Phase Transitions in N(p-n-Bu toxybenzylidene) p-n-Alkyl Anilines: Density and Refractive Index Studies

Abstract

Abstract The density and refractive index variation with temperature in N(p-n-butoxybenzylidene)p-n-alkylanilines viz., 40.m compounds for m = 4 to 12 are presented. The density, thermal expansion coefficient and the refractive index results infer first order character for IN, AB and CB transitions and a second order character for NA and AC transitions. Pretransitional effects are discussed at IN and AB transitions. The odd-even effect is observed at both the IN and NA phase transitions. The variation of refractive index anisotropy as a function of temperature, in the nematic phase of the compounds in a homologous series has shown an interesting phenomena. The temperature dependence of nematic refractive index anisotropy yields mean field exponent v = 1 in the vicinity of NA transition. The influence of molecular chemical constitution, the nematic thermal range and the McMillan parameter values on the order of NA transition is discussed in detail.