A Study of Thermal Properties of Some Nematogenic Schiff’s Bases

Abstract

The thermal properties of four nematogenic Schiff’s bases, n-butyl-to-n-heptyl of bis (4-n-alkyloxybenzylidine)-2,3,5.6- tetramethyl-1, 4-phenylenediamine, have been studied. The transition temperatures and enthalpies of transition were examined by differential scanning calorimeter (DSC). Several correlations were carried out; those included the relations between transition temperatures, enthalpies and entropies of transition with increasing the
number of carbon atoms in the terminal alkyl chains. In addition, new regular relations were found between the ratio of the enthalpies and of the entropies,  for noematic-isotropic transition and crystal-isotropic transition ( ΔΗ_Î-i/AH_C-I, ΔS_N-1/ AS_C-I ), with increasing terminal alkyl chain lengths. Many interesting conclusions, concerning the relation
between the anisotropic molecular shape and the thermal properties of the above nematogens, have been arrived at.