Inorganic/organic poly(methylmethacrylate-acrylic acid-divinylbenzene) iron oxide Janus magnetic nanoparticles(P(MMA-AA-DVB)/Fe_3O_4) with strong magnetic domains and unique surface functionalities were prepared using a solvothermal process.The P(MMA-AA-DVB) nanoparticles were prepared via soapfree emulsion polymerization and used as a precursor for preparing Janus nanoparticles.The morphology and magnetic properties of the magnetic Janus nanoparticles formed were characterized using a laser particle size analyzer,transmission electron microscopy,Fourier transform infrared spectroscopy,vibrating sample magnetometry,and thermogravimetric analysis.The synthesized P(MMA-AA-DVB)/Fe_3O_4 magnetic Janus nanoparticles were characterized by a Janus structure and possessed a stable asymmetric morphology after being dually functionalized.The particle size,magnetic content,and magnetic domain of the P(MMA-AA-DVB)/Fe_3O_4 magnetic Janus nanoparticles were 200 nm,40%,and 25 emu/g,respectively.The formation mechanism of the Janus nanoparticles was also investigated,and the results revealed that the reduction of Fe~(3+) ions and growth of Fe_3O_4 took place on the surface of the P(MMA-AA-DVB) polymeric precursor particles.The size of the Janus particles could be controlled by narrowing the size distribution of the P(MMA-AA-DVB) precursor nanoparticles. Inorganic / organic poly (methylmethacrylate-acrylic acid-divinylbenzene) iron oxide Janus magnetic nanoparticles (P (MMA-AA-DVB) / Fe_3O_4) with strong magnetic domains and unique surface functionalities were prepared using a solvothermal process.The P -DVB) nanoparticles were prepared via soapfree emulsion polymerization and used as a precursor for preparing Janus nanoparticles. The morphology and magnetic properties of the magnetic Janus nanoparticles formed were characterized using a laser particle size analyzer, transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and thermogravimetric analysis. The synthesized P (MMA-AA-DVB) / Fe_3O_4 magnetic Janus nanoparticles were characterized by a Janus structure and possessed a stable asymmetric morphology after being dually functionalized. The particle size, magnetic content, and magnetic domain of the P (MMA-AA-DVB) / Fe 3 O 4 magnetic Janus nanoparticles were 200 nm, 40%, and 25 emu / g, respectively.The f ormation mechanism of the Janus nanoparticles was also investigated, and the results revealed that the reduction of Fe ~ (3+) ions and growth of Fe_3O_4 took place on the surface of the P (MMA-AA-DVB) polymeric precursor particles. size of the Janus particles could be controlled by narrowing the size distribution of the P (MMA-AA-DVB) precursor nanoparticles.