Gelator-doped liquid-crystal phase grating with multistable and dynamic modes

Abstract

We demonstrate a gelator-doped nematic liquid-crystal (LC) phase grating, which can be operated in both the multistable mode and the dynamic mode. Thermoreversible association and dissociation of the gelator molecules can vary and fix the multistable diffraction efficiencies of the gratings. A voltage (V) can also be applied to modulate dynamically the diffraction efficiencies of the grating, which behaves as a conventional LC grating. Experimental results show that the variations of the diffraction efficiencies in the multistable and dynamic modes are similar. The maximum diffraction efficiency is approximately 30% at V = 2 V.

Fast Response and Spontaneous Alignment in Liquid Crystals Doped with 12-Hydroxystearic Acid Gelators

“…At a dopant concentration of 0.7 wt %, various transmissions at process voltages could be maintained, and the T–V curve was similar to that obtained when a voltage was applied (the blue asterisk curve in Figure 7 a). In this cell, the gelator molecules automatically assembled in the direction of the reoriented LCs and stabilized the LC molecules at any tilt angles under the process voltage, achieving multistable LC orientations [ 26 , 27 ]. When the gelator concentration was high (1 wt %), the LC molecules oriented almost vertically, as shown in Figure 8 d. The multistable characteristic of the cell could be observed, but the change of transmittance was very weak.…”

“…Both positive and negative dielectric anisotropic LCs were used. The positive dielectric anisotropic LCs used were HFW59200-200 [ 26 , 27 , 28 ] (clearing temperature T c = 113 °C, FUSOL MATERIAL) and E7 [ 29 , 30 , 31 ] ( T c = 58 °C, ECHO CHEMICAL). The birefringence (Δ n ) at 589 nm and dielectric constant anisotropy (Δ ε ) at 1 kHz of HFW59200-200 are 0.107 and 9.5, respectively, while E7 has Δ n = 0.2246 and Δ ε = 13.8.…”

“…All LCs were in nematic state at room temperature. The doping material utilized was 12-hydroxystearic acid (12-HSA) [ 26 , 27 , 32 ], which can be produced by hydrogenation of the double bond of castor oil and is an organic gelator with a low molecular weight. The chemical structure of 12-HSA is shown in Figure 1 .…”

“…Achieving LC alignment by dispersing NPs into LCs is an easier method than using conventional polymer layers. In recent researches, gelator-doped LCs have shown to possess the multistable characteristic, and some devices, such as phase gratings and phase-retardation plates based on gelator-doped LCs have also been realized [ 26 , 27 ]. In this investigation, the spontaneous vertical alignment of gelator-doped LC cells was examined.…”

Effects of quenching temperature on threshold, driving voltage and morphology of reverse mode liquid crystal gel films

“…The most important parameter for nucleation is the interaction between the solvent and gelator molecules. Generally, the network structures are divided into two categories depending on the order of T sol-gel of the gelator and T iso-N of LC [38][39][40][41]. When the LC is in the nematic state and T sol-gel is higher than T iso-N , the gelator molecules are irregularly distributed between LC molecules.…”