Abstract

We obtained carbon nanotubes (CNTs) doped polymer dispersed liquid crystal (PDLC) films using the nematic E7 and polymethyl methacrylate, a composite that combines the benefic characteristic of the liquid crystals (LC) and carbon nanoparticles. The clearing temperatures recorded by differential scanning calorimetry for the PDLC blends were found to be lower than the value recorded for pure E7 LC mixture with no significant impact of the CNTs’ concentration. Broadband dielectric spectroscopy (DS) measurements were performed in the \( (10^{ - 1} \div 10^{7} )\;{\text{Hz}} \) frequency range, in the temperature domain (280–350) K. From the DS study, a two order magnitude variation of the conductivity over the entire temperature range was observed. The presence of CNTs results in an increase of electrical conductivity, with increasing concentration. Because the loss tangent spectra have complex shapes, they were fitted using the generalized Havriliak–Negami functions, and the characteristic relaxation times were extracted. The dependency of the characteristic relaxation time on temperature was modeled using the Vogel–Fulcher–Tammann function, and it showed a temperature variation according to the Arrhenius law. The increase of the CNT concentration increases the activation energy of the molecular electric dipoles of the LC. The interface LC-polymer interactions influence the nematic to isotropic phase transition of the LC.

Graphic abstract

中文翻译：

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碳纳米管掺杂聚合物分散液晶膜的介电研究

摘要

我们使用向列型E7和聚甲基丙烯酸甲酯获得了掺有碳纳米管（CNT）的聚合物分散液晶（PDLC）膜，该复合材料结合了液晶（LC）和碳纳米颗粒的有益特性。发现通过差示扫描量热法记录的PDLC混合物的清除温度低于纯E7 LC混合物记录的温度，而对CNT的浓度没有明显影响。宽带介电谱（DS）测量是在\（（10 ^ {-1} \ div 10 ^ {7}）\; {\ text {Hz}} \）中进行的在温度范围（280-350）K的频率范围内。从DS研究中，可以观察到整个温度范围内电导率的两个数量级变化。CNT的存在导致电导率随浓度增加而增加。由于损耗角正切谱具有复杂的形状，因此可以使用广义的Havriliak–Negami函数进行拟合，并提取特征弛豫时间。使用Vogel–Fulcher–Tammann函数对特征驰豫时间对温度的依赖关系进行建模，并根据阿伦尼乌斯定律显示了温度变化。CNT浓度的增加会增加LC分子电偶极子的活化能。

图形摘要