Research Of The Templating Technique And The Chiral Monomer Doping Of Blue Phase Liquid Crystal

Blue phase liquid crystals(BPLCs)usually exist in a narrow temperature range,1~2 ~oC,between an isotropic phase and chiral nematic(N*)phases as a self-organized three-dimensional(3D)photonic crystal usually.Compared with the conventional liquid crystal material,BPLCs exhibit several attractive features,such as sub-millisecond response time owing to the short propagation distance of liquid crystal molecules in the double twist cylinders(DTCs)structure whose pitch is only around several nanometers,enabling color sequential displays,a low-power consumption technology,without noticeable color breakup;Alignment free owing to its self-assembled structure which simplifies the fabricating process and reduces the cost;Optical isotopic status without electric field which makes a good view angle.In 2002,polymer-stabilized blue phase liquid crystal(PS-BPLC)has been proposed which shows great performance on broadening the temperature range of BP to more than 60 ~oC,which makes BPLCs showing a great promise for the next-generation display technology and photonics application.Recently,a templating technique has been applied to PS-BPLC,which can broad the temperature range of blue phase liquid crystal to 250~oC.However,the polymer concentrations of the templated BP material system in prior works are much higher than that of the conventional PS-BPLC material system,which may degrade the driving capacity of BPLC device.Therefore,we have investigated a low polymer concentration template for the BP reconstruction and its electro-optic properties.The study of the templated blue phase can make a contribution to the wide application to blue phase liquid crystal.To optimize the material system of the templated blue phase,the dissertation has investigated the template fabrication parameters through the experiments,including the stiffness of the polymer network of the blue phase template for the blue phase reconstruction,the threshold polymer concentration of the template to reconstruct the BP and the reconstruction range of helical twisting power(HTP).The dissertation has also studied the reconstruction capability of the templates formed by different material system,the refilling effect of the chiral liquid crystal on the templates and electro-optical properties of the templated blue phase.It has found that the anchoring energy of the template may reassemble the DTCs of BPLC by refilling either the same-handed or reverse-handed chiral materials within a certain range of HTP.Meanwhile,because of the lowered anchoring energy,the kerr constant of the reconstructed BPLC increased to 2 times by refilling the reverse-handed chiral material.The dissertation has also analyzed the properties and effect of every composition in PS-BPLC system.Upon the analyzation,a chiral monomer has been introduced to be hoped to simplify the polymer system by replacing part of the composition in PS-BPLC system.It is found that the introduction of chiral monomer can decrease the driving voltage of the PS-BPLC by 28%by reducing part of chiral dopant and monomers,which provides the foundation for the research on the optimization of BPLC materials.