Molecular Crystals and Liquid Crystals, Vol.524, 54-67, 2010
Design, Synthesis and Characterization of Hydrogen-Bonded Ferroelectric Liquid Crystals
A novel series of hydrogen-bonded ferroelectric liquid crystals has been isolated. A hydrogen bond was formed between chiral ingredient (S)-(+)-6-methoxy--methyl-2-naphthaleneacetic acid (Nap) and mesogenic p-n alkyloxy benzoic acids. A phase diagram was constructed from the transition temperatures obtained by differential scanning calorimetry (DSC) and polarizing optical microscopic (POM) studies. Thermal and dielectric properties exhibited by these complexes, namely, Nap+nBA (where n=6 to 11), are discussed. A phase diagram of the present hydrogen-bonded series was compared with that of the free alkyloxy benzoic acids (nBA). Nap+nBA series exhibits cholesteric, smectic C*, smectic G*, and smectic F* phases. Dielectric relaxations were studied in selected members of the homologous series that exhibits cholesteric and smectic GF* phases. Dielectric studies indicate multiple relaxation processes in the cholesteric phase and a single relaxation process in smectic G*, smectic F* phase. Activation energies calculated from the respective Cole-Cole plots are discussed.
Keywords:Chemical synthesis;dielectric response;liquid crystals;optical properties;phase transitions