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

Area of Science:

• Materials Science
• Organic Chemistry
• Supramolecular Chemistry

Background:

• Photochromic materials reversibly change properties with light, with applications in liquid crystals (LCs).
• Acylhydrazones are underexplored photochromic groups with advantageous synthesis, photoisomerization, and gelation properties.

Purpose of the Study:

• To introduce a second acylhydrazone unit into linear polycatenar molecules.
• To investigate the effects of structural variations on thermal, mesomorphic, switching, and gelation properties.
• To explore the potential of acylhydrazone-based molecules in developing multifunctional materials.

Main Methods:

• Synthesis of six new linear polycatenar molecules with varying acylhydrazone units and peripheral chains.
• Systematic investigation of thermal, mesomorphic, photochromic switching, and gelation properties.
• Correlation of self-organization and properties with molecular design and intermolecular interactions.

Main Results:

• Five out of six synthesized molecules exhibited liquid crystal (LC) properties.
• Mesomorphism was stabilized, with self-organization into hexagonal columnar (Colh) and bicontinuous cubic (Cubbi) phases observed.
• Acylhydrazone orientation influenced mesomorphism, photoisomerization rates, and induced mild luminescence.
• Two molecules formed stable, photoisomerizable gels.

Conclusions:

• The incorporation of a second acylhydrazone unit significantly enhances the properties of polycatenar molecules.
• Acylhydrazone-based LCs offer tunable self-organization and photoresponsive behavior.
• These findings highlight the potential of acylhydrazones in creating advanced multifunctional materials, including photoresponsive gels.