The still undiscovered fluid ferroelectric nematic phase is expected to exhibit a much faster and easier response to an external electric field compared to conventional ferroelectric smectic liquid crystals; therefore, the discovery of such a phase could open new avenues in electro‐optic device technology. Here, experimental evidence of a ferroelectric response to a switching electric field in a low molar mass nematic liquid crystal is reported and connected with field‐induced biaxiality. The fluid is made of bent‐core polar molecules and is nematic over a range of 120 °C. Combining repolarization current measurements, electro‐optical characterizations, X‐ray diffraction and computer simulations, ferroelectric switching is demonstrated and it is concluded that the response is due to field‐induced reorganization of polar cybotactic groups within the nematic phase. This work represents significant progress toward the realization of ferroelectric fluids that can be aligned at command with a simple electric field.

Recently we investigated the occurrence of static periodic stripes in a hybrid aligned nematic cell. Assuming that the tilt anchoring was stronger at the planar wall than at the homeotropic wall, we have found the critical thickness of the cell for the transition from planar to periodic alignment as a function of the surface energy in the presence of a magnetic field. Here we study, for the same kind of cell, the critical thickness between the periodic and the aperiodic deformed structure by means of an appropriate numerical technique. As expected, such a threshold was found to be greater than the asymptotic threshold between planar and aperiodic structures. We performed an experiment, which allowed us to give an estimate of the surfacelike elastic constant K,4.

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A study of textural changes is presented concerning the nematic phase of 4-n-alkyloxybenzoic acids (in particular, 4-n-heptyl-and 4-n-octyl-oxybenzoic acids), by means of a statistical approach to the image data observed by polarized light microscopy (orthoscopic mode). A new image processing method is developed in order to detect with high sensitivity any structural change in the image frame. To do this, a set of parameters is introduced, charaterizing the observed textures. Such a set is a vector, working like a path® nder strongly increasing the human eyeÐ or in general the sensor Ð skilfulness to appreciate any change of the optical texture, both in space and in time. This is suitable for revealing smooth transitions, such as phase transitions between smectic and nematic phases (or between di erent smectic phases), or order transitions, like alignment transitions in poorly oriented nematic layers. In fact, by using this method for detecting the order transition between two nematic`subphases' of 4-n-alkyloxybenzoic acids, the sensitivity turns out to be enhanced by a factor higher than 10 with respect to that for standard techniques. The new method allows us to de® ne a characteristic size of the image texture: this concept is applied to analyse several image data for estimating the mean size of the domains appearing in the smectic and in the nematic phase of the compounds under study.

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