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1,4-Bis(Acylhydrazone)-Based Polycatenar Liquid Crystals: Self-Assembly, Molecular Switching, and Gelation Properties

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Photochromic materials allow their properties to be reversibly modulated by using light, offering broad applicability and significant scientific interest. In the case of liquid crystals (LCs), this opens up possibilities for controlling the self-organization, its properties, and even extinguishing mesomorphism. Among the diverse liquid crystalline functional groups, acylhydrazones remain the underexplored photochromic group despite their advantageous characteristics, such as ease of synthesis, versatility, reversible E-Z photoisomerization, and gelation. Building on efforts to demonstrate the versatility of this group, this study introduces, for the first time, a second acylhydrazone unit into linear polycatenar molecules, enabling a systematic investigation of the effects of structural variations, including the number of peripheral alkoxy chains, the orientation of the acylhydrazone group, and expansion of the rigid core. These modifications led to the synthesis of six new molecules, whose thermal, mesomorphic, switching, and gelation properties were systematically investigated. The results demonstrated that the introduction of a second acylhydrazone unit significantly enhanced these properties, with 5 molecules showing LC properties. Depending on the molecular design, mesomorphism was stabilized, and self-organization varied between hexagonal columnar (Col h ) and bicontinuous cubic (Cub bi ) phases. The orientation of the acylhydrazone units influenced mesomorphism, drastically altered the photoisomerization rate, and induced mild luminescence. These properties were correlated with intermolecular interactions and the way they promoted self-organization in the respective mesophases. Additionally, the two molecules formed stable, photoisomerizable gels, highlighting the versatility of acylhydrazone units in the development of multifunctional materials.

Source: ACS Omega

DOI: 10.1021/acsomega.5c00974

Authors: Wilson Aparecido de Oliveira, Mohamed Alaasar, Yu Cao, Eduard Westphal

Institutions: Universidade Tecnológica Federal do Paraná, Universidade Federal de Santa Catarina, Cairo University, Martin Luther University Halle-Wittenberg, Xi'an Jiaotong University

Language: English

Topic: Liquid Crystal Research Advancements

Subfield: Electronic, Optical and Magnetic Materials

Field: Materials Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,935