerization of styrene (St) and methyl methacrylate (MMA) in mixed solvent of ethanol and deionized water, using azodiisobutyronitrile (AIBN) as the initiator, polyvinylpyrrolidone (PVP) as stabilizer and trimethylolpropane trimethylacrylate (TMPTMA) as crosslinking agent. Microspheres with 3—4 μm in diameter with narrow particle size distribution were achieved by feeding the second monomer under starved condition. Then electroless nickel plating on microspheres were carried out and magnetic microspheres were synthesized suceessfully. Morphology and content of microspheres before and after plating were analyzed by SEM technology coupled with EDAX analysis. The optimal plating condition was: using process II with gel palladium solution as activation step, acid plating solution B with pH of 6.0, adding rate of plating solution of 0.5 mL/min. Under the optimal condition, perfect nickelplating layer was obtained, which were strongly adhere to macromolecule microspheres without breakoff and crazed phenomena during ultrasound and centrifugal process. The mass density of plated NiP(StMMA) microsphere was 2.3—2.5 g/cm3. The microspheres are as light as macromolecule material and show excellent nickel magnetism, which provides a novel adsorptive or catalytic degradation material for pollution control of industrial wastewater.