The preparation and smart electrorheological behavior of MOF-Ti@PANI core-shell nanoparticles

Abstract

In this paper, a kind of core–shell composite nanoparticles for electrorheological (ER) fluid was successfully prepared and showed good ER effect. The material possesses the high specific surface area and low density of metal organic frameworks (MOFs), and combines with the excellent dielectric properties of polyaniline (PANI). PANI precursors were prepared by a rapid mixing method, and then MOF-Ti (an MOF containing Ti) grew in situ on PANI under the solvothermal conditions. The MOF-Ti@PANI composite nanoparticles with core–shell structure were generated. These characteristics of PANI and MOF-Ti are conducive to stronger interfacial polarization of nanoparticles, which in turn leads to a good ER effect. The nanoparticle morphology as well as its ER and dielectric properties was modulated by using different amounts of PANI addition. The addition amount of PANI had a certain effect on the particle morphology, which was proved by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We also determined particle size at the nanoscale in this process. The measured results of the X-ray powder diffractometer (XRD) are consistent with the characteristic peaks of MIL-125 (a kind of MOF-Ti). The internal chemical structure of the material and the chemical environment of the elements were analyzed using Fourier infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Finally, the ER and dielectric properties of the nanoparticles in ER Fluids were investigated using high-speed rotational rheometry and broadband dielectric spectroscopy. The analysis revealed that the MOF-Ti@PANI core–shell nanoparticles have good ER properties under proper coating. For the core–shell modified MOFs, it is expected to be a promising development direction in the field of ER materials.