Improvement of the Electro-Optical Properties of Nematic Liquid Crystals by Doping with ZIF-8 Materials

ZIF-8 (zeolitic imidazolate framework-8), a kind of metal-organic framework material, is one of the most important energy materials and widely used in various fields because of its high specific surface area and excellent thermal stability. In this research, we synthesized ZIF-8 by the traditional hydrothermal synthesis method in a purely methanol system. The obtained particles were ~250 nm in diameter with a rhombic dodecahedron morphology. Moreover, the prepared ZIF-8 materials exhibited good thermal stability and a large surface area. We also found that the rhombic dodecahedral ZIF-8 enhanced the electro-optical (E-O) properties of nematic liquid crystal (N-LC) depending on the ZIF-8 doping concentrations. ZIF-8 in N-LC cells adsorbs ionic impurities and suppresses the screen effect, leading to a lower driving voltage and faster response time. At a ZIF-8 doping concentration of 0.05%(w, mass fraction), the N-LC cells showed the best E-O properties, including the lowest threshold voltage (V th) of 0.92 V, the lowest saturation voltage (V sat) of 1.31 V, and a short response time of 10.04 ms. However, above a doping concentration of 0.05%(w) ZIF-8 aggregated in N-LC cells, affecting the arrangement of the LC molecules and trapping less impurity ions, which deteriorated the E-O properties of N-LC.