Research Of Multiple-doping Polymer Network System Of Blue Phase Liquid Crystal

Blue phase(BP) liquid crystals(LCs)(BPLCs) appear as a regular array of double twist cylinders(DCTs) separated by network of disclination lines in a narrow temperature range between the chiral nematic phase and the isotropic phase. Owing to their interesting features such as sub-millisecond response time, alignment free, optical isotropic status without electric field, and periodic double twisted structure on the order of the visible wavelength, BPLCs have attracted people's interests for potential applications in field sequential displays, phase modulator devices, and three-dimensional tunable photonic crystals. Although the unique features of blue phases are very attractive, the temperature range at which they are available is only on the order of 1 K, which prohibits consideration with regard to potential applications. Since the temperature range broadened to more than 60 K by stabilizing the disclination lines with polymer network, blue phase liquid crystal has attracted people's interest for its great potential application in field sequential displays, phase modulator devices, and photonic crystals.However, some critical issues, such as high driving voltage, hysteresis, residual birefringence, and weak thermal stability must be solved before they can be widely applied. In this paper, effect of chiral dopants and polymers of the blue phase liquid crystal are investigated to improve the electro-optic properties of blue phase liquid crystals and analyze the mechanism that affect the electro-optic properties of the blue phase liquid crystal's device.In this paper, a novel material system with conductive polymer was proposed to increase the effective electric field of the LC device which may improve the driving capacity of PS-BPLC. The effect of different concentration of N-vinylpyrrollidone(NVP) and polyaniline functionalized graphene(G-PANI) is also studied. The driving capability of blue phase liquid crystal can be much improved in that the Kerr constant of blue phase liquid crystal doped with 1 wt.% NVP and 0.05 wt.% polyaniline functionalized graphene is increased by about 68% compared with that of blue phase liquid crystal without polyaniline functionalized graphene. Meanwhile, this composite exhibits no degradation of electro-optic properties, such as response time, hysteresis and residual birefringence.