Thermochimica Acta, Vol.525, No.1-2, 78-86, 2011
Effect of exchange of terminal substituents on the mesophase behavior of laterally methyl substituted phenyl azo benzoates in pure and mixed systems
Two groups of the formulae, 4-(4'-hexyloxy)phenylazo-2-(and 3)methyl phenyl-4 ''-substituted benzoates (Ia-e and IIa-e were prepared and investigated for their mesophase behavior. Each group consists of five derivatives that differ from each other by the terminal polar substituent X which varies between CH3O, CH3, Br, NO2, and CN. Two other isomeric groups, IIIa-e and IVa-e that exchange the terminal substituents, X and C6H13O, were also prepared and similarly characterized. Four different types of binary phase diagrams were constructed in which both components are corresponding isomers one from each of the four groups (I-IV). In the two binary mixtures. I/II and III/IV, the two components are positional isomers that differ in the position of the lateral methyl group, while in the other two systems, I/III and IV/IV, the two components are again positional isomers that exchange the two wing substituents.The study is undertaken to investigate the effect of exchange of the terminal substituents on the mesomorphic properties of the produced derivatives in their pure or mixed states. (C) 2011 Elsevier B.V. All rights reserved.