Electrical Conductivity and Multiple Glassy Dynamics of Crown Ether-Based Columnar Liquid Crystals

Area of Science:

• Materials Science
• Physical Chemistry
• Organic Chemistry

Background:

• Triphenylene crown ether-based compounds are known for their liquid crystalline properties.
• Understanding their phase behavior and molecular dynamics is crucial for material applications.

Purpose of the Study:

• To investigate the phase behavior and molecular mobility of two unsymmetrical triphenylene crown ether-based columnar liquid crystals (KAL465 and KAL468).
• To characterize the relaxation processes and conductivity contributions within different phases.

Main Methods:

• Differential scanning calorimetry (DSC) for phase behavior analysis.
• Broadband dielectric spectroscopy (BDS) for molecular mobility studies.
• Advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy.

Main Results:

• Observed plastic crystalline (Cry), columnar liquid crystalline (Colh), and isotropic phases with two glass transitions in the Cry phase.
• Identified three dielectric active relaxation processes (γ, α2, α3) and a second dynamic glass transition (α1) not detected by BDS.
• Found a conductivity contribution in both Cry and Colh phases, increasing significantly at the Cry to hexagonal phase transition.

Conclusions:

• Distinct relaxation processes (α1, α2, α3) with different temperature dependencies were identified, suggesting varied molecular assignments.
• The study provides comprehensive insights into the complex phase behavior and molecular dynamics of these liquid crystals.