Insight into Out‐of‐Layer Fluctuations in the Smectic A Stability of 3,5‐Diarylisoxazole Liquid Crystals

Abstract

Polar‐terminated 3,5‐diarylisoxazole liquid crystals (ILCs) were synthetized and characterized. ILCs are composed by rigid core 3,5‐diarylisoxazol, alkyl chain and polar‐terminated flexible spacer. Hydroxyl‐, ketal‐ and 1,2‐diol‐terminated ILCs rendered smectic C and A mesophase, while bromine‐terminated ILCs showed smectic A and B mesophase, for monosubstituted and linear ILCs. For branched alkyl chain monotropic SmA was detected and for disubstituted ILCs no mesophase was detected. Out‐of‐layer fluctuations (OLFs) are discussed based on X‐ray diffraction date and textures. The OLFs are dependent on the bromine atom hardness, hydrogen bonding through collective actions and conformational effects at the interface between layers. Smectic translational order parameter (TOP) Σ was also obtained for orientated bromine‐ and hydroxyl‐terminated ILCs and related it with OLFs. For 1,2‐diol‐terminated ILCs two SmC sublayers were founded, probably related to the intramolecular hydrogen bond favoring the 5‐membered and 6‐membered formation.

Smart Supramolecular Self-Assembled Nanosystem: Stimulus-Responsive Hydrogen-Bonded Liquid Crystals

“…Many supramolecular LC systems were formed between LC molecules, units or other components, and appeared in different new phases [32][33][34][35]. Different from conventional LC, these highly ordered supramolecular architectures would be paid much attention due the response ability, not the nature of LC (e.g., phase transition, thermal stability and spatial order).…”

Origin of the Monolayer and Bilayer Arrangement in Smectic A and C Mesophases and Nematic Cybotactic Domains: The Case Study of Benzyloxy-Terminated Isoxazole Liquid Crystals

“…3,5-Diarylisoxazoles synthesized by (3 + 2) 1,3-dipolar cycloaddition in two steps offers many opportunities to synthesize a collection of new isoxazole liquid crystals (ILCs) with a variety of substituents connected to the isoxazole ring. The stabilization of the smectic mesophase depends on some factors such as the out-of-layer fluctuations (OLFs), which is related to the nature and size of the substituents connected to the rigid core of LCs. − The performance of a device based on LC materials depends on several parameters . One of them is the molecular alignment in smectic-based material devices presenting the N-SmA-SmC transition.…”