Effect of Alkyl Tail on the Visible Spectra and Order Parameters S of some Azo N-Ester-1,8-naphthalimide(ANEN) Disperse Dyestuff

This research is an attempt to measure the effect of alkyl tail on the visible spectra and order parameters S of some azo N-ester-1,8-naphthalimide(ANEN) disperse dyestuff. For the first time, the visible absorption spectra of two azo N-ester-1,8-naphthalimide(ANEN) dyes with identical molecular size and diverse alkyl tails were obtained in liquids and liquid crystalline solvent. Ordinary organic solvents with different polarity and chemical nature (i.e. cyclohexane, 1,4-dioxane, tetrachloromethane, benzene, diethyl ether, chloroform, dichloromethane, 1-butanol, acetone, ethanol and methanol) accompanied by nematic liquid crystal matrix (5CB) were used. In the visible region of parallel aligned samples the intensity of the absorption bands was measured, thereby the dichroic ratios R and order parameters S of the dyes were determined. Then, the interaction of these dyes was investigated and compared with the anisotropic surroundings and those of the isotropic organic solvents. It was found that the electronic absorption spectra of the dyes in the alcoholic (methanol and/or ethanol) surroundings are shifted to red compared to that of the isotropic organic solutions. Thus, there are strong molecular interactions between the dye molecules and methanol molecules. Also, the electro-optical effects of the guest-host systems were investigated through polarized spectroscopic method.