Significantly Improved Electrorheological Performance of MIL-125@PPy-Based Electrorheological Fluid

A novel core–shell composite material was synthesized, consisting of the metal organic framework (MOF) MIL-125 as the core and the conductive polymer polypyrrole (PPy) as the shell. The composite promotes electroresponsive performance and dispersion stability by combining the high surface area and porosity of MIL-125 with the conductivity of PPy. Structural and chemical features were examined by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), while particle morphology was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structural change of the materials-based electrorheological (ER) fluids was observed with or without an applied electric field using optical microscopy (OM). Rheological properties, including shear stress, shear viscosity, on–off switching effect, and dielectric characteristics, were investigated by using a rotational rheometer at different electric field intensities. The volume fraction of composite 14.1% and applied electric field of 3 kV/mm, the ER fluid exhibited a dynamic yield stress of 630 Pa and ER efficiency of 3038 at 0.1 s^–1 shear rate, demonstrating its promising potential for practical application.