Fe3O4纳米粒子/负性液晶红外屏蔽薄膜的制备与电-光-热性能的研究

In this study, a liquid crystalline material of negative dielectric anisotropy with a smectic A (SmA)- twist grain boundary (TGB)-cholesteric (N*) phase transition will be prepared. The effects of the molecular structure and composition of the material and the content of the chiral dopant on the phase transition temperature, the temperature ranges of the SmA, the TGB and the N* phase, the pitch length of N* phase will be studied. Fe3O4 nanoparticles with different diameters will be prepared, and then modified by using different surface modifiers. The effects of the content , the diameter and the surface modification methods on the dispersity of Fe3O4 nanoparticles in the liquid crystals will be discussed. Finally, a Polymer network/ Fe3O4 nanoparticles/liquid crystalline material composite film sandwiched between two pieces of transparent ITO conductive films will be prepared. The regulation method of pitch gradient of the coexistence of the N* and the TGB phases corresponding to reflecting 750-3000 nm circular polarized infrared light selectively will be researched. On the application of a high-frequency electric field, the relationship between the temperature, the temperature incrasing rate of the film and the concentration and the diameter of Fe3O4 nanoparticles will be discussed, which will provide experimental data and theoretical direction for the fabrication of infrared light shielding films,windshield defrosters and defoggers.

本课题拟制备具有近晶A（SmA）-扭曲晶界（TGB）-胆甾（N*）相转变的负性液晶材料，研究液晶材料中单体液晶的分子结构和组成、手性化合物的含量对该相转变温度、SmA、TGB和N*相的温度范围、N*相的螺距等参数的影响规律。制备不同粒径的Fe3O4纳米粒子，调节其粒径均匀性，对其进行表面修饰，然后将其分散在液晶材料中，研究Fe3O4纳米粒子的浓度、粒径及表面修饰方法等对其在液晶中分散性能的影响规律。在此基础上，制备具有螺距梯度微结构的高分子网络/ Fe3O4纳米粒子/液晶复合材料薄膜，研究可反射750-3000 nm波段的红外光的薄膜中螺距梯度的调控方法及Fe3O4纳米粒子对薄膜的光透过率和选择反射波段的反射率的影响规律。研究在高频电场作用下，薄膜的温度和升温速率与电场频率、Fe3O4纳米粒子粒径及浓度等参数之间的关系，为制备具有节能环保、除霜和除雾功能的薄膜提供理论和实验根据。

本课题设计并制备了多种具有SmA-TGB-Ch相转变的液晶材料；将光聚合单体/手性化合物/紫外吸收染料/光引发剂/负性单体液晶进行共混制备出胆甾相液晶材料；制备出磁性Fe3O4纳米粒子，研究Fe3O4纳米粒子浓度对其在液晶中分散性能的影响规律；将Fe3O4纳米粒子掺杂入上述胆甾相液晶材料中，制备出高分子网络/Fe3O4纳米粒子/液晶复合材料薄膜，研究了可反射近红外波段红外光的螺距梯度调控方法，研究了Fe3O4纳米粒子对薄膜的光透过率和选择性反射波段反射率的影响规律；同时，研究了在高频电场作用下，复合薄膜的电磁-热效应及其影响因素，即薄膜的温度升高值与Fe3O4纳米粒子浓度、电场参数（加电时长、电压大小、电压频率）等参数之间的关系。为开发兼具红外光屏蔽和电控除霜功能的薄膜材料提供了实验数据和理论指导。