Influence of Terminal Groups on the Mesogenic Properties of Self-Assembly Systems

Two novel hydrogen-bonded liquid crystal homologous series are synthesized and characterized. A hydrogen bond is formed between various p-n alkyloxy benzoic acids and chloro/hydroxy benzaldehyde. The formation of hydrogen bonds is evinced through Fourier Infra Red Spectroscopy studies. The terminal group of the aldehyde group has been varied and the thermal, optical, and electrical results are compared and analyzed. Both series exhibit rich liquid crystalline-phase polymorphism. Phase diagrams are constructed from the Differential Scanning Calorimetry and optical polarizing microscopic data. The phase sequence is same for both the series, with nematic, smectic C, and smectic G phases. A noteworthy point is the observation of optical shuttering action in the homologous series with the chloro terminal group of the aldehyde group and absence of the same in the other homologous series. The influence of terminal group of the aldehyde group with respect to occurrence of phase variance, tilt angle, optical shuttering action, and odd-even effect is discussed.