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We present the properties of different achiral orthogonal polar smectic phases observed in a homologous series of bent-core molecular compounds. The macroscopically uniaxial SmAPR phase transforms to biaxial state by the application of higher electric fields and biaxial SmAPA phase undergoes biaxial-uniaxial-biaxial texture transformation with increasing electric fields, i.e., initial antiferroelectric structure transforms into ferroelectric state under higher electric fields and it shows three different optically distinguishable states. The SmAPAR phase shows an entirely different response compared to other polar smectic phases under study. The dielectric measurements in the SmAPAR phase is the evidence of antiferroelectric behavior of uniaxial state. The polarizing microscopy texture observation supports the corresponding biaxiality measurements. [ABSTRACT FROM PUBLISHER]

The mesomorphic properties of a homologous series of achiral bent-core compounds are studied by polarizing optical microscopy, electro-optics and polarization measurements. Induction of a new orthogonal smectic phases with the increase of alkyl side chain length was observed. One of the compounds exhibits a unique phase transition between four non-tilted smectic phases (SmAPA–SmAPAR-SmAPR-SmA). The uniaxial but antiferroelectric nature of SmAPAR phase was confirmed by POM, current response, the 2nd harmonic electro-optic response and polarization measurements. The structure of SmAPAR phase was studied theoretically by Next-Nearest-Neighbor model and was identified as SmAPα. [ABSTRACT FROM PUBLISHER]

We report the observation of biaxial nematic phase in a bent-core molecular system in which the biaxiality exists on a microscopic scale using polarizing microscopy, electro-optics and dielectric spectroscopy. An application of electric field induces a macroscopic biaxiality and therefore electro-optic switching. The observed electro-optic switching is explained in terms of the interaction of the ferroelectric clusters with the electric field. Dielectric spectra of the sample shows existence of low-frequency collective processes related to the microscopic polar clusters. The dielectric constant changes its sign from positive to negative and again to positive values. [ABSTRACT FROM AUTHOR]

We report the structural and relaxation investigations of an achiral bent-core compound in SmAPA phase. The studied material undergoes transition from one biaxial state to the other via a uniaxial state under electric field. These transformations are explained as successive transition from antiferroelectric to ferroelectric states, where, the intermediate uniaxial state has the molecular secondary directors in the neighbouring smectic layers perpendicular to each other. We also found that near SmAPR to SmAPA phase transition the second harmonic electro-optic response, induced polarization, and the dielectric behaviour hint softening behaviour in the material. [ABSTRACT FROM AUTHOR]