Poly(dimethylsiloxane)-Stabilized Magnetic Fluid Remains Flowable in the Absence of a Carrier Medium

Abstract

A magnetic fluid has been synthesized on the basis of magnetite particles stabilized with poly(dimethylsiloxane) (PDMS) having a molecular weight of 4670. PDMS-stabilized particles retain their mobility after the twofold dilution of this fluid with n-pentane and cooling to a temperature of –95°C. A concentrated sample of the magnetic fluid containing only particles with stabilizing shells has been obtained by centrifugation. Despite the absence of a base carrier liquid, this sample retains its fluidity. Thus, a new type of so-called “solvent-free nanofluids” has been synthesized, with these nanofluids being promising components of various technical devices. The concentrated sample of the magnetic fluid shows the rheological properties characteristic of pseudoplastic fluids. The fluid pseudoplasticity exponent is close to unity and nonmonotonically varies with temperature. The temperature dependence of the concentrated sample viscosity at high shear rates in fact reproduces the temperature dependence of the viscosity of the PDMS stabilizer. When the concentrated sample is diluted with a low-viscosity liquid, oligo(diethylsiloxane), the logarithmic relative viscosity of the sample decreases linearly with an increase in the volume fraction of the oligomer.