缺陷控制对胆甾相液晶材料双稳态性能的影响及其应用  

Effects of controllable defects on the bistable properties of cholesteric liquid crystal materials and the potential application

作　　者：于美娜 邹呈 高延子 杨槐 YU Mei-na;ZOU Cheng;GAO Yan-zi;YANG Huai(Institute for Advanced Materials and Technology,University of Science and Technology Beijing,Beijing 100083,China;Beijing Advanced Innovation Center for Materials Genome Engineering,Beijing 100083,China;School of Materials Science and Engineering,Peking University,Beijing 100871,China)

机构地区：[1]北京科技大学新材料技术研究院,北京100083 [2]北京材料基因工程高精尖创新中心,北京100083 [3]北京大学材料科学与工程学院,北京100871

出　　处：《工程科学学报》2022年第4期712-721,共10页Chinese Journal of Engineering

基　　金：国家自然科学基金资助项目(52103071,51720105002);中央高校基本科研业务费资助项目(FRF-IDRY-20-037)。

摘　　要：通过弯曲分子的掺杂实现了胆甾相液晶平面态油丝缺陷的调控和焦锥形貌的稳定,研究了各因素对双稳态稳定性的影响,并展示了双稳态的潜在应用.偏光显微镜观察和透过率−电压曲线测试结果表明,弯曲分子的引入可以调控甚至消除平面态的油丝缺陷,实现透过率增加,同时调节焦锥态的形貌,使扇形畴更细小破碎,有利于增强焦锥态的散射和稳定性,实现双稳态效果.这是因为弯曲分子具有很小的弯曲弹性常数,进而对胆甾相液晶的弯曲弹性常数和扭曲弹性常数相对大小进行调节.平面取向层的锚定越强,对双稳态(主要是焦锥态)的稳定越不利,但锚定作用太弱,不利于平面态的完美排列.可以通过取向作用强弱调节、盒厚调整来达到较优的效果.少量聚合物的引入有利于实现双稳态的稳定.最后,基于缺陷调制后的双稳态特性制备了无色和彩色的调光膜,展示了双稳态的潜在应用.The worldwide energy crisis necessitates the urgent need for energy conservation,especially in buildings whose energy consumption has already surpassed that of transportation and industrial sectors.Most of the energy loss in buildings is related to windows because their heat transfer coefficient is different from other building fabrics.Therefore,smart window technologies are proposed to eliminate energy usage,among which cholesteric liquid crystals show great potential due to their electrically controlled bistable properties.Cholesteric liquid crystals are characterized by two stable states:(1)the planar state that shows selective reflection or high light transmittance and(2)focal conic state that scatters incident light and shows opaque appearance.To realize a bistable state in which both the planar state and the focal conic state could be maintained without an external field is of vital importance for the application,since it could save considerable energy.In this study,oily streak defects and stability of the focal conic state are controlled by introducing a type of bent molecular materials.Effects of various factors on the bistable states are investigated,and the potential applications are explored.Results show that the bent molecule CB7CB could diminish the oily streak defects in the planar state and reduce the domain size of the focal conic state because it has a smaller bent elastic constant.The electro-optical test implies that bistable states are acquired in the composite containing CB7CB.Factors such as the anchoring strength of the alignment layer and cell thickness are then investigated and results reveal that strong anchoring and thinner cell thickness are not favored by the focal conic state.Moreover,bistable states could be stabilized by introducing a small amount of polymer followed by polymerization.Based on the above guidelines,colorless and colorful bistable light shutters are demonstrated,which could maintain both transparent and opaque states without any external electric field.The light shut

关 键 词：胆甾相液晶 双稳态 弯曲分子 油丝缺陷 电光性能 

分 类 号：TB381[一般工业技术—材料科学与工程] TB332