Undulation textures at the phase transitions of some alkyloxybenzoic acids

We observed undulated smectic textures for some compounds of the 4,n-alkyloxybenzoic (nOBAC) acid series, at transitions between the smectic and the isotropic phase and between the smectic and nematic phase. Studied compounds were 12OBAC, 16OBAC and binary mixtures of 12- and 16OBAC. The undulations are dressing a usual Schlieren texture. An interesting fingerprint pattern is observed at the smectic-nematic in the case of the binary mixture, approximately 1 : 1 in weight.