The recent literature in the field of liquid crystals shows that “banana-shaped” mesogenic materials represent a bewitching and stimulating field of research that is interesting both academically and in terms of applications. Numerous topics are open to investigation in this area because of the rich phenomenology and new possibilities that these materials offer. The principal concepts in this area are reviewed along with recent results. In addition, new directions to stimulate further research activities are highlighted.

Materials that exhibit high nonlinear optical (NLO) susceptibilities are considered as promising candidates for a wide range of photonic and electronic applications. Here, we argue that the ferroelectric nematic (N_F) materials have sufficient potentialities to become materials for the next-generation of NLO devices. We have carried out a study of the efficiency of optical second-harmonic generation in a prototype N_F material, finding a nonlinear susceptibility of 5.6 pm.V⁻¹ in the transparent regime, one of the highest ever reported in ferroelectric liquid crystals. Given the fact that the studied molecule was not specifically designed for NLO applications, we conclude there is still margin to obtain N_F materials with enhanced properties that should allow their practical use. GRAPHICAL ABSTRACT

A liquid crystal material of bent-core molecules is investigated by means of optical texture observations, x-ray measurements, and miscibility studies. While the x-ray and miscibility data point towards a $B_2$ phase, the texture is however unusual, showing optical isotropy and segregation in two domains with opposite gyrations. It is shown that the texture can be interpreted successfully in terms of a smectic-$C_A{P}_A$ structure in small domains with random orientations. The optical activity data are also explained semiquantitatively.

The design, synthesis and nonlinear optical (NLO) response of some bent compounds, at both the molecular and macroscopic level, are reported. Based on a bent-core NLO-phore with a μβ₀ in the range of 390 × 10⁻⁴⁸ esu (1907 nm), the second order susceptibility tensor for second harmonic generation is evaluated at excitation wavelengths of 1064 and 1600 nm in a mesogenic material with a SmCP mesophase. The NLO coefficients are in the range 10–100 pm V⁻¹ . Thus it is deduced that a molecular design leading to bent-core liquid crystals with large β values is a correct strategy to achieve NLO-materials for bulk second order effects.