Columnar Liquid Crystalline Glasses by Combining Configurational Flexibility with Moderate Deviation from Planarity:...

Area of Science:

• Materials Science
• Organic Chemistry
• Crystallography

Background:

• Columnar liquid crystals are investigated for their potential in molecular alignment and anisotropic optical properties.
• Achieving stable, ordered states at room temperature is crucial for practical applications.

Purpose of the Study:

• To synthesize and characterize novel triazine-hexaalkyl esters with phenanthryl and tetrahelicenyl substituents.
• To investigate the liquid crystalline behavior, particularly the glass transition and columnar ordering, of these new compounds.
• To evaluate their suitability for orienting guest emitters for anisotropic emission.

Main Methods:

• Synthesis of triply phenanthryl- and tetrahelicenyl-substituted triazine-hexaalkyl esters.
• Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) for thermal analysis and phase identification.
• X-ray diffraction (XRD) to study the columnar order and lattice structure.

Main Results:

• Compounds exhibit hexagonal columnar liquid crystalline phases with glass transitions above room temperature, leading to solid columnar order.
• Tetrahelicenyl derivatives show favorable melting and clearing temperatures for face-on alignment on substrates.
• An unusual phase transition between two columnar mesophases with different lattice regularities was observed in a phenanthryl derivative.

Conclusions:

• The synthesized materials offer a stable solid columnar matrix at room temperature, suitable for guest emitter alignment.
• The molecular design, particularly the use of tetrahelicenyl groups, facilitates substrate alignment for anisotropic emission.
• Further investigation into the observed phase transition could reveal new insights into columnar liquid crystal behavior.