Study On The Preparation And Properties Of Liquid Crystal Materials With Selective Reflection

Chiral liquid crystal materials with chiral groups have unique optical properties-selective reflection.Among them,cholesteric liquid crystal materials have become one of the research hotspots in chiral liquid crystal systems because of their tunable selective reflection.Color is ubiquitous in nature,and the use of color or spectrum is very important in information technology.The color of an object is determined by the wavelength of light produced or emitted by the object.The cholesteric liquid crystal material has a spirally ordered structure and can selectively reflect light.If selective reflection occurs in the visible light region,the cholesteric liquid crystal will display an iridescent color.The process of using the selective reflection of cholesteric liquid crystal materials to produce colors has received considerable attention,mainly due to several potential applications,such as tunable color filters,thermal cutting,reflective display,and sunscreenless lasers.In this paper,a new exploration of the structure and properties of chiral liquid crystal materials is carried out.Based on the high optical purity of L-menthol and cholesterol,three new chiral liquid crystal compounds and one achiral nematic liquid crystal compound are designed and synthesized,based on four liquid crystals.The compound prepared two series of liquid crystal blends and two series of linear side-chain liquid crystal polymers,which provided new ideas and theoretical basis for the design and synthesis of liquid crystal materials with selective reflection properties,and also provided research on the optical applications of liquid crystal materials.More options.The specific research content includes:(1)Using menthol as the chiral center,a chiral liquid crystal compound 4-(4-allyloxybenzoyloxy)phenyl4-(4-(menthyloxy)-4-oxobutanoyloxy)benzoate(Mt)was synthesized;Chiral liquid crystal compounds cholesteryl 4-allyloxybenzoate(Ch)and cholesteryl 4-(undec10-enoyloxy)benzoate(CH)were synthesized with cholesterol as the chiral center;At the same time,the achiral monomer 4-(4-butylbenzoyloxy)phenyl 4-allyloxybenzoate containing butyl end groups was prepared,and three chiral liquid crystal properties and selective reflection properties were discussed.(2)Based on the physical blending method,the achiral monomer N containing butoxy end groups and the chiral monomer Ch containing cholesteryl group are blended in different molar ratios to prepare blends M-Ch1N6～M-Ch6N1;The chiral monomer Mt containing menthol group and the chiral monomer CH containing cholesteryl group were blended in different molar ratios to prepare blends M-Mt1CH6～M-Mt6CH1.And the effect of their liquid crystal properties and proportions on their selective reflection properties was systematically discussed.(3)Based on the flexible main chain of linear siloxane,the achiral monomer N containing butoxy end groups and the chiral monomer Ch containing cholesteryl group were copolymerized with linear polysiloxane(PMHS)in different molar ratios to synthesize P-ChxNy series;the chiral monomer Mt containing menthol group and a chiral monomer CH containing cholesteryl group were copolymerized with linear polysiloxane in different molar ratios to prepare P-MtxChy series.P-ChxNy and P-MtxChy are new linear side-chain liquid crystal polymers with selective reflection properties,and optical films are prepared after high temperature quenching.The results of the blend series liquid crystal compound series show that with the increase of cholesteric liquid crystal monomer,the Tc of the two liquid crystal blend series gradually increase,and the liquid crystal texture of the two liquid crystal mixture series gradually changes from fingerprint texture to complete focal conic texture during the cooling process,indicating that the P value of the liquid crystal mixture gradually decreases.Using UV/Vis spectroscopy to study the selective reflection performance of the mixture,it is obtained that the N*phase of the two mixtures has selective reflection performance during the heating process,and the selective reflection area is located in the red-green region.The blending of different proportions can control the wavelength range to obtain different colors.The linear side chain liquid crystal polymers P-ChxNy series and P-MtxCHy series both have a wide ΔT,and both have good thermal stability.Both the P-ChxNy series and the PMtxCHy series show an N*phase during the heating and cooling process,and the copolymer does not introduce a new liquid crystal phase through the copolymerization of the two monomers in different molar ratios.During the heating process,the P-ChxNy series and P-MtxCHy series have a very small red shift as T increases.By adjusting the composition of the polymer side chain and the molar ratio of the components to adjust the P value,The λm of the P-Ch4N3,P-Mt4CH3 and P-Mt3CH4 was successfully placed in the visible light region.The optical film prepared by high temperature quenching of P-Ch4N3 polymer selectively reflects bright colors at room temperature,and the optical film is bright green.The visible light range of the optical film is not only dependent on temperature,but also dependent on the incident angle.As the incident angle becomes smaller,the λm blue shift of the optical film.The optical film prepared by the P-Mt3CH4 polymer after high temperature quenching is green at room temperature,and the P-Mt4CH3 optical film is light red.The optical film is not only temperature-dependent in the visible light range,but also dependent on the incident angle.As the incident angle becomes smaller,the λm of the optical film blue shifts.