Poly(methyl methacrylate)/magnetite (PMMA/Fe₃O₄) nanocomposites were prepared with a two–step technique involving sonication. Fe₃O₄ nanoparticles were synthesized by ultrasound–assisted co–precipitation, and then PMMA/Fe₃O₄ (1–5 wt%) nanocomposites were synthesized via ultrasound–assisted in–situ emulsion polymerization. Best physical properties of the nanocomposites for different Fe₃O₄ loadings were: Tensile strength (2 wt%) = 40.28 MPa, Young’s modulus (2 wt%) = 2.4 GPa, percentage elongation (2 wt%) = 2.24%, glass transition temperature (2 wt%) = 122.5 °C, thermal inflection point (2 wt%) = 383 °C, electrical conductivity (5 wt%) = 2.0 × 10^–13 S/cm, coercivity = 59.85 Oe (2 wt%), magnetic saturation (5 wt%) = 5.12 emu/g, magnetic remanence (5 wt%) = 0.56 emu/g, and electromagnetic interference shielding effectiveness (5 wt%) = 1.45 dB. This unique combination of physical properties at relatively low Fe₃O₄ loading is attributed to ultrasound–mediated uniform dispersion of the nanofiller in the polymer matrix.

聚（甲基丙烯酸甲酯）/磁铁矿（PMMA / Fe ₃ O ₄）纳米复合材料是通过涉及超声处理的两步技术制备的。通过超声辅助共沉淀法合成Fe ₃ O ₄纳米粒子，然后通过超声辅助原位乳液聚合法合成PMMA / Fe ₃ O ₄（1-5 wt％）纳米复合材料。纳米复合材料对不同Fe ₃ O _4的最佳物理性能载荷为：抗张强度（2 wt％）= 40.28 MPa，杨氏模量（2 wt％）= 2.4 GPa，伸长率（2 wt％）= 2.24％，玻璃化温度（2 wt％）= 122.5°C，热拐点（2 wt％）= 383°C，电导率（5 wt％）= 2.0×10 ^–13 S / cm，矫顽力= 59.85 Oe（2 wt％），磁饱和（5 wt％）= 5.12 emu / g，剩磁（5 wt％）= 0.56 emu / g，电磁干扰屏蔽效果（5 wt％）= 1.45 dB。Fe ₃ O ₄含量相对较低时物理性能的这种独特组合归因于超声介导的纳米填料在聚合物基质中的均匀分散。