Hysteresis-Free Blue Phase Liquid-Crystal-Stabilized by ZnS Nanoparticles
Hysteresis-Free Blue Phase Liquid-Crystal-Stabilized by ZnS Nanoparticles
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由 ZnS 纳米颗粒稳定的无滞后蓝相液晶
DOI：
10.1002/smll.201200052
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发表时间：
2012-07-23
期刊：
影响因子：
13.3
通讯作者：
Lu, Yunfeng
中科院分区：
文献类型：
--
作者：
Wang, Ling;He, Wanli;Lu, Yunfeng
电场作用下的BP开关动力学的理论研究表明，立方结构（尤其是BPI）是不稳定的，并且在强电场区难以可逆地开关。[6]实验结果表明，在纯BP中观察到严重的滞后现象，这可能是由于场诱导的从BP到手性双相的相变。[7]有趣的是，聚合物稳定的BP（PSBP）可以以微秒响应时间可逆地切换，[5]但是由于掺杂了超过10.0重量%的单体，这些系统的驱动电压相对较高，并且聚合物网络的长期稳定性是剩余的技术挑战。[1，8]此外，BPIII也可以在小于10.0 V μm− 1的AC场下进行可逆切换，但响应速度相对较慢（约几毫秒），这是因为在具有高手性或粘度的系统中通常观察到具有宽温度范围的BPIII。[9]因此，迫切需要探索一种新的策略来解决立方BPs对电场的不稳定性，开发无滞后、响应速度快、驱动电压低的BP复合材料。近年来，由于液晶纳米科学在开发具有激发光和电光性能的新型复合材料方面的潜在应用，引起了人们的特别关注。[10]用纳米颗粒（NP）掺杂双相液晶（LC）导致了许多有前途的LC电光特性，包括低驱动电压，[11]短响应时间，[12]频率调制响应，[13]和记忆效应。[14]特别地，NP在BP中的悬浮液被认为用颗粒自身的体积取代了部分能量昂贵的向错区域，降低了LC织构的总能量，从而增强了BP的稳定性。[5，15]在本文中，我们首次报道了纳米颗粒稳定的BP中的另一个令人兴奋的现象：在由少量ZnS NP分散的BPI中可以实现可逆的电光开关，如PSBP;导通状态电压远低于PSBP的导通状态电压，并且滞后非常小，以至于可以认为在0.5-0.7重量%掺杂水平下是无电致伸缩的。这些研究必将为改善新型BP液晶显示器的电光性能提供一种简单有效的方法。
Theoretical investigations of the BP switching dynamics in presence of an electric field have shown that cubic structure (especially, BPI) is unstable and difficult to be reversibly switched in the strong field region.[6] It has been experimentally demonstrated that serious hysteresis was observed in the pure BPs, which may be due to the field induced phase transition from BP to a chiral nematic phase.[7] Interestingly, polymer-stabilized BPs (PSBP) could be reversibly switched with microsecond response time,[5] but the driving voltage of these system is relatively high due to the doping of∼ 10.0 wt% monomers, and the long-term stability of polymer network is a remaining technical challenge.[1, 8] Moreover, BPIII could also undergo a reversible switching with an AC field of less than 10.0 V μm− 1 but the response speed is relatively slow (about several millisecond) due to the fact that BPIII with wide temperature range is usually observed in the systems with high chirality or viscosity.[9] Therefore, there is an urgent need to explore a novel strategy to solve the instability of cubic BPs against an electric field and develop the BP composites without hysteresis, with fast response speed, and with low driving voltage.Liquid-crystal nanoscience has attracted special attention in recent years due to the potential applications in developing new composite materials with exciting optical as well as electro-optical properties.[10] Doping nematic liquid crystals (LC) with nanoparticles (NPs) has lead to many promising LC electro-optical characteristics including low driving voltages,[11] short response time,[12] frequency modulation response,[13] and memory effect.[14] In particular, suspensions of NPs in BPs were believed to replace part of the energetically costly disclination region with the particles’ own volume, lowering the overall energy of the LC texture, consequently enhancing the stability of BPs.[5, 15] Herein, we firstly report another exciting phenomenon in the nanoparticle-stabilized BPs: a reversible electro-optical switching like PSBP could be achieved in a BPI dispersed by a small amount of ZnS NPs; the on-state voltage is much lower than that of PSBP, and the hysteresis is so small that it can be considered as hysteresisfree at a 0.5–0.7 wt% doping level. These studies will certainly provide a simple and effective method to improve the electro-optical (EO) performances of the new promising BP liquid-crystal displays (LCDs).