Study On Blue Phase Liquid Crystals Stabilized By Inorganic Nanomaterials And Their Optoelectronic Properties

Liquid crystals have been widely used in display,phase modulation,optical switching and other fields due to their fluidity of liquids and the anisotropy of crystals,and they play an important role in the development of adaptive optics and integrated optics.However,the response time of the conventional nematic liquid crystal electro-optic device is usually on the order of milliseconds or even seconds,so long response time which limits the further development of the liquid crystal electro-optical device.Blue Phase(BP)is a phase of a narrow temperature range(about 1 to 2 ?)in the liquid crystal between the cholesteric and isotropic phases and the phase state is stable.It is called blue phase because it usually appears blue.Blue phase LCD has the following advantages:(1)The response time is sub-millisecond;(2)No need for color filters and alignment layers;(3)Large viewing angle,insensitive to box thickness and easy to make large display.However,there are many problems in the blue phase liquid crystal.The main problem are the narrow temperature range and high driving voltage.In order to improve the optoelectronic characteristics of blue-phase liquid crystals and design blue-phase liquid crystal devices with good parameters,the main contents are summarized as follows:1.Different liquid crystal hosts BP-001.BP-002,BP-003,BP-004 and different polymer monomers 2-Propenoic acid(C12A),1,4-Bis-[4-(3-acryloyloxypropyloxy)benz oyloxy]-2-methylbenzene(RM257)and trimethylpropane triacrylate(TMPTA)were used to search for a liquid crystal formulation with wider blue-phase temperature range.Then,the polymer monomer composition was changed to conduct polymerization,broadening the blue phase temperature range and to obtain a polymer-stabilized blue-phase liquid crystal.It was found that the temperature range of the liquid crystal hosts of the BP-003 can be extended to more than 30 ?,but the overall temperature is in the lower temperature range through designing experiments,preparing liquid crystal boxes and characterizing electro-optical properties.And we find the liquid crystal host BP-004 has a better blue phase texture,the upper temperature limit is 80.0 ?,and the temperature range is above 90 ? which covers the use range of the basic display.2.The blue phase liquid crystals were systematically studied by doping nanomaterials.First,the blue phase liquid crystal doped nanoparticles were initially explored by doping the barium titanate nanoparticles into the blue phase liquid crystal.Since surface modification of nanoparticles can improve the solubility,oleic acid-modified lanthanum fluoride nanoparticles are then prepared.After analyzing the effects of different levels of lanthanum fluoride doping on the photoelectric properties of blue phase liquid crystals.As a result,it was found that the driving voltage of the polymer-stabilized blue phase liquid crystal doping 0.8 wt.%,0.4 wt%,0 wt.%lanthanum fluoride was 55 V,62 V and 92 V at room temperature,respectively.There exists a decrease of 40%compared with that before doping.Simultaneously,the temperature range has been greatly broadened.The temperature range is above 90 ? and the phase change process and temperature range are repeatable during the cooling and heating process.Due to the high conductivity of carbon nanotubes,it is speculated that if the doping of carbon nanotubes increases the conductivity of the polymer network,and the effective electric field in the blue-phase liquid crystal material will increase accordingly,which will result in a decrease in the driving voltage of the blue-phase liquid crystal device.The experimental design was used to adjust the proportion of carbon nanotubes in the liquid crystal formulation and it was found that the blue phase liquid crystal driving voltages doped with 0.8 wt.%,0.3 wt.%,and 0 wt.%carbon nanotubes were 50 V,67 V,and 90 V at room temperature respectively,which was a decrease of 44%compared with that before doping.The experimental results show that nanomaterials can play a stable role in the liquid crystal system.These research results will have a guiding role in the selection and development of blue phase materials with excellent parameters.