Preparation and evaluation of some newly liquid crystal as antioxidant for base stocks

Four liquid crystal compounds of the form, 2-Sec-butyl-4-[(4-x-phenyl) diazenyl) phenyl-4-(octadecyloxy] benzoate symbolized as I18a, I18b, I18c and I18d were prepared in which the substituent (X) was taken CH3O-, CH3-, Br- and -NO2 respectively. Characterization of prepared compounds is done using FT-IR, 1H-NMR, Mass Spectroscopy and Elemental Analysis. Their mesophase behavior was investigated by Differential Scanning Calorimetry (DSC). Their antioxidant efficiency for Egyptian lubricating base oil was tested. The oxidation processes were monitored using the change in the Total Acid Number (TAN). The obtained results showed that the efficiency of these compounds was ranked as follows I18d I18c I18b I18a.