Liquid crystalline phases in a doubly homologous series of benzylideneanilines-textures and scanning calorimetry

We have investigated the phase behavior of 35 N -(p -alkoxybenzylidene)-p -n -alkylaniline compounds, CnH2n + 1O–φ–CHN–φ–CmH2m + 1′ with n values ranging from 1 to 7 and m from 4 to 8 by means of thermal microscopy and differential scanning calorimetry. We report transition energies and entropies in addition to transition temperatures. From textures we determined the existence of nematic as well as smectic A, C, and B phases in many of the compounds. The microscopy and calorimetry evidence are consistent with a possible second order nature for the smectic C to smectic A transition. An interesting and useful smectic textural transition phenomenon is reported.