A novel smectic liquid crystalline phase exhibited by W-shaped molecules

Abstract

A novel smectic phase has been discovered in the W-shaped molecular system of N,N′-bis[2-hydroxy-5-(4′-n-tetradecylphenylazo)benzylidene]-4-nitro-1,3-phenylenediamine. On slowly cooling this material from the isotropic phase, fine filaments of a chiral nature appear. When they cover the whole surface, schlieren-like textures with two-brush defects are observed. In the texture, fine stripes formed by the filaments exist, which represent an orientational map. Each filament in a specific region has its own chiral character and forms chiral domains, as identified by uncrossed polarizers. According to X-ray analysis, a layer structure with a periodicity of the molecular length is clearly seen. Several diffuse but distinct wide-angle diffraction peaks are observed in the smectic phase and become sharp in the lower-temperature crystalline phases. Based on these experimental results, we can conclude the existence of a new phase with a chiral nature.