Theoretical study on mesogenic core structures of nematic liquid crystalline compounds

Area of Science:

• Physical Chemistry
• Materials Science

Background:

• Liquid crystals (LCs) are crucial in display technologies.
• Understanding intermolecular forces in LC mesogens is key to designing new materials.

Purpose of the Study:

• To investigate the intermolecular interaction energies of 10 dimers within typical liquid crystalline (LC) structures.
• To elucidate the contributions of dispersion, electrostatic, and exchange-repulsion energies to dimer stability.
• To correlate calculated interaction energies with experimentally measured viscosities.

Main Methods:

• Computational chemistry methods, specifically MP2/6-31G(d) level of theory, were employed.
• Structures and interaction energies of 10 representative LC dimers were calculated.
• Geometrical orientations and their impact on energy components were analyzed.

Main Results:

• Dispersion energy significantly contributes to the total interaction energy of LC dimers.
• Even with bulky substituents, interaction energies remain substantial.
• Electrostatic interactions, particularly quadrupole-quadrupole attraction, dominate at longer distances, forming stable dimers.
• All energy components (dispersion, electrostatic, exchange-repulsion) are highly sensitive to molecular orientation.
• A clear linear relationship was observed between calculated interaction energies and experimental viscosities.

Conclusions:

• Intermolecular forces, especially dispersion and electrostatic interactions, play a critical role in the stability of liquid crystalline (LC) dimers.
• Molecular geometry and orientation strongly influence these interactions.
• A direct correlation exists between calculated interaction energies and macroscopic properties like viscosity, offering predictive potential for LC material design.