Abstract
A novel series of chiral hydrogen bonded liquid crystals have been isolated. Hydrogen bond was formed between chiral non mesogen ingredient levo tartaric acid and mesogenic p-n alkoxy benzoic acids. Phase diagram was constructed from the transition temperatures obtained by DSC and polarizing optical microscopic (POM) studies. Thermal and electrical properties exhibited by three complexes namely LTA+8BA, LTA+7BA and LTA+5BA were discussed. Salient feature of the present work was observation of a reentrant smectic C* ordering in LTA+8BA complex. This reentrant phenomenon was confirmed by DSC thermograms, optical textures of POM and temperature variation of capacitance and dielectric loss studies. Tilt angle was measured in Smectic C* and reentrant smectic Cr* phases. Goldstone mode which is manifestation of ferroelectric ordering was detected in smectic C* phase of these hydrogen bonded complexes. Two types of relaxation named as type I and type II were observed in smectic C* and smectic G phases of the present hydrogen bonded complexes respectively and a theoretical modeling was presented towards the origination of various types of relaxation mechanisms.
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