Liquid-crystalline properties of 4-octyloxybenzylidene-4′-alkyloxyanilines and their mixtures with 4-pentyloxybenzylidene-4′-heptylaniline

Liquid-crystalline properties of the homologous series of 4-octyloxybenzylidene-4′-alkyloxyanilines are described. Based on the polarization microscopy (POM and TOA methods) and the calorimetric (DSC) measurements a rich polymorphism was detected. Investigated compounds exhibit nematic, smectic C, smectic I and smectic G mesophases with their characteristic configurations. The presence of all mesophases was confirmed by the miscibility method, using 4-heptyloxybenzilidene-4′-pentylaniline (I), 4-octyl-4′-decyloxyazobenzene (II) and 4-octyl-4′-undecyloxyazobenzene (III) as the mesophase standards. The influence of an alkyl chain length on the mesophase sequence and the entropic effects are extensively discussed.