Relationship between the Electrical Conductivity and the Order Parameter of Dye-Doped Liquid Crystals
|Keywords:||液晶;染料;導電率;秩序參數;liquid crystals;dyes;conductivity;order parameter|
In this study, Dielectric characteristics and optical effects of nematic liquid crystals (NLCs) doped with different types of dichroic dyes are investigated by means of dielectric and absorption spectroscopies. The dichroic dyes used in this study are divided into two types; azo and anthraquinone dyes, according to their chemical structures. Dielectric spectroscopy was employed to determine the effect of ionic charge transport in the dye-LC mixtures. In addition, absorption spectra of dye-LCs were measured to obtain the parallel and perpendicular components of absorptivity of dye molecules. Finally, mathematical calculation on the order parameter of dye-LC cells were performed according to the results on absorption spectra. Experimental results show that the difference of the imaginary part of dielectric permittivity of dye-LCs as a function of dopant concentration result from the intermolecular forces between the LC and dye in the cells. For the dye materials having conjugated structure with alternative connecting of single and dobule bonds in their main chain, electrons or charges are allowed to move along the molecular chains or the cross-chains. Because of the positive correlation between the imaginary parts of dielectric and the conductivity, it is implied that the overall conductivity of compound is directly impacted by the intermolecular behaviors as well. Furthermore, this study reveals the significant impact of continuity of the intermolecular conjugated structure on the order parameter and conductivitiy of the mixure.
|Appears in Collections:||Thesis|
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