Phase transition studies in 4(4'-n-alkyloxy benzoyloxy benzylidene)-2''-methylaniline homologous series

As a part of our program of study of phase transitions in groups of liquid crystals, we report here the phase transition studies on 4(4'-n-Alkyloxy benzoyloxy benzylidene)-2''-methylaniline homologous series (alkyl = C-7, C-8, C-9, C-10, C-11 and C-12) using a variety of experimental techniques. These are Differential Scanning Calorimetry, Thermal Microscopy, Electron Spin Resonance Spectroscopy and Density determination. The Isotropic-Nematic transition is found to be first order in all the compounds. The Nemaric-Smectic A transition is exhibited by C-10, C-11 and C-12 homologues of the series only and is found to be weakly first order in all these three compounds. The experimental results are compared with those of the previous results and with those of the theoretical predictions of molecular field theory of Smectic A liquid crystals.