非均匀分布的纳米银掺杂的聚合物分散液晶全息光栅等效电路建模研究
投稿时间:2017-01-19  修订日期:2017-02-21  点此下载全文
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作者单位E-mail
刘悠嵘 上海理工大学 yourongliu@sina.com 
郑继红 上海理工大学 jihongzheng@sina.com 
桂坤 上海理工大学 183367852@qq.com 
基金项目:上海市重点学科项目第三期(S30502)、国家重大科学仪器设备开发专项(2012YQ15008720)
中文摘要:聚合物分散液晶全息光栅具有电场可调的特点,材料中掺杂纳米银颗粒,能够有效降低光栅的驱动电压。由于聚合动力学的影响,会造成纳米银颗粒在光栅中的非均匀分布,即纳米银在聚合物和液晶区分布含量不均匀,表现出不同的电场调控特性。通过等效电路建模的方法研究驱动电压阈值与所施加交流电场的频率之间的关系。根据Maxwell-Wagner效应建立纳米银分别被液晶和聚合物包围的等效电路模型,具体研究在液晶条纹中,纳米银含量占总纳米银比例不同的条件下,纳米银掺杂的聚合物分散液晶全息光栅的介电弛豫时间和弛豫振荡的频率数值变化,进一步调节驱动电场频率,获得更低的驱动电压阈值。通过最优驱动电场频率范围来初步确定纳米银在光栅中的分布结构,并证明纳米银颗粒集中在液晶条纹,少量分布在聚合物条纹中。
中文关键词:聚合物分散液晶全息光栅,弛豫振荡频率,阈值驱动电压,非均匀分布
 
Equivalent circuit modeling of non-uniformly distributed nano Ag doped polymer dispersed Liquid Crystal Holographic Grating
Abstract:The diffraction efficiency of the polymer dispersed liquid crystal holographic grating can be adjusted by the applied electric field. Doping Ag nanoparticles can effectively reduce the driving voltage of gratings.Due to the influence of polymerization kinetics, Ag nanoparticles are distributed unevenly in the grating ,that is the distribution of nano Ag in the polymer and liquid crystal area is not uniform and exhibit different electric field control characteristics. It was found that the threshold driving voltage can indeed be reduced by selecting proper modulation frequency. The Ag nanoparticles and polymer, Ag nanoparticles and liquid crystal, will produce Wagner - Maxwell effect on the surface, the external electric field will affect the dielectric surface relaxation oscillation, thereby affecting the threshold voltage. The equivalent circuit modeling method is used to study the frequency relationship between the threshold voltage and the applied electric field. The equivalent circuit model of Ag nanoparticles surrounded by liquid crystal and polymer is established according to the Maxwell-Wagner effect. Through the equivalent circuit model, we can see that the distribution of Ag nanoparticles in the grating will affect the relaxation oscillation time, thus affecting the applied electric field frequency. In the liquid crystal stripes, under the different proportion of Ag nanoparticles content condition, we study the relaxation time and relaxation frequency of Ag nanoparticles doped polymer dispersed liquid crystal holographic gratings. The driving electric field frequency is further adjusted to realize a lower driving voltage threshold. The optimal applied electric field frequency is related to the nonuniform distribution of Ag nanoparticles in the material system and can be calculated using the equivalent circuit model. In the liquid crystal stripes, when the proportion of Ag nanoparticles content is increased, the applied electric field frequency corresponding to the grating''s the lowest threshold voltage is also increasing. The distribution of Ag nanoparticles in the grating can be determined by the optimum driving electric field frequency range, and it is confirmed that the Ag nanoparticles are concentrated in the liquid crystal strip and distributed in a small amount in the polymer stripes.
keywords:Holographic polymer dispersed liquid crystal, relaxation oscillation frequency, Threshold driving voltage, Non-uniform distribution
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