Dissymmetric Triaryltriazines: Small Mass Columnar Glasses

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Organic Electronics

Background:

• Columnar liquid crystals (CLCs) are crucial for advanced materials due to their ordered structures.
• Developing CLCs with low molecular mass and high thermal stability remains a challenge.
• Sym-triazine cores offer a versatile platform for designing functional mesogens.

Purpose of the Study:

• To synthesize and characterize novel CLCs based on dissymmetrically substituted sym-triazine.
• To investigate the influence of molecular symmetry and ester group length on mesophase stability and glass transitions.
• To evaluate the film-forming properties and thermal stability of the resulting liquid crystalline materials.

Main Methods:

• Mixed dissymmetric substitution of sym-triazine with phenyl, phenanthryl, or tetrahelicenyl moieties bearing ester groups.
• Differential scanning calorimetry (DSC) to determine thermal transitions.
• Optical microscopy and X-ray diffraction to analyze mesophase structure.
• Fluorescence spectroscopy to assess emission properties of cast films.

Main Results:

• Achieved columnar liquid crystals with very low molecular masses forming anisotropic glasses well above room temperature.
• Stabilized mesophases over large temperature ranges due to low molecular symmetry, configurational flexibility, and short polar ester moieties.
• Demonstrated that short ester groups (ethyl) are sufficient for liquid crystallinity, minimizing insulating alkyl peripheries.
• Drop-cast films exhibited stable fluorescence emission upon annealing, indicating direct formation of columnar hexagonal mesoscopic order resistant to crystallization.

Conclusions:

• Novel sym-triazine-based CLCs with low molecular mass and high thermal stability were successfully synthesized.
• Molecular design strategies involving dissymmetric substitution and short ester groups are effective for tuning liquid crystalline properties.
• The materials form ordered, stable films directly from solution, showing potential for applications in organic electronics and photonics.