Preparation and characterization of polydimethylsiloxane based magnetic fluid

The present work reports the preparation of stable polydimethylsiloxane (PDMS)-based magnetic fluid with Fe ₃O ₄ magnetic nanoparticle dispersion. The Fe ₃O ₄ nanoparticles are modified by the silane coupling agent (SCA) to form a hydroxyl-alkane layer, which provides hydrogen bonding sites. The amino-silicone molecules of surfactant are adsorbed on the particle surface through hydrogen bonds and formed a polymer layer, ensuring good suspension of particles and stability of composed magnetic fluid. The crystal and chemical structures of modified particles were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The morphology and coating status of the particles were observed using high resolution transmission electron microscope (HRTEM). The images confirmed an average particle size of 10 nm and single-domain Fe ₃O ₄ phase. The volatilization rate of the magnetic fluid at 80℃ under vacuum reached 1.4*10 ^-4 g/cm ²·h while maintaining good fluidity at −55℃. Thermostability and magnetic properties were determined by thermal gravimetric analyzer (TGA) and vibrating sample magnetometer (VSM). The material demonstrates superparamagnetic behavior due to the particle diameter being below the critical size (D _c). The rheological properties of magnetic fluid were investigated, along with the impact of surfactant viscosity on these properties. The magneto-viscous effect and polymer-like characteristics imparted by surfactant molecular chains significantly influence the non-Newtonian behavior. Surfactant molecules alter the magnetorheological response by influencing the formation of field-induced particle structures.