Synthesis and Investigation of Nematic Liquid Crystals with Flexoelectric Properties

• Published in: Chemistry of materials Vol. 17; no. 25; pp. 6354 - 6360
• Main Authors: Wild, Janine H, Bartle, Kevin, Kirkman, Nicola T, Kelly, Stephen M, O'Neill, Mary, Stirner, Tom, Tuffin, Rachel P
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.12.2005
• DOI: 10.1021/cm051682y
• ISSN: 0897-4756

We describe the synthesis and characterization of a series of model nematic liquid crystals with transverse dipole moments used to study the flexoelectric effect in guest−host mixtures with commercial liquid crystal host. The flexoelectric coefficicent of the mixtures, containing only 10% by weight of the dopant, are up to 6 times higher than those of the pure hosts. The length, bend angle, and dipole moments of the molecules are systematically varied to investigate any correlations with the flexoelectric effect. We find that the flexoelectric coefficients increase with molecular length, are inversely correlated with the bend angle, and are independent of the dipole moment of the dopant. Although these findings seem to contradict predictions from dipolar flexoelectric theories, they can be reconciled by considering the properties of both the guest and host in the mixture. Thiophenes and dimesogens show particularly large flexoelectric effects. This work should inform the molecular design of new materials with enhanced flexoelectric properties.