de Oliveira Wilson Aparecido, Alaasar Mohamed, Cao Yu, Westphal Eduard
Departamento Acadêmico de Química e Biologia, Universidade Tecnológica Federal do Paraná, Curitiba 81280-340, Brazil.
Department of Chemistry, Universidade Federal de Santa Catarina, Florianópolis 88040-900, Brazil.
ACS Omega. 2025 May 23;10(21):21637-21647. doi: 10.1021/acsomega.5c00974. eCollection 2025 Jun 3.
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 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) and bicontinuous cubic (Cub) 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.
光致变色材料能够通过光照可逆地调节其性能，具有广泛的适用性并引起了科学界的极大兴趣。对于液晶（LC）而言，这为控制其自组装、性能甚至消除介晶性开辟了可能性。在各种液晶官能团中，酰腙尽管具有易于合成、多功能性、可逆光异构化和凝胶化等优势特性，但仍是未被充分探索的光致变色基团。基于证明该基团多功能性的努力，本研究首次将第二个酰腙单元引入线性多链节分子中，从而能够系统地研究结构变化的影响，包括外围烷氧基链的数量、酰腙基团的取向以及刚性核的扩展。这些修饰导致合成了六个新分子，并对其热性能、介晶性能、开关性能和凝胶化性能进行了系统研究。结果表明，引入第二个酰腙单元显著增强了这些性能，其中5个分子表现出液晶性能。根据分子设计，介晶性得以稳定，自组装在六方柱状（Col）相和双连续立方（Cub）相之间变化。酰腙单元的取向影响介晶性，极大地改变了光异构化速率，并诱导出微弱的发光。这些性能与分子间相互作用以及它们在各自介晶相中促进自组装的方式相关。此外，这两个分子形成了稳定的、可光异构化的凝胶，突出了酰腙单元在多功能材料开发中的多功能性。
