Occurrence of Ambient Temperature and Reentrant Smectic Ordering in an Intermolecular Hydrogen Bonding between Alkyl Aniline and Alkoxy Benzoic Acids

Abstract

A homologous series of inter-hydrogen-bonded complexes between p-n-alkoxybenzoic acids (12A + nBA) and alkyl aniline was isolated. The mesogenic p-n-alkoxybenzoic acids formed a hydrogen bond with liquid-crystal intermediate 4-dodecyl aniline. The isolated homologous series compounds were analyzed by Fourier transform infrared (FTIR), polarizing optical microscope, dielectric studies, and differential scanning calorimetry (DSC). An interesting feature of these homologous series was the occurrence of an ambient smectic ordering in some of the isolated mesogens. The phase diagrams of the p-n-alkoxybenzoic acids and the present homologous series were computed and compared. The hydrogen bond formation was evinced through FTIR spectral studies. Two higher member mesogens of the present homologous series were found to exhibit monotropic smectic G phase. Results of free p-n-alkoxybenzoic acids and the hydrogen-bonded homologous series are discussed in the light of increment alkoxy carbon number, mesogenic phases exhibited, and mesogenic thermal range.