碳纳米管掺杂影响液晶物理参数与显示性能的实验及第一性原理计算

Experiment and First-principles Calculation on Effect of Carbon Nanotubes Doping on Physical Parameters and Display Properties of Liquid Crystal

将4"-正戊基-4-氰基联苯(5CB)液晶与液晶4-[反式-4-[(E)-1-丙烯基]环己基]苯腈以5:1的比例混合,并将预处理的碳纳米管分别与5CB单晶和混晶复合,测试两种掺杂碳纳米管的液晶的光电和介电性能。结果表明:碳纳米管的掺入影响了液晶体系的阈值电压和介电各向异性,其中介电各向异性的增幅最高达到4.671%,并且展曲弹性常数也有所增大;碳纳米管的掺入也影响液晶体系的响应时间和粘滞系数,其中粘滞系数的降幅最高达到25.131%。实验还表明,混晶的介电各向异性高于单晶,且其响应时间和粘滞系数的降幅均比5CB单晶明显。混晶的更大优势是,与碳纳米管复合、改善复合体系的物理参数和显示性能。同时,理论研究结果表明,碳纳米管与液晶分子的结合能介于液晶分子与液晶分子、碳纳米管与碳纳米管之间,并且在液晶分子的诱导下碳纳米管产生诱导偶极矩,印证了碳纳米管掺杂可提高液晶的介电各向异性、降低其响应时间的实验结果。

A mixed liquid crystal was firstly prepared with liquid crystals 4-Cyano-4’-pentylbiphenyl(5CB) and 4-[trans-4-[(E)-1-propenyl] cyclohexyl] benzonitrile in a ratio of 5:1 as raw material.Then the plain liquid crystal 5CB and the mixed liquid crystal were compounded with the pretreated carbon nanotubes(CNTS) respectively,which were characterized in terms of their photoelectric and dielectric properties.The results show that the addition of CNTS affects the threshold voltage and dielectric anisotropy of the liquid crystal systems,as a result,the dielectric anisotropy increases by 4.671%,and the flexural elastic constant also increases;The addition of CNTS also affects the response time and viscosity coefficient of the liquid crystal systems,while the viscosity coefficient decreases by 25.131%.The experimental results also show that the dielectric anisotropy of the mixed liquid crystal is higher than that of the plain liquid crystal 5CB,while the decrease of response time and viscosity is more obvious.The greater advantage of the mixed liquid crystal is that the doping of carbon nanotubes can result in significant improvement in the physical parameters and display performance of the composite system.At the same time,the theoretical research results show that the binding energies of carbon nanotubes and liquid crystal molecules are between those of liquid crystal molecule pairs and carbon nanotube pairs respectively,as a result,dipole moments may be induced by the asymmetric charge distribution of the liquid crystal molecules adsorbed on carbon nanotubes,which can well interpretate the fact that the doped carbon nanotubes can improve the dielectric anisotropy of liquid crystal materials,while reduce the response time.